Dynamic Analysis of the Transmissibility of the Rear Suspension of a Mini-Baja Vehicle

This work presents a dynamical analysis of the transmissibility of an off-road vehicle rear suspension, which was developed in CEFET-RJ for the Mini-Baja / SAE-Brazil competition. A finite element model was developed to identify the critical points of the structure. Afterwards, electric strain gages were bonded at the most critical points to measure the dynamic strains due to an impact load. Accelerometers were bonded before and after rear suspension system to measure the main transmissibility characteristics of the suspension. The data obtained through an A/D converter with instrumentation software was used to evaluate the transmissibility of the rear suspension and other important dynamic characteristics. Finally, a simple twodegree of freedom model was developed to study the behavior of the rear suspension and the influence of the main parameters in the transmissibility of accelerations and
loads to the structure. An estimate for an optimal suspension adjustment was obtained with this simple model. The results obtained with this methodology indicates that it can be used as an effective tool for the design and improvement for Mini-Baja vehicle, as the designer can work with more realistic loads.

DOWNLOAD – Dynamic Analysis of the Transmissibility of the Rear Suspension of a Mini-Baja Vehicle
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MSC Apex Competition : Simulating Reality Contest 2017

Simulating Reality Contest 2017

MSC’s annual Simulating Reality Contest acknowledges its customers by demonstrating how utilizing MSC’s Software simulation technology is driving innovation and delivering certainty in their product designs!

About the Contest

Participants will be divided into two categories, Industry and University
Following are the sub categories:
  • Aerospace
  • Automotive
  • Machinery/Robotics
  • Other
Two groups will be competing separately. 10 finalists for each group will be selected  and showcased on the MSC Software website and receive a finalist certificate. Of those finalists, the top 3 winners  from each category will be awarded 1st, 2nd, or 3rd place. Each winner will be  interviewed on their project and published in multiple publications such as Engineering.com, Digital Engineering, Medical Design & Outsource, and more!
1st place winner will receive a cash prize of $400 USD
2nd place winner will receive a cash prize of $250 USD
3rd place winner will receive a cash prize of $100 USD

Courtesy : MSC Softwares

ANSYS LS-DYNA User’s Guide

DOWNLOAD > Ansys LS-DYNA USER GUIDE

1. Introduction ………………………………………………………………………………………………………………………….. 1

1.1. Starting ANSYS LS-DYNA ……………………………………………………………………………………………………. 1

1.2. Overview of Steps in an Explicit Dynamic Analysis ………………………………………………………………….. 1

1.3. Commands Used in an Explicit Dynamic Analysis ……………………………………………………………………. 2

1.4. A Guide to Using this Document …………………………………………………………………………………………. 4

1.5. Where to Find Explicit Dynamics Example Problems ……………………………………………………………….. 5

1.6. Additional Information ……………………………………………………………………………………………………… 5

2. Elements ………………………………………………………………………………………………………………………………. 7

2.1. Solid and Shell Elements ……………………………………………………………………………………………………. 8

2.1.1. SOLID164 ………………………………………………………………………………………………………………… 8

2.1.2. SHELL163 ………………………………………………………………………………………………………………… 9

2.1.2.1. General Shell Formulations …………………………………………………………………………………. 9

2.1.2.2. Membrane Element Formulation ……………………………………………………………………….. 10

2.1.2.3. Triangular Shell Formulations …………………………………………………………………………….. 10

2.1.3. PLANE162 ……………………………………………………………………………………………………………… 13

2.1.4. SOLID168 ………………………………………………………………………………………………………………. 14

2.2. Beam and Link Elements ………………………………………………………………………………………………….. 15

2.2.1. BEAM161 ………………………………………………………………………………………………………………. 15

2.2.2. LINK160 ………………………………………………………………………………………………………………… 16

2.2.3. LINK167 ………………………………………………………………………………………………………………… 16

2.3. Discrete Elements …………………………………………………………………………………………………………… 16

2.3.1. COMBI165 Spring-Damper ……………………………………………………………………………………….. 16

2.3.2. MASS166 ………………………………………………………………………………………………………………. 17

2.4. General Element Capabilities …………………………………………………………………………………………….. 17

3. Analysis Procedure ……………………………………………………………………………………………………………….. 19

3.1. Build the Model ……………………………………………………………………………………………………………… 19

3.1.1. Define Element Types and Real Constants ……………………………………………………………………. 19

3.1.2. Specify Material Properties ……………………………………………………………………………………….. 20

3.1.3. Define the Model Geometry ……………………………………………………………………………………… 20

3.1.4. Mesh the Model ……………………………………………………………………………………………………… 20

3.1.5. Define Contact Surfaces …………………………………………………………………………………………… 21

3.1.6. General Modeling Guidelines ……………………………………………………………………………………. 22

3.2. Apply Loads and Obtain the Solution …………………………………………………………………………………. 22

3.2.1. Loads ……………………………………………………………………………………………………………………. 22

3.2.2. Initial Velocities ………………………………………………………………………………………………………. 23

3.2.3. Constraints ……………………………………………………………………………………………………………. 24

3.2.4. DOF Coupling ………………………………………………………………………………………………………… 24

3.2.5. Data Smoothing ……………………………………………………………………………………………………… 24

3.2.6. Specify Explicit Dynamics Controls …………………………………………………………………………….. 24

3.2.7. Save Database and Solve ………………………………………………………………………………………….. 25

3.3. Review the Results ………………………………………………………………………………………………………….. 25

3.4. The Definition of Part ………………………………………………………………………………………………………. 26

3.4.1. Part Assemblies ………………………………………………………………………………………………………. 29

3.5. Adaptive Meshing …………………………………………………………………………………………………………… 29

4. Loading ………………………………………………………………………………………………………………………………. 33

4.1. General Loading Options …………………………………………………………………………………………………. 33

4.1.1. Components ………………………………………………………………………………………………………….. 34

4.1.2. Array Parameters …………………………………………………………………………………………………….. 35

4.1.3. Applying Loads ………………………………………………………………………………………………………. 36

4.1.4. Data Curves …………………………………………………………………………………………………………… 38

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4.1.4.1. Using Data Curves with Material Models ……………………………………………………………… 38

4.1.4.2. Using Data Curves for Loading ………………………………………………………………………….. 39

4.1.5. Defining Loads in a Local Coordinate System ……………………………………………………………….. 39

4.1.6. Specifying Birth and Death Times ………………………………………………………………………………. 40

4.2. Constraints and Initial Conditions ………………………………………………………………………………………. 40

4.2.1. Constraints ……………………………………………………………………………………………………………. 40

4.2.2. Welds ……………………………………………………………………………………………………………………. 41

4.2.3. Initial Velocity …………………………………………………………………………………………………………. 42

4.3. Coupling and Constraint Equations ……………………………………………………………………………………. 43

4.4. Nonreflecting Boundaries ………………………………………………………………………………………………… 44

4.5. Temperature Loading ………………………………………………………………………………………………………. 44

4.6. Dynamic Relaxation ………………………………………………………………………………………………………… 45

5. Solution Features …………………………………………………………………………………………………………………. 47

5.1. Solution Process …………………………………………………………………………………………………………….. 47

5.2. LS-DYNA Termination Controls ………………………………………………………………………………………….. 47

5.3. LS-DYNA Parallel Processing Capabilities …………………………………………………………………………….. 48

5.3.1. Shared Memory Parallel Processing ……………………………………………………………………………. 48

5.3.2. Massively Parallel Processing …………………………………………………………………………………….. 49

5.4. Double Precision LS-DYNA ……………………………………………………………………………………………….. 50

5.5. Solution Control and Monitoring ……………………………………………………………………………………….. 50

5.6. Plotting Small Elements …………………………………………………………………………………………………… 51

5.7. Editing the LS-DYNA Input File ………………………………………………………………………………………….. 52

5.7.1. Using a Preexisting File.K ………………………………………………………………………………………….. 54

6. Contact Surfaces ………………………………………………………………………………………………………………….. 55

6.1. Contact Definitions …………………………………………………………………………………………………………. 55

6.1.1. Listing, Plotting and Deleting Contact Entities ………………………………………………………………. 58

6.2. Contact Options …………………………………………………………………………………………………………….. 59

6.2.1. Definition of Contact Types ………………………………………………………………………………………. 60

6.2.2. Definition of Contact Options ……………………………………………………………………………………. 60

6.3. Contact Search Methods ………………………………………………………………………………………………….. 63

6.3.1. Mesh Connectivity Tracking ………………………………………………………………………………………. 63

6.3.2. Bucket Sort Method ………………………………………………………………………………………………… 63

6.3.3. Limiting the Contact Search Domain ………………………………………………………………………….. 63

6.4. Special Considerations for Shells ……………………………………………………………………………………….. 64

6.5. Controlling Contact Depth ……………………………………………………………………………………………….. 64

6.6. Contact Stiffness …………………………………………………………………………………………………………….. 65

6.6.1. Choice of Penalty Factor …………………………………………………………………………………………… 65

6.6.2. Symmetry Stiffness ………………………………………………………………………………………………….. 65

6.7. 2-D Contact Option …………………………………………………………………………………………………………. 66

7. Material Models …………………………………………………………………………………………………………………… 67

7.1. Defining Explicit Dynamics Material Models ………………………………………………………………………… 68

7.2. Explicit Dynamics Material Model Descriptions …………………………………………………………………….. 69

7.2.1. Linear Elastic Models ……………………………………………………………………………………………….. 70

7.2.1.1. Isotropic Elastic Model ……………………………………………………………………………………… 70

7.2.1.2. Orthotropic Elastic Model …………………………………………………………………………………. 70

7.2.1.3. Anisotropic Elastic Model ………………………………………………………………………………….. 70

7.2.1.4. Elastic Fluid Model …………………………………………………………………………………………… 71

7.2.2. Nonlinear Elastic Models ………………………………………………………………………………………….. 72

7.2.2.1. Blatz-Ko Rubber Elastic Model ……………………………………………………………………………. 72

7.2.2.2. Mooney-Rivlin Rubber Elastic Model …………………………………………………………………… 72

7.2.2.3. Viscoelastic Model …………………………………………………………………………………………… 73

7.2.3. Nonlinear Inelastic Models ……………………………………………………………………………………….. 74

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ANSYS LS-DYNA User’s Guide

7.2.3.1. Bilinear Isotropic Model ……………………………………………………………………………………. 74

7.2.3.2.Temperature Dependent Bilinear Isotropic Model ………………………………………………….. 74

7.2.3.3.Transversely Anisotropic Hardening Model …………………………………………………………… 75

7.2.3.4. Transversely Anisotropic FLD Hardening Model …………………………………………………….. 75

7.2.3.5. Bilinear Kinematic Model ………………………………………………………………………………….. 76

7.2.3.6. Plastic Kinematic Model ……………………………………………………………………………………. 76

7.2.3.7. 3-Parameter Barlat Model …………………………………………………………………………………. 77

7.2.3.8. Barlat Anisotropic Plasticity Model ……………………………………………………………………… 79

7.2.3.9. Rate Sensitive Power Law Plasticity Model ……………………………………………………………. 80

7.2.3.10. Strain Rate Dependent Plasticity Model ……………………………………………………………… 80

7.2.3.11. Piecewise Linear Plasticity Model ……………………………………………………………………… 81

7.2.3.12. Modified Piecewise Linear Plasticity Model …………………………………………………………. 82

7.2.3.13. Composite Damage Model ……………………………………………………………………………… 83

7.2.3.14. Concrete Damage Model ………………………………………………………………………………… 84

7.2.3.15. Power Law Plasticity Model ……………………………………………………………………………… 84

7.2.3.16. Elastic Viscoplastic Thermal Model ……………………………………………………………………. 85

7.2.4. Pressure Dependent Plasticity Models ………………………………………………………………………… 86

7.2.4.1. Elastic-Plastic Hydrodynamic Model ……………………………………………………………………. 86

7.2.4.2. Geological Cap Model ………………………………………………………………………………………. 87

7.2.5. Foam Models …………………………………………………………………………………………………………. 89

7.2.5.1. Closed Cell Foam Model ……………………………………………………………………………………. 89

7.2.5.2. Viscous Foam Model ………………………………………………………………………………………… 90

7.2.5.3. Low Density Foam Model ………………………………………………………………………………….. 91

7.2.5.4. Crushable Foam Model …………………………………………………………………………………….. 91

7.2.5.5. Honeycomb Foam Model ………………………………………………………………………………….. 92

7.2.6. Equation of State Models ………………………………………………………………………………………….. 93

7.2.6.1. Linear Polynomial Equation of State ……………………………………………………………………. 93

7.2.6.2. Gruneisen Equation of State ………………………………………………………………………………. 93

7.2.6.3. Tabulated Equation of State ………………………………………………………………………………. 94

7.2.6.4. Bamman Plasticity Model ………………………………………………………………………………….. 95

7.2.6.5. Johnson-Cook Plasticity Model ………………………………………………………………………….. 95

7.2.6.6. Null Material Model …………………………………………………………………………………………. 96

7.2.6.7. Zerilli-Armstrong Model ……………………………………………………………………………………. 97

7.2.6.8. Steinberg Model ……………………………………………………………………………………………… 98

7.2.7. Discrete Element Models ………………………………………………………………………………………… 101

7.2.7.1. Linear Elastic Spring Model ……………………………………………………………………………… 101

7.2.7.2. General Nonlinear Spring Model ………………………………………………………………………. 101

7.2.7.3. Nonlinear Elastic Spring Model ………………………………………………………………………… 101

7.2.7.4. Elastoplastic Spring Model ………………………………………………………………………………. 101

7.2.7.5. Inelastic Tension- or Compression-Only Spring Model …………………………………………… 101

7.2.7.6. Maxwell Viscosity Spring Model ……………………………………………………………………….. 102

7.2.7.7. Linear Viscosity Damper Model ………………………………………………………………………… 102

7.2.7.8. Nonlinear Viscosity Damper Model ……………………………………………………………………. 102

7.2.7.9. Cable Model …………………………………………………………………………………………………. 102

7.2.8. Other Models ……………………………………………………………………………………………………….. 103

7.2.8.1. Rigid Model ………………………………………………………………………………………………….. 103

8. Rigid Bodies ………………………………………………………………………………………………………………………. 105

8.1. Defining Rigid Bodies …………………………………………………………………………………………………….. 105

8.2. Specifying Inertia Properties …………………………………………………………………………………………… 105

8.3. Loading ………………………………………………………………………………………………………………………. 106

8.4. Switching Parts from Deformable to Rigid …………………………………………………………………………. 106

8.5. Nodal Rigid Bodies ………………………………………………………………………………………………………… 107

v

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ANSYS LS-DYNA User’s Guide

9. Hourglassing ……………………………………………………………………………………………………………………… 109

10. Mass Scaling …………………………………………………………………………………………………………………….. 111

11. Subcycling ……………………………………………………………………………………………………………………….. 113

12. Postprocessing …………………………………………………………………………………………………………………. 115

12.1. Output Controls ………………………………………………………………………………………………………….. 115

12.1.1. Results (Jobname.RST) vs. History (Jobname.HIS) Files …………………………………………. 115

12.1.2. Creating Components for POST26 …………………………………………………………………………… 115

12.1.3. Writing the Output Files for POST26 ………………………………………………………………………… 116

12.2. Using POST1 with ANSYS LS-DYNA …………………………………………………………………………………. 116

12.2.1. Animating Results ……………………………………………………………………………………………….. 117

12.2.2. Element Output Data ……………………………………………………………………………………………. 117

12.2.3. Postprocessing after Adaptive Meshing …………………………………………………………………… 118

12.3. Using POST26 with ANSYS LS-DYNA ……………………………………………………………………………….. 120

12.3.1. Nodal and Element Solutions …………………………………………………………………………………. 120

12.3.2. Reading ASCII Files for Miscellaneous Output Data …………………………………………………….. 121

12.3.3. Data Smoothing ………………………………………………………………………………………………….. 121

12.4. Finding Additional Information ……………………………………………………………………………………… 121

13. Restarting ………………………………………………………………………………………………………………………… 123

13.1. The Restart Dump File ………………………………………………………………………………………………….. 123

13.2. The EDSTART Command ……………………………………………………………………………………………….. 123

13.2.1. A New Analysis ……………………………………………………………………………………………………. 124

13.2.2. A Simple Restart ………………………………………………………………………………………………….. 124

13.2.3. A Small Restart ……………………………………………………………………………………………………. 124

13.2.4. A Full Restart ………………………………………………………………………………………………………. 125

13.3. Effect on Output Files …………………………………………………………………………………………………… 127

14. Explicit-to-Implicit Sequential Solution ……………………………………………………………………………….. 129

14.1. Performing an Explicit-to-Implicit Sequential Solution ……………………………………………………….. 129

14.2. Troubleshooting a Springback Analysis ……………………………………………………………………………. 132

14.2.1. Springback Stabilization ……………………………………………………………………………………….. 133

15. Implicit-to-Explicit Sequential Solution ……………………………………………………………………………….. 135

15.1. Structural Implicit-to-Explicit Solution for Preload ……………………………………………………………… 135

15.1.1. Special Considerations for Thermal Loading ……………………………………………………………… 139

15.2. Thermal Implicit-to-Explicit Solution ……………………………………………………………………………….. 139

16. Arbitrary Lagrangian-Eulerian Formulation …………………………………………………………………………. 145

16.1. Performing an ALE Analysis …………………………………………………………………………………………… 147

17. Drop Test Module ……………………………………………………………………………………………………………… 149

17.1.Typical Drop Test Procedure …………………………………………………………………………………………… 149

17.1.1. Basic Drop Test Analysis Procedure …………………………………………………………………………. 150

17.1.1.1. STEP 1: Create or import the model …………………………………………………………………. 150

17.1.1.2. STEP 2: Set up the DTM …………………………………………………………………………………. 150

17.1.1.3. STEP 3: Define the magnitude of (g) …………………………………………………………………. 151

17.1.1.4. STEP 4: Specify the drop height ………………………………………………………………………. 151

17.1.1.5. STEP 5: Orient the object ……………………………………………………………………………….. 151

17.1.1.6. STEP 6: Specify solution controls ……………………………………………………………………… 151

17.1.1.7. STEP 7: Solve ……………………………………………………………………………………………….. 151

17.1.1.8. STEP 8: Animate results …………………………………………………………………………………. 152

17.1.1.9. STEP 9: Obtain Time-History Results …………………………………………………………………. 152

17.1.2. Screen Coordinates Definition ……………………………………………………………………………….. 152

17.1.3. Additional Notes on the Use of the DTM …………………………………………………………………… 153

17.2. Advanced DTM Features ……………………………………………………………………………………………….. 153

17.2.1. Object Initial Velocity ……………………………………………………………………………………………. 153

17.2.2. Modifying the Target ……………………………………………………………………………………………. 154

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17.2.2.1. Target Position …………………………………………………………………………………………….. 155

17.2.2.2. Target Size ………………………………………………………………………………………………….. 155

17.2.2.3.Target Orientation ………………………………………………………………………………………… 155

17.2.2.4. Target Material Properties ……………………………………………………………………………… 155

17.2.2.5. Specifying Friction Coefficients ………………………………………………………………………. 156

17.3. Drop Test Set-up Dialog Box ………………………………………………………………………………………….. 156

17.3.1. Using the Drop Test Set-up Dialog Box …………………………………………………………………….. 156

17.3.2. Basic Tab of the Drop Test Set-up Dialog Box …………………………………………………………….. 157

17.3.3. Velocity Tab of the Drop Test Set-up Dialog Box …………………………………………………………. 159

17.3.4. Target Tab of the Drop Test Set-up Dialog Box …………………………………………………………… 160

17.3.5. Status Tab of the Drop Test Set-up Dialog Box …………………………………………………………… 162

17.4. Picking Nodes …………………………………………………………………………………………………………….. 163

17.5. Postprocessing – Animation …………………………………………………………………………………………… 163

17.6. Postprocessing – Graph and List Time-History Variables ………………………………………………………. 164

A. Comparison of Implicit and Explicit Methods …………………………………………………………………………….. 167

A.1. Time Integration …………………………………………………………………………………………………………… 167

A.1.1. Implicit Time Integration ………………………………………………………………………………………… 167

A.1.2. Explicit Time Integration ………………………………………………………………………………………… 167

A.2. Stability Limit ………………………………………………………………………………………………………………. 168

A.2.1. Implicit Method ……………………………………………………………………………………………………. 168

A.2.2. Explicit Method …………………………………………………………………………………………………….. 168

A.3. Critical Time Step Size of a Rod ………………………………………………………………………………………… 169

A.4. ANSYS LS-DYNA Time Step Size ……………………………………………………………………………………….. 169

B. Material Model Examples ……………………………………………………………………………………………………….. 171

B.1. ANSYS LS-DYNA Material Models ……………………………………………………………………………………… 171

B.2. Material Model Examples ……………………………………………………………………………………………….. 173

B.2.1. Isotropic Elastic Example: High Carbon Steel ………………………………………………………………. 173

B.2.2. Orthotropic Elastic Example: Aluminum Oxide ……………………………………………………………. 174

B.2.3. Anisotropic Elastic Example: Cadmium ………………………………………………………………………. 174

B.2.4. Blatz-Ko Example: Rubber ……………………………………………………………………………………….. 174

B.2.5. Mooney-Rivlin Example: Rubber ………………………………………………………………………………. 174

B.2.6. Viscoelastic Example: Glass ……………………………………………………………………………………… 174

B.2.7. Bilinear Isotropic Plasticity Example: Nickel Alloy …………………………………………………………. 175

B.2.8. Transversely Anisotropic Elastic Plastic Example: 1010 Steel …………………………………………… 175

B.2.9. Transversely Anisotropic FLD Example: Stainless Steel ………………………………………………….. 175

B.2.10. Bilinear Kinematic Plasticity Example:Titanium Alloy ………………………………………………….. 176

B.2.11. Plastic Kinematic Example: 1018 Steel ……………………………………………………………………… 176

B.2.12. 3 Parameter Barlat Example: Aluminum 5182 ……………………………………………………………. 176

B.2.13. Barlat Anisotropic Plasticity Example: 2008-T4 Aluminum ……………………………………………. 177

B.2.14. Rate Sensitive Powerlaw Plasticity Example: A356 Aluminum ……………………………………….. 177

B.2.15. Strain Rate Dependent Plasticity Example: 4140 Steel …………………………………………………. 177

B.2.16. Piecewise Linear Plasticity Example: High Carbon Steel ……………………………………………….. 178

B.2.17. Modified Piecewise Linear Plasticity Example: PVC ……………………………………………………… 178

B.2.18. Powerlaw Plasticity Example: Aluminum 1100 …………………………………………………………… 179

B.2.19. Elastic Viscoplastic Thermal Example ……………………………………………………………………….. 179

B.2.20. Geological Cap Example: SRI Dynamic Concrete ………………………………………………………… 180

B.2.21. Johnson-Cook Linear Polynomial EOS Example: 1006 Steel ………………………………………….. 181

B.2.22. Johnson-Cook Gruneisen EOS Example: OFHC Copper ………………………………………………… 181

B.2.23. Null Material Linear Polynomial EOS Example: Brass ……………………………………………………. 182

B.2.24. Null Material Gruneisen EOS Example: Aluminum ………………………………………………………. 182

B.2.25. Steinberg Gruneisen EOS Example: Stainless Steel ……………………………………………………… 183

B.2.26. Cable Material Example: Steel ………………………………………………………………………………… 183

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ANSYS LS-DYNA User’s Guide

B.2.27. Rigid Material Example: Steel …………………………………………………………………………………. 183

C. ANSYS LS-DYNA to LS-DYNA Command Mapping ………………………………………………………………………. 185

D. Thermal/Structural Preload Example ………………………………………………………………………………………… 189

Bibliography …………………………………………………………………………………………………………………………… 195

Index …………………………………………………………………………………………………………………………………….. 197

List of Figures

2.1. Integration Points ………………………………………………………………………………………………………………… 12

4.1. Constrained Shell to Solid ……………………………………………………………………………………………………… 41

6.1. LS-DYNA Drawbead Representation ………………………………………………………………………………………… 63

7.1. Surface of the Two-invariant Cap Model …………………………………………………………………………………… 88

9.1. Hourglass Deformations ………………………………………………………………………………………………………. 109

11.1. Time Step Sizes Before and After Subcycling ………………………………………………………………………….. 113

16.1. High Speed Impact of a Metal Bar ………………………………………………………………………………………… 145

16.2. Lagrangian Impact Solution ……………………………………………………………………………………………….. 146

16.3. Eulerian Channel Flow Solution …………………………………………………………………………………………… 146

16.4. ALE Impact Solution ………………………………………………………………………………………………………….. 147

17.1. Two Views of the Target ……………………………………………………………………………………………………… 154

17.2. Drop Test Set-up Dialog Box – Basic Tab …………………………………………………………………………………. 157

17.3. Drop Test Set-up Dialog Box – Velocity Tab …………………………………………………………………………….. 159

17.4. Drop Test Set-up Dialog Box – Target Tab ……………………………………………………………………………….. 160

17.5. Drop Test Set-up Dialog Box – Status Tab ……………………………………………………………………………….. 162

17.6. Graph and Time-History Variables Dialog Box …………………………………………………………………………. 165

List of Tables

3.1. Loads Applicable in an Explicit Dynamics Analysis ……………………………………………………………………… 23

3.2. LS-DYNA Solution and Output Control Options ………………………………………………………………………….. 24

Ansys Analysis Tutorials with Example

Ansys Analysis Tutorials > DOWNLOAD

Example 1: 2-D Static Stress Analysis in ANSYS Analysis Tutorials ………………2

Example 2: 3-D Static Stress Analysis ……………………………………………………….5

Example 3: 2-D Frame With Multiple Materials and Element Types……………10

Example 4: 3-D Truss…………………………………………………………………………….15

Example 5: Simple 2-D Heat Transfer ……………………………………………………..20

Example 6: Modal Analysis…………………………………………………………………….22

Example 7: Plate Buckling Analysis Part 1: Eigenvalue Buckling Analysis….26

Example 8: Plate Buckling Analysis Part 2: Nonlinear Buckling Analysis……31

Example 9: Simple Dynamic Analysis……………………………………………………..35

Example 10: Box Beam ………………………………………………………………………….39

ANSYS Tutorials & Projects for BAJA-SAE

Ansys Tutorial with Examples

Altair Solid Thinking: Conceptual Design Inspired by Bone Growth

The concept of a part taking shape as it reacts to its environment may be new to engineers, but nature has been doing this for a long time. Take for instance the evolution of bones—long skeletal bones will grow and change shape as they are subjected to loads and boundary conditions.

Altair’s solidThinking has programmed this bone-like behaviour into Inspire, a concept modeling application for mechanical design. Essentially, Inspire uses a bone growth algorithm to create the shape of a part from little more than loads, boundary conditions and a space that represents a maximum build volume.

Inspire is an interesting example of early concept CAE design. Instead of bringing simulation into the initial CAD design, Inspire works backwards. It will “grow” a near optimal concept using FEA simulations.

“Inspire is based on human bone growth algorithms developed at the University of Michigan in the mid ‘80s,” said Kroeger. “We mimic what nature would do. We took this high-end engineering technology, OptiStruct from Altair, and made it simple and easy to use for designers. That technology was put together with FEA solvers which essentially allowed you to figure out what the best structure is.”

Analysis During Conceptual Design

Keeping initial concept CAE tools simple is important in the design engineering world. Products can benefit a lot from simulation-based insights to ensure concepts are already near optimal in the early stages based on reduced mass, maximum stiffness, or frequency.

“Companies get more value from engineering tools the earlier they are used in the design process,” said Shaun Kroeger, Director of Partner Sales at solidThinking. “Inspire takes engineering tools and puts them in the very front, in the concept design phase.”

Maximizing the Concept Creation Potential of Inspire

“If the user uses CAD then Inspire is a cake walk,” joked Jaideep Bangal, Senior Application Engineer at solidThinking. “The most difficult part is thinking outside the box when designing a part with the tool.”

For example, Bangal told the story of a customer who designed an engine mount the same way for 10 years. When they input their standard packaging space and loads, the customer was confused to find a similar design to the original part.

“They used the same packaging space that the old part occupied as their starting point. The idea is to start with the biggest possible packaging space you have,” said Bangal. “If you force the packaging of your current optimized part you will not get the most out of Inspire. You need to think outside the box of your current packaging.”

Essentially, Inspire will mesh a part based on the packaging space. If an area of the mesh experiences a load, Inspire will keep or remove material based on that load distribution and natural bone-growth algorithms.

Seeing an optimization tool like this build a concept design out of thin air might make some engineers worry about job security. However, Bangal assures that this isn’t the case. “The main role is to create a design that works with all the parameters and is still manufacturable. All we give an engineer is a starting point. Before, engineers started with a block. We say the starting point should be our results so they don’t have to go through the iterative process.”

“Can a design engineer come up with these design[s]?” He added, “Maybe, but the easy route is an I-beam. Our results are stronger and lighter, but they also allow design engineers to come out of their I-beam cocoons. It allows them to come up with the most efficient and organic design.”

Besides, anyone can design an I-beam, and with the help of Inspire engineers can be more creative—even artistic.

For a video transcript please follow this link.

How to Use Inspire to Create a Near Optimal Concept

The Inspire workflow is designed to be simple and intuitive for use in the early design cycles.

The workflow leads engineers to move through the ribbon tool icons from left to right.

“You don’t have to be an expert to use the tool,” says Bangal. “It takes about 4 hours in our training class to become productive. We have even had a few customers watch YouTube videos to start using it … And if you do make a mistake, you can hit ‘ctrl-z’ any number of times to undo the last action.”

Though Inspire isn’t a CAD package it does have some sketching abilities. This allows users to start from scratch by building a packaging space. Alternatively, users can import a design or revisit an old part by importing a CAD geometry. However, Bangal reminded users to “not constrain yourself to the existing geometry pockets. Remove fillets, holes, and increase the packaging space as much as you can.”

It takes a detailed eye to create a CAE tool focused on usability. For instance, take the mouse pointer icons within Inspire. The pointer icon will change based on the part feature you are hovering over. This helps engineers to determine what they will select when they click the mouse. There is a different mouse pointer for points, curvatures, faces and edges.

The tools in Inspire work in a similar fashion. This means if you learn the workflow of one tool you should be able to use the others. “The load and support definition is common to the contact definition. The program also doesn’t default to pull down menus or model trees unless the user prefers to use them,” clarified Bangal.

With the geometry built, users can then set displacement constraints, boundary conditions, materials, and loads onto a part. When defining a mass loading, for instance, “you don’t need to draw an engine in CAD,” said Bangal, “all you need is a center of mass, where it is mounted, and how much it weighs.” As for the material definition, users can choose from a library or create their own. Users can also define multiple load cases to ensure the part is optimized for all use cases. When inputting these values, users don’t have to worry about keeping their units. Inspire will keep track of units.

For most CAE software the next step is to build a mesh based on your geometry. Given the role that the mesh plays in Inspire’s optimization of the part, it is surprising that users have little control over mesh generation. To ensure simple usability and quick turnaround, Inspire builds the mesh automatically.

For instance, localized mesh constraints would be useful to engineers that are concerned about the force distribution involved at a certain section of a part. However, the current control of the mesh is limited to the definition of the following global parameters: minimal part thickness, minimal element size and average element size.

Therefore, once the boundary conditions, loads, and packaging space are defined the user determines the goal of the study. They can optimize the concept part based on maximum stiffness, minimal mass and resonant frequency.

“The maximum stiffness is based on the given loads while the minimization of mass is based on a given factor of safety,” clarified Bangal. “Frequency optimization ensures that the part is designed to avoid a frequency.”

Once the concept part is created, users can run FEA analysis within the Inspire platform to assess the geometry. This will help the engineer to determine which concept designs to pursue with their CAD programs.

Bangal explains that Inspire will make designs that are organic and mathematically correct to handle the given loads and boundary conditions within the current packaging space.

However, due to the organic nature of these shapes, there may be no means to fabricate the design using traditional manufacturing practices. As such, the concept parts are often constructed first via 3D printing.

However, “We realize that not everyone has 3D printers yet and there’s a lot of traditional manufacturing,” said Kroeger. “So we have shape controls in our solver that force the answers to be something that could be cut out of sheet metal, or something that could be cast. That really allows any user to benefit from Inspire.”

Once satisfied with the geometry, engineers can send it to CAD to finalize the design.

“Inspire uses Parasolid as a communication mechanism,” said Kroeger. “So we can actually read in CAD files directly and we write out Parasolid of these ideal shapes. Then you can bring that into your preferred CAD software, and use that to start your designs.”

This model transferability stresses the point that “the result from Inspire is still a concept part,” said Bangal. “Engineers will have a better idea of the final changes the part will need. But with Inspire, many of our customers were able to experience massive savings for their part, some almost halved the weight.”

ANSYS Tutorials & Projects for BAJA-SAE

For proper analysis of your vehicle you need to conduct structural analysis of your cage for side, roll, front, rear & torsional impacts.

The primary aim in your analysis should be to reduce weight of the vehicle and to test for failure.The un-sprung weight, rotating mass and roll cage are primary weight reduction areas and you should try to reduce the weight of your car to 300 kg with higher stiffness of the roll cage to help your car achieve the highest acceleration while maintaining a sufficient factor of safety. The driver comfort and sturdiness of the vehicle is considered of primary importance.

For weight reduction of the cage, You can test a number of cage types having different pipe thicknesses in ANSYS Mechanical with various types of impacts and then evaluated the maximum stress. The final cage is selected by considering the resulting stresses & applying a suitable factor of safety.

ANSYS Tutorial-BAJA SAE
Frontal Impact Test of Roll Cage
Front impact Stress Analysis
Front impact Stress Analysis

 

Online Tutorial Links

 

 

Mail us if you need further detailed helps and tutorials on ANSYS for BAJA-SAE Competitions.

Courtsey : Ansys (http://www.ansys.com/Industries/Academic/Tools/Curriculum+Resources/Tutorials,+Examples+&+Curriculum)

ANSYS Classic – Mini BAJA Car Frame Exmple

The Society of Automotive Engineers sponsors the Mini Baja design competition as part of their collegiate design series.  The purpose of the event is to have teams of engineering students design, build, and race a prototype of a four-wheel, one passenger, off-road vehicle intended for off-road recreation.  North Dakota State University has participated in this competition for numerous years.

The most important aspect of the vehicle design is the frame.  The frame contains the operator, engine, brake system, fuel system, and steering mechanism, and must be of adequate strength to protect the operator in the event of a rollover or impact. The roll cage must be constructed of steel tubing, with minimum dimensional and strength requirements dictated by SAE.

The frame shown below was designed and constructed by a recent NDSU Mini-Baja team.  All tubes are round and made of steel (E = 30 Msi, ν = 0.30).  All tubes with the exception of the diagonal braces have a 1 in OD with a 0.083 in wall thickness.  The diagonal braces have a 1 in OD with a 0.065 in wall thickness.

In this example, we will use ANSYS to investigate the response of the frame (e.g., stresses and

deflections) under various types of impact.  Specifically, we will consider a direct frontal impact that results in an 8g horizontal loading (deceleration), and a one-wheel impact that results in a simultaneous

4g horizontal loading, 6g vertical loading, and 2g lateral loading.  The applied forces are obtained by multiplying the deceleration value by the overall weight of the vehicle and driver, assumed here to be

500 lb.  The impact loading is simulated by restricting displacements at certain locations, and applying discrete forces at various points on the frame where the weight is concentrated.  The frame will be modeled in ANSYS using 3D elastic beam elements (BEAM4).

The BEAM4 element (shown below) requires the following cross-sectional properties to be calculated and entered as Real Constants:  cross-sectional area, area moment of inertia about the z-axis (Izz), area moment of inertia about the y-axis (Iyy), thickness along the z-axis (outer edge-to-edge), and thickness along the y-axis (outer edge-to-edge).

The details are attached in PDF

http://www.ndsu.edu/me/images/Kallmeyer/477/Baja%20Example.pdf