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NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
OpenVSP Structural Modeling Capability
Presented by:
Justin Gravett
Empirical Systems Aerospace, Inc.
Work Supported by:
AFRL SBIR PHASE II: OpenVSP Smart Conceptual Design Tool
Improvements, Including Aerodynamic Analysis, Conformal Feature,
and Structure Modeling
NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
Agenda
• Introduction
• Development Overview
• Structural Entities
• VSP Terminology
• Typical Workflow
• GUI Overview– FEA Part Types
• Results
• Demo
• Tutorial
• API & Scripting
• Known Issues
• Contact Information
NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
Introduction
• Goal:– Extend OpenVSP to support modeling of aerospace
structures and generation of FEA meshes
• Features:– Parametric modeling of full depth structural members
– Extension of sub-surface capabilities to structural modeling
– Support for beam and shell FEA elements
– Key point identification of FEA nodes
– Export to NASTRAN, Abaqus/Calculix, and Gmsh FEA mesh formats
NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
Development Overview
Structures v2 Capabilities:
• Maximum one structure per vehicle
• Only wing geometries with ribs and
spars
• Shell elements only
• Smeared material properties for
partial or zero-depth entities
• Point mass not included in mesh
Structures v3 Capabilities:
• Multiple structures on multiple
geometries
• 12 total FEA part types
• Zero-depth entities
• Materials and properties library
• Mesh visualization tools
• Point mass as fixed mesh node
NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
Structural Entities
Full-depth:
• Shell type of structure
• Extend completely
through skin
• Examples: rib, spar,
floor, pressure dome,
fully-closed bulkhead
Partial-depth:
• Shell or beam types
• Do not extend
completely through
skin
• Examples: former,
frame, partially-
open bulkhead
• NOT SUPPORTED
Zero-depth:
• Beam type of structure
• Sub-surface edge or
intersection curve
• Cross-section properties
• Examples: stringer,
longeron, stiffener
Key-points:
• Fixed FEA node
• Provide connectivity
to other structures
• Application of point
load or mass at
specific locations
Reference:
https://www.faa.gov/regulations_policies/handbooks_manuals/aircraft/amt_airframe_handbook/media/ama_ch01.pdf
NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
VSP Terminology
Structure
• A collection of FEA Parts
• More than one structure allowed per geometry
• Only one geometry per structure
FEA Part
• A structural entity
• Includes full-depth, zero-depth, key-points, etc.
FEA Element
• A group of interconnected FEA Nodes
• Elements are assigned element properties
FEA Node
• A coordinate point used to build FEA Elements
• An FEA Node can be assigned to multiple FEA Elements
• Key-Point or Fixed Point is a specific FEA Node
Shell
• Triangular FEA elements (full-depth)
• NASTRAN: CTRIA6; Abaqus/Calculix: S6
Cap
• Beam FEA elements (zero-depth)
• NASTRAN: CBEAM; Abaqus/Calculix: B32
Structure
FEA
Parts
Cap
Shell
FEA
Node
NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
Optional Settings
External Tools
Add Geom
Add/Modify
PropertiesAnalysis->
FEA Mesh…
Add and
Modify Parts
Add Materials
Run “Mesh
and Export”
Visualize
Results
Post-Process
and Analyze
Calculix
NASTRAN
Gmsh
Abaqus
Add
Structure
Adjust Mesh
Settings
Typical Workflow
NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
GUI Overview: Structure Tab
Consistent Unit System
Structure
Browser
Geom & Surface Selection
Status Window
Add/Delete
StructureStructure Name
Execution of
Current
Selection
Features:
• Structures for all geometry
types except Blank and
Hinge
• Multiple structures per
geometry
Display Degen
Preview
NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
GUI Overview: Part Tab
FEA Part ReorderingFEA Part
Browser
Type Specification &
Add/Delete FEA Part
FEA Element Type and
Property AssignmentFEA Part
Visibility
FEA Part
Name &
Editing
Features:
• Selection and control of
multiple FEA parts
• Reordering for sub-surface
overlap priority
• Shell: triangle elements;
Cap: beam elements
NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
FEA Part: Slice
1. Slice
• Cutting plane defined by orientation, center location, and rotation
• Orientation: parallel plane for slice defined from body or absolute axes
• Distance specified as relative or absolute
➢ Relative: fraction of length
➢ Absolute: fixed location
• Slice can be full-depth, zero-depth, or both
1
Shell
Cap
Shell
& Cap
NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
FEA Part: Rib and Spar
2. Rib (wing only)
• Slice defined from leading edge to trailing edge
• Option for perpendicularity to wing leading edge, trailing edge, or any spar
3. Spar (wing only)
• Slice defined from root to tip
• Option to constrain to specific wing section
2 3
NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
FEA Part: Dome
4. Dome
• Semi-ellipse cutting surface
• Defined by radius (A, B, C), center location (X, Y, Z), and rotation
• Note: Must be oversized correctly to intersect skin
• Not available for Wing geometries
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NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
FEA Part: Fix Point
5. Fixed Point
• Forced FEA Node
• Specified on parent skin surface or any FEA Part surface
• Defined in surface coordinates (U, W)
• Point mass support
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NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
FEA Part: Sub-Surface
6. Line
7. Rectangle
8. Ellipse
9. Control Surface
FEA Sub-Surfaces:
• All “normal” sub-surface options and parameters
available for FEA sub-surfaces
• Tag: Identifies triangular shell elements for the
sub-surface
• Cap (no tris): Only beam elements, used to create
holes or stiffeners
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NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
FEA Part: Array
10. Rib Array
11. Slice Array
12. Line Array
• Caps only
FEA Arrays:
• Group of FEA Parts defined by spacing, starting
location, and direction
• Distance: “Relative” for fixed # of parts; “Absolute”
for fixed distance between parts
• “Individualize” creates independent FEA Parts
➢ Note: This action cannot be reversed
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NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
Features:
• Only linear, temperature-independent,
and isotropic materials
• Material library available to all structures
GUI Overview: Material
NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
Features:
• Property library available to all
structures
• Properties specific to element type
➢ Shell property: Defined by material
and thickness
➢ Beam property: Defined by
material, cross-section area, and
area moment/products of inertia
GUI Overview: Property
NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
Features:
• Mesh settings specific to each structure
• Half mesh for symmetric structures
• Exports:
➢ *.stl and *.msh (no material
properties)
➢ Mass data file
➢ NASTRAN
➢ Abaqus/Calculix
GUI Overview: Mesh
NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
Features:
• Mesh must be generated first
• Colors distinguish elements and nodes
for different FEA Parts
• Visualization of triangle orientation
vector and beam normal vector
• Separate sets for shell and beam
elements
GUI Overview: Display
NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
Set Boundary
Condition Nodes
OpenVSP FEA Mesh
Set Load
Nodes
Export to
Calculix
Results
NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
Results
Modal Analysis:
Mode 2
Displacement
Concentrated
Load on Wing
Tip Nodes
NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
Demo
NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
Tutorial
NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
API & Scripting
• Structure Functions in API:– AddFeaStruct( const string & in geom_id, bool init_skin = true, int
surfindex = 0 )
– DeleteFeaStruct( const string & in geom_id, int fea_struct_ind )
– SetFeaMeshVal( const string & in geom_id, int fea_struct_ind, int type, double val )
– SetFeaMeshFileName( const string & in geom_id, int fea_struct_id, int file_type, const string & in file_name )
– ComputeFeaMesh( const string & in geom_id, int fea_struct_ind, int file_type )
– AddFeaPart( const string & in geom_id, int fea_struct_id, int type )
– AddFeaSubSurf( const string & in geom_id, int fea_struct_id, int type )
– AddFeaMaterial( )
– AddFeaProperty( int property_type = 0 )
• Examples:– \repo\src\geom_api\APITestSuite.cpp
– \repo\examples\scripts\FEAMesh.vspscript
NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
Known Issues
Issue Status Notes
Mesh errors for slice on wing root or tipPlanned
Progress
Rib placement
currently constrained
No surfaces identified if all feature lines
suppressedIn Progress
Issues with overlapping planar surfacesPlanned
Progress
Status message display occasionally fails In ProgressIssue in FEA and
CFD mesh GUIs
General beam properties not fully supported
by CalculixNo Plan
*BEAM GENERAL
SECTION not
recognized
Problems with multiple slice intersections
along length of Pod
Planned
Progress
NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
Questions?
NNX09CC86P SBIR Review, Presented to NASA, July 7th, 2009OpenVSP Workshop 2017 Aug. 30th – Sept. 1st
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Empirical Systems Aerospace, Inc. www.esaero.com
Contact Information
Justin Gravett