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
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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
