201051792337561

Applications of Advanced Simulation

Student GuideJuly 2006

MT15020 — NX4.0.2

Publication Numbermt15020_g NX 4

Copyright and trademarks

Proprietary and Restricted Rights Notices

This software and all related documentation are proprietary to UGS Corp.

Copyright

©2006 UGS Corp. All Rights Reserved.

All trademarks belong to their respective holders.

©2006 UGS CorporationAll Rights Reserved.Produced in the United States of America.

2 Applications of Advanced Simulation — Student Guide mt15020_g NX 4

Contents

Course overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Course description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Intended audience . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9How to use this manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Symbols used in this guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

Advanced Simulation overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1- 1Advanced Simulation file structure . . . . . . . . . . . . . . . . . . . . . . . . . 1- 2Advanced Simulation workflow . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1- 4Simulation Navigator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1- 5

Nodes in the Simulation Navigator . . . . . . . . . . . . . . . . . . . . . . 1- 6Simulation File View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1- 8

Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-10Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-10

Geometry idealization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

Geometry idealization overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 2- 1Modifying features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2- 1

Edit Feature Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2- 2Suppress Feature/Unsuppress Feature . . . . . . . . . . . . . . . . . . . . 2- 2Master Model Dimension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2- 5

Modifying geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2- 7Idealize Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2- 7Defeature Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10Partition Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11Midsurface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14Face Pair midsurface method . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-15Offset midsurface method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-16User Defined midsurface method . . . . . . . . . . . . . . . . . . . . . . . . 2-18Sew . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-19Subdivide Face . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-22

Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-23Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-23

3D meshing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

3D Tetrahedral Mesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3- 1

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3D Swept Mesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3- 4Solid from Shell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3- 6Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3- 8Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3- 8

2D meshing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

2D meshing overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4- 1Editing a 2D mesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4- 4Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4- 5Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4- 5

1D and 0D meshing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

1D Mesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5- 11D element meshing methods . . . . . . . . . . . . . . . . . . . . . . . . . . 5- 2

Create Weld Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5- 51D Element Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5- 70D Mesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5- 9Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-11Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-11

Mesh points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

Mesh points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6- 1Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6- 2Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6- 2

Mesh and object display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

Mesh Display preferences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7- 1Object display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7- 2Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7- 4Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7- 4

Geometry abstraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1

Geometry abstraction overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8- 1Comparing geometry idealization and geometry abstraction . . . . . . 8- 2Understanding polygon geometry . . . . . . . . . . . . . . . . . . . . . . . . . . 8- 2Understanding the geometry abstraction process . . . . . . . . . . . . . . . 8- 3Fillet identification process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8- 6Auto Heal Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8- 9Split Edge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-10Split Face . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-11Merge Edge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-13Merge Face . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-13Match Edge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-14Collapse Edge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-17Face Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-19

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Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-20Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-21Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-21

Element attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1

Element attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9- 1Attribute Editor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9- 3

Attribute Editor – point selection . . . . . . . . . . . . . . . . . . . . . . . . 9- 3Attribute Editor – curve/element selection . . . . . . . . . . . . . . . . . 9- 4Attribute Editor – face selection . . . . . . . . . . . . . . . . . . . . . . . . 9- 6Attribute Editor – body selection . . . . . . . . . . . . . . . . . . . . . . . . 9- 7Attribute Editor – 3D mesh selection . . . . . . . . . . . . . . . . . . . . . 9- 8Attribute Editor – 2D mesh selection . . . . . . . . . . . . . . . . . . . . . 9- 9Attribute Editor – 1D mesh selection . . . . . . . . . . . . . . . . . . . . . 9-10Attribute Editor – 0D mesh selection . . . . . . . . . . . . . . . . . . . . . 9-11Attribute Editor – Contact mesh selection . . . . . . . . . . . . . . . . . 9-13Attribute Editor – Surface contact mesh selection . . . . . . . . . . . 9-15

Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-16Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-16

Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1

Materials overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10- 2Customizing the material library . . . . . . . . . . . . . . . . . . . . . . . . . 10- 4Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10- 5Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10- 5

Boundary conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1

Boundary conditions overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11- 2Supported boundary conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . 11- 2Creating loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11- 5Creating constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11- 6Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11- 6Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11- 6

Model information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12-1

Model information overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12- 2Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12- 4

Model checking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-1

Model Check overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13- 2Comprehensive check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13- 2Element Shapes check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13- 3Element Shapes Threshold Values . . . . . . . . . . . . . . . . . . . . . . . . 13- 3Element Outlines check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-10Nodes check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-10


Contents

2D Element Normals checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-11Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13-11

Solving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14-1

Solving overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14- 2Solving the model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14- 2Analysis Job Monitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14- 3Batch solving . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14- 3Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14- 4Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14- 4

Post-processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1

Post-processing introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15- 2Results in the Simulation Navigator . . . . . . . . . . . . . . . . . . . . . . . 15- 2The Post Control toolbar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15- 3Import Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15- 4Post View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15- 6Post view templates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15- 7Post view layouts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15- 7Overlay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15- 8Combining load cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15- 9Animation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-10Identify . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-10Generating reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-12Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-12Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-12

Reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16-1

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16- 2Creating the report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16- 4Exporting the report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16- 4Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16- 4Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16- 4

Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17-1

Units overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17- 2Units Manager . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17- 2Units Converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17- 4Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17- 5Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17- 5

Mesh connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-1

Mesh Mating Condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18- 2Edge Face Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18- 5Weld Mesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18- 6


Contents

Contact Mesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18- 9Surface Contact Mesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-10Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-11Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-11

Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-1

Optimization overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19- 2Optimization Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19- 2Optimization analysis options . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19- 3Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19- 4Constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19- 5Design Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19- 6Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19- 7Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19- 8

Durability (fatigue) analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20-1

Durability overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20- 2Preparing the model for a durability analysis . . . . . . . . . . . . . . . . 20- 2Creating a durability solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20- 3Evaluating fatigue results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20- 4Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20- 5Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20- 6

Buckling analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21-1

Linear buckling overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21- 2Loads in linear buckling analysis . . . . . . . . . . . . . . . . . . . . . . . . . 21- 2Supported environments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21- 3Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21- 4Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21- 4

Modal analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22-1

Modal analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22- 2Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22- 4Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22- 5

Thermal analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23-1

Thermal analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23- 2Activity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23- 4Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23- 4

Contact and gluing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24-1

Surface to Surface Contact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24- 2Advanced Nonlinear Contact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24- 3Surface to Surface Gluing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24- 5


Contents

Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24- 6Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24- 6


Course overview

Course descriptionApplications of Advanced Simulation introduces the finite element modelingand analysis tool integrated in NX. It is intended for design engineers andanalysts who want to learn the details of how to do finite element analysis onNX models. This course covers the details of the FEA processes from modelpreparation, mesh generation and manipulation, material definition, loadsand boundary conditions, FEA model checking and solving, to postprocessingthe results.

Intended audience• Design engineers

• Analysts

Prerequisites• Practical Applications of NX course or self-paced equivalent.

• Working knowledge of NX Modeling.

• Basic understanding of finite element analysis principles.

How to use this manualThe general format for lesson content is:

• presentation

• activity in the Applications of Advanced Simulation Workbook

• summary

It is important that you use the Student Guide and Workbook in the sequencepresented. Later lessons assume you have learned concepts and techniquestaught in earlier lessons. If necessary, you can always refer to any previousactivity where a method or technique was originally taught.


How to use this manual

Symbols used in this guide

The following symbols are used throughout this guide:

This is a tip.

This is a note.

This is a warning.


1Lesson

1 Introduction

Objective

• This lesson is a fundamental introduction to Advanced Simulation.

Advanced Simulation overviewAdvanced Simulation is a comprehensive finite element modeling and resultsvisualization product that is designed to meet the needs of experiencedanalysts. Advanced Simulation includes a full suite of pre-and post-processingtools and supports a broad range of product performance evaluation solutions.

Advanced Simulation provides seamless, transparent support for a numberof industry-standard solvers, such as NX Nastran, MSC Nastran, ANSYS,and ABAQUS. For example, when you create either a mesh or a solution inAdvanced Simulation, you specify the solver you plan to use to solve yourmodel and the type of analysis you want to perform. The software thenpresents all meshing, boundary conditions, and solution options using theterminology or “language” of that solver and analysis type. Additionally, you

©UGS Corporation, All Rights Reserved Applications of Advanced Simulation — Student Guide 1-1

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Introduction

can solve your model and view your results directly in Advanced Simulationwithout having to first export a solver file or import your results.

Advanced Simulation provides all the functionality available in DesignSimulation, plus numerous additional features that support advancedanalysis processes.

• Advanced Simulation features data structures, such as the separateSimulation and FEM files, that help facilitate the development of FEmodels across a distributed work environment. These data structuresalso allow analysts to easily share FE data to perform multiple typesof analyses.

• Advanced Simulation offers world class meshing capabilities. Thesoftware is designed to produce a very high quality mesh while usingan economic element count. Advanced Simulation supports a completecomplement of element types (0D, 1D, 2D, and 3D). Additionally, AdvancedSimulation gives analysts control over specific meshing tolerances whichcontrol, for example, how the software meshes complex geometry, suchas fillets.

• Advanced Simulation includes a number of geometry abstraction toolsthat give analysts the ability to tailor the CAD geometry to the needs oftheir analysis. For example, analysts can use these tools to improve theoverall quality of their mesh by eliminating problematic geometry, such astiny edges.

• Advanced Simulation features the new NX Thermal and NX Flow solvers.

– NX Thermal is a fully integrated finite difference solver. It allowsthermal engineers to predict heat flow and temperatures in systemssubjected to thermal loads.

– NX Flow is a Computational Fluid Dynamics (CFD) solver. It allowsanalysts to perform steady-state, incompressible flow analysis andpredict flow rates and pressure gradients for movement of fluid in asystem.

You can use NX Thermal and NX Flow together to perform coupledthermal/flow analyses.

Advanced Simulation file structureAs you progress through the Advanced Simulation workflow, you will use fourseparate, yet associated, files to store information. To work efficiently inAdvanced Simulation, you need to understand what data is stored in whichfile, and thus which file needs to be the active work part when you create thatdata. These four files parallel the simulation process.

1-2 Applications of Advanced Simulation — Student Guide ©UGS Corporation, All Rights Reserved mt15020_g NX 4

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Introduction

The original design part file being analyzed

A part file has a .prt extension. For example, a part might be namedplate.prt.

The part file contains the master part or an assembly, and the unmodifiedpart geometry.

If you start with a model designed by someone else, you might not havepermission to modify it. The master part file is generally not modifiedduring the analysis process.

The idealized copy of the design part file

An idealized part has a .prt extension. By default, when an idealizedpart file is created, fem#_i is appended to the part name. For example,an idealized part would be named plate_fem1_i.prt if the original partwas named plate.prt.

An idealized part is an associative copy of the original, and you canmodify it.

The idealization tools let you make changes to the design features of themodel using the idealized part. You can perform geometry idealizationas needed on the idealized part without modifying the master part. Forexample, you may remove and suppress features such as small geometrydetails that can be ignored in the analysis.

You can use multiple idealized files for different types of analysis of thesame original design part file.

The FEM file


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Introduction

A FEM file has a .fem extension. By default, when a FEM file is created,_fem# is appended to the part name. For example, a FEM file may benamed plate_fem1.fem if the original part was named plate.prt.

A FEM file contains the mesh (nodes and elements), physical properties,and materials.

Once you create the mesh, you can use the abstraction tools to removedesign artifacts that can affect the overall quality of the mesh such assliver faces, small edges, and isthmus conditions. The abstraction toolsallow you to mesh the geometry at a level of detail that sufficientlycaptures the design intent relevant to a particular finite element analysis.

The geometry abstraction occurs on polygon geometry stored in the FEM,not in the idealized or master part.

Since multiple FEM files can reference the same idealized part, you canbuild different FEMs for different types of analyses.

The Simulation file

A Simulation file name has a .sim extension. By default, when aSimulation file is created, _sim# is appended to the part name. Forexample, a Simulation file may be named plate_sim1.sim if the originalpart was named plate.prt.

The Simulation file contains all the simulation data, such as solutions,solution setup, loads, constraints, element-associated data, physicalproperties, and overrides. You can create many Simulation files associatedto the same FEM file.

Advanced Simulation workflowBefore you begin an analysis, you should have a thorough understanding ofthe problem you are trying to solve. You should know which solver you will beusing, what type of analysis you are performing, and what type of solution isneeded. The following outline summarizes the general workflow in AdvancedSimulation.

1. In NX, open a part file.

2. Open the Advanced Simulation application.

Specify the default solver (which sets the environment, or language) forworking in the FEM and Simulation files.

You could also choose to create only the FEM file first, and thencreate a Simulation file later.

3. Create a solution.


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Introduction

Select the solver (such as NX Nastran), analysis type (such as Structural),and solution type (such as Linear Statics).

4. If necessary, idealize the part geometry.

Once you make the idealized part active, you can remove unnecessarydetails such as holes or fillets, partition the geometry to prepare for solidmeshing, or create midsurfaces.

5. Make the FEM file active, and mesh your geometry.

It is a good practice to first mesh your geometry automatically using thesoftware defaults. In the great majority of cases, the software defaultsprovide a robust, high-quality mesh you can use without modification.

6. Check your mesh quality.

If necessary, you can refine your mesh by returning to the idealized partand further idealizing the part geometry. In addition, in the FEM you canuse the abstraction tools to eliminate issues with the CAD geometry thatcan cause undesirable results when you mesh your model.

7. Apply a material to the mesh.

8. When you are satisfied with your mesh, make the Simulation file active,and apply loads and constraints to your model.

9. Solve your model.

10. Examine your results in Postprocessing.

Simulation NavigatorThe Simulation Navigator provides you with a graphical way of viewing andmanipulating the different files and components of a CAE analysis within atree structure. Each file or component is displayed as a separate node inthe tree.

The Simulation Navigator provides direct access to the entities in it throughshortcut menus. You can perform most operations directly in the SimulationNavigator instead of using icons or commands. For example, to create a newsolution definition, you can drag loads and constraints from one container toanother in the Simulation Navigator.


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Introduction

Nodes in the Simulation Navigator

The top panel of the Simulation Navigator shows the contents of the displayedfile. The figure below shows an example of the containers that can bedisplayed within a top-level Simulation file. The check boxes let you controlthe display of the items.


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Introduction

The following table presents a high-level overview of the various nodes in theSimulation Navigator.

Icon Node Name Node DescriptionSimulation Contains all the simulation data, such as

solutions, solution setup, solver-specificsimulation objects, loads, constraints, andoverrides. You can have multiple Simulationfiles associated with a single FEM file.

FEM Contains all the mesh data, physical properties,material data, and polygon geometry. The FEMfile is always associated to the idealized part.You can associate multiple FEM files to a singleidealized part.

idealized part Contains the idealized part that the softwarecreates automatically when you create a FEM.

master part When the master part is the work part,right-click on the master part node to create anew FEM or display existing idealized parts.

PolygonGeometry

Contains the polygon geometry (polygon bodies,faces, and edges). Once you mesh the FEM,any further geometry abstraction occurs onthe polygon geometry, not the idealized or themaster part.

0D Meshes Contains all 0D meshes.




SimulationObjectContainer

Contains solver- and solution-specific objects,such as thermostats, tables, or flow surfaces.

LoadContainer

Contains loads assigned to the currentSimulation file. In a Solution container, theLoad Container contains the loads assigned togiven subcase.

ConstraintContainer

Contains constraints assigned to the currentSimulation file. In a Solution container, theConstraint Container contains the constraintsassigned to the solution.


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Introduction

Icon Node Name Node DescriptionSolution Contains the solution objects, loads, constraints,

and subcases for the solution.Subcase

Step

Contains solution entities specific to eachsubcase within a solution, such as loads,constraints, and simulation objects.

Results Contains any results from a solve. In the postprocessor, you can open the Results node and usethe visibility check boxes within the SimulationNavigator to control the display of variousresults sets.

Simulation File View

The bottom section of the Simulation Navigator contains the Simulation FileView panel, which shows the overall “roadmap” of the files you have open. Towork on a particular file, double-click it make it active.


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Introduction

Part file bracket.prt

Idealized part file bracket_fem_i.prt

FEM file bracket_fem1.fem

Simulation file bracket_sim1.sim


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Introduction

ActivitySee the “Introduction” activity in the Applications of Advanced SimulationWorkbook.

In this activity you will work through the Advanced Simulation workflow byanalyzing a part — a connecting rod — using a 3D (solid) mesh.

SummaryIn this lesson you:

• Learned about the capabilities of Advanced Simulation.

• Learned about the files that are used by Advanced Simulation.

• Learned about basic workflow for using Advanced Simulation.

• Created FEM and Simulation files.

• Worked with files in the Simulation Navigator.

• Worked through the finite element analysis workflow in AdvancedSimulation.


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Lesson

2 Geometry idealization

Objective

• Learn how to use model preparation tools to simplify your model beforemeshing.

Geometry idealization overviewGeometry idealization is the process of removing or suppressing features fromyour model prior to defining a mesh. You can also use geometry idealizationcommands to create additional features, such as partitions, to supportyour finite element modeling goals. For example, you can use geometryidealization commands to:

• Remove features, such as bosses, that aren’t significant to your analysis.

• Modify the dimensions of the idealized part using interpart expressions.

• Partition a larger volume into multiple smaller volumes to facilitatemapped meshing.

• Create midsurfaces to facilitate shell meshing of thin-walled parts.

The software performs all geometry idealization operations on the idealizedpart, which is an assembly instance of your master model. No idealization isperformed directly on the master model.

You can use the commands on the Model Preparation toolbar to idealize thegeometry in your model.

To use the commands on the Model Preparation toolbar, you mustmake the idealized part the displayed part.

Modifying featuresSeveral tools let you modify features of the idealized part:

• Edit Feature Parameters

• Suppress Feature and Unsuppress Feature


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Geometry idealization

• Master Model Dimension

Edit Feature Parameters

In Advanced Simulation, when you use the Midsurface tool, you createa midsurface feature parameter that you can edit using Edit Feature

Parameters .

Additionally, you can edit any existing feature parameters in your modelbased on the method and parameter values used when it was created. Theinteraction depends on the type of feature you select.

Suppress Feature/Unsuppress Feature

Use Suppress Feature to automatically select features to besuppressed, or to manually select one or more features and temporarilyremove them from the target body and the display.

To successfully access features for suppression, you must first enablesuppression for the relevant part features in Modeling (Modelingapplication → Edit → Feature → Suppress by Expression).


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A suppressed feature still exists in the database but appears to be removedfrom the model. You can retrieve any suppressed features using Unsuppress

Feature .

Use Suppress Feature to:

• Reduce the size of large models, thereby reducing the creation, objectselection, edit, and display time.

• Remove non-critical features such as small holes, blends, and chamfersfrom your model for analysis work. Note that suppressed features are notmeshed in Advanced Simulation.

• Create features in locations where there is conflicting geometry. Forexample, if you need to position a feature using an edge that has alreadybeen blended, you do not need to delete the blend. You can suppress theblend, create and position the new feature, and then unsuppress the blend.

UGS recommends that you do not create new features where asuppressed feature exists.


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Suppressing associated features

When you suppress a feature that has associated features, the associatedfeatures are also suppressed (see figure below).


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Suppressing features

1. Click Suppress Feature .

2. Select the feature(s) to be suppressed, either from the list in the dialog orin the graphics window. You can also click the Selection Criteria buttonfor automatic selection of suppressable features using a criteria filter.

3. If you do not want the Suppress Feature selection dialog to include anydependents in the Selected Features list, turn the List Dependents toggleswitch to Off. (Doing so can noticeably improve performance time if theselected features have a lot of dependents.)

4. Click OK or Apply to suppress the selected features.

Master Model Dimension

The Master Model Dimension tool launches the Edit Dimension dialogbox. Edit Dimension lets you modify the idealized part’s dimensions, takingadvantage of interpart expressions. Use the Edit Dimension dialog box tomodify any feature or sketch dimension without affecting the master partdimensions.


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Editing master model dimensions

1. Click Master Model Dimension to open the Edit Dimension dialogand select a feature. Associated expressions or descriptions display inthe list window.


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2. Use the Expression or the Description option to display the selectedfeature’s dimensions as either an interpart expression or as standarddescriptions for the feature type.

3. Select a dimension from the list to modify.

4. (Optional) Click Used By to view a list of where the selected expressionis used.

5. Enter a new value for the selected dimension.

6. Click Apply to apply the new dimension value, and repeat steps 3 – 5 forthe remaining features and dimensions. Click OK to apply the new valueand close the Edit Dimensions dialog.

Modifying geometrySeveral tools let you modify the geometry of the idealized part:

• Idealize Geometry

• Defeature Geometry

• Partition Model

• Midsurface

• Sew

• Subdivide Face

Idealize Geometry

Use Idealize Geometry to simplify a model’s geometry by removingfeatures from a body or a region of a body that satisfy certain criteria, orthat you explicitly select for removal. For example, you may want to removesmall geometric features that would otherwise cause too many additionalelements to be created.

To use Idealize Geometry , you must have the idealized partdisplayed in the graphics window.


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Idealizing Geometry on a Body

1. With the idealized part displayed in the graphics region, click Idealize

Geometry .

2. In the Idealize dialog, click Body .

3. In the graphics window, select the body.

You can now select options that identify features to be removed.

4. (Optional) To remove specific faces, click Removed Faces (Optional)

, and select faces to remove.

5. (Optional) To remove blends, select Chain Selected Blends. In thegraphics window, select a blend.

The software selects adjacent blends with the same radius.


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6. (Optional) To automatically remove features, select Holes or Blends inAutomatic Feature Removal. Enter a value for the criteria.

The software selects all features in the body that meet the criteria.

7. Click OK.

The selected features are removed.

Idealizing Geometry in a Region

1. With the idealized part displayed, click Idealize Geometry .

2. In the Idealize dialog, click Region .

3. In the graphics window, select a seed face (the first face in the region).

You can now select features to be removed.

4. (Optional) To define an outer boundary for the region, click Boundary

Faces (Optional) and select the face or a set of faces.

5. (Optional) To automatically select adjacent faces to include in the region,select Tangential Edge Angle, and enter an angle value.

The software selects faces adjacent to the seed face if the angle betweenthe normal to the seed face and the normal of an adjacent face is lessthan or equal to the angle value.

6. (Optional) To remove specific faces, click Removed Faces (Optional)

, and select faces to remove.

7. (Optional) To remove blends, turn on Chain Selected Blends. Selecta blend.

The software selects the adjacent blends with the same radius.

8. Click Preview Region to see the outline of the region to be simplified.

9. (Optional) To automatically remove features, select Holes or Blends inAutomatic Feature Removal. Enter a value for the criteria.

The software selects all features that meet the criteria.

10. Click OK.


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All selected features are removed.

Defeature Geometry

Defeature Geometry provides a streamlined method for featureremoval. When you defeature a model, you simplify geometry by usingselections in the graphics window to remove a face or set of faces. This is aquick way to remove larger model features such as bosses containing multiplefaces.

Defeaturing geometry

To remove a feature or set of features, follow these basic steps:

1. Click Defeature Geometry .

If the Selection Intent toolbar is not visible in the graphicswindow, position the cursor in the toolbar area outside thegraphics window and click MB3 to enable Selection Intent.

2. Select Add Region Boundary from the Face drop-down list in SelectionIntent.

In the graphics window, the cursor becomes available for face selection.

3. Select a seed face for the feature you want to remove.

4. Select a boundary face as the outer limit for feature removal.

5. Click MB2 to update the surface region. The second figure in the followinggraphic shows an example of a resulting surface region.

6. Click on the Defeature dialog bar, or click MB2 again to executefeature removal.

To edit the removed feature, click on the Part Navigator tab in the ResourceBar and locate the Defeature node. Use MB3 menu options to edit featureparameters.


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Partition Model

Partition Model provides a way to associatively partition solid bodies ina simulation model. This feature is most often used to partition bodies intosweepable solids to create a swept mesh model.

This feature creates a named group of features, which can be seen in themodel navigation tool. The objects selected for the trimming operationdetermine the contents of the named feature. Furthermore, the groupedfeature allows users much greater flexibility in editing.

In addition to the geometric operation of splitting the body, a glued meshmating condition is automatically created at the partitioning geometrylocation, so that applied meshes are continuous from one body to the other.

The model partitioning function is also useful for controlling a tetrahedralmesh using, for example, different global element sizes on sub-bodies.Because of this, the geometry model needs to be broken down into smallerunits that can be more easily and automatically meshed. Model partitioningbreaks down a volume into sub-volumes associatively.


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Partition Model provides a way to associatively partition solid bodies ina simulation model. This feature is most often used to partition bodies intosweepable solids to create a swept mesh model.

This feature creates a named group of features, which can be seen in themodel navigation tool. The objects selected for the trimming operationdetermine the contents of the named feature. Furthermore, the groupedfeature allows users much greater flexibility in editing.

In addition to the geometric operation of splitting the body, a glued meshmating condition is automatically created at the partitioning geometrylocation, so that applied meshes are continuous from one body to the other.

The model partitioning function is also useful for controlling a tetrahedralmesh using, for example, different global element sizes on sub-bodies.Because of this, the geometry model needs to be broken down into smallerunits that can be more easily and automatically meshed. Model partitioningbreaks down a volume into sub-volumes associatively.


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Partitioning the model

1. Click Partition Model .

The Partition Model dialog is displayed.

2. Click Body to Partition and select the solid body to be partitioned.

3. Click Partitioning Geometry , and select the desired partitiongeometric tool (datum plane, sheet body, curve/edge, etc.) to subdividethe body or bodies. Select an option from the Filter drop-down menu toaid in selection.

When Blank Partition Geometry is selected (the default), partitioninggeometry is blanked following the partitioning operation.


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4. If necessary, click Direction and choose a Vector Method to define adirection vector to extrude or revolve a selected section.

5. Click Apply to create the partition.

If you are partitioning the model to prepare for swept meshing,

click Show Unsweepable Solids to highlight bodies thatrequire further partitioning.

Repeat steps 2 – 4 to fully partition the model.

Midsurface

Use Midsurface to simplify thin-walled geometry and create acontinuous surface feature that resides between two opposing faces within asingle solid body. The points and normals of the parent faces (surface pairs)are averaged at corresponding parameters. The new surface, or midsurface,contains information about the geometric thickness of the surface pairs.

Midsurface creation methods

Use one of the following methods to create a midsurface feature:

• Face Pair: This method creates a midsurface halfway between theopposing face pairs. The face pair method is useful for creatingmidsurfaces for thin-wall geometries with ribs.

• Offset: This method offsets the midsurface from one side of the solid bodyby a depth ranging from 0 to 100% (the thickness of the solid).


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• User Defined: This method defines a sheet body you’ve previously createdas the midsurface of a part. That is, you can manually model a sheet bodyto approximate the midsurface of a thin-walled part, and then define thatbody as a midsurface feature of your part.

Face Pair midsurface method

The Face Pair method uses opposing face pairs to create a midsurface locatedhalfway between the two faces. This type of midsurface can only be createdfrom a single solid body that contains opposing faces.

Automatically Creating a Face Pair

1. Click Midsurface .

2. In the dialog, choose Method →Face Pair.


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3. Select a face for side one and click MB2.

Note that the solid body is promoted at this point.

4. Choose AutoCreate.

The software creates as many face pair features as possible.

5. Manually define or edit any remaining face pair features, if necessary.

Manually Creating a Face Pair Midsurface


2. In the dialog, choose Method →Face Pair.

3. Select a face for side one and click MB2. Note that the solid body ispromoted at this point.

4. Select an opposing face for side 2.

Alternatively, select the Automatic Progression check box. When thisoption is turned on, the software selects the most likely side 2 face foreach side 1 face you select.

5. Continue to select pairs in this manner until all face pair featuresare defined. Watch the cue line to ensure that you select the correctcorresponding face at the right time.

Offset midsurface method

With the Offsetmethod, a midsurface generated from a seed face is positionedmidway between the seed face and its opposing face. The distance betweenthe seed face and the opposing face is the thickness of the solid. The offsetmethod requires a solid of uniform thickness.

You can define any number of faces to be offset, but you first must selecta seed face.

Once you begin, you cannot switch from the offset method to the facepair method.

The midsurface thickness created using the offset method is added as an NXattribute attached to the midsurface sheet body. The name of the attributeis "Midsurface_thickness." You can verify the thickness using Format →Attribute → Object.


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Defining a midsurface with the offset method


2. In the Midsurface dialog, choose Method → Offset.

3. Select the solid body and click MB2 to advance to the next selection step.

4. Click Target Body and select the body.

5. Click Seed Face and select a seed face for the midsurface.

6. Set the Cliff Angle. The default is 75 degrees.


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7. Preview the generated face to be offset by clicking the Region or FullBoundary preview buttons.

8. If necessary, adjust the Cliff Angle to ensure that the correct face isselected. When the previewed face is correct, click OK.

If Blank Original is selected, the original solid body is blanked;only the sheet body is displayed.

User Defined midsurface method

With the User Defined method, you use an existing sheet body to create amidsurface in a solid body. This method can be useful in situations wherealternate methods of midsurface creation did not produce satisfactory results.If the sheet body you create is within the confines of the solid body, thesoftware will automatically generate the midsurface, even if the body is notuniformly thick.

All faces connected to the seed face that satisfy smoothness and boundaryface criteria are offset as a midsurface half the thickness into the solid.

The software terminates midsurface creation when it encounters a boundaryface. A boundary face is defined as a face oriented in the thickness direction,at an angle greater than or equal to the cliff angle value. The seed face willpropagate in all directions until it reaches the edge on a boundary face.

Thickness Outside Body guidelines

The user-defined midsurface can contain surfaces that extend. For example,if you have a sheet body containing small holes and you want the holes to beignored in the midsurface creation, enter a value for the Thickness OutsideBody option. This value tells the software how thick to define the "virtual"solid body when it encounters what are actually the small holes.


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Note that an outside body thickness value of greater than zero isrecommended. Although it is unlikely that a zero value will cause midsurfacecreation problems, the solve could fail, especially if the midsurface extendsbeyond the solid body, because the shell thickness will be interpreted as zero.In the following graphic, the yellow portion of the midsurface ignores the holein the solid, while the dark green area extends beyond its boundaries. Thesoftware approximates a thickness for these regions, which you can modify.

Defining a midsurface with the user defined method


2. In the Midsurface dialog, choose Method → User Defined.

3. Select the solid body and click MB2 to advance to the next selection step.

4. Select the sheet body.

If some part of the selected sheet body is not fully contained within thesolid body, enter a value in the Thickness Outside Body field for thesoftware to use when formatting the element thickness for a solve.

Sew

Use Sew to join together selected sheet or solid bodies.

You can use Sew to join together:


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• Two or more sheet bodies to create a single sheet. If the collection ofsheets to be sewn encloses a volume, the software creates a solid body.

• Two solid bodies if they share one or more common faces.

Creating a solid vs. sheet body

If you want to create a solid body by sewing a set of sheets together, theselected sheets must not have any gaps larger than the specified SewTolerance. Otherwise, the resulting body is a sheet, not a solid.


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Sewing two solid bodies together

You can sew two solid bodies together only if they share one or more common(coincident) faces. When you use Sew, the software deletes the commonface(s) and sews the solid bodies into a single solid body.

Sew All Instances

• If a selected body is part of an instance array and you select the Sew AllInstances option, the software sews the entire instance array.

• If you deselect the Sew All Instances option, the software only sews theselected instance.

Sew Tolerance

The software sews edges together, whether there is a gap between them orwhether they overlap, if the distance between them is less than the specifiedSew Tolerance. If the distance between them is greater than this tolerance,the software cannot sew them together.


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Subdivide Face

Subdivide Face lets you automatically subdivide multiple faces whilemaintaining associativity, using a variety of subdividing geometries. Thisfunction allows you to control a 2D mesh using global element size for aportion of the model. It is also useful if you want to subdivide a face intofour-sided regions to facilitate mapped meshing with quadrilateral elements.The edges and faces of a subdivided face are associative and are combinedinto a group feature.

For simple edges and curves, the behavior will be as follows:


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• Where a datum plane, sheet body, or face is used as a tool, the tool isintersected with the selected face to be subdivided, and the resultingcurves are used for subdividing. These intersect curve features will showup in the grouped feature.

• Where the Two Points option is chosen in the filter, you can specify the endpoints of a line. The last two points selected are used to create the line.The end points are associative to the underlying geometry. The resultingline will be used to subdivide the face, projecting the line as required.

Geometry objects that are associated with the subdivided face feature cannotbe deleted.

If you transform the objects associated with a subdivided face, the face itselfis also updated. If you transform the solid body on which any subdividedfaces reside, their associated curves do not move. However, the subdividedfaces are updated accordingly.

ActivitiesSee the “Geometry idealization” activities in the Applications of AdvancedSimulation Workbook.

In these activities, you will idealize a part.


• Learned about tools for modifying features in the idealized part, includingEdit Feature Parameters, Suppress Feature, Unsuppress Feature, andMaster Model Dimension.

• Learned about tools for modifying geometry in the idealized part,including Idealize Geometry, Defeature Geometry, Partition Model,Midsurface (three methods), Sew, and Subdivide Face.


3

Lesson

3 3D meshing

Objectives

• Learn how to mesh solid bodies using 3D tetrahedral elements.

• Learn how to mesh solid bodies using 3D swept mesh elements.

• Learn how to mesh solid bodies by creating a solid mesh generated fromshell elements.

3D Tetrahedral Mesh

The 3D Tetrahedral Mesh function supports the creation of 4-noded and10-noded tetrahedral elements. You can create a 3D mesh on solid bodies forall supported solvers.


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3D meshing

3D Mesh Options

The 3D Mesh Options dialog box defines how the meshing algorithmprocesses small features and fillets.


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3D meshing

Failed elements

After meshing, the element quality is checked against the Maximum Jacobianthreshold:

• If the quality measure violates this threshold, the element is highlightedin red.

• If the quality measure is within 10% of the this threshold, the element ishighlighted in yellow.

If you have a high number of poor quality elements, you can:

• Further idealize the part’s geometry to remove problematic areas.

• Modify surface or solid mesh size variation to improve node distribution.

• Use the abstraction tools to improve the quality of the polygonal geometry.


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3D meshing

• Increase the threshold value for Maximum Jacobian if element quality isnot critical in that area of the model.

Creating a 3D mesh

1. Click 3D Tetrahedral Mesh .

2. In the graphics window, select the solid body to mesh.

3. In the dialog, choose an element type from the drop-down list.

4. Enter an element size. Or, click to have the softwarecalculate an appropriate element size.

5. (Optional) Click Preview to view the resulting nodes on edges for themesh. If you are not satisfied, you can modify the Overall Element Sizevalue.

6. (Optional) To specify small feature tolerances and fillet processingparameters, click the Mesh Options button.

7. Click OK or Apply to generate the mesh.

3D Swept Mesh

3D Swept Mesh generates a mesh of either 8– (linear) or 20–noded(parabolic) hexahedral elements on any two-and-one-half dimensional solidby sweeping the mesh from a source face through the entire solid.

When you create a swept mesh, the software first meshes the specified sourceface of the volume with linear quadrilateral elements. The software thenpropagates that mesh into the volume layer by layer with the first layerresulting in the first set of hexahedral elements, and so on.

You can also use an existing (linear or parabolic) triangular or (linear orparabolic) quadrilateral surface mesh to generate (linear or parabolic) wedgeor (linear or parabolic) hexahedral swept mesh elements.

The mesh generation proceeds from the selected source face to the target face,which the software determines by evaluating the volume. If the initial meshoriginating from the source face contains one or more triangular elements,the swept mesh will also contain corresponding wedge elements.


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3D meshing

System checks

Once you click OK or Apply on the dialog box, the software:

• Checks whether the solid is geometrically sweepable and generates anappropriate error if not.

• Checks whether the meshes on the solid’s faces or mated faces can be usedfor sweeping and generates an appropriate error if not.

• Checks whether the target face has already been meshed and generatesan error if yes.

Mesh mating conditions

For each face in the solid, the software checks to see whether mesh matingconditions on an adjacent solid are satisfied. If they are and if a mesh isfound on the face adjacent to the source face for the swept mesh, this will beused for mesh mating conditions as long as it matches the defined sweptmesh, as follows.

• For a linear or parabolic wedge swept mesh, the adjacent body must havean existing linear triangular/wedge or parabolic triangular/wedge mesh.

• For a linear or parabolic hexahedral swept mesh, the adjacent bodymust have an existing linear quadrilateral/hexahedral or parabolicquadrilateral/hexahedral mesh.


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3D meshing

If no mesh is found on the adjacent body that satisfies other mesh matingconditions, a surface mesh is created. Free mesh or mapped mesh will bedetermined based on whether the face is a wall face. (All wall faces must bemap-meshed.) For each edge, the same logic is applied.

Generating a swept mesh from a sweepable solid

1. Click 3D Swept Mesh .

2. In the graphics window, select the sweepable solid body to mesh.

3. In the dialog, select an element type from the drop-down menu.

4. Enter an element size, or click to have the softwarecalculate an appropriate element size.

5. (Optional) Click Preview to view the resulting nodes on edges for themesh. If you are not satisfied, you can modify the Overall Element Sizevalue.


Generating a swept mesh from a meshed surface

1. Click 3D Swept Mesh .

2. In the graphics window, select an existing meshed surface on a sweepablesolid.

3. Select an element type from the drop-down menu.

Note that the element size is determined by the size of the seed mesh.


Solid from Shell

Use Solid From Shell to generate a solid tetrahedral mesh from atriangular shell mesh.


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3D meshing

Solid meshes created from shell elements have no associativity tothe bounding shell mesh or the underlying geometry. Solid meshescreated by the Solid From Shell command are not editable. Inaddition, if any shell mesh bounding a 3D mesh created by Solid fromShell requires an update, the 3D mesh is automatically deleted. Youmust re-create the solid mesh following the shell mesh update.

To generate a solid mesh, the shell mesh must meet the followingrequirements:

• All 2D triangular elements must be of the same order (linear or parabolic).

Use caution when generating a solid shell from parabolicelements. Unless the parabolic triangular shell elements havestraight edges, the resulting parabolic tetrahedral mesh willlikely contain elements that fail Jacobian tests.

• The shell elements must completely enclose a volume. Otherwise, thesoftware can’t generate the solid elements.

• There are no coincident triangular elements in the shell mesh.


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3D meshing

Use Check Nodes to identify duplicate nodes. This is a good checkfor coincident elements.

Use Element Outlines to check for element free edges. A free-edgecheck will reveal any gaps in volume boundary.

You can use the 2D Edit Mesh commands to repair any gaps in yourshell mesh.

When selected, Mesh Interior Volumes generates multiple solid meshesfrom selected shell meshes that enclose interior volumes. This is useful formodeling thermal or flow problems, in which the interior volumes wouldtypically represent a heat sink or source, or a flow obstacle.

Creating a solid mesh from shell elements

To create a solid tetrahedral mesh from triangular shell elements

1. Choose Solid from Shell .

2. Review and modify the dialog options as needed.

3. Select one or more 2D, triangular shell meshes that completely encloseone or more volumes.

4. Click OK.

ActivitySee the “3D meshing” activity in the Applications of Advanced SimulationWorkbook.

In this activity, you will generate and refine a 3D mesh.

SummaryIn this lesson you learned about the three 3D meshing commands:

• 3D Tetrahedral Mesh

• 3D Swept Mesh

• Solid from Shell


4

Lesson

4 2D meshing

Objectives

• Learn how to generate a 2D mesh.

• Learn about tools for editing a 2D mesh.

2D meshing overview

2D Mesh generates 3- and 6-noded triangular elements as well as 4-and 8-noded quadrilateral elements. 2D elements are also commonly knownas shell or plate elements. For Tri6 and Quad8 elements, midnode snappingand a specified Jacobian ratio are supported.

The default element size does not specify the final size of the elements butdefines the parameter used to control the edge length of the element. Actualelement edge lengths are approximately equal to the specified overall elementsize.

The software automatically adjusts for problematic element sizes onrectangular or nearly rectangular surfaces (non-planar included). Theresulting element size will be "safe" and yield a higher quality mesh.


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2D meshing

Mesh Options

The 2D Mesh Options dialog box specifies how the meshing algorithmprocesses small features and fillets.


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2D meshing

Creating a 2D mesh

1. Click 2D Mesh .

2. Select the midsurface or faces you want to mesh.

In the dialog, use the Filter drop-down menu to help you select from faces,bodies, or an existing mesh.

3. From the Type drop-down menu, choose the element type.

4. Enter a size for the Overall Element Size, or click toautomatically calculate a suggested element size.

5. If necessary, click the More Options arrow to display additional optionsfor this mesh.


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2D meshing

6. To specify small feature tolerances and fillet processing parameters, clickthe Mesh Options button.

7. Click Preview to view the resulting nodes on edges for the mesh. If youare not satisfied with the node number and location, you can modify theOverall Element Size value.


Editing a 2D meshThe 2D Edit Mesh functionality provides you with a basic set of shell elementand/or node editing capabilities for the purpose of fixing elements of poor andunsatisfactory quality produced by the automatic mesh.

Edit Mesh features the following options:

Icon Label Description

Split Quad Allows you to divide quadrilateralelements (quads) into triangularelements (tris).

Splitting occurs along thesmaller of the two diagonals.

Combine Tris Allows you to combine triangularelements (tris) into quadrilateralelements (quads).

Move Node Allows you to relocate a nodalposition.

Delete Element Allows you to delete elements of yourchoice.

Create Element Allows you to create a quad or trielement that will be added to theexisting 2D mesh. If the mesh hashigher order elements, the newlycreated element will also havemidnodes.

Unlock Mesh Allows you to unlock the edited meshfor an update operation.

Assign NodalDisplacementCoordinate System

Allows you to manually define a nodaldisplacement coordinate system forselected nodes or geometry.


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2D meshing

Icon Label Description

Assign NodalDisplacementCoordinate System

Allows you to determine thecoordinate system assigned to nodes,or the nodes to which a coordinatesystem is assigned.

ActivitySee the “2D meshing” activity in the Applications of Advanced SimulationWorkbook.

In this activity, you will generate and refine a 2D mesh.


• Learned how to generate a 2D mesh.

• Learned about tools for editing a 2D mesh.


5

Lesson

5 1D and 0D meshing

Objectives

• Learn how to create a mesh of 1D elements.

• Learn how to create weld elements.

• Learn how to create a 1D element section.

• Learn how to create a 0D mesh.

1D Mesh

1D Mesh lets you create a mesh of one-dimensional elements. You cancreate or edit one-dimensional elements, along or between points, curves,or edges.

One-dimensional elements are two-noded elements which, depending ontype, may or may not require an orientation component. A one-dimensionalelement is one in which the properties of the element are defined along a lineor curve. Typical applications for the 1D element include beams, stiffeners,and truss structures.


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1D and 0D meshing

1D element meshing methods

The following section describes methods available for creating different typesof 1D mesh. These methods are based on the way you select geometry usingSelection Step icons in the 1D Mesh dialog.

Ordered Nodes method

Using this method (which requires selection of a point or points for Group 1 aswell as Group 2), two ordered sets of point locations are created. These pointlocations are associated to the parent data from which they were selected.


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1D and 0D meshing

Depending on the quantity of data selected for this method, several outputsare possible:

• If the number of points created in each set (Group 1 and Group 2)are equal, then a single 1D element is generated between each set ofcorresponding points, as shown in the graphic above.

• If the number of points created in each set are unequal, then 1D elementsare created from all of the points in Group 1 to all points in Group 2.This option provides a "one to many" type of connection, as shown in thefollowing figure.

Point-to-Point Chaining method

This method, which requires Group 1 selection only, generates a chain of 1Delements between the points that you select. The elements that are createdform a consecutive link between the successive point locations.


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1D and 0D meshing

Along a Curve (Edge) method

This method, which requires Group 1 selection only, generates a series of 1Delements along single or multiple curves or edges. You can specify a totalnumber of elements or an element size for the elements. Nodes created atcoincident point locations on adjacent curves/edges are shared.

Point-to-Curve (Edge) method

For this method, which requires selection of a Group 1 point and a Group 2curve, elements are created similarly to the Ordered Nodes method. In thePoint-to-Curve method, however, the curve you select for Group 2 infers thesecond curve set, as shown in the following figure.

Curve-to-Curve method

This method, which requires selection of a curve for both Group 1 andGroup 2, generates 1D elements between two curves or edges. The point


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1D and 0D meshing

locations associated to the parent curve/edge will be used to determine thecorresponding node locations.

If the two sets of point locations do not contain the same number of points,the software matches all possible points and build the rest of the elementsbetween a point on one curve and the remaining points on the other curve.

Creating a 1D mesh

1. Click (1D Mesh).

2. In the dialog, choose an element type.

3. Choose either Default Element Number or Size and enter a value:

• If you select Number, enter an element density. If you enter 9 forexample, and select an edge, the software will distribute nine elementsalong the selected edge.

• If you select Size, enter a size in model units.

4. (Optional) Select Create Mesh Points to create selectable mesh points onor relative to CAE geometry. For example, you could create a mesh pointat an arc centerpoint to create a spider mesh at a large hole. Or you couldcreate mesh points to force a node location on an edge or improve nodedistribution on a curve.

5. Use the Selection Steps (Group 1, Group 2) to define sections.

6. Choose Apply or OK. 1D elements are built along or between the objectsyou selected for meshing.

Create Weld ElementsCreate Weld Elements allows you to model welds by projecting a set of pointsto top faces and using the resulting points to project to bottom faces, usingthe Normal to Face option in both projections.


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1D and 0D meshing

Weld mesh effect on 1D mesh

When you exit the Create Weld Elements dialog box, the ordered set of pointsfrom the top faces will be added to Group 1 selection step of the 1D Meshdialog, and the ordered set of points from the bottom faces will be added toGroup 2. You can then create any type of 1D element available. In addition,the software honors the weld elements during 2D face meshing.

Support for interior hard curves in meshing

This feature gives you the ability to associate curves to faces to representweld locations in the Create Weld Elements dialog. These weld points aretreated as interior hard curves. The point locations on the hard curves arehonored by the software during 2D meshing.

Creating a weld element mesh

1. Click 1D Mesh .

2. Choose an element type.

3. Choose either Default Element Number or Size and enter a value:

• If you select Number, enter an element density. If you enter 9 forexample, and select an edge, the software will distribute nine elementsalong the selected edge.

• If you select Size, enter a size in model units.

4. Click Create Weld Elements.

The Create Weld Elements dialog is displayed.

5. Using the Points/Curves selection step, select points, curves, or edges. Usethe Filter menu to pinpoint selection. Click OK to confirm the selection.


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1D and 0D meshing

6. Use the Top Faces selection step to project the points, curves, or edges.Click OK to confirm the selection.

7. Use the Bottom Faces selection step to choose the bottom face and clickOK to confirm the selection. Temporary points are displayed at theprojected locations.

8. Click OK or Apply to return to the 1D Mesh dialog. The Top Facesselection is added to Group 1 and the Bottom Faces selection is addedto Group 2.

9. Click OK or Apply to project the points and create weld elements. Theelements are created between each pair of points (the point on the top faceand the corresponding point on the bottom face).

1D Element Section

1D Element Section helps you create sections, which you canthen assign and analyze for comparison to a bar or beam element mesh,curves/edges, or points, and display the results.

This feature also lets you create associative section properties from theanalysis, which can then be used for beam model analysis. Since sectionproperties are associative, they are updated whenever changes are made tothe data from which they are derived.


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1D and 0D meshing


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1D and 0D meshing

Types of sections include:

• thin wall rectangle

• hollow circle

• thin wall channel

• thin wall hat

• thin I-beam

• solid cylinder

• solid rectangle

• user–defined properties

• user–defined thin wall

• user–defined solid

Order of precedence when using sections

The following is the order of precedence for each section type when there areconflicts in the section assignment:

• Section on points (smart points for the Along a Curve option)

• Section on curves/edges

• Section on bar/beam mesh

A section assigned to a hard point on a curve will be used in place of thesection on the curve. A section on a curve/edge will precede a section found ona beam mesh. A warning message will be issued by both the Section dialogand the Attribute Editor when you attempt to add a section to a beam mesh ifthe underlying curve/edge already has a section.

You can align the sections to bar or beam elements by specifying thedesired orientation vectors.

0D Mesh

0D Mesh provides you with the tools to create concentrated masselements at specific nodes. Zero-dimensional elements are also referred toas scalar elements. To create concentrated mass elements on nodes, you canselect points, lines, curves, faces, edges, solids, or meshes.


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1D and 0D meshing

Creating a 0D mesh

To create a concentrated mass using a mesh of 0D elements:

1. Click 0D Mesh and select the entity for the mass in the graphicswindow, or choose Create Mesh Point to concentrate the mass on a point.

2. If necessary, choose an element type.

3. In the dialog, choose either Default Element Number or Size and entera value:

• If you select Number, enter an element density. If you enter 9, forexample, and select an edge, the software will distribute nine elementsalong the selected edge.

• If you select Size, enter a size in model units. This size is the averagedistance between 0D elements.

4. Click either Apply or OK. Notice that 0D elements are built along thegrids of the object you selected for meshing.


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1D and 0D meshing

5. To specify mass properties for the 0D mesh, with the FEM file as theactive part, select Simulation Navigator→ FEM node → 0D Meshes→ the0D mesh → RMB → Edit Attributes. Specify total mass, CG, and inertialproperties attributes on the Element tab. Specify mass distribution andmesh density attributes on the Mesh tab.

ActivitySee the “1D and 0D meshing” activity in the Applications of AdvancedSimulation Workbook.

In this activity, you will generate beam (1D) elements and define a beamcross section.


• Learned how to create a mesh with 1D elements.

• Learned how to create a mesh with 0D elements.

• Learned how to create a 1D element section.

• Learned how to create a 0D mesh.


6

Lesson

6 Mesh points

Objectives

• Learn how to use mesh points.

Mesh points

When you mesh your model, the software automatically creates a node at allmesh point locations.

You create mesh points directly on the polygon geometry in your FEM file.You can position them using the standard NX Snap Point toolbar icons.

Mesh points are useful for ensuring that the software creates nodes at specificlocations. You can also define point-based loads or boundary conditions onmesh points.

The following example illustrates one use of mesh points. Suppose you wantto transfer a load from the centerpoint of the hole to the nodes on the edge.You could use the Mesh Point to create a mesh point at the centerpoint of thehole and then use the Arc Center tool on the Snap Point toolbar to constrainthe new point.


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Mesh points

You could then create a spiderweb mesh of rigid bar elements to connect themesh point to the nodes on the edge of the hole and define a fixed constraintat the mesh point.

Where do I find it?

(With the FEM file active in the Simulation Navigator) Insert→ ModelPreparation→ Mesh Point

ActivitySee the “Mesh points” activity in the Applications of Advanced SimulationWorkbook.

In this activity, you will create mesh points.


• Learned how to use mesh points.


7

Lesson

7 Mesh and object display

Objectives

• Learn how to set mesh display preferences.

• Learn how to control object display.

Mesh Display preferencesMesh Display lets you define preferences for basic finite element modelvisualization capabilities such as color, element shrink, and 2D elementnormals.


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Mesh and object display

Where do I find it?

Preferences→ Mesh Display

Object displayTwo commands help you manage and control your display:

• Show Only

• Show Adjacent

Both commands are designed to make it easier to limit and control the objectsbeing displayed, which is particularly useful when you’re working with avery complex finite element model.


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• Show Only lets you easily display only the entities you select. Forexample:

– When you’re working with a mesh in a FEM file, you can use ShowOnly to display only selected polygon faces.

– When you’re working with boundary conditions in a Simulation file,you can use Show Only to display selected polygon geometry andassociated simulation objects, such as points, splines, conics, meshes,loads, boundary conditions, and mesh points.

• Show Adjacent works with the Show Only command. Show Adjacentshows all faces adjacent to the selected face. For example, once you’ve usedShow Only to limit your display, to only a selected set of polygon faces, youcan then use Show Adjacent to selectively add additional adjacent facesto that display. This process can be useful, for example, for examining anarea where you might want to create a mesh mating condition.

In the following example, we used Show Only (A) to display only the polygonface on the selected fillet. (B) shows the resulting display.

We then used Show Adjacent (C) to add all adjacent faces (all faces thatshare an edge with the displayed face) to the current display. (D) shows theresulting display.


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Show Only and Show Adjacent work similarly to the Blank commandsin the Edit menu, but they require far fewer clicks to display only selectedgeometry of interest.

ActivitySee the “Mesh and object display” activity in the Applications of AdvancedSimulation Workbook.

In this activity, you will learn how to modify the display of a mesh.


• Learned how to set mesh display preferences

• Learned how to control display of objects such as geometry, meshes, loads,and constraints


8

Lesson

8 Geometry abstraction

Objectives

• Learn about geometry abstraction techniques.

• Understand the difference between geometry idealization and geometryabstraction.

• Learn about polygon geometry.

• Learn how to detect fillets before meshing.

• Learn about various geometry abstraction tools.

Geometry abstraction overviewThe Model Cleanup toolbar contains a set of commands that let you performgeometry abstraction operations on your model. Geometry abstraction letsyou eliminate issues with the CAD geometry that can cause undesirableresults when you mesh your model.

For example, you can use geometry abstraction tools to:

• Improve the quality of your mesh by manually eliminating problematicgeometry.

• Create boundaries on which to define loads and constraints.

The Model Cleanup toolbar contains a set of commands that let you performgeometry abstraction operations on your model. Geometry abstraction letsyou eliminate issues with the CAD geometry that can cause undesirableresults when you mesh your model.

For example, you can use geometry abstraction tools to:

• Improve the quality of your mesh by manually eliminating problematicgeometry.

• Create boundaries on which to define loads and constraints.


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Geometry abstraction

Comparing geometry idealization and geometry abstractionGeometry idealization and geometry abstraction operations are similar intheir intent in that both allow you to specifically tailor the geometry to theneeds of your analysis. However, the two are fundamentally distinct processesthat operate on different aspects of your model.

• You perform geometry idealization operations on the idealized part.Geometry idealization lets you simplify and streamline your model byremoving or suppressing unnecessary features. For example, you can:

– Add features to the idealized part to facilitate the analysis.

– Partition a large volume to facilitate the meshing of that volume.

– Create a midsurface on a thin-walled part to facilitate 2D meshing

• You perform geometry abstraction operations on the polygon geometrywithin the FEM file. Geometry abstraction lets you eliminate issues withthe CAD geometry that can cause undesirable results when you meshyour model. For example, you can use geometry abstraction commands to:

– Remove very small surfaces or small edges from your model that candegrade element quality in that region.

– Add geometry to your model for use in the analysis. For example, youcan add edges to the polygon geometry to either control the mesh inthat region or to define additional edge-based loads or constraints.

Understanding polygon geometryWhen you create a FEM file, the software automatically creates “polygon”geometry from the idealized part. Polygon geometry is a facetedrepresentation of the geometry in the master part. Polygon geometry allowsyou to:

• Tailor the design geometry to fit the needs of your CAE analysis.

• Repair issues with the design geometry, such as narrow regions or tinyedges, that can prevent the software from meshing or solving your model.

Changes you make to the polygon geometry do not affect the master part.This gives you the flexibility and control to idealize the geometry to suitthe needs of your analysis, without impacting the CAD design process andwithout requiring that you own the CAD part.

The polygon geometry is initially a one-for-one representation of your originalmaster part. That is, for every body, face, and edge in your model, the softwarecreates a corresponding polygon body, polygon face, and polygon edge.


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In some cases with particularly complex geometry, the software maybe unable to generate a complete, faceted representation of the masterpart. In those cases, the polygon geometry may contain missing faces.When this occurs, you can use the Face Repair command on theModel Cleanup toolbar to construct a new face.

Understanding the geometry abstraction processThere are two different ways you can abstract the polygon geometry in yourFEM file to optimize it for meshing:

• You can use the software’s automatic abstraction capabilities (availablethrough the Mesh Options form) during either 2D or 3D meshing.

• You can use the Auto Heal Geometry command on the Model Cleanuptoolbar to manually abstract your model.

Whether you choose to perform the abstraction during meshing or by usingAuto Heal Geometry, the abstraction process is the same. In both cases, thesoftware searches your model for geometric features that are so small thatthey can prevent the software from being able to mesh or solve your model.During the abstraction process, the software eliminates:

• Short edges.

• Sliver faces.

• Highly pinched regions of the geometry.

Small feature tolerance

The key difference between the different ways to perform the abstractionis in how you define the small feature tolerance. The software uses thesmall feature tolerance to determine which features to eliminate during theabstraction.

• On the Mesh Options dialog, you define the small feature tolerance as apercentage of your overall element size.

• On the Auto Heal Geometry dialog, you define the small feature toleranceas an absolute measurement.

In general, the abstraction process is designed to abstract features that aresmaller than 10% of your overall element size. Removing features below thatsize helps ensure that your model will mesh with elements that have anaspect ratio greater than 10:1, which is required by many solvers. However,you should always use caution not to set the small feature tolerance too high.


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In general, the small feature tolerance should not be larger than 20% of theelement size you intend to use to mesh the geometry.

Abstraction process limitations

The abstraction process is limited to abstracting away small features. Theabstraction process does not:

• Suppress holes.

• Transform radius corners of fillets into 90° angles.

• Turn sheet bodies into solid bodies.

Removing short edges

The software abstracts any edges that are shorter than the specified smallfeature tolerance. This prevents the software from creating an element witha very short edge on that portion of the geometry.

Removing sliver faces

The software abstracts any sliver faces whose width (W) is smaller than thespecified small feature tolerance.

The following graphic shows an example of a sliver face on polygon geometry.

When the software meshes the geometry, the software abstracts away thesliver face. Notice how the software doesn’t include this face in the mesh.


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Eliminating pinched regions

The software also abstracts away any highly pinched regions of the geometry.A pinched region is a very narrow region of a surface whose width is smallerthan the specified small feature tolerance.

In the case of a pinched region, the software evaluates the extent of thepinched region, isolates the pinched region, and then tries to merge it withthe adjacent geometry. The following graphic shows an example of a pinchedregion.


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When the software meshes the geometry, the pinched region is absorbedinto the adjacent geometry.

Fillet identification processThe software’s meshing and geometry abstraction operations contain acapability that allows the software to intelligently detect fillets within yourmodel. By identifying fillets prior to meshing, the software can create a betterdiscretized, mapped mesh in those regions.


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The software always tries to create a mapped mesh on fillet surfaces.However, this is not possible in all cases. If the software cannotcreate a mapped mesh on a fillet, the software tries to create a sizeconsistent free mesh.

If you select Fillet Processing on either the Mesh Options or Auto HealGeometry dialogs, the software searches your model for fillets thatmeet criteria you specify (minimum and maximum radius dimensions).Importantly, this search is not based on the part’s history data. Rather,the software detects fillets by searching for surfaces whose boundary edgesmeet certain characteristics. There are two stages in the fillet identificationprocess. The software:

• Searches the faces in the model to identify fillets.

• Categorizes any detected fillets into inside and outside radius fillets.

Process of identifying fillets

In general, fillets have four logical sides and are defined by a chain of edgesthat form a closed loop. The edges of fillets must also have a radius that fallsbetween the minimum and maximum fillet radii values you specify on eitherthe Mesh Options or the Auto Heal Geometry dialogs. If 30% of the edges ona face are fillet edges, the software considers the face to be a fillet.

Categorizing fillets into inside and outside radius fillets

Once the software identifies the faces that are fillets, it categorizes themas either inside or outside radius fillets. During this process, the softwareconstructs a vector between the centerpoint of the fillet’s edge and a point onthe edge. The software then compares the direction of this vector against thenormal of the surface at the point on edge.

• If the vector’s direction is different from the direction of the surface’snormal, then the software categorizes the fillet as an inside radius fillet.


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• If the vector’s direction is the same as the direction of the surface’snormal, then the software categorizes the fillet as an outside radius fillet.


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Auto Heal Geometry

Auto Heal Geometry lets you abstract certain types of features fromyour model that may be problematic for meshing.

When you create a 2D or 3D mesh on your model, the software automaticallyabstracts the polygon geometry to repair problematic topology, such as smallfeatures, that can degrade the quality of your mesh. With both 2D and 3Dmeshing, you use the options on the Mesh Options dialog to control theabstraction.

The Auto Heal Geometry command gives you an alternative way ofperforming the same abstraction operations that are embedded within the2D and 3D meshing commands. However, there are some subtle differencesbetween the two methods.

• How you specify the Small Feature Tolerance on the Auto Heal Geometrydialog is different from the way you specify it on the Mesh Options dialog.On the Auto Heal Geometry dialog, you define the small feature toleranceas an absolute measurement. On the Mesh Options, you define the smallfeature tolerance as a percentage of overall element size.

• Auto Heal Geometry lets you abstract the geometry without generatinga mesh on it. This can be advantageous if you intend to perform moremanual abstraction operations on your model prior to meshing.


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You can use Auto Heal Geometry to abstract your model at any point in thefinite element modeling process prior to meshing. Additionally, if you useAuto Heal Geometry to abstract your model, the software won’t abstract thepart again during meshing.

Limitations

Auto Heal Geometry does not:

• Suppress through holes or features.

• Turn sheet bodies into solid bodies.

• Transform manifold bodies into non-manifold bodies.

Automatically healing polygon geometry

1. Click Auto Heal Geometry .

2. On the dialog, specify a Small Feature tolerance value in model units.Features smaller than this value are abstracted during meshing.

3. If you want special processing to apply to filleted faces during meshing,choose whether you want special processing applied to inside-radiusfillets, outside-radius fillets, or all fillets. Otherwise, select No Fillets.

4. Enter the minimum and maximum radius that you want the software touse during the fillet identification process.

5. Click OK or Apply.

Split Edge

Split Edge splits a single edge into two separate edges at the locationyou specify.

Split Edge lets you split any polygon edge in your model into two separateedges. You may want to split an edge when:

• You want to define separate boundary conditions on different portionsof an edge.

• You’re preparing to split a face.


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Splitting an edge

1. Click Split Edge .

2. Select the polygon edge you want to split.

3. Use the selection mode icons on the Snap Point toolbar to select thelocation where you want to split the edge.

• Mid Point lets you select a location at 50% of the total length of thecurve.

• Quadrant Point lets you select a point at the quarter points of an arcor ellipse.

• Point on Curve lets you select any point along the curve.

4. Click MB2 or click OK on the Split Edge dialog bar to split the edge atthe selected location.

Split Face

Use Split Face to divide a selected polygon face into two separate faces.

For example, you can use Split Face to:

• Add an edge to divide a face so that you can apply an edge-based load.

• Divide an irregular face into several smaller faces on which you can definemapped meshes.

• Restore an edge that was previously removed by another abstractioncommand, such as Merge Face or Auto Heal Geometry, or by theautomatic abstraction that occurs during 2D or 3D meshing.

Splitting faces by points or suppressed edges

The Split Face command has two separate modes of use.

• Use the Split face by points mode to split a polygon face by selectingtwo points on one of the face’s edges.

• Use the Split face by suppressed edges mode to split a polygon faceby restoring an edge that was previously removed by another abstractioncommand or process.


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Splitting a face by selecting points

1. Click Split Face .

2. Click Split face by points on the Split Face dialog bar.

3. Select the first point on a polygon edge.

The selection mode icons on the Snap Point toolbar help you select thepoint.

• End Point lets you select a point at the end of a curve.

• Mid Point lets you select a point at 50% of the total length of the curve.



4. Select the second point on a polygon edge on the same face.

5. The software creates a new polygon edge between the two selected points.Click MB2 or click OK on the dialog bar to accept the new edge and splitthe face at that location.

Splitting a face by selecting suppressed edges

1. Click Split Face .

2. Click Split face by suppressed edges on the Split Face dialog bar.

The software displays any previously suppressed polygon edges in thegraphics window.

3. Select a suppressed edge.

4. Click MB2 or click OK to restore the edge and divide the face at thatlocation.


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Merge Edge

Use Merge Edge to merge two edges together at a selected end-of-edgelocation.

Merge Edge allows you to combine selected polygon edges at a selectedendpoint. This is useful, for example, when you want to create a larger ormore continuous boundary edge prior to meshing. You can also use MergeEdge to recombine edges that you had previously divided with the SplitEdge command.

You cannot use Merge Edge to combine edges when more than twopolygon edges intersect at a single endpoint.

Merging edges

1. Click Merge Edge .

2. Select the point at the end of the polygon edge that you want to mergewith the adjacent edge.

The End Point option on the Snap Point toolbar lets you easilyselect points at the end of polygon edges.

3. Click MB2 or click OK on the Merge Edge dialog bar to merge the twoedges together at the selected location.

Merge Face

Merge Face lets you merge two separate polygon faces into a singlepolygon face along a common polygon edge.

You can use Merge Face to combine two adjacent polygon faces into a singleface. This is useful, for example, if you want to create larger faces prior tomeshing. You can also use Merge Face to recombine faces you previouslydivided with Split Face.

Manual or Automatic Face Merging

With the Merge Face command, you can either manually combine faces atlocations you select, or you can have the software automatically combinefaces based on criteria you specify. The options on the Merge Face dialog letyou choose between the manual and automatic methods. You can also useoptions on the Merge Face dialog to specify the criteria the software shoulduse when automatically merging faces.


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Merging adjacent faces manually

1. Click Merge Face .

2. Click Merge Faces on the Merge Face dialog bar to display the MergeFaces dialog.

3. Use Auto Remove Vertices to control whether the software automaticallyremoves associated vertices (end-of-edge points) when you remove anedge between two faces

4. Click Merge and then select the polygon edge between the two adjacentfaces you want to merge together.

5. Click OK or Apply on the Merge Faces dialog.

Automatically merging adjacent faces

1. Click Merge Face .

2. Click Merge Faces on the Merge Face dialog bar to display the MergeFaces dialog.

3. Click Auto Merge.

4. Use Auto Remove Vertices to control whether the software automaticallyremoves associated vertices (end-of-edge points) when you remove anedge between two faces

5. Specify the maximum Edge Angle and Vertex Angle in degrees.

6. In the graphics window, select the faces that you want to have thesoftware automatically evaluate for merger using the edge and vertexangle criteria you specified.

7. Click OK or Apply on the Merge Faces dialog.

Match Edge

Use Match Edge to match the first edge you select to the second edgeyou select.


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Match Edge lets you repair small cracks or gaps in your model by matchingan edge (the source edge) to another edge (the target edge). You can useMatch Edge on any solid polygon body that contains free (unstitched) edges.

• If you use Match Edge to connect free edges within the same solid or sheetbody, the software stitches the free edges together and creates a single,common edge. When you mesh these edges, the software creates duplicatenodes along the area where the edges were matched.

• If you use Match Edge to connect free edges between different solid orsheet bodies, the software matches the free edges together. This results intwo coincident, but separate edges.

Projecting versus not projecting edges

You can choose from two different methods on the Match Edge dialog tocontrol how the software matches the first edge to the second edge.

• With Project, the software projects the source edge onto the target edge.


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• With No Project, the software interpolates the source edge point-by-pointonto the target edge.

Match Edge limitations

• You cannot use Match Edge to stitch together the free edges betweenseparate solid bodies.

• You cannot use Match Edge to stitch together the free edges betweenseparate sheet bodies.

• You can’t use the Match Edge method when the source edge is unstitchedand the target edge is stitched within the same sheet or solid body. Youcan only use Match Edge when the source edge is stitched and the targetedge is stitched within a different sheet or solid body.

Matching edges

1. Click Match Edge .


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2. Select the edge to match (the source edge).

3. On the Match Edge dialog, set the Project Switch:

• Click Project to project the source edge to the target edge withoutchanging its length or shape.

• Click No Project to map, endpoint-to-endpoint, the source edge ontothe target edge.

4. Select the edge to match to (the target edge).


Collapse Edge

Use Collapse Edge to collapse an edge to either one of its end points orto a specified point along the edge.

Collapse Edge lets you manually remove very small edges, such as thoseshown below, from your model by collapsing them to a point.

You can use Collapse Edge to collapse a selected polygon edge to any pointalong that edge.

For example, the following graphic shows an example of a very small polygonedge.


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We then used Collapse Edge to collapse the edge to its end point, as shownbelow.

Collapsing an edge to a point

1. Click Collapse Edge .

2. In the graphics window, select the polygon edge to collapse.

3. Use the tools on the Snap Point toolbar to help select the point to whichyou want to collapse the edge.

• End Point lets you select a point at the end of a curve.


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• Mid Point lets you select a point at 50% of the total length of the curve.



4. Click MB2 or click OK on the Collapse Edge dialog bar to collapse theedge to the selected point.

Face Repair

Use Face Repair to create new polygon faces from free polygon edgeson the surrounding body.

When you first create a FEM file, the software creates polygon geometry fromthe idealized part. The polygon geometry is a one-for-one, faceted (tessellated)representation of your original geometry. Occasionally, the software mayencounter problems during this process and may be unable to completely orproperly tessellate certain faces. Face Repair lets you repair polygon facesthat are either damaged or missing entirely. For example, you can use FaceRepair to:

• Repair a corrupt or poor quality polygon face that did not tessellateproperly when the software created the polygon geometry.

• Create a new polygon face to fill a missing void in your model.

Repairing and replacing damaged faces

1. Click Face Repair .

2. Set the Type Filter in the Selection toolbar to the type of polygon geometryyou need to select.

• To create a new polygon face from a set of free edges, set the TypeFilter to Polygon Edge.

• To replace a damaged polygon face with a new face, set the Type Filterto Polygon Face

3. With the Pick Loops selection step active:

• If you’re creating a new face from a set of free edges, select a free edge.The software constructs a loop of free edges.


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• If you’re replacing a damaged face, select the damaged face. Thesoftware automatically deletes the face, leaving a loop of free edges.

4. Subdivide the loop as necessary:

a. Click the first Point selection step icon, and select a point along afree edge of the loop.

b. Click the second Point selection step icon. Select a second point todefine a curve that subdivides the free loop so that you can create aquality face. Use the Snap Point toolbar options to help select specificpoints.

c. Click Create Face from Loops. Select an edge to define an outer loop,and, if necessary, select a second edge to define an inner loop (i.e.,a hole).

d. Click Complete Set and Start Next Set to generate the face and returnto the Point selection step.

5. Repeat step three until you’ve defined a new polygon face to connect thefree edges.

6. Click OK.

Reset

Use Reset to restore abstracted polygon geometry to its original state.

Reset lets you remove changes you have made to the polygon geometry withthe geometry abstraction tools, such as Split Face and Match Edge. Whenyou use Reset, the software returns the portion of the polygon geometry youselect to its original state prior to any modifications.

Collapse Edge limitation

In general, Reset removes all changes to the polygon geometry from thegeometry abstraction commands. The one exception to this is the CollageEdge command. Because Collapse Edge can cause fundamental changes inthe polygon geometry, the software can’t always reset all the changes causedby the Collapse Edge command.

Resetting geometry

1. Click Reset .


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2. Select the polygon geometry on which you want to remove changes causedby the geometry abstraction commands. You can:

• Select one or more faces or bodies to reset the abstractions made tothose faces or bodies.

• Choose Edit → Selections → Select All to reset all abstractions madeto the polygon geometry.

3. Click OK to reset the selected geometry.

ActivitySee the “Geometry abstraction” activity in the Applications of AdvancedSimulation Workbook.

In this activity, you will simplify geometry to improve mesh quality.


• Learned about geometry abstraction techniques.

• Learned the difference between geometry idealization and geometryabstraction.

• Learned about polygon geometry.

• Learned how to detect fillets before meshing.

• Learned about various geometry abstraction tools.


9

Lesson

9 Element attributes

Objectives

• Learn how to modify element attributes.

• Learn how to override element attributes.

• Learn how to use the Attribute Editor to modify element attributes.

Element attributesThe Element Attributes dialogs let you define and modify the materials andphysical properties for the elements, as well as additional mesh properties.

The default language Solver setting for the FEM file determines whichelements can be used, as well as their corresponding element attributes.

The dialog below shows the element attributes for a beam element.

In the same dialog, if you pick the mesh tab, you can modify additional meshattributes:


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Element attributes

Where do I find it?

Simulation Navigator→mesh node→right click→Edit Attributes

Element attribute overrides

When you’re working in a Simulation file, you can define element “overrides.”Element overrides let you change the value of selected element attributes,such as materials or physical properties, without requiring that you copy theentire mesh (FEM file). When you solve a model that contains an override,the software uses the values you modified in the override instead of the valuesyou defined in the original model. For example, this allows you to use a singleFEM model to perform a series of material studies, which saves disk spaceas well as modeling time and effort. You can also use overrides to quicklyanalyze the effect of varying the element thickness within a 2D mesh.

The graphic below shows an example of an element override that is used tovary the element thickness. When we initially created the original FEM file,we didn’t define a thickness value. However, we then created two differentoverrides in the files SIM1 and SIM2 in which we defined override values forthe element thickness of 2mm and 2.5mm, respectively.


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Element attributes

Attribute Editor

The Attribute Editor lets you select any editable FEM entity and reviewand revise its attributes. The entities that you can select include:

• Meshes, including 0D, 1D, 2D, 3D, contact meshes, and surface contactmeshes. Once you select a mesh, you can edit the element attributes andmaterials assigned to the elements. The attributes that you can editdepend on the element type.

These properties are the same ones that you can modify through theElement Attributes dialogs available in the Simulation Navigator.

• Geometry, including point/mesh point, curve/edge, face, and body. Onceyou select geometry, you can edit attributes that will help you control themesh definition on this geometry.

Attribute Editor – point selection

The following illustration shows the Attribute Editor dialog that displaysafter selecting a point. The dialog presents a variety of point attributes thatmay be reviewed and edited.


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Element attributes

Attribute Editor – curve/element selection

The following illustration shows the Attribute Editor dialog that displaysafter selecting a curve or edge. The dialog presents a variety of curve/edgeattributes that may be reviewed and edited.


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Element attributes

Edge Density Type and Edge Density value

These two options work in combination, allowing you to specify densitycontrol for the 2D mesher on local edges. You can apply or assign edgedensities to model edges and curves using any of the following:

• Edge Density Number

• Edge Density Size

• Edge Density Chordal Tolerance

• Edge Density Geometric Progression

Number

When the Edge Density Type is set to Number, the number entered in theEdge Density field reflects the number of elements on the edge.

Edge Density Size

When the Edge Density Method is set to Size, the value entered in the EdgeDensity field reflects the approximate size of the element on the edge. Thenumber of elements is rounded to the closest integer.

Edge Density Chordal Tolerance

Chordal tolerance is defined as the maximum distance between an arc alongthe curve and the curve itself. The Chordal Tolerance option allows you toproduce a parametric set of node locations that are derived from equationsrelated to the curvature of the curve or edge. Nodes are placed in highcurvature areas (where curvature is greater) and in lower curvature areas.

Edge Density Geometric Progression

Geometric Progression allows you to specify a ratio of node locations alongan edge or curve. This produces a series of node locations that are more denseat one end and less dense at the other. This option should be used to definecritical areas of interest. Finer, more controlled meshes are produced in thesecritical areas, allowing a coarser mesh to be generated in less critical areasof the part.

Edge Density Ratio

The Edge Density Ratio field becomes active when the Geometry Progressionoption is selected. The default value for Edge Density Ratio is 1.0. With thedefault value, the result is the specified Number of Points value (or nodelocations) divided into equal parameter spacing, based on the arc length.Geometric Progression allows spacing of a set of points based on a geometricratio.


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Element attributes

For example, if a ratio of 0.75 is entered, the distance from one point to thenext is multiplied by 0.75 (as shown below).

It is important to note that the Geometric Progression option is dependentupon direction. The distribution of the nodes always begins at the naturalstart of the curve (indicated by the direction of the temporary display arrow).The arrow always points from the natural start of the edges or curves toits end.

Applying the inverse value for the Edge Density allows you to reverse thedirection of node distribution.

Attribute Editor – face selection

The following illustration shows the Attribute Editor dialog that displays afterselecting a face. The dialog presents a variety of face attributes that may bereviewed and edited. Shown below is a brief description of each option.


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Element attributes

Face Density

Face Density allows you to set the approximate element size for the selectedface.

Attribute Editor – body selection

The following illustration shows the Attribute Editor dialog that displaysafter selecting a solid body. The dialog presents a variety of solid bodyattributes that may be reviewed and edited.


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Element attributes

Attribute Editor – 3D mesh selection

The following illustration shows the Mesh tab on the Attribute Editor dialogthat displays after selecting a solid (3D) CTETRA10 mesh. The dialogpresents a variety of solid mesh attributes that may be reviewed and edited.


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Element attributes


The following illustration shows the Attribute Editor dialog that displaysafter selecting a shell (2D) CQUAD4 mesh. The dialog presents a variety ofmesh and element attributes that may be reviewed and edited.


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Element attributes


The following is a typical Attribute Editor dialog that displays after you haveselected a beam mesh. The dialog presents a variety of mesh and elementattributes of the mesh for your review and/or edit, if desired.


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Element attributes


The following image shows the Mesh tab on the Attribute Editor dialog thatdisplays after you have selected a 0D mesh (concentrated mass). The dialogpresents a variety of mesh and element attributes of the mesh for your reviewand/or edit, if desired.


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Element attributes


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Element attributes

Mesh Density method and value

Mesh Density allows assignment of a default density to the element to becreated. The two options are:

• Number - Use this option to specify the number of elements to be createdon the geometry.

• Size - Enter the approximate size of the element to be created.

Mesh Density Value allows specification of a desired density value for themesh.

Distribute Mass

When toggled on, the Distribute Mass option instructs the system to distributethe concentrated mass elements along the selected object (face, edge, etc.).

Attribute Editor – Contact mesh selection

The following image shows the Attribute Editor dialog that displays after youhave selected a contact mesh.


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Element attributes


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Element attributes

Attribute Editor – Surface contact mesh selection

The following image shows the Attribute Editor dialog that displays after youhave selected a surface contact mesh.


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Element attributes

ActivitiesSee the “Element attributes” activities in the Applications of AdvancedSimulation Workbook.

In these activities, you will improve the mesh by modifying element andmesh attributes.


• Learned how to apply element attributes.

• Learned how to modify element overrides.

• Learned how to use the Attribute Editor.


10

Lesson

10 Materials

Objectives

• Learn how to assign a material to a mesh or geometry.

• Learn how to customize the material database.


10

Materials

Materials overview

Use Materials to select and define materials and material properties touse in the simulations and mechanisms you build.


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Materials

From the Materials dialog box, you can:

• Create, review, and edit isotropic, anisotropic, orthotropic, and fluidmaterials.

• Add, review, and edit temperature-dependent fields for these materialtypes.

• Control the orientation of the material by aligning it with a coordinatesystem.

• Use the material library, which includes standard as well as user-definedmaterials.

Isotropic materials

The isotropic material is the most commonly used material property.An isotropic material is defined as a material having the same materialproperties in any or all directions.

Isotropic material types are used when certain assumptions are made. Use ofan Isotropic material assumes that the material is homogeneous and that theproperties (Young’s Modulus, for example) are the same in all directions.

On the Materials dialog, you select the Isotropic tab to enter the isotropicmaterial properties.

Orthotropic materials

An orthotropic material is a special case of an anisotropic material that maybe used with plate and shell elements. It contains three orthogonal planes ofmaterial symmetry at a given location in the model structure. It is commonto model composite structures (laminates) using an orthotropic material,especially when the parts are constructed from fiber composites.

the Orthotropic tab on the Materials dialog shows the material propertiesfor this material type. You may want to re-size the dialog to better see thecontents of the scroll window.

Anisotropic materials

An anisotropic material has different properties in each direction at anygiven location in the model structure. No material plane of symmetry isassociated with an anisotropic material (meaning that properties may varyin all directions).

Anisotropic specification consists of three matrices. The two square matricesare symmetrical so that you need only enter data at the bottom half. As aconvenience, the paired value is a label which will be updated automaticallyeach time the opposite twin value is entered. When complete, the entiresymmetric matrix will be shown.


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Materials

Fluid materials

Fluid material properties are those applicable to 3D elements modeling theliquid or gas in a fluid volume.

Assigning a material

1. Click Materials .

2. On the Materials dialog, click Library .

3. When the **Unsatisfied Title** dialog opens, click OK. A list of availablematerials appears.

4. Select one or more materials and click OK. Use Shift-click or Control-clickto select multiple items.

5. Select the material name in the Materials dialog, then pick the geometryin the graphics window and click Apply. A status message appears,indicating that the material has been assigned.

Customizing the material library

Adding a new material

To add a new material to the library, use the following basic steps:

1. From ${UGII_BASE_DIR}\ugii\materials, make a backup copy ofphys_material.dat. If you are running NX as a client, copy the followingfiles to a local directory: phys_material.dat and phys_material.tcl.

2. Make sure the necessary environment variables are pointing to thelocation of the modified phys_material.dat file, and to locations of thecurrent phys_material.def and phys_material.tcl files. If you are runningNX as a client, you may need to set the variables manually.

To add a new material to the database:

1. Open the phys_material.dat file in a text editor application.

2. Go to the bottom of the materials list. Copy the full line of the bottom-mostmaterial and paste it on the next line down.

3. Enter a new material name and unique ID.

4. Change the values in the material property fields, as necessary.


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Materials

5. Add temperature-dependent properties.

6. Save the file and exit the text editor.

7. From a command shell or the System Properties dialog, set theappropriate environment variables for running the software with themodified file. (see Setting material library environment variables)

8. Launch the software with a test part to make sure the new material isworking as intended.

Setting material library environment variables

To ensure that the material library database is accessed from the correctlocation, make sure the ugii_env.dat file has the following environmentvariables set correctly, or set them directly:

•phys_material.def - UGII_PHYS_MATERIAL_LIB_DIR=${UGII_BASE_DIR}\ugii\materials\${UGII_LANG}\

•phys_material.dat - UGII_PHYS_MATERIAL_LIB_DATA_DIR=${UGII_BASE_DIR}\ugii\materials\

•phys_material.tcl - UGII_PHYS_MATERIAL_LIB_PATH=${UGII_BASE_DIR}\ugii\materials\

•ug_metric.def or ug_english.def - UGII_DEFAULTS_FILE=[default directory ${UGII_BASE_DIR}\ugii\]

When defining the environment variable path, UGS recommends thatyou use an end backslash. Otherwise, you may get an error messagewhen you try to use the updated library.

ActivitySee the “Materials” activity in the Applications of Advanced SimulationWorkbook.

In this activity you will apply a material to a mesh, and create a new material.



10

Materials

• Learn how to assign a material to a mesh or geometry.

• Learn how to customize the material database.


11Lesson

11 Boundary conditions

Objectives

• Learn about the boundary conditions that can be defined for a model.

• Learn how to create loads.

• Learn how to create constraints.


11

Boundary conditions

Boundary conditions overviewLoads, constraints, and simulation objects are all considered boundaryconditions. The Simulation Navigator provides tools that let you create, edit,and display boundary conditions. You can also create boundary conditionsusing icons on the Advanced Simulation toolbar.

The options that appear on the boundary conditions dialogs are specific to theactive solution and its associated solver.

For example, if the active solution uses the NX Nastran solver, the CreateForce dialog provides options that are specific to the NX Nastran FORCEcard.

You can create boundary conditions before or after you create a solution:

• If you create a solution first, the loads, constraints, and simulation objectsare stored in their respective containers in the Simulation: the LoadContainer, Constraint Container, and Simulation Objects Container.They are also stored in the solution.

• If you create the loads, constraints, and simulation objects first, they arestored in their respective containers in the Simulation. You can then dragand drop individual boundary conditions into solutions you create.

Supported boundary conditionsThe tables list the Advanced Simulation boundary conditions (loads,constraints, simulation objects), the associated analysis types, and theNastran solver cards that they support.

Icon Load Nastran Analysis Type Supported NastranCards

ForceStructural (all exceptSEMODES 103)

Axisymmetric StructuralFORCE

Moment Structural (all exceptSEMODES 103) MOMENT

Bearing Structural (all exceptSEMODES 103) FORCE

Torque Structural (all exceptSEMODES 103) FORCE


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Boundary conditions

Icon Load Nastran Analysis Type Supported NastranCards

PressureStructural (all exceptSEMODES 103)

Axisymmetric Structural

PLOAD4 (Structuralonly)

PLOAD2 (Structuralonly)

PLOAD1(Structuralonly)

PLOADX1(AxisymmetricStructural only)

HydrostaticPressure

Structural (all exceptSEMODES 103) PLOAD4

GravityStructural (all exceptSEMODES 103)

Axisymmetric StructuralGRAV

CentrifugalStructural (all exceptSEMODES 103)

Axisymmetric StructuralRFORCE

TemperatureLoad

Structural (all exceptSEMODES 103)

Axisymmetric StructuralTEMP

Heat FluxThermal

Axisymmetric Thermal

QBDY3

QBDY2

QHBDY

RadiationThermal

Axisymmetric ThermalRADBC

HeatGeneration Thermal QVOL

Icon Constraint Nastran Analysis Type SupportedNastran Cards

User DefinedConstraint

Structural

Axisymmetric Structural

SPC (Structuralonly)

SPC1


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Boundary conditions

Icon Constraint Nastran Analysis Type SupportedNastran Cards

EnforcedDisplacementConstraint

Structural SPCD

FixedConstraint

Structural

Axisymmetric StructuralSPC

FixedTranslationConstraint

Structural SPC

Fixed RotationConstraint Structural SPC

SimplySupportedConstraint

Structural SPC

PinnedConstraint Structural SPC

CylindricalConstraint Structural SPC

SliderConstraint Structural SPC

RollerConstraint Structural SPC

SymmetricConstraint Structural SPC

Anti-SymmetricConstraint Structural SPC

ThermalConstraints

Thermal

Axisymmetric ThermalSPC

ConvectionThermal

Axisymmetric ThermalCONV


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Boundary conditions

IconSimulationObject Nastran Analysis Type Supported

Nastran Cards

Surf to SurfContact

SESTATIC 101 (SingleConstraint and MultiConstraint), ADVNL 601,106

BCRPARAM

BCTPARM

BCTSET

BSURF

BSURFS

BCTPARA (ADVNLonly)

Surf to SurfGluing

Structural (all except NXNastran ADVNL 601, 106) BGSET

InitialTemperatures

NLSTATIC 106

NX Nastran ADVNL 601,106

NLSCH 153

TEMP

Creating loadsThe procedure for creating most structural and thermal loads is similar.

1. In the Simulation Navigator active structural or thermal solution,right-click on Loads.

2. Choose New Load.

3. From the menu, choose the type of load that you want to create.

4. (Optional) In the dialog box, choose the type of load to create.

5. Select the object to apply the load to.

Boundary conditions can be applied to geometry, including faces, edges,curves, points, mesh points, vertices, or the entire model. They can also beapplied to nodes or elements. The type of boundary condition determinesthe objects that you can apply it to.

6. (Optional) For some thermal loads, click (Optional Control Point),and select a control point.


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Boundary conditions

7. (Optional) Click the arrow next to (Inferred Vector) and enter adirection for the load.

8. Enter a magnitude for the load.

Creating constraintsThe procedure for creating most constraints is similar.

1. In the Simulation Navigator active solution, right-click on Constraints.

2. Choose New Constraint.

3. From the menu, choose the constraint that you want to create.

4. (Optional) On the Create (Constraint) dialog, choose the Type.

5. Select the object to apply the constraint to.

Boundary conditions can be applied to geometry, including faces, edges,curves, points, mesh points, vertices, or the entire model. They can also beapplied to nodes or elements. The type of boundary condition determinesthe objects that you can apply it to.

6. (Optional) For a convection boundary condition, click the Optional ControlPoint icon, and select a control point.

7. (Optional) Enter a direction for the constraint.

8. (Optional) Enter a magnitude for the constraint.

ActivitySee the “Boundary conditions” activity in the Applications of AdvancedSimulation Workbook.

In this activity, you will apply loads and constraints to your model.


• Learned about the boundary conditions that can be defined for a model.

• Learned how to create loads.


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Boundary conditions

• Learned how to create constraints.


12

Lesson

12 Model information

Objectives

• Learn how to display information about your model.


12

Model information

Model information overviewThe Information feature is available with every NX application producinggeometric and part relationship data. The Information→AdvancedSimulation menu lets you query finite element entities or objects. In addition,you can obtain a simulation summary which gives more detailed informationon mesh nodes, element numbers, etc.

Information options provide general and specific information for selectedobjects, expressions, parts, layers, etc. Data is displayed in the Informationwindow. The Information window has its own menu bar that supports cut,copy and paste operations, as well as capability to save output to a file and/orprint to the default printer. The data that is output to the Informationwindow differs depending upon the chosen Information option(s).

• Identify lets you display element or node labels.

The image shows element and node labels displayed for 2D elements.


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Model information

• When the FEM is active, you can list information on a mesh, material,section, and mesh mating condition. Finite Element Summary listsdetailed information about number of nodes, elements, and other entities.

The figure shows an information listing for one element.

• When the Simulation file is active, you can list information on a mesh,load, constraint, Simulation object, solution, step, material. Identify letsyou display element or node labels. Simulation Summary lists informationabout the solutions in the Simulation file.


12

Model information


• Learned how to display information about your model.


13

Lesson

13 Model checking

Objectives

• Learn how to perform model checks.

• Understand threshold values.


13

Model checking

Model Check overview

Model Check provides complete information about the model and allits finite element components. Model Check is a good predictor of whetherthe model is ready to solve.

Comprehensive checkUse the Comprehensive check to see if your model contains all the necessaryelements for the analysis. When you perform a Comprehensive check, thesoftware verifies that the model contains:

• Elements

• Element attributes (such as thickness)

• Loads

• Constraints

• Materials

The software displays the results of a Comprehensive check in a separateInformation window, along with an error summary for each topic.


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Model checking

Element Shapes checkUse the Element Shapes check to detect elements that may be too distortedto yield good analysis results. For accurate results, finite element analysissolvers require elements that are not distorted.

Element Shapes Threshold ValuesThreshold values are the maximum allowable value for each test. Anyelement whose test results exceed these values will fail the test. You may alsoaccept the software’s defaults for the threshold values.

The values you enter depend on the accuracy you need from your analysisand the type of solver specified in the environment.


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Model checking

The Jacobian zero threshold is an exception. An element fails theJacobian zero test if its test results fall below the threshold valueyou enter.

Note that the shape tests do not check for misplaced midside nodes.

Aspect Ratio

Aspect ratio is the ratio of an element’s length to its width.


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Model checking

Tri Aspect Ratio

The aspect ratio for a triangular element is calculated as the ratio of thelength (h2) to the height (h1). This ratio (h2/h1) is then multiplied bySQRT(3)/2, such that an element in the shape of an equilateral trianglewill equal 1. This procedure is repeated for the remaining two edges of thetriangle and the largest value is retained as the aspect ratio for the element.

Quad Aspect Ratio

The aspect ratio for a quad element is determined using a test proposedby Robinson and Haggenmacher (J. Robinson and G. W. Haggenmacher,"Element Warning Diagnostics," Finite Element News. June and August,1982). This test is based on a projection plane created by first bisecting thefour element edges, then creating a point on the plane at the vector average ofthe corners. The x-axis extends from the point to the bisector on edge 2. Theratio is determined as the ratio of the length from the origin to the bisector of


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Model checking

edge 2 to the length from the origin to the bisector of edge 3. If the ratio isless than 1.0, it is inverted.

Tet Aspect Ratio

The aspect ratio for a tetrahedral element is computed by taking the ratio ofthe height of a vertex to the square root of the area of the opposing face.

The maximum height to area value is multiplied by a factor cf = 0.805927,which is the ratio of height to edge length for an equilateral tetrahedron.This result is the aspect ratio. With an equilateral tetrahedral element, thesoftware report a value of 1.

Aspect ratio = Max(cf(hi)/sqrt(Ai)), where i = 1,2,3,4.

Warp

Warp allows for measurement of out-of-plane element deviation.

Quad Warp

The warp value is determined using a test proposed by Robinson andHaggenmacher which uses the following method of calculating Quad elementWarp. The test is based on a projection plane created by first bisecting thefour element edges, then creating a point on the plane at the vector average of


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Model checking

the corners (where the x-axis extends from the point to the bisector on edge2). The plane normal is in the direction of the cross product of the x-axis andthe vector from the origin to the bisector of edge 3. Every corner of the quadis a distance h from the plane. The length of each half edge is measured andthe shortest length is assigned a value of 1. The warp angle is the arcsine ofthe ratio of the projection height h to the half edge length 1.

Skew

Skew allows for measurement of angular deviation of an element using anedge bisector method.

Tri Skew Angle

Three potential skew angles are computed for each triangular element. Tocalculate each skew angle, the software constructs two vectors: one from avertex to the mid-point of the opposite edge; the other between the mid-pointsof the adjacent edges. The software subtracts the angle between these twovectors from 90° (skew angle = 90°-a). This procedure is repeated for theother two vertices. The largest of the three computed angles is the skew anglefor that element (skew factor = (90°-a)/90).

Quad Skew Angle

Prior to testing for skew, the software checks each element for convexity.Elements which fail the convexity check double-back on themselves. Thiscauses the element stiffness terms to contain either a zero or negative value.


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Model checking

This skew test is based on a reference frame created by first bisecting the fourelement edges, then creating an origin at the vector average of the corners(where the x-axis extends from the origin to the bisector on edge 2). Thez-axis is in the direction of the cross product of the x-axis and the vector fromthe origin to the bisector of edge 3. The y-axis is in the direction of the livecross product of the x- and z-axes as shown above.

The Robinson and Haggenmacher skew test uses the angle (alpha) betweenthe edge 2 and 4 bisector and the test y-axis. The resulting angle is subtractedfrom 90 degrees to yield the skew angle.

Tet Skew Angle

Each face of the tet element is tested for skew as if it were a tri element. Thehighest resulting angle for each element is retained as the skew angle.

Quad Taper

Taper allows for measurement of the geometric deviation of a quadrilateralelement from a rectangular shape.


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Model checking

Quadrilateral element taper is determined using a test proposed by Robinsonand Haggenmacher. Four triangles are created bounded by the elementedge and the edges created by connecting the element verification referenceframe origin with the two nodes at the element edge. The resulting fourtriangular areas are calculated and summed. The ratio of the smallesttriangular area to the total area of the element is the taper ratio (taper ratio= 4*a(smallest)/a1+a2+a3+a4)

Jacobian

A Jacobian is a determinant used to describe the variance of somecharacteristic at two different positions in a system. For example, a Jacobianmight be used to describe the variance of slope between two points on a curve.Jacobians are useful tools for measuring distortion. A Jacobian could be usedto compare the orientation between two edges of an element. For shape checkthe Jacobian is evaluated at each vertex. These values are then used togenerate results for the Jacobian Ratio and Jacobian Zero tests.

Jacobian measures the ratio between the area or volume of an element to theideal parametric element. The software calculates this value by mapping aparent element (in computational space) against the actual element.

Jacobian Ratio

Jacobian Ratio is a ratio of the largest Jacobian determinant to the smallest.This ratio gives you an idea of overall distortion in an element. The Jacobianratio test is helpful for identifying when the interior corner angles of anelement deviate too much from 90 degrees. An element will fail this test ifthe ratio is higher than the value entered in the data field. A ratio close orequal to 1.0 is desired.

Jacobian Zero

The determinant of the Jacobian (J) is calculated at all integration points foreach element selected. The minimum value for each element is determined.This element verification test can be used to identify incorrectly shaped


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Model checking

elements. For a well formed element, J is positive at each Gauss pointand is not significantly different from the J value at other Gauss points. Japproaches zero as an element vertex angle approaches 180 degrees. TheJacobian Zero is the smallest determinant. An element will fail this test if itsJacobian Zero is below the value entered in the data field.

Element Outlines checkUse the Element Outlines check to display free edges (element edges thatare unconnected to any other element) of 2D meshes and display free faces(element faces that are unconnected to any other element) of 3D meshes.

Nodes checkUse the Nodes check to detect and merge duplicate (coincident) nodesbetween meshes. This check operates only between boundary nodes on yourgeometry (for example, edges of faces and faces of bodies, etc.). Moreover, thesoftware only merges nodes of identical types. For example, the software willnot merge a midnode with an end node.

The ability to detect and merge duplicate nodes is particularly usefulwhen you’re working with assembly models or with models that containmultiple meshes. If you try to solve a model that contains coincident nodes,singularities or other rigid body motion errors can occur during the solve.


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Model checking

2D Element Normals checksUse the 2D Element Normals check to display and reverse 2D elementnormals. You can check the normals on individual faces or within individualmeshes, or you can check all 2D elements in the current part. Once youreverse an element’s normal, the software maintains that reversal acrossall mesh updates.



13

Model checking

• Learned how to perform model checks.

• Learned about threshold values.


14

Lesson

14 Solving

Objectives

• Learn how to solve the finite element model.

• Learn how to do a batch solve.


14

Solving

Solving overviewOnce you have prepared your FE model by defining a mesh and applyingboundary conditions, you can perform a solve.

A solve formats the bulk data deck or input file, then automatically beginsprocessing. You can also choose to write out the input file without solving it.

You can also write out an input file with File →Export. This commandlets you control the location of the input file, as well as the units forthe file. You can write out the active FE Model and Simulation, oronly the active FE Model.

Solving the modelTo ensure a successful solve and accurate results, run a comprehensive check,as well as element quality checks, before you solve the model.

1. In the Simulation Navigator, select the solution node.

2. Click .

3. On the Solve dialog, select an option from the Submit menu.

4. To edit solution attributes, choose Edit Solution Attributes.

5. To edit solver parameters, choose Edit Solver Parameters.

6. Click OK to run the solve.

The Analysis Job Monitor appears. When the analysis is complete, aResults node appears in the Simulation Navigator.


14

Solving

Analysis Job MonitorThe Analysis Job Monitor lets you keep track of the progress of the analysisjob you submitted, and also lets you know when the analysis job is completed.

The Analysis Job Monitor automatically appears after you run a solve.

Batch solvingSolve All Solutions allows you to perform batch solves. You can choosebetween launching all solves simultaneously or in sequential order.


14

Solving

ActivitySee the “Solving” activity in the Applications of Advanced SimulationWorkbook.

In this activity, you will learn the process for preparing and solving a model.


• Learned how to solve the finite element model.

• Learned how to do a batch solve.


15

Lesson

15 Post-processing

Objectives

• Learn how to use Post-processing.

• Learn how to use the tools on the Post Control toolbar.


15

Post-processing

Post-processing introductionUse the post-processor to view the results of all analysis types supported byAdvanced Simulation. You can enter Post-processing by double-clicking onany Results node in the Simulation Navigator.

Opening the post-processor

To open the post-processor:

• Double-click on the Results node in the Simulation Navigator.

• Click the Enter Post Processing on the Advanced Simulationtoolbar.

• From the main menu, choose Tools→Results→Enter Post Processing

Results in the Simulation NavigatorUse the Simulation Navigator to display and manage results in Post–processing. Available options include the following:

Node Name Description and FunctionsResults node Result types are displayed under

the Results node in the SimulationNavigator. You can expand each resulttype to access all data componentsavailable for the selected result type.Select or clear the visibility check box (

) for a result type or data component,and the graphics window displayupdates dynamically.

You can use MB3 options availablefrom the Results node to do thefollowing:

• Create and append post views

• Combine load cases


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Post-processing

Node Name Description and FunctionsPost View node Provides access to the current post

view. Double-clicking on a post view inthe Navigator designates that view asthe new work view. To manage displayfeatures of a particular view, select theview in the Navigator, then right-clickto access the following options:

• Load - Populates the graphicswindow with the selected post view.

• Rename - Renames the post view.

• Clone - Creates an identical copyof the post view in the SimulationNavigator.

• Delete - Deletes the selected postview.

• Overlay - Adds the post view to thecurrent working post view.

• Append to Display - adds the postview to the current layout.

• Save As Template - Lets yousave the selected post view as atemplate.

The Post Control toolbarUse the Post Control toolbar to access the following Post-processing features:

Icon Option DescriptionFinish PostProcessing

Exits Post-processing.

Alternatively, you canexit Post-processing bydouble-clicking the FEModel node in SimulationNavigator.

Post View Controls the display of results inselected post views.


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Post-processing

Icon Option DescriptionIdentify Probes and displays node and

element information in the workview.

Display Marker Switches the display of minimumand maximum result markers onand off.

Display Marker Drag Allows you to reposition minimumand maximum result markers.

View Layout Displays results in multiple layoutviews.

Select All Views Selects all layout views.

Deselect All Views Deselects all selected layout views.

Overlay Superimposes one set of results onanother in the same view.

Animation Setup Controls animation settings.

Previous Steps backward through theanimation one frame at a timewhen the animation is paused.

Next Steps forward through theanimation one frame at a timewhen the animation is paused.

Play Plays the animation using thecurrent settings.

Pause Pauses the current animation.

Stop Stops the current animation.

Import ResultsYou can import and access results for solves performed outside of the currentset of solutions. The following file formats are supported for importing results:

• Nastran (.op2)

• Structures P.E. (.vdm)

• Ansys Structural (.rst)


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Post-processing

• Abaqus Thermal (.rth)

• Abaqus (.fil)

• I-DEAS results file (.unv)

• I-DEAS Bun file (.bun)

Importing results

To import and view results:

1. From the Simulation Navigator, right-click on the Simulation file andselect Import Results.

2. From the Import Results dialog, name the imported results file.

3. Click on the File Open button to select a file type and path for the filename. Click OK.

4. Review the results units. If necessary, click Change and select new unitsfrom the Import Results units dialog.

5. Click OK. The imported results node appears in the Simulation Navigator.

Using imported results

Once you have successfully imported a results file, the imported results nodebehaves somewhat like a solution node in the Simulation Navigator. You cantherefore perform the following operations on imported results:

• Post-process and view the results

• Re-solve for new results

• Edit attributes of the imported results


15

Post-processing

Post ViewWhen you enter Post-processing, the Results node expands to display allresult types available. Beneath the Results node is a post view, which iscreated automatically by the software from solver results. A post viewrepresents result settings displayed in the graphics window that includeresult type, data component, cutting plane, deformation, and so on. You cancreate additional post views, and save settings as templates.

You can manage the settings for each view using the Post View dialog.

• The Post View Display tab provides options for displaying results such ascontour type, deformed display options, and where to display results. Youcan also manage cutting plane options from the Post View Display tab.

• The Color Bar tab lets you select results data for post processing. Optionsare also provided for linear or log display and for viewing optimizationresults in tabular and graph form.

• The Edges and Faces tab controls the display of element edges and faces.

• The Preferences tab controls display marker, synchronization, dynamicviewing and text color preferences.


15

Post-processing

Post view templatesPost View templates provide a way to save data from one or more post viewsfor future re-use. Depending on how many views are currently displayed, youcan save the template as a single view or as a layout.

Creating a Single-View Template

1. Select the post view node of the view you want to save as a template.

2. Right-click on the post view and choose Save as Template.

3. In the Save Post Template dialog, enter a Name and choose additionaloptions, if necessary. For example, you can save this template as thedefault, and you can choose to use the part model image for the templateicon.

4. Click OK. This template is stored in the Post Processing Templatespalette, available from the resource bar.

Post view layoutsPost-processing displays up to nine models simultaneously. The Layout viewalso lets you save templates in layout format.

Creating a viewport layout

To create a viewport layout, click the down arrow next to the layout iconon the Post Control toolbar. From the drop-down list, select a layout fromone to nine views.


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Post-processing

Overlay

The Overlay icon ( ) becomes active only after you have created anoverlay using the Simulation Navigator. Use Overlay to superimpose one ormore sets of results on another. Use the Overlay dialog to select the view toapply changes to when modifying an overlay, and to remove overlays.

Creating an Overlay

Create an overlay using the Simulation Navigator. Overlay is notactive until an overlay exists. To create an overlay display:

1. Ensure that you have created at least two post views in the SimulationNavigator.

2. Ensure that the layout in the graphics window for the current work viewis single-view only.

3. Right-click on a non-work view, and select Overlay. The non-work view issuperimposed over the work view in the graphics window.

4. Select additional views to superimpose, if desired.

You can now use Overlay in the Post Control toolbar to launch theOverlay dialog.


15

Post-processing

Combining load casesYou can add linear static load cases and view their combined results. Youcan scale results to compare the results of similar loading conditions atdifferent loading values. This feature is useful for viewing results for varyingcombinations of load cases without spending analysis time, resources anddisk space for every instance of a load case combination.

Combined load case definitions are saved in the Simulation file and areavailable from session to session.

Prior to using the Combine Load Cases functionality, you shouldgive some thought to how you set up your analysis. Be sure to createa separate subcase for each load case you intend to combine. If youwill be applying a scale factor, you may find it useful to define loadsusing unit values.

Combining load cases

To combine and scale load cases in the post-processor:

1. Right-click on the Results node in Simulation Navigator and chooseCombined Loadcases.

2. Enter a short, meaningful name for the combined load case and clickCreate.

The combined load case name appears selected in the Combined LoadCases list box. The Load Case Component list box is now active.

3. The Load Case Component list box lists the solved subcases for thesolution. Select the first load case to combine.

The Scale field and the Add/Edit button are now active.

4. If you are applying a scale factor to this load case, enter a value in theScale field.

5. Click Add/Enter.

The load case, multiplied by the entered scale factor, appears in theCombined Load Case Definition list.

6. Repeat steps 3 – 5 for each load case you want to combine.


The combined load case appears below the results node along with thesubcases. You can create post views displaying the combined results.


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Post-processing

Animation

Animation allows you to generate and control the display of animationframes. You can animate displays to better visualize how the model respondsto a particular solution.

Using the animation tools

You can quickly animate static displacement or stress results (using thedefault settings) using the Animation tools:

1. Click Play on the Post Control toolbar.

The software first generates and steps through the individual frames ofthe animation, and then plays the animation.

2. (Optional) Step through the animation frame by frame. Click Pause

, and then click Previous or Next to step backward orforward through each animation frame.

3. Click Stop to delete the animation frames and return to the staticdisplacement or stress display.

Identify

Use Identify to probe and display nodal and elemental information forthe Work view display. You can display the IDs or the current results value.You can also list results for selected nodes and elements, and you can save aparticular selection.

Identifying results at nodes or elements

1. Click Identify .


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Post-processing

2. In the dialog, choose a filter from the Filter menu.

• If you select n Highest or n Lowest Nodes or Elements, enter a valuefor N=. For example, to view the 10 nodes with the highest values forthe current result, enter N= 10.

• If you select Node IDs or Element IDs, enter node or element ID in theIDs: field. Use commas or spaces to separate multiple node IDs.

• If you select a geometry-based filter (or no filter), use the resultingProbe cursor to interactively select nodes or elements.

Selected elements are marked using the marker indicated in the Markfield: Values, node IDs, or just the node location highlight.

3. Click List Information in Window or List Information in Spreadsheet togenerate a listing of results data for all nodes or elements matching theprobe criteria. To include all data components in the listing, be sure toselect the List All Components check box.


15

Post-processing

Generating reportsThe report is an HTML document containing .gif images and other FE modeldata. It consists of a title page and multiple chapters. Each chapter containsautomatically generated information, with some sections including optionalinformation that you can enter or edit.

Use Create Report to generate a report.

ActivitySee the “Post-processing” activity in the Applications of Advanced SimulationWorkbook.

In this activity, you will explore some of the techniques that you can use topost-process the results from a solve.


• Learned how to use the post-processor.

• Learned how to use the tools on the Post Control toolbar.


16

Lesson

16 Reports

Objectives

• Learn how to generate an HTML report.


16

Reports

Overview

To generate a report, use Create Report .

The report is an HTML document containing .gif images and other FE modeldata. It consists of a title page and multiple chapters. Each chapter containsautomatically generated information, with some sections including optionalinformation that you can enter or edit.

You can create a report at any time after you create a solution. That is,the solution need not be complete and solved. For example, suppose thatyou define the loads and constraints for a model that will be meshed bya colleague. You may want to create a report detailing the loading beforehanding off the solution to the colleague performing the meshing.

The figure shows a typical report structure displayed in the SimulationNavigator.


16

Reports


16

Reports

Creating the report

1. Click (Create Report), or right-click on the Solution node in theSimulation Navigator and select Create Report. An HTML-formattedreport is automatically generated and displays as a node in the SimulationNavigator.

2. Expand the Reports node in Simulation Navigator so you can see thechapters and their contents.

3. Use MB3 options in the Simulation Navigator to modify the report, asnecessary.

• Clear the visibility check box ( ) next to a report item to exclude itfrom the current report, or MB3 → Clear.

• MB3 → Edit to display a text editor where you can add or edit text tothe sections of the report.

Exporting the reportTo export the report, right-click on the Report node in the SimulationNavigator and choose Export. The report is written to a number of HTMLand graphics files, and stored in your local temp directory. When the filesare written, the software launches your default browser and displays theresulting report.

ActivitySee the “Reports” activity in the Applications of Advanced SimulationWorkbook.

In this activity, you will create an HTML report of model data, solution data,and images.


• Learned how to generate an HTML report.


17

Lesson

17 Units

Objectives

• Learn how to create new units of measure.

• Learn how to calculate unit conversions.


17

Units

Units overviewThe NX software provides two default unit system files: English and metric.You can choose one of these unit systems when you create a new part file. Thesettings for that unit system are then applied to and stored with the file.

Within a part, you can modify the default unit settings as follows:

• In key dialogs, drop-down selections let you change the unit systemdynamically rather than having to manually calculate conversions. Forexample, if you are creating a load set and want to enter the force inNewtons instead of pound-feet, select Newtons from the unit optionsand enter a value.

• The Units Manager dialog lets you create new units and unit systems thatare saved to the part and become available from all key dialogs.

• The Units Converter dialog provides a utility to calculate unit conversions.

All unit modifications are stored with the part and are therefore preservedbetween sessions. In addition, the unit values are automatically converted tothe NX standard or metric system when you perform a solve.

Units ManagerUnits Manager lets you make changes to units of measure. New informationfrom each Units Manager session is dynamically updated in all key dialogs.


17

Units

Creating a new unit of measure

To create a new unit of measure:

1. Choose Analysis → Units Custom → Units Manager.

TheUnits Manager dialog opens. The default unit system is displayed,with the Default Unit option selected.

2. Choose Measure to change or add a unit of measure, such as Temperature.Each unit of measure is assigned a unique conversion equation, whichappears in the Conversion Parameters section of the dialog and updatesautomatically whenever you change the unit of measure.

3. Select or enter a new unit name. When you switch from the original unitsystem, the software updates the dialog by clearing the Default Unit checkbox.


17

Units

4. Enter a Unit Display Name, which is the abbreviated name for the unit.

5. Enter a full-name description for the unit of measure.

6. In the Conversion Parameters section, enter a multiplication factor and,if necessary, an addition factor for the unit of measure equation.

7. Choose New Unit.

The new unit measurement is available immediately. For example, if you justdefined dyne as a unit of force in the Units Manager dialog, the dyne unitappears as a selectable option the next time you open the Loads dialog.

You can delete or update units you’ve manually created in the Units Managerdialog as long as they haven’t been used elsewhere.

Units ConverterThe Units Converter dialog provides a utility to calculate unit conversions.You can use the converted values as input in other dialogs, or to simplycompare with other values.

Calculating a conversion value

1. Choose Analysis → Units Custom → Units Converter.

2. In the dialog, select a Quantity.

3. In the From field, enter a value and select a unit system for the originalunit.

4. In the To field, select the new unit system. The software automaticallycalculates a conversion value.


17

Units

ActivitySee the “Units” activity in the Applications of Advanced Simulation Workbook.

In this activity, you will create and work with custom units.


• Learned how to create new units of measure.

• Learned how to calculate unit conversions.


18

Lesson

18 Mesh connections

Objectives

• Learn how to connect parts using various tools, including Mesh MatingCondition, Edge-Face Connection, Weld Mesh, Contact Mesh, SurfaceContact Mesh.


18

Mesh connections

Mesh Mating Condition

Use Mesh Mating Condition to connect two separate solid bodies andtheir associated 3D meshes.

The Mesh Mating Condition capability lets you assemble individual meshestogether at a specified interface. The software ensures that connectivity ismaintained at that interface.

For example, you can use Mesh Mating Condition to:

• Connect the meshes on similar bodies within an assembly.

• Create identical meshes on two faces to facilitate contact definition.

Understanding the roles of the source and target faces

In a mesh mating condition, the software creates a connection between themesh on the face of one body and the mesh on the face of another body. Oneface serves as the source face for the mating condition, and the other faceserves as the target face. The source face controls the density of the mesh atthe interface. In general, the source face should have a finer mesh, and thetarget face should have a more coarse mesh. However, when you define a meshmating condition, you actually select the faces of the part and not the meshes.


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Mesh connections

You can use the Reverse Direction icon at the bottom of the MeshMating Conditions dialog to reverse which face is the source andwhich face is the target.

Selecting faces automatically or manually

On the Mesh Mating Conditions dialog, the Type options let you choosewhether you want the software to automatically search your model forappropriate source and target faces or whether you want to manually selectpairs.

If you select Auto Create to have the software select the pairs, you can usethe Face Search option to control the criteria the software should use tofind pairs.

• Choose All Pairs to have the software find all pairs of source and targetsurfaces within the specified Distance Tolerance.

• Choose Identical Pairs to have the software find only pairs of source andtarget surfaces within the specified Distance Tolerance. that are alsogeometrically identical (for example, they must have the same number ofedges, the same area, etc.).

Selecting a mesh mating condition type

The Mesh Mating Conditions dialog lets you define the following types ofmating conditions:

• A Glue Coincident condition.

• A Glue Non-Coincident condition.

• A Free Coincident condition.

Glue Coincident conditions

With a Glue Coincident condition, if two faces are geometrically identical,the software imprints the mesh from the source face onto the target face. Itthen merges the nodes at the interface between the source and target so thatthe two faces share the same nodes.

Glue Non-Coincident conditions

With a Glue Non-Coincident condition, the software creates multi-pointconstraints (MPCs) or constraint equations between the nodes on the sourceand target faces.


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Mesh connections

You can create this type of mesh mating condition between anytwo faces irrespective of their relative positioning. However, thesoftware uses the Distance Tolerance to connect the nodes at thetime you solve. Therefore, if the two faces are far apart relative tothe tolerance, no relationship is created between the two meshes, andthe bodies are likely to move independently.

Free Coincident conditions

With a Free Coincident condition, the software aligns the mesh on boththe source and target face but does not connect the meshes. With FreeCoincident, this results in duplicate nodes at the interface between the sourceand target faces. This is useful, for example, for setting up surface-to-surfacecontact problems.

Managing Mesh Mating conditions in the Simulation Navigator

When you create a mesh mating condition, the software adds it to theConnection Meshes → Mesh Mating Conditions container in your FEM filein the Simulation Navigator. You can use MB3 options in the SimulationNavigator to delete, rename, and manage mesh mating conditions.

Automatically Creating Mesh Mating Conditions

1. Click Mesh Mating Condition .

2. Select Auto Create on the Mesh Mating Condition dialog.

3. Optionally, select a region of your model to limit the face pair search. Ifyou don’t select a region of faces, the software searches the entire visiblemodel.

4. Choose the Mesh Mating Type.

5. Choose the Face Search Option. To limit the face pair search to coincidentfaces, select Identical Pairs Only.

6. Adjust the Distance Tolerance as necessary for the size and scale ofyour model.

7. Click Preview to highlight all face pairs that match the criterion you’veset.

If the previewed face pairs do not meet your expectations, you may need toadjust theMesh Mating Type, Face Search Option, or Distance Tolerance.You can also change the Type to Manual and manually select the


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Mesh connections

8. Click OK or Apply to create the mesh mating condition.

Manually creating mesh mating conditions

1. Click Mesh Mating Condition .

2. Select Manual on the Mesh Mating Condition dialog.

3. Choose the Mesh Mating Type.

4. Depending on the size and scale of your model, you may want to adjustthe Distance Tolerance.

5. Select the source face.

6. Select the target face.

7. Click OK or Apply to create the mesh mating condition.

Edge Face Connection

Use Edge-Face Connection to define the connection between a set ofedges and a set of faces. Use this feature whenever there are meshes to beconnected in T-junction configuration, for example, fins or stiffeners attachedto surfaces.

When you use Edge-Face Connection functionality, the software tiesthe selected edges to the faces using rigid links and MPCs (multi-pointconstraints). The existing meshes on the edges or faces are not disturbed.


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Mesh connections

Understanding the edge-face connection process

Once you finish making selections on the Edge-Face Connection dialog, clickOK or Apply to create rigid links between the selected edges and selectedfaces. The software creates the connection as follows:

• If are no meshes exist on the edges, each selected edge is seeded withnodes corresponding to the number specified in the Default Element field.

• From these seeded node locations, element nodes are located (GlueMeshes) or points are projected and corresponding nodes created on theselected faces (Match Meshes).

• Rigid links are created between the face nodes and the edge nodes.

• The rigid link elements are displayed in preview.

Weld Mesh

Weld Mesh lets you locate/automate the recognition of weldfeatures (connections) and then automate the creation of their FE modelrepresentation, including consideration for midsurfaces.


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Mesh connections

Use Weld Mesh to create weld elements (1D mesh) from weld features(connections).

Resistance spot welds

Resistance spot welds are used to connect multiple layers of sheet metal. Theoriginal spot weld locations (weld points) are projected onto the face, and thesoftware creates weld elements (Rigid Link or Spring type elements) betweenthe projection points.

• The original spot welds are first projected to the first body using a normalto the surface projection.

• The second and subsequent bodies are projections of the first body’slocations, again projected normal to the first body’s surface.

• The software treats the weld points as hard points. This means that thesoftware honors the weld points during face meshing.

Weld element process

You can get spot locations for each layer of metal faces from the weld feature.The software creates hard points at the spot locations defined in the weldfeature. The software sorts face pairs from top to middle, and middle tobottom. It then creates the recipe for the weld mesh recipe. Finally, the


18

Mesh connections

software creates 1D elements between the projection points for each pairof faces.

Resistance seam welds

Resistance seam welds connect multiple layers of sheet metal, just asresistance spot welds do. They differ from resistance spot welds in thatthe weld geometry is modeled by curve. Points on the original curves areprojected on to the faces, and weld elements (Rigid Link/Spring) are createdbetween the projected points.

• Resistance seam welds connect multiple layers of sheet metal, just asspot welds do. They differ from spot welds in that the weld geometry ismodeled by a curve. As with spot welds, the points on the "original" curvesare projected to the first body’s surface, and then the resulting projectionpoints are projected to each subsequent body.

• The software creates the rigid elements between each pair of points (pointon top face and the corresponding point on the bottom face).

• The software treats the weld points as hard points. This means that thesoftware honors the weld points during face meshing.


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Mesh connections

Contact Mesh

Use Contact Mesh to create point-to-point contact between two edgesor a portion of two edges defined by limiting points.

Result types supported in Post Processing for contact mesh includeNormal Force, Sliding Force, Element Status, and Gap/Penetration.

Creating a contact mesh

1. Click Contact Mesh .

2. Select the desired contact edge and click OK.

3. Select the desired target edge.


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Mesh connections

4. Click Apply to build the contact mesh.

5. (Optional) You can also use the other selection step icons to control thelimiting points definition.

You can define or edit the element properties of the contact meshyou built using the Attribute Editor.

Surface Contact Mesh

Surface Contact Mesh lets you create and define contact elementsbetween two selected faces of a solid or between different components.The options available in the Surface Contact dialog depend on the solverenvironment selected as the currently active solution.

Using surface contact, you can choose between four contact conditions:standard, rough, no separation, or bonded. Depending on the solver you planto use, you define the contact elements as surface contacts or node-to-nodegap elements.

Creating a surface contact mesh

1. Click Surface Contact Mesh .

2. (Optional) Select Auto Create Contact Pairs, and enter the desiredCapture Distance to specify the surface proximity value by which theoverlapping faces can be detected.


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Mesh connections

3. (Optional) To more specifically define contact, use the Selection Stepsinstead of Auto Create. First, select the source face and then the targetcontact face.

4. Change other properties as desired.

5. Click Apply to build the surface contact mesh, and then click OK.

ActivitySee the “Mesh connections” activity in the Applications of AdvancedSimulation Workbook.

In this activity, you will create mesh connections and generate a mesh.

SummaryIn this lesson you learned how to use various mesh connection tools:

• Mesh Mating Condition

• Edge Face Connection

• Weld Mesh

• Contact Mesh

• Surface Contact Mesh


19

Lesson

19 Optimization

Objectives

• Learn how to use optimization.


19

Optimization

Optimization overviewOptimization is a process that helps you arrive at the best solution for a givendesign goal. To achieve the design goal, you set convergence parameters forthe design objective, constraints, and design variables. The software thenperforms a series of iterations to converge on a solution.

After you perform an optimized solve, you can access the results in PostProcessing.

Where do I find it?

To run optimization, do one of the following:

• In the Simulation Navigator, right-click on the simulation → NewSolution Process → Optimization

• Advanced Simulation toolbar → Optimization Setup

Optimization SetupUse the Optimization Setup dialog to specify an optimization type, thendefine a design objective, constraints, design variables, and convergenceparameters. You can also use this dialog to specify the number of iterationsfor the optimization run and to view defined optimization settings.


19

Optimization

Optimization analysis optionsTwo types of optimization are available:

• Global Sensitivity Studies

• Altair HyperOpt™

Global Sensitivity Studies

Global Sensitivity Studies iterates through the limits of each selected designvariable one at a time, to see how sensitive the design objective is to eachvariable.


19

Optimization

The design variable values are varied over a specified number of steps. Forexample, if a design variable has a lower limit of 0.0, an upper limit of 10.0,and you specified 5 steps for the global sensitivity study, there will be fiveiterations during which the design variable is incremented by a value of 2.0for each iteration.

The total number of iterations for a global sensitivity study is equal to:

( number of steps + 1 ) * number of selected design variables

The results for study are displayed in the Sensitivity Spreadsheet, which youcan access from Results → Type in the Post-Processor.

Upon initiating an analysis or study, a copy of the part is saved. In general,you should not attempt to modify a model while an optimization analysis isin progress.

Altair HyperOpt™

Altair HyperOpt™ provides full support for shape optimization, including theuse of feature parameters and expressions as design variables.

Once you have defined a set of design variables, design constraints, and anoptimization goal, the software stores this information and uses it duringoptimization to determine how many iterations are needed for a convergedsolution.

During the optimization, a graph displays that dynamically updates foreach iteration to show the objective result (y axis) vs. iteration (x axis).When the run is complete, the graph closes and quits, and the OptimizationSpreadsheet automatically launches.

ObjectivesUse the Objective dialog to select and define a design objective to be appliedto the optimization problem. Optimization objectives include response typesfrom supported solvers. You can select:

• Volume or weight (for static analysis)

• Frequency (for modal analysis)

• Additional selections such as stress, displacement, and temperature (forthermal analysis)


19

Optimization

ConstraintsUse the Constraints dialog to make constraint selections for optimizing aspecific problem. Constraints can be applied to the model as a whole orto specific geometries.


19

Optimization

Design VariablesUse the Design Variables dialog to define the design variables, which areindependent quantities that you can vary in order to achieve the optimumdesign. Upper and lower limits define a maximum range of variation andserve as constraints on the allowable amount of change.


19

Optimization

ActivitySee the “Optimization” activity in the Applications of Advanced SimulationWorkbook.

In this activity, you will use shape optimization to minimize the weight of apart.


19

Optimization


• Learned how to use optimization to achieve your design goals.


20

Lesson

20 Durability (fatigue) analysis

Objectives

• Learn how to create a durability solution.

• Learn about the types of durability results.


20

Durability (fatigue) analysis

Durability overviewFatigue life can be defined as "failure due to repeated load...involving theinitiation and propagation of a crack or cracks to final fracture" (Fuchs,1980). Structural fatigue analysis is a tool for evaluating a design’s structuralworthiness, or its durability, under various simple or complex loadingconditions, also known as fatigue duty cycles. Results of a fatigue analysis aredisplayed as contour plots that show the duration of cyclic loading (number offatigue duty cycles) the structure can undergo before crack initiation occurs.

Fatigue analysis uses the cumulative damage approach to estimate fatigue lifefrom stress or strain time histories. Estimation is accomplished by reducingdata to a peak/valley sequence, counting the cycles, and calculating fatiguelife. A library containing standard fatigue material properties is provided.

Fatigue analysis process

To perform a fatigue or durability analysis, prepare the model as you wouldfor a finite element analysis and then provide certain fatigue-specificinformation:

• Fatigue material properties

• Fatigue load variations

• Fatigue analysis options

Fatigue results

During the solve, the load variation parameters are combined with otherfatigue criteria, and the software performs fatigue analysis calculations toevaluate the structure’s durability. Durability is assessed and displayed ascontour plots in the following areas:

• Structural strength (Stress Safety Factor)

• Fatigue strength (Fatigue Safety Factor)

• Fatigue life (Fatigue Life)

Preparing the model for a durability analysisTo prepare the model for a durability analysis, first perform the initial stepsfor a linear static analysis:

1. Open or create the part or assembly.

2. In Advanced Simulation, create new FEM and Simulation files.

3. Create a linear statics solution. You will not need to perform a solve.


20


4. Apply loads and constraints; mesh the model.

5. Make sure to assign a material that contains fatigue properties.

Creating a durability solutionTo create a durability solution:

1. With the Simulation node selected, create a new solution process (MB3 →New Solution Process → Durability Solution).

2. Assign a name to the solution and specify durability parameters. ClickOK.

3. In the Simulation Navigator, select the Durability solution node.Right-click and select New Load Variation.


20


4. Select the Durability solution node you just created; right-click and selectSolve.

5. After the solve is complete, select the Results node in the SimulationNavigator; double-click. Post Processing opens.

6. Under the Results node, pick one of the results types.

Evaluating fatigue resultsThe fatigue result types correspond to the fatigue evaluation options:

• Stress Safety Factor

• Fatigue Safety Factor

• Fatigue Life Factor

You can view each of these result sets in a post processing display. Stresssafety results are displayed as linear scale by default, while fatigue safetyand fatigue life results are displayed as log scale.


20


Viewing fatigue results

To access fatigue results:

1. After the solve is complete, select the Results node in the SimulationNavigator; double-click. Post Processing opens.

2. Under the Results node, pick one of the results types (see below fordescription).

Stress Safety Factor results

The software calculates Stress Safety Factor as a function of the time historyof effective stress (von Mises, maximum or minimum principal stresses) todetermine the failure index results set for the structure. Values greater than1 are acceptable; values less than 1 indicate failure.

Fatigue Safety Factor results

Fatigue safety results reflect the fatigue safety factor due to the cyclic loadingconditions you defined in the fatigue duty cycle. For a design to be consideredfeasible, the fatigue safety factor must be greater than 1.

In addition:

• An area where the fatigue safety factor approaches infinity may be overlydesigned for this particular event. You probably don’t need to pay muchattention to it.

• An area where the fatigue safety factor is less than or equal to 1 willeventually be damaged by repeating the given fatigue duty cycle.

• Lower fatigue safety factor values indicate that the cyclic stress rangeduring the fatigue duty cycle was high.

Fatigue Life results

Fatigue life is expressed as a real scalar results set that evaluates the numberof fatigue duty cycles before crack initiation occurs.

ActivitySee the “Durability (fatigue) analysis” activity in the Applications ofAdvanced Simulation Workbook.

In this activity, you will perform a durability (fatigue) analysis.


20



• Learned how to create a durability solution.

• Learned about durability results types.


21Lesson

21 Buckling analysis

Objectives

• Use linear buckling in an analysis


21

Buckling analysis

Linear buckling overviewBuckling analysis is a technique used to determine buckling loads andbuckled mode shapes. A buckling load is the critical load at which a structurebecomes unstable, and a buckled mode shape is the characteristic shapeassociated with a structure’s buckled response.

A linear buckling analysis identifies the loading conditions that make astructure unstable and result in various buckled mode shapes, as determinedby the eigenvalue extraction method and the number of modes for whichthe analysis is solved.

In a linear statics analysis, a structural model is normally considered to bein a state of stable equilibrium. As you remove the load previously applied,the structure goes back to its original position. However, under certainloading combinations, the structure becomes unstable. When this loading isreached, the structure continues to deflect without an increase in the loadingmagnitude and "buckles" or becomes unstable.

To build the model for a linear buckling analysis, choose the Linear Bucklinganalysis. Before performing the Solve operation, enter a number for therequired buckled shape modes and, if desired, the upper and lower eigenvaluerange. A default value (usually the lowest number of modes) is given if thesevalues are not defined.

Loads in linear buckling analysisIf the analyzed model only contains a buckling load (that is, a load, whichwhen large enough, would cause the system to become unstable), the criticalbuckling load is the load multiplied by the eigenvalue.

The model can contain one or more buckling loads and also other loads thatwould not cause buckling on their own, but instead act on the part by makingit more (or less) likely to become unstable. The figure below illustrates onesuch case.


21

Buckling analysis

P1 is the buckling load and P2 is a load that makes the part more likely tobecome unstable. The part in the example will become unstable for a lowervalue of P1 than the same part without P2.

P2 may be a known load acting on the part. You may want to find out thevalue of P1 at which the part becomes unstable.

With a linear buckling solution, you cannot keep P2 constant and analyze thepart only for buckling caused by P1. The linear buckling solution considersall loads as a system. The relation between the loads is not considered tochange. For example, if the part is analyzed with P1=1 and P2=0.5 and thelowest eigenvalue turns out to be 500, the system is calculated to be unstablefor the load combination: P1=500 and P2=250.

Supported environmentsAdvanced Simulation supports the following linear buckling environments:

• Nastran - SEBUCKL105

• ANSYS - Buckling

• ABAQUS - Buckling Perturbation Substep


21

Buckling analysis

ActivitySee the “Buckling analysis” activity in the Applications of AdvancedSimulation Workbook.

In this activity, you will analyze a strap to determine the first three bucklingmodes.


• Learned how to use linear buckling in an analysis.


22

Lesson

22 Modal analysis

Objectives

• Learn how to perform a modal analysis.


22

Modal analysis

Modal analysisDynamic analysis is an important part of any design involving non-staticstructure. These analyses are frequently performed to ensure that the naturalfrequency of a given part does not coincide with that of a certain input orforcing function. These forcing functions can occur in nature from such causesas wind or other parts of a mechanical system (such as a nearby engine).

Use of modal analysis

Below are a couple reasons for running a dynamic analysis and verifying thatthe forcing function frequency does not coincide with the part being analyzed:

• If the natural frequency of the part happens to be the same as that of theforcing function, an amplification of vibration may result, imparting moreload into the part than intended. This amplification can also carry overinto any mating parts, resulting in a vibrating system.

• If the natural frequencies are close, the product may vibrate. Althoughthe vibration may not be detrimental to the strength of the system, itcan present discomfort to the user.

Modal analysis and material properties

In order to perform a dynamic analysis, the density must be specified in thematerial properties listing. Failure to specify the density and assign it to themesh will yield a result without natural frequencies.

Submitting a dynamic analysis

Several parameters must be specified before submitting a dynamic analysis.Upon selecting Solve, choose Edit Solution Attributes, and the Edit Solutiondialog is displayed.


22

Modal analysis

To submit the analysis, you must first specify the frequency range of interestand number of modes you wish to find. From the Modal Generation menu,


22

Modal analysis

choose Modes/Frequency to activate the Frequency Range Lower Limit andUpper Limit fields.

Knowing the input frequency, you would typically specify a broad rangearound it, within the range of interest field. For example, for a forcingfrequency of 500 Hz, you could specify a lower limit of 0 and an upper limit of1000. It should be noted that this frequency range is in Hertz units.

The Number of Desired Modes corresponds with the number of mode shapesfor that part. Typically there is one natural frequency that corresponds to agiven mode shape. The higher the number of mode shape, the less extremeare the deflections that correspond to the frequency of that mode. The firstmode shape normally results in the highest local deflection of a part. The firstfour mode shapes are typically requested when performing an analysis.

Generally, a dynamic analysis is submitted without any type of loading;however, the part must be constrained in accordance with a real-life situation.If a structural analysis is being performed, the simplest way to transition to adynamic analysis is to delete the loads and submit the model with constraintinformation only.

Mode shapes of a modal analysis

Mode shapes illustrate the deflection of the part when subjected to vibration.A mode shape develops when the vibration frequency reaches the naturalfrequency. At this point the part is considered to be in a steady state.

Post processing a modal analysis

For modal analysis the frequency results are displayed, ranging from lowestto highest natural frequency in the specified range.

The results are ordered by mode shape, with the lowest natural frequencybeing the first mode shape, the next highest the second mode shape, andso on. Selection of the various results shows the mode shape. The naturalfrequency for that mode shape is displayed with the result selection.

All post processing tools are available when processing the model results.This includes the animation tool. The animation tool is particularly usefulwhen visualizing mode shapes.

The displayed deflections are relative to other grid points in the model andshould not necessarily be considered true deflections.

ActivitySee the “Modal analysis” activity in the Applications of Advanced SimulationWorkbook.

In this activity, you will perform an modal analysis on a speaker cabinet.


22

Modal analysis


• Learned how to perform a modal analysis.


23

Lesson

23 Thermal analysis

Objectives

• Learn how to perform a thermal analysis.


23

Thermal analysis

Thermal analysisThermal analysis is an important part of any design intended to function overa broad range of temperatures. There are usually certain design conditionsthat a given part must be designed to withstand. Thermal analysis is onetool employed to verify this criterion.

Thermal model preparation

Preparation of a thermal model is similar to preparation of a structuralmodel. With a structural model, the part must be both constrained and loadedto obtain a result. With a thermal model, constraints only may be specified ora combination of constraints and loads, depending on the application.

There are a number of different types of loads and constraints available whenperforming a thermal analysis.

One parameter that is required with a thermal analysis is the coefficientof conductivity. A value must be assigned to the mesh. Failure to enter aconductivity coefficient will yield no results as the solver does not know therate at which heat flows through the assigned material.

Post processing a thermal model

Thermal models are post processed similar to dynamic and structural models.

When viewing the results of a thermal model, you can animate the result andview the temperature changes throughout the model.

Also helpful as an available option is the ability to target the highesttemperature node or element.

Determining thermal stresses and strains

From various strength of materials and linear elasticity concepts, we knowthat thermal loading is not capable of causing direct stress, but insteadcauses thermal strains. Depending on how the part is constrained, thesethermal strains may result in thermal stresses.

For example, if a part is constrained at both ends over a length and issubjected to a positive temperature load, the part will tend to grow. Becausethe part is fully constrained at both ends, it is not able to grow. This resultsin thermal stresses. If one end of the part was free, the part would growwithout incident and no thermal stress would develop.

To calculate these stresses and strains the part must first be loaded with thethermal loads or constraints. The part is then structurally constrained. Themodel would then be run as a structural analysis and post processed. If thereare no structural loads applied, the resulting stresses and strains must bedue to thermal loading. It should be noted that in linear elastic analysis,


23

Thermal analysis

these thermal stresses and strains are additive to the structural stressesand strains.

Submitting a thermal model for analysis

When submitting a thermal model for analysis, choose Edit SolutionAttributes on the Solve dialog. On the Edit Solution dialog, enter the DefaultInitialization Temperatutre, which is a start temperature for all the nodesthat do not have a temperature assigned. This gives the solver a startingpoint that is closer to the ending temperature, resulting in fewer iterations.This can actually lower the run time of the model.

Material considerations of temperature

When considering varying ranges of temperature, attention must be paid tothe material properties. Material properties typically vary with temperature.


23

Thermal analysis

As a material is removed from room temperature, property degradation willoccur. For an accurate analysis, this degradation must be accounted for.

One way to accomplish this is to use multiple names of the same materialwith different material values. For example, aluminum may be denoted bythe numbers 1 through 5. They can then be defined as being in a category of atemperature range. Consult your local material information specificationsfor temperature range and degradation amounts.

ActivitySee the “Thermal analysis” activity in the Applications of AdvancedSimulation Workbook.

In this activity, you will perform a thermal analysis. You will also create andsolve a second solution using the same model.


• Learned how to perform a thermal analysis.


24

Lesson

24 Contact and gluing

Objectives

• Learn how to analyze surface to surface contact

• Learn how to analyze advanced nonlinear contact

• Learn how to analyze gluing


24

Contact and gluing

Surface to Surface Contact

Surf to Surf Contact lets you define contact between two surfaces.

To define the contact, select a source region and target region in theSimulation model. On the Create Surf to Surf Contact dialog, enter theparameters to define contact between these two surfaces.

To define additional contact parameters for the solver and solution type, usethe Edit Solution dialog. These solvers and solution types support surface tosurface contact:

Solver Solution Type

NX Nastran SESTATIC 101 (Single Constraintand Multi Constraint)

ANSYSLinear Statics

Nonlinear StaticsABAQUS Structural — General Analysis


24

Contact and gluing

When the solution is set to the NX Nastran solution type SESTATIC101, there are two commands for defining surface contact: Surf toSurf Contact, and the legacy command Surface Contact Mesh. UGSrecommends that you use Surf to Surf Contact to define contactbetween two surfaces. Unlike Surf to Surf Contact, Surface ContactMesh generates contact (or gap) elements between the two surfaces.

Defining surface to surface contact

To define surface to surface contact:

1. In the Simulation Navigator, right-click on Simulation Objects Container→ New Simulation Object → Surf to Surf Contact.Make sure that your solution supports surface to surface contact.

2. Select the first surface (the source region).

3. In the Create Surf to Surf Contact dialog, click Target Region.

4. Select the second surface (target region).

5. In the Create Initial Temperature dialog, enter parameters for the contactbetween these two surfaces and click OK.

Advanced Nonlinear Contact

Create Advanced Nonlinear Contact lets you define surface-to-surfacecontacts on shell and solid element faces in an advanced nonlinear solutionfor NX Nastran. This dialog box is available when the Solution Type isADVNL 601,106.


24

Contact and gluing

To define the contact, select a source region and target region in theSimulation model. On the dialog box, enter the parameters to define contactbetween these two surfaces. Specify the Target Region Type as FLEX(flexible) or RIGID. When you use a rigid target region (meaning the targetcontact surface is rigid and the rest of the target part is flexible), you canuse the optional selection step, Optional node for rigid target displacement

. Choose this step to select a single node or point as a “master” nodeto control the motion of the rigid target region. Internally, rigid links willconnect all the nodes on the rigid target region to this master node.

Defining advanced nonlinear contact

Only NX Nastran SOL 601,106 supports advanced nonlinear contacts.

1. In the Simulation Navigator, right-click on Simulation Objects Container→ New Simulation Object → Advanced Nonlinear Contact.


3. In the Create Advanced Nonlinear Contact dialog, click Target Region

.


24

Contact and gluing

4. Select the second surface (the target region).

5. If you set the Target Region Type to RIGID, you can click Optional node

for rigid target displacement . Then select a single node or pointas a “master” node to control the motion of the rigid surface. Internally,rigid links will connect all the nodes on the rigid target region to thismaster node.

6. Enter any additional parameters for the contact between the two contactsurfaces and click OK.

Surface to Surface Gluing

Create Surf to Surf Gluing lets you connect two surfaces to preventrelative motion in all directions.

To glue two surfaces, you must first define the regions where you want tocreate glue elements (stiff springs that connect and constrain the surfaces).A region is a collection of element free faces in a section of the model whereyou expect gluing (or contact) to occur. These regions can be created usingshell elements and using free faces of solid elements. Select a source regionand target region in the Simulation model. In the Create Surf to Surf Gluingdialog box, enter the parameters to define the contact between these twosurfaces.


24

Contact and gluing

This option is available for all structural NX Nastran solution sequencesexcept for SOL 601 and 701. It is not supported in thermal or axisymmetricsolutions.

Defining surface to surface gluing

Only NX Nastran supports surface-to-surface gluing.

1. In the Simulation Navigator, right-click on Simulation Objects Container→ New Simulation Object → Surf to Surf Gluing.


3. In the Create Surf to Surf Gluing dialog, click Target Region.

4. Select the second surface (the target region).

5. Enter parameters for the contact between these two surfaces and click OK.

ActivitiesSee the “Contact and gluing” activities in the Applications of AdvancedSimulation Workbook.

In these activities, you will learn how to set up and perform contact andgluing analysis problems.


• Learned how to define surface to surface contact.

• Learned how to define advanced nonlinear contact.

• Learned how to define surface to surface gluing.


201051792337561

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