let’s get together: using fasteners in fea

Let’s get together: Using fasteners in FEA

Andrew Sartorelli David TruyensTechnical Support Specialist Simulation Business Development Specialist

This class covers the use bolted connections, welds, and other fastener types to join parts within multi-body assemblies inside Autodesk Nastran In-CAD, Fusion Ultimate, and Simulation Mechanical. Models will be demoed to show off the different workflows and to show how various approaches can affect results.

Class summary

At the end of this class, you will be able to:

Explain the differences between various fastener approaches

Understand the limitations of using fasteners over solid model components

Use automated connectors like Bolted Connections

Develop skills to construct connectors manually

Key learning objectives

Fasteners

What is a fastener?

Connector

Idealization

Bolt Weld JointSpring Rigid Body Elements

FastenersGlobal vs Local

Pre-processing Idealization methods Pre-loading Applications

Bolt – Pre-ProcessingBolt Calculator

Three main approaches

Contact

Solids

Beams and Bars

Bolts – Idealization Methods

Bolt – IdealizationContact

Bolts – Idealization MethodsSolids Hexagonal Head

Threads

Bevels

Strength Markings

Bolts – Idealization MethodsSolids

Bolts – Idealization Methods1D Elements

Bolt – Pre-load

Why is tensioning important?

Direct impact on stiffness

Bolt – Pre-loadBeamNastran In-CAD Fusion Simulation Mechanical

No ability to add an axial pre-load to solid elements

Or is there?

Yes! Thermal loading

Bolt – TensioningSolid

Bolt – Pre-loadingSolid

Use thermal loading to induce axial compression

𝜎 =𝐹𝑜𝑟𝑐𝑒

𝐴𝑟𝑒𝑎→ 𝐹𝑜𝑟𝑐𝑒 = 𝜎 ∗

𝐴𝑟𝑒𝑎

𝐸= 𝜀 → 𝜎 = 𝜀 ∗ E

𝜀 = α ∗ ∆𝑇 𝐹𝑜𝑟𝑐𝑒 = α ∗ ∆𝑇 ∗ E ∗ Area

𝐹𝑜𝑟𝑐𝑒 = α ∗ ∆𝑇 ∗ E ∗Area

α =𝐹𝑜𝑟𝑐𝑒

∆𝑇∗E ∗Area Assume ∆𝑇 = 1℃ Orthotropic material

α in axial direction from above

α in other directions should be ~0

Bolt – Pre-loadingSolid

α =𝐹𝑜𝑟𝑐𝑒

∆𝑇∗E ∗Area

α =700𝑙𝑏𝑓

1𝐹∆∗2.9e7 ∗0.25𝑖𝑛2∗𝑝𝑖

α = 1.229e-4 / F

Case Study: Eccentric Bolt Loading

P = 1200 lbf L = 8” W = 6” t = .375”

Bolt Diameter is variable

By the instantaneous center theory

Fm = 707 lbf

Case Study: Eccentric Bolt LoadingFree Body Diagram

Bolt 1

Fy = P/4 + Fm cos(θ)

Fy = 200lbf

Fz = Fm sin(θ)

Fz = 500lbf

Diameter Mesh Density Linear or Non-linear

0.25”

0.50”

0.75”

0.03”

0.07”

0.2”

0.4”

0.6”

Case Study: Eccentric Bolt LoadingComputed Force in Y direction for Bolt 1

0.03" 0.07" 0.2" 0.4" 0.6" .8" 1"

Mesh Sizing

Shear Force - Y, Linear

0.75" Diameter

0.5 Diamater

0.25 Diameter

Analytical Solution

0.03" 0.07" 0.2" 0.4" 0.6" .8" 1"

Mesh Sizing

Shear Force - Y, Non-Linear

0.75" Diameter

0.5" Diameter

0.25" Diameter

Analytical Solution

Case Study: Eccentric Bolt LoadingComputed Force in Z direction for Bolt 1

0.03" 0.07" 0.2" 0.4" 0.6" .8" 1"

Mesh Sizing

Shear Force - Z, Linear

0.75" Diameter

0.5 Diamater

0.25 Diameter

Analytical Solution

0.03" 0.07" 0.2" 0.4" 0.6" .8" 1"

Mesh Sizing

Shear Force - Z, Non-Linear

0.75" Diameter

0.5" Diameter

0.25" Diameter

Analytical Solution

Case Study: Eccentric Bolt LoadingMesh Sensitivity Study

0.00E+00

1.00E+05

2.00E+05

3.00E+05

4.00E+05

5.00E+05

6.00E+05

7.00E+05

0.030.070.20.4

Mesh Size (in)

Stress - Linear Stress - Non-linear

Case Study: Eccentric Bolt LoadingShells

Key tips for using plates Check your normal

direction

Use a contact offset

Select edges for bolt connector

Case Study: Eccentric Bolt LoadingShells

Variance in shear forces regardless of mesh density

Correlation of displacements to solid models

Appropriate bolt size and preload should be done before FEA

Refining the mesh around the bolt holts doesn’t improve results!

Case Study: Eccentric Bolt LoadingTakeaways

0.03" 0.07" 0.2" 0.4" 0.6" .8" 1"

Mesh Sizing

Shear Force - Y, Non-Linear

0.75" Diameter

0.5" Diameter

0.25" Diameter

Analytical Solution

0.03" 0.07" 0.2" 0.4" 0.6" .8" 1"

Mesh Sizing

Shear Force - Z, Non-Linear

0.75" Diameter

0.5" Diameter

0.25" Diameter

Analytical Solution

Are we concerned with load transfer or weld failure?

Load transfer

Global modeling approach using contact

Weld failure

Local modeling approach to extract forces

Welds - Idealization Methods

1. All Solids

2. Plates with solid fillet welds

3. Plates with in-plane weld elements (Different properties)

4. Plates with shells mapping to theoretical weld face placement

5. Node-to-Node Rigid Links

6. Continuous Plate Intersections

7. Beam Stiffeners at Plate Intersections

Modeling of Seam Welds

1 3 4 5 62

All methods are used regularly in a variety of industries

Varying amounts of effort required based both on method and automated tools in FE pre-processor

Consider meshing error Shell-Solid interfaces Contact

None of them improve the local validity of in-weld stress but…

All transfer load with varying degrees of correctness

#1 – Solids may allow you to validate a weld size choice (Hard)

#6 – Allows calculation of the right weld size (Easy)

Modeling of Seam Welds

Extracting Weld Loads | Autodesk Nastran In-CAD

1,000# separate load case in each direction

2.0 in.

5.0 in. Weld Forces:Normal = 1,000 lb/5 in = 200 lb/inShear = 1,000 lb/5 in = 200 lb/inMoment = (1,000 lb * 2 in)/5 in

= 400 in-lb/in

Tip 1 – Align Element Direction to Surface Direction

Tip 2 – Plot Unaveraged Elemental Results

Shell Membrane FYShell Membrane FXYShell Moment MY

Tip 4 - Use Element Groups!

Tip 3 – Add Element Force to Output Set

Max = 500 lb/inAvg = 200 lb/in

Max = 271 lb/inAvg = 200 lb/in

Max = 390 in- lb/inAvg = 375 in- lb/in

Why so far off?OK to max Nodal force

Other Connectors

Rigid Connectors

Rigid and rods

Rigid Interpolation

Results

Interpolation Interpolation

Rod Rod NL Ridgid Ridgid NL

Displacement VM

Results

Ridgid Rod Interpolation Ridgid NL Interpolation

Rod NL

Stess VM

Cables

Are always nonlinear Use preload or pre-slack

Cables

2D Model

When working with frame generator make sure to add work points at assembly level

A mast is Non-Linear due to cables and P-Delta effect

Buckling

Easy to switch in Nastran In-CAD

Vibration

Best to use a dedicated model for each cable

Other considerations

3D and cables

Use RGB’s to connect to the solid Turn on forces

3D and cables

Your class feedback is critical. Fill out a class survey now.

Use the AU mobile app or fill out a class survey online.

Give feedback after each session.

AU speakers will get feedback in real-time.

Your feedback results in betterclasses and a better AU experience.

How did we do?

Autodesk is a registered trademark of Autodesk, Inc., and/or its subsidiaries and/or affiliates in the USA and/or other countries. All other brand names, product names, or trademarks belong to their respective holders. Autodesk reserves the right to alter product and services offerings, and specifications and pricing at any time without notice, and is not responsible for typographical or graphical errors that may appear in this document. © 2016 Autodesk, Inc. All rights reserved.

let’s get together: using fasteners in fea

Documents

industrial & automotive fasteners by fasteners & fittings,...

stainless steel fasteners fasteners product catalogue...

fea information inc. worldwide news for january - fea...

fea 2016 (v1.1) release date: june 25,...

roofing fasteners range - fortress fasteners fortress... ·...

1 automotive fasteners 2 fasteners for every application

fasteners bolts and clamps by twist fasteners, new delhi

introduction to finite element analysis (fea) or finite...

the common core and science - fea - njpsa and fea

versaclipper 4000 - vertex fasteners - vertex fasteners

wood shop: fasteners, joinery, & adhesives metal shop:...

fea/iri/usp coordinator: ricardo abramovay ·...

fea information engineering solutions april 2012 - fea...

fixings & fasteners // product finder fixings & fasteners

fea plantations project 2009 -...

is 1367-18 (1996): industrial fasteners - threaded steel...

fea-2107 fea-2107-bb fea-2107-d fea-2807 model...

fea-2x07, fea-2x07-d series ecdis operator’s guide about

particle dynamics with mbd and fea using...

automotive fasteners & components · locks & locking...