Ansys LS-DYNA USER 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

iii Release 12.1 – © 2009 SAS IP, Inc. All rights reserved. – Contains proprietary and confidential information

of ANSYS, Inc. and its subsidiaries and affiliates.

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

Release 12.1 – © 2009 SAS IP, Inc. All rights reserved. – Contains proprietary and confidential information

of ANSYS, Inc. and its subsidiaries and affiliates. iv

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

Release 12.1 – © 2009 SAS IP, Inc. All rights reserved. – Contains proprietary and confidential information

of ANSYS, Inc. and its subsidiaries and affiliates.

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

Release 12.1 – © 2009 SAS IP, Inc. All rights reserved. – Contains proprietary and confidential information vi of ANSYS, Inc. and its subsidiaries and affiliates.

ANSYS LS-DYNA User’s Guide

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

vii Release 12.1 – © 2009 SAS IP, Inc. All rights reserved. – Contains proprietary and confidential information

of ANSYS, Inc. and its subsidiaries and affiliates.

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

Tagged:

Leave a Reply

Your email address will not be published. Required fields are marked *