268795495 Solidworks Simulation Training Chapter 3

Ι © Dassault Systèmes Ι Confidential Information Ι

SolidWorks Simulation Training SolidWorks 2012

1


About this course

     

Prerequisites Course Design Philosophy Using this book A note about files Conventions used in this book Class Introductions

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Design Validation Products Simulation Premium


SolidWorks Premium

Simulation Professional Frequency/ Buckling

Nonlinear Fatigue

Optimization

Static Composites

SolidWorks Motion

Thermal

Drop Test

3

Pressure Vessel

Advanced Dynamics

What is Finite Element Analysis? Example: Brick road from home to mailbox – measure the distance of a curved path using yard stick


 Curved path is approximated by straight segments  Measure using a yard stick

4


Building the FEA Model CAD Model Stress Results

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Building the FEA Model - Fixtures


 Represent how the given model is attached to the rest of the world  Fixed on a Surface or Edge or Point  Allow Sliding or Rotation

 Fixtures used to reduce the size of the problem to a component level or subassembly level

6

Building the FEA Model - Loads 

Loads applied to exterior surfaces of the model 


 



Forces on Surfaces or Edge or Points Torque, Moment Pressure

Loads acting on entire model  

Gravity, Centrifugal force Thermal loads

7


FEA for structural analysis

Split the fitting into small tetrahedral pieces and approximate the deformation on each piece

Example of a fitting

8



Example of a bracket

Split the surfaces of bracket into small triangular pieces and approximate the deformation on each piece 9



Example of a frame structure

Split the members of frame into small straight pieces and approximate the deformation on each piece 10


Mesh, Nodes, Elements, …

 MESH – Approximate representation of the CAD geometry using Tetrahedra or Triangles  ELEMENTS – Tetrahedra or Triangles in the Mesh  NODES - Points at which different elements are jointed together; nodes are the locations where values of unknowns (usually displacements) are to be approximated

11

Using Stress Results to Validate Design  Stresses at a point are defined by 6 quantities – 3 normal stress and 3 shear stresses – depend on orientation of coordinate system


 Von Mises “Equivalent” Stress =

VON is independent of coordinate system  Principal Stresses – 3 normal stresses specified in a special coordinate system for which shear stresses are zero  Factor of Safety =

12


Assumptions in Linear, Static Analyses  Response is proportional to the applied loads  If you double the load, deformation also gets doubled  If you remove the load, model has no deformation  Material is linearly elastic  The part returns to its original shape if the loads are removed (no permanent deformation)  Loads are static  Loads are applied slowly and gradually. Rapidlyapplied loads cause additional displacements, strains, and stresses 13

Small deformation

Large deformation

Check list for SolidWorks Simulation

1.

Material?




2.

Steel 1040

Physical Working Condition?  

3.

Pressure or force Bolted or Welded

Modeling in SolidWorks Simulation 

4.

TRAINING

Is my Design OK (Results)  

Factor of Safety Stress

14


Lesson 1 The Analysis Process

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Lesson 1 Topics  Introduction to the Simulation interface  Perform linear static analysis – Static study • Material properties • Restraints • Loads • Mesh • Run  Influence of mesh density on displacement and stress results  Post-processing 16

SolidWorks Simulation interface CommandManager tab Analysis library


Toolbar

Study tree Simulation Advisor Study tabs

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Loads and restraints

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Lesson 1: Results


von Mises Stresses in coarse study

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Lesson 1: Results


von Mises Stresses in default study

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Lesson 1: Results


von Mises Stresses in fine study

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Lesson 1: Results


Summary of results – convergence study

Finer mesh More accurate results

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More computational time

Lesson 1 Results


 Comparison with analytical

 Which result is correct???

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Exercise 1: Bracket

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Exercise 2: Compressive Spring Stiffness

k

F 0 .1   234.7 N m 3 u 0.426 10 25


Exercise 3: Container Handle

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Lesson 1: Questions

27

Lesson 2 Ι © Dassault Systèmes Ι Confidential Information Ι

Mesh Controls, Stress Concentrations and Boundary Conditions

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Lesson 2: Topics    

Using SolidWorks Configurations Use of mesh controls, automatic transition FEA Convergence issues Different boundary conditions

fillet configuration

no fillet configuration

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Loads and restraints

30


Lesson 2: Results No fillet configuration

31

Lesson 2: Results


Stress Results – mesh1, mesh2 and mesh3

1- When increasing the number of elements, will the stresses converge? 2- Why?

32

Lesson 2: Results


Fillet, Mesh Control

No Mesh Control

Mesh Control 33

Lesson 2: Results


Welded boundary condition

Fixed edge produces unrealistic stresses at the support location. 34


Lesson 2: Boundary Conditions

 Can greatly simplify the model  Can also affect results  Know your assumptions

35


Exercise 4: C-bracket

No fillet Filleted edge

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Exercise 4 Fixed hole

Stress concentrations

37


Exercise 5: Bone Wrench

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Exercise 6: Foundation Bracket

0.5 mm

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Exercise 6: Foundation Bracket

0.5 mm

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Lesson 2: Questions

41


Lesson 3 Assembly Analysis with Contact

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Lesson 3: Topics  Assembly Analysis Basics  Interference Detection  Global and Local Contact/ Gaps conditions

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Interference Detection

44

Global contact


 Default: Bonded  Global contact conditions  No penetration  Bonded (No clearance)  Allow Penetration

 Component Contact

 Uncheck Global Contact box  Overrides Global Contact

45


Contact/Gap Hierarchy

 Global and Component contact apply only to initial touching areas  Global contact for most common condition, component and local contact as needed 46

Local Contact Conditions


 For structural studies     

No Penetration Bonded Allow Penetration Shrink Fit Virtual Wall

 For thermal studies  Insulated (similar to Free in a static study)  Thermal contact resistance

 Friction at the local level for touching entities  Initial gap (clearance) can be ignored or accounted for by specifying it here 47

Loads and restraints, mesh 225 N


i) ii)

Global No Penetration contact Local contact

Fixed

225 N

48

Lesson 3: Results


Von Mises stresses - Global contact (225 N force)

(You can plot stresses in exploded configuration) 49

Lesson 3: Results


Von Mises stresses – With local contact (4500 N force)

Could we study the stresses on contact surfaces?

50


Exercise 7: Two Ring Assembly

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Lesson 3: Questions

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Lesson 4 Ι © Dassault Systèmes Ι Confidential Information Ι

Symmetrical and Free Self-Equilibrated Assemblies

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Lesson 4: Topics

 Analyze shrink-fit problem  Use of symmetry  Review stress results in local coordinate systems  Solver options to eliminate rigid body modes

54

Local Contact Conditions


Contact conditions (global & local) – review

Contact conditions (local only) – Shrink fit 1 - Program creates a shrink fit condition between selected faces. 2 - The faces may or may not be cylindrical.

(NOTE: Virtual wall – a sliding support (roller), with friction and wall elasticity capability)

55


Boundary conditions

56


Contact and Mesh

57

Lesson 4: Results


Hoop stress (using local cylindrical coordinates)

Why is there a jump in the hoop stress value across the interface? Would the assembly experience a similar jump58in radial stresses?


Exercise 8: Chain Link

59

Exercise 9: Chain Link 2


Incorrect solution

Correct solution

60


Lesson 5 Assembly Analysis with Connectors

61


Lesson 5: Topics

 Connectors  Rigid  Spring  Pin  Elastic Support  Bolt  Spot Weld  Edge Weld  Link  Bearing  Global and local contact conditions 62


Connectors

Spring Pins (three in all)

63


Boundary conditions and Mesh 225 N

Fixed 225 N

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Lesson 5: Results

65


Exercise 10 & 11

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Exercise 12: Shock Absorber Simplify the model


1. Suppress the original helical spring from the analysis. 2. Introduce “Spring Connector”.

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Exercise 12: Shock Absorber

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Exercise 13: Spot Welds Connector types – Spot Welds


Spot Welds

Spot Welds

69

Exercise 13: Spot Welds


Spot Welds - solid models - stress results

We notice high stresses in the vicinity of welds. Would the subsequent mesh refinement in these regions bring more accurate stress distribution? 70


Lesson 6 Compatible/Incompatible Meshing

71


Lesson 6: Topics

 Compatible solid element mesh with Bonded contacts  Incompatible solid element mesh with Bonded contacts  Simplified bonding for incompatible solid meshes

72


Compatible solid mesh

Bonding of touching parts is achieved by imprinting and merging the nodes. 73


Incompatible solid mesh

Bonding of touching parts is achieved by additional constraint equations. 74


Incompatible solid mesh: More Accurate Bonding

Surface based contact. Results at the contact interface are uniform but solution time is longer. 75


Incompatible solid mesh: Simplified Bonding

Node based contact. Results at the contact interface may be patchy but solution time is lower. 76


Lesson 7 Assembly Analysis Mesh Refinement

77


Lesson 7: Topics  Analyze larger assembly using solid elements  Remote load feature  Define multiple contact conditions  Nontraditional contact and connector use  Analyze mesh quality and question the results of the simulation

78

Remote loads


 Load (Direct transfer)  Load/Mass (Rigid connection)  Displacement (Rigid connection)

79


Bolt connectors

    

Bolt type Tight fit Material Pre-load Bolt series 80


Virtual wall

 Type of contact that replaces modeling a component  Rigid or Flexible

81

Lesson 7: Results


Draft mesh: mesh parameters and results

Mesh parameters are not ideal leading to excessive von Mises stress results 82

Lesson 7: Results


High mesh: mesh parameters and results

Mesh parameters improved, so did the results of the simulation. (NOTE: The time required to complete the simulation increased as well.) 83


Exercise 14: Bolt Connectors

84


Exercise 15: Awning

85


Lesson 7: Questions

86


Lesson 8 Analysis of Thin Components

87


Lesson 8: Topics

      

Shell Elements Mid-plane and surface shell element meshing Alignment of shell mesh Evaluating mesh sizes Evaluating results for shell elements Reaction forces Solid vs. Shell meshing

88

Lesson 8: Results Solid Elements – Von Mises Stress 55449 DOF

987978 DOF (2 element per thickness)


(1 element per thickness)

89


Shell elements Defined by:  Existing surface or sheet metal bodies  Mid-plane surfaces  Outside/inside faces of solid bodies

Mid-plane surface

Outside faces 90


Shell Type

Kirchoff Theory span  20 thickness

Mindlin Theory span 10   20 thickness

Thin shells ignore shear deformation through the thickness of the shell

91

Shell Element Alignment Shell Elements - Alignment


Misaligned shell elements

Incorrect stress result representation

92

Lesson 8: Results Shell Elements (midplane) – Von Mises Stress

Bottom (orange)


Top (gray)

93

Lesson 8: Results Shell vs. Solid Elements Shell elements can greatly decrease the required computational time. Ι © Dassault Systèmes Ι Confidential Information Ι

Modeling with shell elements is more demanding than with solids. * See results of Exercise 16

94


Case Study: Joist Hanger

Shell elements generated automatically for sheet metal features

95


Exercise 16: Bracket

96

Exercise 17: Shell Mesh Using Outer/Inner Faces Shell Elements (surfaces) – Von Mises Stress

Bottom (orange)


Top (gray)

Top

Bottom 97

Exercise 18: Spot Welds - Shell mesh


Spot Welds - shell model - stress results

Both solid and shell models predict similar behavior. Which one would you choose?

98

Exercise 19: Edge Weld Connector


Edge Welds - shell model – weld bead sizes

Design the size of the edge weld beads.

99

Exercise 20: Container Handle Weld


Self-guided exercise

Design double sided fillet welds connecting the container handle to the square plates.

100


Lesson 8: Questions

101


Lesson 8: Questions

102


Lesson 9 Mixed Meshing Shells & Solids

103


Lesson 9: Topics

   

Mixed meshing Solid-shell bonding Shell offset Mesh failure diagnostics

104

Mixed meshing


Why Mixed Meshing?

Some design assemblies may contain “bulky” parts suitable for solid mesh, as well as thin parts ideal for shell elements. 105


Solid and Shell Elements

 Compatibility problems in mixed solid and shell element meshing  Use of mixed mesh in simulation How many DOF does a solid element have?

How many DOF does a shell element have?

106


Bonding between solids and shells

 Hinge formed at the connecting edge  May introduce rigid body modes if not handled properly  Mesh incompatible at the interface  Bond generated through multi-point constraints internally (mortar bonding)

107

Hinge


Shell offset    

Mid-surface Top surface Bottom surface Ratio

 By default, mesh located at mid-plane  Orientation important when defining shells with different thickness

108


Mesh failure diagnostics

    

Incompatible mesh Mesh control Auto-looping Check geometry Switch mesher 109


Lesson 9: Results

Why are the stresses highest at the base near the support and bonded contacts? 110


Exercise 21: Mixed Mesh Analysis

111


Lesson 9: Questions

112


Lesson 10 Mixed Meshing Solids, Beams & Shells

113


Lesson 10: Topics

   

Beam elements Joints Bonding of beams Post-processing of beam elements

114


Beam elements

6 DOFs 115


Joints

 joints are connected to two or more beam members.  joints are connected to a single member only 116


Bonding of beams

Bond joints or entire beam to target entities • Beam profile imprinted on target entities • Accurate results at the interface

117


Lesson 10: Results

118

Results for beam elements


 Stress: Axial, bending, worst-case, torsional, shear  Displacement  Axial force diagrams  Shear & bending moment diagrams  Reaction forces & moments

Simply supported with uniform distributed loading 119


Exercise 22: Beam Elements

120


Exercise 23: Cabinet

121


Exercise 24: Frame Rigidity

122


Exercise 24: Frame Rigidity

123


Lesson 11 Design Study

124


Lesson 11: Topics  Design Study – performing several studies for different input data (model geometry or loads)  Stresses in vehicle suspension when vehicle is:     

Stationary and loaded Moving at constant acceleration on a smooth road Moving on a bumpy road Moving at a constant speed on a banking road Different loads in different directions

 Review different connectors and fixtures

125


Design Scenario with loads input

126


Lesson 11: Results (Loads input)

127


Design Scenario with geometry input

128


Lesson 11: Results (Geometry input)

129


Exercise 25: Design Scenarios

130


Lesson 12 Thermal Stress Analysis

131


Lesson 12: Topics    

Static analysis with temperature load Use of various contact conditions Temperature dependent material properties Soft spring and Inertia relief options

132

Lesson 12: Results Averaging across boundaries ON


Averaging across boundaries OFF

133

Lesson 12: Results


Axial strain at the sensor locations

134


Lesson 12: Results

135


Lesson 13 Adaptive Meshing

136

Lesson 13: Topics Why and What is Adaptivity?


What do FEM results depend on? 1. Mesh 2. Type and order of the elements used (Draft or High quality) 3. Other phenomena (numerical errors, modeling errors etc.) What is our Goal? Is it just to obtain a solution? Make sure our results are close to some defined accurate solution. (typical parameter is strain energy density) How to achieve it? 1. Modify and refine the mesh topology

h-adaptivity

2. Modify the “order” of elements

p-adaptivity

137

Adaptive Finite Element Analysis h-Adaptivity, p-Adaptivity


Refining the mesh (h-Adaptivity)

Changing the “order” of elements (p-Adaptivity)

… 1st order (Draft Quality)

5th order

2nd order (High Quality)

138

Lesson 13: Results


h-Adaptivity - results

98% convergence criteria (2% accuracy) was achieved in 6 iterations 139

Lesson 13: Results


p-Adaptivity - results

0.05% convergence criteria was/was not achieved in 4 iterations 140

Lesson 13: Results


Summary

Max. displacement difference: 0.2% Max. Von Misses stress difference:10%

Which method would you use? 141


Lesson 14 Large Displacement Analysis

142


Lesson 14: Topics

 Surface contact  Contact analysis with the large displacement option  Evaluate mesh adequacy for modeling bending stresses  Limitations of the linear material model

143

Lesson 14: Results


Small displacement contact analysis – Incorrect Displacements

144

Lesson 14: Results


Large displacement contact analysis – Correct Displacements

145


Lesson 14: Questions

146

268795495 Solidworks Simulation Training Chapter 3

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