ANSYS LS-DYNA User's Guide

203 Pages·2004·1.08 MB·English

ANSYS LS-DYNA User's
Guide
ANSYS Release 9.0
002114
November 2004
ANSYS, Inc. is a
UL registered
ISO 9001: 2000
Company.

ANSYS LS-DYNA User's Guide
ANSYS Release 9.0
ANSYS, Inc.
Southpointe
275 Technology Drive
Canonsburg, PA 15317
[e-mail]
http://www.ansys.com
(T) 724-746-3304
(F) 724-514-9494
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Table of Contents
1. Introduction ........................................................................................................................................ 1–1
1.1. Overview of Steps in an Explicit Dynamic Analysis ......................................................................... 1–1
1.2. Commands Used in an Explicit Dynamic Analysis ........................................................................... 1–1
1.3. A Guide to Using this Document ................................................................................................... 1–3
1.4. Where to Find Explicit Dynamics Example Problems ...................................................................... 1–4
1.5. Additional Information ................................................................................................................. 1–4
2. Elements .............................................................................................................................................. 2–1
2.1. Solid and Shell Elements ............................................................................................................... 2–1
2.1.1. SOLID164 ............................................................................................................................. 2–1
2.1.2. SHELL163 ............................................................................................................................. 2–3
2.1.2.1. General Shell Formulations .......................................................................................... 2–3
2.1.2.2. Membrane Element Formulation ................................................................................. 2–4
2.1.2.3. Triangular Shell Formulations ...................................................................................... 2–4
2.1.3. PLANE162 ............................................................................................................................ 2–6
2.1.4. SOLID168 ............................................................................................................................. 2–8
2.2. Beam and Link Elements ............................................................................................................... 2–9
2.2.1. BEAM161 ............................................................................................................................. 2–9
2.2.2. LINK160 ............................................................................................................................. 2–10
2.2.3. LINK167 ............................................................................................................................. 2–10
2.3. Discrete Elements ....................................................................................................................... 2–10
2.3.1. COMBI165 Spring-Damper ................................................................................................. 2–10
2.3.2. MASS166 ........................................................................................................................... 2–11
2.4. General Element Capabilities ....................................................................................................... 2–11
3. Analysis Procedure .............................................................................................................................. 3–1
3.1. Build the Model ............................................................................................................................ 3–1
3.1.1. Define Element Types and Real Constants ............................................................................. 3–1
3.1.2. Specify Material Properties ................................................................................................... 3–1
3.1.3. Define the Model Geometry ................................................................................................. 3–2
3.1.4. Mesh the Model ................................................................................................................... 3–2
3.1.5. Define Contact Surfaces ....................................................................................................... 3–3
3.1.6. General Modeling Guidelines ............................................................................................... 3–4
3.2. Apply Loads and Obtain the Solution ............................................................................................ 3–4
3.2.1. Loads ................................................................................................................................... 3–4
3.2.2. Initial Velocities .................................................................................................................... 3–5
3.2.3. Constraints .......................................................................................................................... 3–5
3.2.4. DOF Coupling ...................................................................................................................... 3–6
3.2.5. Data Smoothing ................................................................................................................... 3–6
3.2.6. Specify Explicit Dynamics Controls ....................................................................................... 3–6
3.2.7. Save Database and Solve ...................................................................................................... 3–7
3.3. Review the Results ........................................................................................................................ 3–7
3.4. The Definition of Part .................................................................................................................... 3–7
3.4.1. Part Assemblies .................................................................................................................. 3–10
3.5. Adaptive Meshing ....................................................................................................................... 3–10
4. Loading ................................................................................................................................................ 4–1
4.1. General Loading Options .............................................................................................................. 4–1
4.1.1. Components ........................................................................................................................ 4–2
4.1.2. Array Parameters ................................................................................................................. 4–2
4.1.3. Applying Loads .................................................................................................................... 4–4
4.1.4. Data Curves ......................................................................................................................... 4–5
4.1.4.1. Using Data Curves with Material Models ...................................................................... 4–5
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4.1.4.2. Using Data Curves for Loading .................................................................................... 4–6
4.1.5. Defining Loads in a Local Coordinate System ........................................................................ 4–7
4.1.6. Specifying Birth and Death Times ......................................................................................... 4–7
4.2. Constraints and Initial Conditions .................................................................................................. 4–7
4.2.1. Constraints .......................................................................................................................... 4–7
4.2.2. Welds .................................................................................................................................. 4–9
4.2.3. Initial Velocity .................................................................................................................... 4–10
4.3. Coupling and Constraint Equations ............................................................................................. 4–11
4.4. Nonreflecting Boundaries ........................................................................................................... 4–11
4.5. Temperature Loading ................................................................................................................. 4–12
4.6. Dynamic Relaxation .................................................................................................................... 4–13
5. Solution Features ................................................................................................................................ 5–1
5.1. Solution Process ........................................................................................................................... 5–1
5.2. LS-DYNA Termination Controls ..................................................................................................... 5–1
5.3. Shared Memory Parallel Processing ............................................................................................... 5–2
5.4. Double Precision LS-DYNA ............................................................................................................ 5–2
5.5. Solution Control and Monitoring ................................................................................................... 5–2
5.6. Plotting Small Elements ................................................................................................................ 5–4
5.7. Editing the LS-DYNA Input File ...................................................................................................... 5–4
5.7.1. Method A ............................................................................................................................. 5–5
5.7.2. Method B ............................................................................................................................. 5–5
5.7.3. Using a Preexisting File.K ...................................................................................................... 5–6
6. Contact Surfaces .................................................................................................................................. 6–1
6.1. Contact Definitions ....................................................................................................................... 6–1
6.1.1. Listing, Plotting and Deleting Contact Entities ...................................................................... 6–4
6.2. Contact Options ........................................................................................................................... 6–5
6.2.1. Definition of Contact Types .................................................................................................. 6–5
6.2.2. Definition of Contact Options ............................................................................................... 6–6
6.3. Contact Search Methods ............................................................................................................... 6–9
6.3.1. Mesh Connectivity Tracking ................................................................................................. 6–9
6.3.2. Bucket Sort Method ........................................................................................................... 6–10
6.3.3. Limiting the Contact Search Domain .................................................................................. 6–10
6.4. Special Considerations for Shells ................................................................................................. 6–10
6.5. Controlling Contact Depth .......................................................................................................... 6–10
6.6. Contact Stiffness ......................................................................................................................... 6–11
6.6.1. Choice of Penalty Factor ..................................................................................................... 6–11
6.6.2. Symmetry Stiffness ............................................................................................................. 6–12
6.7. 2-D Contact Option ..................................................................................................................... 6–12
7. Material Models ................................................................................................................................... 7–1
7.1. Defining Explicit Dynamics Material Models .................................................................................. 7–2
7.2. Explicit Dynamics Material Model Descriptions .............................................................................. 7–3
7.2.1. Linear Elastic Models ............................................................................................................ 7–3
7.2.1.1. Isotropic Elastic Model ................................................................................................. 7–3
7.2.1.2. Orthotropic Elastic Model ............................................................................................ 7–4
7.2.1.3. Anisotropic Elastic Model ............................................................................................. 7–4
7.2.1.4. Elastic Fluid Model ....................................................................................................... 7–5
7.2.2. Nonlinear Elastic Models ...................................................................................................... 7–5
7.2.2.1. Blatz-Ko Rubber Elastic Model ...................................................................................... 7–5
7.2.2.2. Mooney-Rivlin Rubber Elastic Model ............................................................................ 7–6
7.2.2.3. Viscoelastic Model ....................................................................................................... 7–7
7.2.3. Nonlinear Inelastic Models ................................................................................................... 7–7
7.2.3.1. Bilinear Isotropic Model ............................................................................................... 7–7
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7.2.3.2. Temperature Dependent Bilinear Isotropic Model ........................................................ 7–8
7.2.3.3. Transversely Anisotropic Hardening Model .................................................................. 7–8
7.2.3.4. Transversely Anisotropic FLD Hardening Model ........................................................... 7–9
7.2.3.5. Bilinear Kinematic Model ........................................................................................... 7–10
7.2.3.6. Plastic Kinematic Model ............................................................................................. 7–11
7.2.3.7. 3-Parameter Barlat Model .......................................................................................... 7–11
7.2.3.8. Barlat Anisotropic Plasticity Model ............................................................................. 7–13
7.2.3.9. Rate Sensitive Power Law Plasticity Model .................................................................. 7–14
7.2.3.10. Strain Rate Dependent Plasticity Model .................................................................... 7–14
7.2.3.11. Piecewise Linear Plasticity Model ............................................................................. 7–15
7.2.3.12. Modified Piecewise Linear Plasticity Model ............................................................... 7–16
7.2.3.13. Composite Damage Model ...................................................................................... 7–18
7.2.3.14. Concrete Damage Model ......................................................................................... 7–18
7.2.3.15. Power Law Plasticity Model ...................................................................................... 7–19
7.2.3.16. Elastic Viscoplastic Thermal Model ........................................................................... 7–19
7.2.4. Pressure Dependent Plasticity Models ................................................................................ 7–21
7.2.4.1. Elastic-Plastic Hydrodynamic Model ........................................................................... 7–21
7.2.4.2. Geological Cap Model ................................................................................................ 7–22
7.2.5. Foam Models ..................................................................................................................... 7–24
7.2.5.1. Closed Cell Foam Model ............................................................................................ 7–24
7.2.5.2. Viscous Foam Model .................................................................................................. 7–25
7.2.5.3. Low Density Foam Model .......................................................................................... 7–25
7.2.5.4. Crushable Foam Model .............................................................................................. 7–26
7.2.5.5. Honeycomb Foam Model .......................................................................................... 7–26
7.2.6. Equation of State Models .................................................................................................... 7–27
7.2.6.1. Linear Polynomial Equation of State ........................................................................... 7–27
7.2.6.2. Gruneisen Equation of State ...................................................................................... 7–28
7.2.6.3. Tabulated Equation of State ....................................................................................... 7–29
7.2.6.4. Bamman Plasticity Model ........................................................................................... 7–29
7.2.6.5. Johnson-Cook Plasticity Model .................................................................................. 7–29
7.2.6.6. Null Material Model ................................................................................................... 7–31
7.2.6.7. Zerilli-Armstrong Model ............................................................................................. 7–31
7.2.6.8. Steinberg Model ........................................................................................................ 7–33
7.2.7. Discrete Element Models .................................................................................................... 7–35
7.2.7.1. Linear Elastic Spring Model ........................................................................................ 7–35
7.2.7.2. General Nonlinear Spring Model ................................................................................ 7–35
7.2.7.3. Nonlinear Elastic Spring Model .................................................................................. 7–36
7.2.7.4. Elastoplastic Spring Model ......................................................................................... 7–36
7.2.7.5. Inelastic Tension- or Compression-Only Spring Model ................................................ 7–36
7.2.7.6. Maxwell Viscosity Spring Model ................................................................................. 7–36
7.2.7.7. Linear Viscosity Damper Model .................................................................................. 7–37
7.2.7.8. Nonlinear Viscosity Damper Model ............................................................................ 7–37
7.2.7.9. Cable Model .............................................................................................................. 7–37
7.2.8. Other Models ..................................................................................................................... 7–38
7.2.8.1. Rigid Model ............................................................................................................... 7–38
8. Rigid Bodies ........................................................................................................................................ 8–1
8.1. Specifying Inertia Properties ......................................................................................................... 8–1
8.2. Loading ........................................................................................................................................ 8–2
8.3. Switching Parts from Deformable to Rigid ..................................................................................... 8–2
8.4. Nodal Rigid Bodies ........................................................................................................................ 8–3
9. Hourglassing ....................................................................................................................................... 9–1
10. Mass Scaling .................................................................................................................................... 10–1
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11. Subcycling ....................................................................................................................................... 11–1
12. Postprocessing ................................................................................................................................ 12–1
12.1. Output Controls ........................................................................................................................ 12–1
12.1.1. Results (Jobname.RST) vs. History (Jobname.HIS) Files ....................................................... 12–1
12.1.2. Creating Components for POST26 .................................................................................... 12–1
12.1.3. Writing the Output Files for POST26 .................................................................................. 12–1
12.2. Using POST1 with ANSYS LS-DYNA ............................................................................................ 12–2
12.2.1. Animating Results ............................................................................................................ 12–2
12.2.2. Element Output Data ....................................................................................................... 12–3
12.2.3. Postprocessing after Adaptive Meshing ............................................................................ 12–4
12.3. Using POST26 with ANSYS LS-DYNA .......................................................................................... 12–5
12.3.1. Nodal and Element Solutions ............................................................................................ 12–5
12.3.2. Reading ASCII Files for Miscellaneous Output Data ............................................................ 12–6
12.3.3. Data Smoothing ............................................................................................................... 12–6
12.4. Finding Additional Information ................................................................................................. 12–7
13. Restarting ........................................................................................................................................ 13–1
13.1. The Restart Dump File ............................................................................................................... 13–1
13.2. The EDSTART Command ........................................................................................................... 13–1
13.2.1. A New Analysis ................................................................................................................. 13–1
13.2.2. A Simple Restart ............................................................................................................... 13–1
13.2.3. A Small Restart ................................................................................................................. 13–2
13.2.4. A Full Restart .................................................................................................................... 13–3
13.3. Effect on Output Files ................................................................................................................ 13–5
14. Explicit-to-Implicit Sequential Solution .......................................................................................... 14–1
14.1. Explicit-to-Implicit Sequential Solution ...................................................................................... 14–1
14.2. Troubleshooting a Springback Analysis ..................................................................................... 14–4
14.2.1. Springback Stabilization ................................................................................................... 14–5
15. Implicit-to-Explicit Sequential Solution .......................................................................................... 15–1
15.1. Structural Implicit-to-Explicit Solution for Preload ...................................................................... 15–1
15.1.1. Special Considerations for Thermal Loading ...................................................................... 15–4
15.2. Thermal Implicit-to-Explicit Solution .......................................................................................... 15–5
16. Arbitrary Lagrangian-Eulerian Formulation ................................................................................... 16–1
16.1. Overview of the ALE Formulation .............................................................................................. 16–1
16.2. Performing an ALE Analysis ....................................................................................................... 16–3
17. Drop Test Module ............................................................................................................................ 17–1
17.1. Introduction ............................................................................................................................. 17–1
17.2. Starting ANSYS With the Drop Test Module ............................................................................... 17–1
17.3. Typical Drop Test Procedure ...................................................................................................... 17–2
17.3.1. Basic Drop Test Analysis Procedure ................................................................................... 17–2
17.3.1.1. STEP 1: Create or import the model .......................................................................... 17–2
17.3.1.2. STEP 2: Set up the DTM ............................................................................................ 17–2
17.3.1.3. STEP 3: Define the magnitude of (g) ......................................................................... 17–3
17.3.1.4. STEP 4: Specify the drop height ................................................................................ 17–3
17.3.1.5. STEP 5: Orient the object .......................................................................................... 17–3
17.3.1.6. STEP 6: Specify solution controls .............................................................................. 17–3
17.3.1.7. STEP 7: Solve ........................................................................................................... 17–3
17.3.1.8. STEP 8: Animate results ............................................................................................ 17–4
17.3.1.9. STEP 9: Obtain Time-History Results ......................................................................... 17–4
17.3.2. Screen Coordinates Definition .......................................................................................... 17–4
17.3.3. Additional Notes on the Use of the DTM ........................................................................... 17–5
17.4. Advanced DTM Features ........................................................................................................... 17–5
17.4.1. Object Initial Velocity ....................................................................................................... 17–6
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17.4.2. Modifying the Target ........................................................................................................ 17–6
17.4.2.1. Target Position ........................................................................................................ 17–7
17.4.2.2. Target Size ............................................................................................................... 17–8
17.4.2.3. Target Orientation ................................................................................................... 17–8
17.4.2.4. Target Material Properties ........................................................................................ 17–8
17.4.2.5. Specifying Friction Coefficients ................................................................................ 17–9
17.5. Drop Test Set-up Dialog Box ...................................................................................................... 17–9
17.5.1. Using the Drop Test Set-up Dialog Box .............................................................................. 17–9
17.5.2. Basic Tab of the Drop Test Set-up Dialog Box .................................................................. 17–10
17.5.3. Velocity Tab of the Drop Test Set-up Dialog Box .............................................................. 17–12
17.5.4. Target Tab of the Drop Test Set-up Dialog Box ................................................................ 17–13
17.5.5. Status Tab of the Drop Test Set-up Dialog Box ................................................................. 17–15
17.6. Picking Nodes ......................................................................................................................... 17–16
17.7. Postprocessing - Animation ..................................................................................................... 17–16
17.8. Postprocessing - Graph and List Time-History Variables ............................................................ 17–17
A. Comparison of Implicit and Explicit Methods ......................................................................................... A–1
A.1. Time Integration .......................................................................................................................... A–1
A.1.1. Implicit Time Integration ..................................................................................................... A–1
A.1.2. Explicit Time Integration ...................................................................................................... A–1
A.2. Stability Limit ............................................................................................................................... A–2
A.2.1. Implicit Method ................................................................................................................... A–2
A.2.2. Explicit Method ................................................................................................................... A–2
A.3. Critical Time Step Size of a Rod ..................................................................................................... A–2
A.4. ANSYS/LS-DYNA Time Step Size ................................................................................................... A–3
B. Material Model Examples ...................................................................................................................... B–1
B.1. ANSYS LS-DYNA Material Models .................................................................................................. B–1
B.2. Material Model Examples .............................................................................................................. B–3
B.2.1. Isotropic Elastic Example: High Carbon Steel ......................................................................... B–3
B.2.2. Orthotropic Elastic Example: Aluminum Oxide ...................................................................... B–3
B.2.3. Anisotropic Elastic Example: Cadmium ................................................................................. B–3
B.2.4. Blatz-Ko Example: Rubber .................................................................................................... B–3
B.2.5. Mooney-Rivlin Example: Rubber ........................................................................................... B–4
B.2.6. Viscoelastic Example: Glass .................................................................................................. B–4
B.2.7. Bilinear Isotropic Plasticity Example: Nickel Alloy .................................................................. B–4
B.2.8. Transversely Anisotropic Elastic Plastic Example: 1010 Steel .................................................. B–4
B.2.9. Transversely Anisotropic FLD Example: Stainless Steel .......................................................... B–5
B.2.10. Bilinear Kinematic Plasticity Example: Titanium Alloy .......................................................... B–5
B.2.11. Plastic Kinematic Example: 1018 Steel ................................................................................. B–5
B.2.12. 3 Parameter Barlat Example: Aluminum 5182 ...................................................................... B–5
B.2.13. Barlat Anisotropic Plasticity Example: 2008-T4 Aluminum ................................................... B–6
B.2.14. Rate Sensitive Powerlaw Plasticity Example: A356 Aluminum .............................................. B–6
B.2.15. Strain Rate Dependent Plasticity Example: 4140 Steel ......................................................... B–6
B.2.16. Piecewise Linear Plasticity Example: High Carbon Steel ....................................................... B–7
B.2.17. Modified Piecewise Linear Plasticity Example: PVC .............................................................. B–7
B.2.18. Powerlaw Plasticity Example: Aluminum 1100 .................................................................... B–8
B.2.19. Elastic Viscoplastic Thermal Example .................................................................................. B–8
B.2.20. Geological Cap Example: SRI Dynamic Concrete ................................................................. B–9
B.2.21. Johnson-Cook Linear Polynomial EOS Example: 1006 Steel ............................................... B–10
B.2.22. Johnson-Cook Gruneisen EOS Example: OFHC Copper ...................................................... B–10
B.2.23. Null Material Linear Polynomial EOS Example: Brass .......................................................... B–11
B.2.24. Null Material Gruneisen EOS Example: Aluminum ............................................................. B–11
B.2.25. Steinberg Gruneisen EOS Example: Stainless Steel ............................................................ B–11
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B.2.26. Cable Material Example: Steel ........................................................................................... B–12
B.2.27. Rigid Material Example: Steel ............................................................................................ B–12
C. ANSYS LS-DYNA to LS-DYNA Command Mapping .................................................................................. C–1
D. Thermal/Structural Preload Example ..................................................................................................... D–1
Bibliography ................................................................................................................................................. 7
Index ................................................................................................................................................. Index–1
List of Figures
2.1. Integration Points ............................................................................................................................... 2–6
4.1. Constrained Shell to Solid ................................................................................................................... 4–9
6.1. LS-DYNA Drawbead Representation .................................................................................................... 6–9
7.1. Surface of the Two-invariant Cap Model ............................................................................................ 7–22
9.1. Hourglass Deformations ..................................................................................................................... 9–1
11.1. Time Step Sizes Before and After Subcycling .................................................................................... 11–1
16.1. High Speed Impact of a Metal Bar .................................................................................................... 16–1
16.2. Lagrangian Impact Solution ............................................................................................................ 16–2
16.3. Eulerian Channel Flow Solution ....................................................................................................... 16–2
16.4. ALE Impact Solution ........................................................................................................................ 16–3
17.1. Two Views of the Target .................................................................................................................. 17–7
17.2. Drop Test Set-up Dialog Box - Basic Tab ......................................................................................... 17–10
17.3. Drop Test Set-up Dialog Box - Velocity Tab .................................................................................... 17–12
17.4. Drop Test Set-up Dialog Box - Target Tab ....................................................................................... 17–13
17.5. Drop Test Set-up Dialog Box - Status Tab ....................................................................................... 17–15
17.6. Graph and Time-History Variables Dialog Box ................................................................................ 17–18
List of Tables
3.1. Loads Applicable in an Explicit Dynamics Analysis ............................................................................... 3–4
3.2. LS-DYNA Solution and Output Control Options ................................................................................... 3–6
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