ANSYS 8.1 - Structural Analysis Guide

Structural Analysis

Guide

Structural Analysis Guide

ANSYS Release 8.1

April 2002 ANSYS 6.1 001612 October 2002 ANSYS 7.0 001695* May 2003 ANSYS 7.1 001788* October 2003 ANSYS 8.0 001901* April 2004 ANSYS 8.1 001972* * ANSYS Documentation on CD.

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Table of Contents

1. Overview of Structural Analyses ... 1–1 1.1. Definition of Structural Analysis ... 1–1 1.2. Types of Structural Analysis ... 1–1 1.3. Elements Used in Structural Analyses ... 1–2 1.4. Material Model Interface ... 1–2 1.5. Types of Solution Methods ... 1–2 2. Structural Static Analysis ... 2–1 2.1. Definition of Static Analysis ... 2–1 2.2. Linear vs. Nonlinear Static Analyses ... 2–1 2.3. Performing a Static Analysis ... 2–1 2.3.1. Build the Model ... 2–1 2.3.1.1. Points to Remember ... 2–1 2.3.2. Set Solution Controls ... 2–2 2.3.2.1. Access the Solution Controls Dialog Box ... 2–2 2.3.2.2. Using the Basic Tab ... 2–2 2.3.2.3. The Transient Tab ... 2–3 2.3.2.4. Using the Sol'n Options Tab ... 2–4 2.3.2.5. Using the Nonlinear Tab ... 2–4 2.3.2.6. Using the Advanced NL Tab ... 2–5 2.3.3. Set Additional Solution Options ... 2–5 2.3.3.1. Stress Stiffening Effects ... 2–5 2.3.3.2. Newton-Raphson Option ... 2–6 2.3.3.3. Prestress Effects Calculation ... 2–6 2.3.3.4. Mass Matrix Formulation ... 2–6 2.3.3.5. Reference Temperature ... 2–7 2.3.3.6. Mode Number ... 2–7 2.3.3.7. Creep Criteria ... 2–7 2.3.3.8. Printed Output ... 2–7 2.3.3.9. Extrapolation of Results ... 2–7 2.3.4. Apply the Loads ... 2–7 2.3.4.1. Load Types ... 2–7 2.3.4.1.1. Displacements (UX, UY, UZ, ROTX, ROTY, ROTZ) ... 2–7 2.3.4.1.2. Forces (FX, FY, FZ) and Moments (MX, MY, MZ) ... 2–7 2.3.4.1.3. Pressures (PRES) ... 2–8 2.3.4.1.4. Temperatures (TEMP) ... 2–8 2.3.4.1.5. Fluences (FLUE) ... 2–8 2.3.4.1.6. Gravity, Spinning, Etc. ... 2–8 2.3.4.2. Apply Loads to the Model ... 2–8 2.3.4.2.1. Applying Loads Using TABLE Type Array Parameters ... 2–8 2.3.4.3. Calculating Inertia Relief ... 2–9 2.3.4.3.1. Inertia Relief Output ... 2–9 2.3.4.3.2. Partial Inertia Relief Calculations ... 2–9 2.3.4.3.3. Using a Macro to Perform Inertia Relief Calculations ... 2–10 2.3.5. Solve the Analysis ... 2–10 2.3.6. Review the Results ... 2–10 2.3.6.1. Postprocessors ... 2–11 2.3.6.2. Points to Remember ... 2–11 2.3.6.3. Reviewing Results Data ... 2–11 2.3.6.4. Typical Postprocessing Operations ... 2–11 2.4. A Sample Static Analysis (GUI Method) ... 2–13

2.4.1. Problem Description ... 2–13 2.4.2. Problem Specifications ... 2–13 2.4.3. Problem Sketch ... 2–14 2.4.3.1. Set the Analysis Title ... 2–14 2.4.3.2. Set the System of Units ... 2–14 2.4.3.3. Define Parameters ... 2–14 2.4.3.4. Define the Element Types ... 2–15 2.4.3.5. Define Material Properties ... 2–15 2.4.3.6. Create Hexagonal Area as Cross-Section ... 2–15 2.4.3.7. Create Keypoints Along a Path ... 2–16 2.4.3.8. Create Lines Along a Path ... 2–16 2.4.3.9. Create Line from Shank to Handle ... 2–17 2.4.3.10. Cut Hex Section ... 2–17 2.4.3.11. Set Meshing Density ... 2–17 2.4.3.12. Set Element Type for Area Mesh ... 2–17 2.4.3.13. Generate Area Mesh ... 2–18 2.4.3.14. Drag the 2-D Mesh to Produce 3-D Elements ... 2–18 2.4.3.15. Select BOTAREA Component and Delete 2-D Elements ... 2–18 2.4.3.16. Apply Displacement Boundary Condition at End of Wrench ... 2–19 2.4.3.17. Display Boundary Conditions ... 2–19 2.4.3.18. Apply Pressure on Handle ... 2–19 2.4.3.19. Write the First Load Step ... 2–21 2.4.3.20. Define Downward Pressure ... 2–21 2.4.3.21. Write Second Load Step ... 2–22 2.4.3.22. Solve from Load Step Files ... 2–22 2.4.3.23. Read First Load Step and Review Results ... 2–22 2.4.3.24. Read the Next Load Step and Review Results ... 2–23 2.4.3.25. Zoom in on Cross-Section ... 2–23 2.4.3.26. Exit ANSYS ... 2–23 2.5. A Sample Static Analysis (Command or Batch Method) ... 2–24 2.6. Where to Find Other Examples ... 2–26 3. Modal Analysis ... 3–1 3.1. Definition of Modal Analysis ... 3–1 3.2. Uses for Modal Analysis ... 3–1 3.3. Overview of Steps in a Modal Analysis ... 3–1 3.4. Build the Model ... 3–1 3.5. Apply Loads and Obtain the Solution ... 3–2 3.5.1. Enter the Solution Processor ... 3–2 3.5.2. Define Analysis Type and Options ... 3–2 3.5.2.1. Option: New Analysis [ANTYPE] ... 3–2 3.5.2.2. Option: Analysis Type: Modal [ANTYPE] ... 3–3 3.5.2.3. Option: Mode-Extraction Method [MODOPT] ... 3–3 3.5.2.4. Option: Number of Modes to Extract [MODOPT] ... 3–4 3.5.2.5. Option: Number of Modes to Expand [MXPAND] ... 3–4 3.5.2.6. Option: Mass Matrix Formulation [LUMPM] ... 3–4 3.5.2.7. Option: Prestress Effects Calculation [PSTRES] ... 3–4 3.5.2.8. Additional Modal Analysis Options ... 3–4 3.5.3. Define Master Degrees of Freedom ... 3–4 3.5.4. Apply Loads ... 3–5 3.5.4.1. Applying Loads Using Commands ... 3–5 3.5.4.2. Applying Loads Using the GUI ... 3–5 3.5.4.3. Listing Loads ... 3–6

3.5.5. Specify Load Step Options ... 3–6 3.5.6. Participation Factor Table Output ... 3–6 3.5.7. Solve ... 3–7 3.5.7.1. Output ... 3–7 3.5.7.1.1. Output From Subspace Mode-Extraction Method ... 3–7 3.5.8. Exit the Solution Processor ... 3–8 3.6. Expand the Modes ... 3–8 3.6.1. Points to Remember ... 3–8 3.6.2. Expanding the Modes ... 3–8 3.7. Review the Results ... 3–10 3.7.1. Points to Remember ... 3–10 3.7.2. Reviewing Results Data ... 3–10 3.7.3. Option: Listing All Frequencies ... 3–10 3.7.4. Option: Display Deformed Shape ... 3–11 3.7.5. Option: List Master DOF ... 3–11 3.7.6. Option: Line Element Results ... 3–11 3.7.7. Option: Contour Displays ... 3–11 3.7.8. Option: Tabular Listings ... 3–11 3.7.9. Other Capabilities ... 3–12 3.8. A Sample Modal Analysis (GUI Method) ... 3–12 3.8.1. Problem Description ... 3–12 3.8.2. Problem Specifications ... 3–12 3.8.3. Problem Sketch ... 3–12 3.9. A Sample Modal Analysis (Command or Batch Method) ... 3–13 3.10. Where to Find Other Examples ... 3–14 3.11. Prestressed Modal Analysis ... 3–14 3.12. Prestressed Modal Analysis of a Large-Deflection Solution ... 3–15 3.13. Comparing Mode-Extraction Methods ... 3–16 3.13.1. Block Lanczos Method ... 3–17 3.13.2. Subspace Method ... 3–17 3.13.3. PowerDynamics Method ... 3–17 3.13.4. Reduced Method ... 3–18 3.13.5. Unsymmetric Method ... 3–18 3.13.6. Damped Method ... 3–18 3.13.6.1. Damped Method-Real and Imaginary Parts of the Eigenvalue ... 3–18 3.13.6.2. Damped Method-Real and Imaginary Parts of the Eigenvector ... 3–18 3.13.7. QR Damped Method ... 3–19 3.14. Matrix Reduction ... 3–19 3.14.1. Theoretical Basis of Matrix Reduction ... 3–19 3.14.1.1. Guidelines for Selecting Master DOF ... 3–19 3.14.1.2. A Note About Program-Selected Masters ... 3–21 4. Harmonic Response Analysis ... 4–1 4.1. Definition of Harmonic Response Analysis ... 4–1 4.2. Uses for Harmonic Response Analysis ... 4–1 4.3. Commands Used in a Harmonic Response Analysis ... 4–2 4.4. The Three Solution Methods ... 4–2 4.4.1. The Full Method ... 4–2 4.4.2. The Reduced Method ... 4–2 4.4.3. The Mode Superposition Method ... 4–3 4.4.4. Restrictions Common to All Three Methods ... 4–3 4.5. How to Do Harmonic Response Analysis ... 4–3 4.5.1. Full Harmonic Response Analysis ... 4–3 Structural Analysis Guide

4.5.2. Build the Model ... 4–4 4.5.2.1. Points to Remember ... 4–4 4.5.3. Apply Loads and Obtain the Solution ... 4–4 4.5.3.1. Enter the ANSYS Solution Processor ... 4–4 4.5.3.2. Define the Analysis Type and Options ... 4–4 4.5.3.3. Apply Loads on the Model ... 4–5 4.5.3.3.1. Applying Loads Using Commands ... 4–8 4.5.3.3.2. Applying Loads and Listing Loads Using the GUI ... 4–9 4.5.3.4. Specify Load Step Options ... 4–9 4.5.3.4.1. General Options ... 4–9 4.5.3.4.2. Dynamics Options ... 4–10 4.5.3.4.3. Output Controls ... 4–10 4.5.3.5. Save a Backup Copy of the Database to a Named File ... 4–11 4.5.3.6. Start Solution Calculations ... 4–11 4.5.3.7. Repeat for Additional Load Steps ... 4–11 4.5.3.8. Leave SOLUTION ... 4–11 4.5.4. Review the Results ... 4–11 4.5.4.1. Postprocessors ... 4–11 4.5.4.2. Points to Remember ... 4–11 4.5.4.3. Using POST26 ... 4–12 4.5.4.4. Using POST1 ... 4–12 4.6. Sample Harmonic Response Analysis (GUI Method) ... 4–13 4.6.1. Problem Description ... 4–13 4.6.2. Problem Specifications ... 4–13 4.6.3. Problem Diagram ... 4–14 4.6.3.1. Set the Analysis Title ... 4–14 4.6.3.2. Define the Element Types ... 4–14 4.6.3.3. Define the Real Constants ... 4–15 4.6.3.4. Create the Nodes ... 4–15 4.6.3.5. Create the Spring Elements ... 4–15 4.6.3.6. Create the Mass Elements ... 4–16 4.6.3.7. Specify the Analysis Type, MDOF, and Load Step Specifications ... 4–16 4.6.3.8. Define Loads and Boundary Conditions ... 4–16 4.6.3.9. Solve the Model ... 4–17 4.6.3.10. Review the Results ... 4–17 4.6.3.11. Exit ANSYS ... 4–18 4.7. Sample Harmonic Response Analysis (Command or Batch Method) ... 4–18 4.8. Where to Find Other Examples ... 4–19 4.9. Reduced Harmonic Response Analysis ... 4–20 4.9.1. Apply Loads and Obtain the Reduced Solution ... 4–20 4.9.2. Review the Results of the Reduced Solution ... 4–21 4.9.3. Expand the Solution (Expansion Pass) ... 4–21 4.9.3.1. Points to Remember ... 4–21 4.9.3.2. Expanding the Modes ... 4–21 4.9.4. Review the Results of the Expanded Solution ... 4–23 4.9.5. Sample Input ... 4–24 4.10. Mode Superposition Harmonic Response Analysis ... 4–25 4.10.1. Obtain the Modal Solution ... 4–25 4.10.2. Obtain the Mode Superposition Harmonic Solution ... 4–25 4.10.3. Expand the Mode Superposition Solution ... 4–27 4.10.4. Review the Results ... 4–27 4.10.5. Sample Input ... 4–27

4.11. Other Analysis Details ... 4–28 4.11.1. Prestressed Harmonic Response Analysis ... 4–28 4.11.1.1. Prestressed Full Harmonic Response Analysis ... 4–28 4.11.1.2. Prestressed Reduced Harmonic Response Analysis ... 4–29 4.11.1.3. Prestressed Mode Superposition Harmonic Response Analysis ... 4–29 5. Transient Dynamic Analysis ... 5–1 5.1. Definition of Transient Dynamic Analysis ... 5–1 5.2. Preparing for a Transient Dynamic Analysis ... 5–1 5.3. Three Solution Methods ... 5–2 5.3.1. Full Method ... 5–2 5.3.2. Mode Superposition Method ... 5–2 5.3.3. Reduced Method ... 5–3 5.4. Performing a Full Transient Dynamic Analysis ... 5–3 5.4.1. Build the Model ... 5–4 5.4.1.1. Points to Remember ... 5–4 5.4.2. Establish Initial Conditions ... 5–4 5.4.3. Set Solution Controls ... 5–6 5.4.3.1. Access the Solution Controls Dialog Box ... 5–6 5.4.3.2. Using the Basic Tab ... 5–7 5.4.3.3. Using the Transient Tab ... 5–7 5.4.3.4. Using the Remaining Solution Controls Tabs ... 5–8 5.4.4. Set Additional Solution Options ... 5–8 5.4.4.1. Prestress Effects ... 5–9 5.4.4.2. Damping Option ... 5–9 5.4.4.3. Mass Matrix Formulation ... 5–9 5.4.5. Apply the Loads ... 5–9 5.4.6. Save the Load Configuration for the Current Load Step ... 5–10 5.4.7. Repeat Steps 3-6 for Each Load Step ... 5–10 5.4.8. Save a Backup Copy of the Database ... 5–10 5.4.9. Start the Transient Solution ... 5–10 5.4.10. Exit the Solution Processor ... 5–11 5.4.11. Review the Results ... 5–11 5.4.11.1. Postprocessors ... 5–11 5.4.11.2. Points to Remember ... 5–11 5.4.11.3. Using POST26 ... 5–11 5.4.11.4. Other Capabilities ... 5–12 5.4.11.5. Using POST1 ... 5–12 5.4.12. Sample Input for a Full Transient Dynamic Analysis ... 5–12 5.5. Performing a Mode Superposition Transient Dynamic Analysis ... 5–13 5.5.1. Build the Model ... 5–13 5.5.2. Obtain the Modal Solution ... 5–13 5.5.3. Obtain the Mode Superposition Transient Solution ... 5–14 5.5.3.1. Points to Remember ... 5–14 5.5.3.2. Obtaining the Solution ... 5–14 5.5.4. Expand the Mode Superposition Solution ... 5–18 5.5.5. Review the Results ... 5–18 5.5.6. Sample Input for a Mode Superposition Transient Dynamic Analysis ... 5–18 5.6. Performing a Reduced Transient Dynamic Analysis ... 5–19 5.6.1. Obtain the Reduced Solution ... 5–19 5.6.1.1. Define the Analysis Type and Options ... 5–20 5.6.1.2. Define Master Degrees of Freedom ... 5–20 5.6.1.3. Define Gap Conditions ... 5–20 Structural Analysis Guide

5.6.1.3.1. Gap Conditions ... 5–20 5.6.1.4. Apply Initial Conditions to the Model ... 5–21 5.6.1.4.1. Dynamics Options ... 5–22 5.6.1.4.2. General Options ... 5–22 5.6.1.4.3. Output Control Options ... 5–23 5.6.1.5. Write the First Load Step to a Load Step File ... 5–23 5.6.1.6. Specify Loads and Load Step Options ... 5–23 5.6.1.7. Obtaining the Solution ... 5–23 5.6.2. Review the Results of the Reduced Solution ... 5–23 5.6.3. Expand the Solution (Expansion Pass) ... 5–24 5.6.3.1. Points to Remember ... 5–24 5.6.3.2. Expanding the Solution ... 5–24 5.6.4. Review the Results of the Expanded Solution ... 5–25 5.7. Sample Reduced Transient Dynamic Analysis (GUI Method) ... 5–26 5.7.1. Problem Description ... 5–26 5.7.2. Problem Specifications ... 5–26 5.7.3. Problem Sketch ... 5–27 5.7.3.1. Specify the Title ... 5–27 5.7.3.2. Define Element Types ... 5–27 5.7.3.3. Define Real Constants ... 5–27 5.7.3.4. Define Material Properties ... 5–28 5.7.3.5. Define Nodes ... 5–28 5.7.3.6. Define Elements ... 5–28 5.7.3.7. Define Analysis Type and Analysis Options ... 5–29 5.7.3.8. Define Master Degrees of Freedom ... 5–29 5.7.3.9. Set Load Step Options ... 5–29 5.7.3.10. Apply Loads for the First Load Step ... 5–29 5.7.3.11. Specify Output ... 5–29 5.7.3.12. Solve the First Load Step ... 5–30 5.7.3.13. Apply Loads for the Next Load Step ... 5–30 5.7.4. Solve the Next Load Step ... 5–30 5.7.4.1. Set the Next Time Step and Solve ... 5–30 5.7.4.2. Run the Expansion Pass and Solve ... 5–30 5.7.4.3. Review the Results in POST26 ... 5–31 5.7.4.4. Review the Results in POST1 ... 5–31 5.7.4.5. Exit ANSYS ... 5–31 5.8. Sample Reduced Transient Dynamic Analysis (Command or Batch Method) ... 5–31 5.9. Performing a Prestressed Transient Dynamic Analysis ... 5–32 5.9.1. Prestressed Full Transient Dynamic Analysis ... 5–32 5.9.2. Prestressed Mode Superposition Transient Dynamic Analysis ... 5–33 5.9.3. Prestressed Reduced Transient Dynamic Analysis ... 5–33 5.10. Other Analysis Details ... 5–33 5.10.1. Guidelines for Integration Time Step ... 5–33 5.10.2. Automatic Time Stepping ... 5–35 5.10.3. Damping ... 5–36 5.11. Where to Find Other Examples ... 5–40 6. Spectrum Analysis ... 6–1 6.1. Definition of Spectrum Analysis ... 6–1 6.2. What is a Spectrum? ... 6–1 6.2.1. Response Spectrum ... 6–1 6.2.1.1. Single-Point Response Spectrum (SPRS) ... 6–1 6.2.1.2. Multi-Point Response Spectrum (MPRS) ... 6–1

6.2.2. Dynamic Design Analysis Method (DDAM) ... 6–2 6.2.3. Power Spectral Density ... 6–2 6.2.4. Deterministic vs. Probabilistic Analyses ... 6–2 6.3. Steps in a Single-Point Response Spectrum (SPRS) Analysis ... 6–2 6.3.1. Build the Model ... 6–3 6.3.1.1. Points to Remember ... 6–3 6.3.2. Obtain the Modal Solution ... 6–3 6.3.3. Obtain the Spectrum Solution ... 6–3 6.3.4. Expand the Modes ... 6–6 6.3.5. Combine the Modes ... 6–6 6.3.6. Review the Results ... 6–8 6.4. Sample Spectrum Analysis (GUI Method) ... 6–10 6.4.1. Problem Description ... 6–10 6.4.2. Problem Specifications ... 6–10 6.4.3. Problem Sketch ... 6–11 6.4.4. Procedure ... 6–11 6.4.4.1. Set the Analysis Title ... 6–11 6.4.4.2. Define the Element Type ... 6–11 6.4.4.3. Define the Real Constants ... 6–11 6.4.4.4. Define Material Properties ... 6–12 6.4.4.5. Define Keypoints and Line ... 6–12 6.4.4.6. Set Global Element Density and Mesh Line ... 6–12 6.4.4.7. Set Boundary Conditions ... 6–13 6.4.4.8. Specify Analysis Type and Options ... 6–13 6.4.4.9. Solve the Modal Analysis ... 6–13 6.4.4.10. Set Up the Spectrum Analysis ... 6–13 6.4.4.11. Define Spectrum Value vs. Frequency Table ... 6–14 6.4.4.12. Solve Spectrum Analysis ... 6–14 6.4.4.13. Set up the Expansion Pass ... 6–14 6.4.4.14. Expand the Modes ... 6–14 6.4.4.15. Start Expansion Pass Calculation ... 6–15 6.4.4.16. Set Up Mode Combination for Spectrum Analysis ... 6–15 6.4.4.17. Select Mode Combination Method ... 6–15 6.4.4.18. Combine the Modes ... 6–15 6.4.4.19. Postprocessing: Print Out Nodal, Element, and Reaction Solutions ... 6–15 6.4.4.20. Exit ANSYS ... 6–16 6.5. Sample Spectrum Analysis (Command or Batch Method) ... 6–16 6.6. Where to Find Other Examples ... 6–17 6.7. How to Do a Random Vibration (PSD) Analysis ... 6–18 6.7.1. Expand the Modes ... 6–18 6.7.2. Obtain the Spectrum Solution ... 6–18 6.7.3. Combine the Modes ... 6–21 6.7.4. Review the Results ... 6–22 6.7.4.1. Reviewing the Results in POST1 ... 6–22 6.7.4.1.1. Read the Desired Set of Results into the Database ... 6–22 6.7.4.1.2. Display the Results ... 6–23 6.7.4.2. Calculating Response PSDs in POST26 ... 6–23 6.7.4.3. Calculating Covariance in POST26 ... 6–23 6.7.5. Sample Input ... 6–24 6.8. How to Do DDAM Spectrum Analysis ... 6–25 6.9. How to Do Multi-Point Response Spectrum (MPRS) Analysis ... 6–25 7. Buckling Analysis ... 7–1 Structural Analysis Guide

7.1. Definition of Buckling Analysis ... 7–1 7.2. Types of Buckling Analyses ... 7–1 7.2.1. Nonlinear Buckling Analysis ... 7–1 7.2.2. Eigenvalue Buckling Analysis ... 7–1 7.3. Commands Used in a Buckling Analysis ... 7–2 7.4. Procedure for Nonlinear Buckling Analysis ... 7–2 7.4.1. Applying Load Increments ... 7–2 7.4.2. Automatic Time Stepping ... 7–2 7.4.3. Important ... 7–2 7.4.4. Points to Remember ... 7–3 7.5. Procedure for Eigenvalue Buckling Analysis ... 7–3 7.5.1. Build the Model ... 7–3 7.5.1.1. Points to Remember ... 7–4 7.5.2. Obtain the Static Solution ... 7–4 7.5.3. Obtain the Eigenvalue Buckling Solution ... 7–5 7.5.4. Expand the Solution ... 7–6 7.5.4.1. Points to Remember ... 7–6 7.5.4.2. Expanding the Solution ... 7–6 7.5.5. Review the Results ... 7–7 7.6. Sample Buckling Analysis (GUI Method) ... 7–8 7.6.1. Problem Description ... 7–8 7.6.2. Problem Specifications ... 7–8 7.6.3. Problem Sketch ... 7–9 7.6.3.1. Set the Analysis Title ... 7–9 7.6.3.2. Define the Element Type ... 7–9 7.6.3.3. Define the Real Constants and Material Properties ... 7–10 7.6.3.4. Define Nodes and Elements ... 7–10 7.6.3.5. Define the Boundary Conditions ... 7–11 7.6.3.6. Solve the Static Analysis ... 7–11 7.6.3.7. Solve the Buckling Analysis ... 7–11 7.6.3.8. Review the Results ... 7–12 7.6.3.9. Exit ANSYS ... 7–12 7.7. Sample Buckling Analysis (Command or Batch Method) ... 7–12 7.8. Where to Find Other Examples ... 7–12 8. Nonlinear Structural Analysis ... 8–1 8.1. What is Structural Nonlinearity? ... 8–1 8.1.1. Causes of Nonlinear Behavior ... 8–1 8.1.1.1. Changing Status (Including Contact) ... 8–2 8.1.1.2. Geometric Nonlinearities ... 8–2 8.1.1.3. Material Nonlinearities ... 8–2 8.1.2. Basic Information About Nonlinear Analyses ... 8–2 8.1.2.1. Conservative versus Nonconservative Behavior; Path Dependency ... 8–5 8.1.2.2. Substeps ... 8–5 8.1.2.3. Load Direction in a Large-Deflection Analysis ... 8–6 8.1.2.4. Nonlinear Transient Analyses ... 8–6 8.2. Using Geometric Nonlinearities ... 8–6 8.2.1. Stress-Strain ... 8–7 8.2.1.1. Large Deflections with Small Strain ... 8–7 8.2.2. Stress Stiffening ... 8–7 8.2.3. Spin Softening ... 8–8 8.3. Modeling Material Nonlinearities ... 8–8 8.3.1. Nonlinear Materials ... 8–8

8.3.1.1. Plasticity ... 8–9 8.3.1.1.1. Plastic Material Options ... 8–10 8.3.1.2. Multilinear Elasticity ... 8–16 8.3.1.3. User Defined Material ... 8–16 8.3.1.4. Hyperelasticity ... 8–17 8.3.1.4.1. Mooney-Rivlin Hyperelastic Option (TB,HYPER) ... 8–18 8.3.1.4.2. Ogden Hyperelastic Option ... 8–18 8.3.1.4.3. Neo-Hookean Hyperelastic Option ... 8–19 8.3.1.4.4. Polynomial Form Hyperelastic Option ... 8–19 8.3.1.4.5. Arruda-Boyce Hyperelastic Option ... 8–19 8.3.1.4.6. Gent Hyperelastic Option ... 8–20 8.3.1.4.7. Yeoh Hyperelastic Option ... 8–20 8.3.1.4.8. Blatz-Ko Foam Hyperelastic Option ... 8–20 8.3.1.4.9. Ogden Compressible Foam Hyperelastic Option ... 8–20 8.3.1.4.10. User-Defined Hyperelastic Option ... 8–21 8.3.1.4.11. Mooney-Rivlin Hyperelastic Option (TB,MOONEY) ... 8–21 8.3.1.5. Creep ... 8–29 8.3.1.5.1. Implicit Creep Procedure ... 8–30 8.3.1.5.2. Explicit Creep Procedure ... 8–31 8.3.1.6. Shape Memory Alloy ... 8–31 8.3.1.7. Viscoplasticity ... 8–32 8.3.1.8. Viscoelasticity ... 8–33 8.3.1.9. Swelling ... 8–34 8.3.2. Material Model Combinations ... 8–35 8.3.2.1. BISO and CHAB Example ... 8–35 8.3.2.2. MISO and CHAB Example ... 8–35 8.3.2.3. NLISO and CHAB Example ... 8–35 8.3.2.4. BISO and RATE Example ... 8–36 8.3.2.5. MISO and RATE Example ... 8–36 8.3.2.6. NLISO and RATE Example ... 8–37 8.3.2.7. BISO and CREEP Example ... 8–37 8.3.2.8. MISO and CREEP Example ... 8–37 8.3.2.9. NLISO and CREEP Example ... 8–38 8.3.2.10. BKIN and CREEP Example ... 8–38 8.3.2.11. HILL and BISO Example ... 8–38 8.3.2.12. HILL and MISO Example ... 8–39 8.3.2.13. HILL and NLISO Example ... 8–39 8.3.2.14. HILL and BKIN Example ... 8–39 8.3.2.15. HILL and MKIN Example ... 8–40 8.3.2.16. HILL and KINH Example ... 8–40 8.3.2.17. HILL and CHAB Example ... 8–41 8.3.2.18. HILL and BISO and CHAB Example ... 8–41 8.3.2.19. HILL and MISO and CHAB Example ... 8–41 8.3.2.20. HILL and NLISO and CHAB Example ... 8–42 8.3.2.21. HILL and RATE and BISO Example ... 8–43 8.3.2.22. HILL and RATE and MISO Example ... 8–44 8.3.2.23. HILL and RATE and NLISO Example ... 8–44 8.3.2.24. HILL and CREEP Example ... 8–45 8.3.2.25. HILL and CREEP and BISO Example ... 8–46 8.3.2.26. HILL and CREEP and MISO Example ... 8–47 8.3.2.27. HILL and CREEP and NLISO Example ... 8–47 8.3.2.28. HILL and CREEP and BKIN Example ... 8–47 Structural Analysis Guide

8.4. Running a Nonlinear Analysis in ANSYS ... 8–48 8.5. Performing a Nonlinear Static Analysis ... 8–48 8.5.1. Build the Model ... 8–49 8.5.2. Set Solution Controls ... 8–49 8.5.2.1. Using the Basic Tab: Special Considerations ... 8–49 8.5.2.2. Advanced Analysis Options You Can Set on the Solution Controls Dialog Box ... 8–50 8.5.2.2.1. Equation Solver ... 8–50 8.5.2.3. Advanced Load Step Options You Can Set on the Solution Controls Dialog Box ... 8–51 8.5.2.3.1. Automatic Time Stepping ... 8–51 8.5.2.3.2. Convergence Criteria ... 8–51 8.5.2.3.3. Maximum Number of Equilibrium Iterations ... 8–52 8.5.2.3.4. Predictor-Corrector Option ... 8–52 8.5.2.3.5. Line Search Option ... 8–53 8.5.2.3.6. Cutback Criteria ... 8–53 8.5.3. Set Additional Solution Options ... 8–53 8.5.3.1. Advanced Analysis Options You Cannot Set on the Solution Controls Dialog Box ... 8–53 8.5.3.1.1. Stress Stiffness ... 8–53 8.5.3.1.2. Newton-Raphson Option ... 8–54 8.5.3.2. Advanced Load Step Options You Cannot Set on the Solution Controls Dialog Box ... 8–55 8.5.3.2.1. Creep Criteria ... 8–55 8.5.3.2.2. Time Step Open Control ... 8–55 8.5.3.2.3. Solution Monitoring ... 8–55 8.5.3.2.4. Birth and Death ... 8–56 8.5.3.2.5. Output Control ... 8–56 8.5.4. Apply the Loads ... 8–56 8.5.5. Solve the Analysis ... 8–57 8.5.6. Review the Results ... 8–57 8.5.6.1. Points to Remember ... 8–57 8.5.6.2. Reviewing Results in POST1 ... 8–57 8.5.6.3. Reviewing Results in POST26 ... 8–59 8.5.7. Terminating a Running Job; Restarting ... 8–59 8.6. Performing a Nonlinear Transient Analysis ... 8–59 8.6.1. Build the Model ... 8–60 8.6.2. Apply Loads and Obtain the Solution ... 8–60 8.6.3. Review the Results ... 8–61 8.7. Sample Input for a Nonlinear Transient Analysis ... 8–61 8.8. Restarts ... 8–62 8.9. Using Nonlinear (Changing-Status) Elements ... 8–63 8.9.1. Element Birth and Death ... 8–63 8.10. Tips and Guidelines for Nonlinear Analysis ... 8–63 8.10.1. Starting Out with Nonlinear Analysis ... 8–63 8.10.1.1. Be Aware of How the Program and Your Structure Behave ... 8–63 8.10.1.2. Keep It Simple ... 8–64 8.10.1.3. Use an Adequate Mesh Density ... 8–64 8.10.1.4. Apply the Load Gradually ... 8–64 8.10.2. Overcoming Convergence Problems ... 8–64 8.10.2.1. Performing Nonlinear Diagnostics ... 8–65 8.10.2.2. Tracking Convergence Graphically ... 8–66 8.10.2.3. Using Automatic Time Stepping ... 8–67 8.10.2.4. Using Line Search ... 8–68 8.10.2.5. Using the Arc-Length Method ... 8–68 8.10.2.6. Artificially Inhibit Divergence in Your Model's Response ... 8–69

8.10.2.7. Turn Off Extra Element Shapes ... 8–70 8.10.2.8. Using Birth and Death Wisely ... 8–70 8.10.2.9. Read Your Output ... 8–70 8.10.2.10. Graph the Load and Response History ... 8–71 8.11. Sample Nonlinear Analysis (GUI Method) ... 8–71 8.11.1. Problem Description ... 8–72 8.11.2. Problem Specifications ... 8–72 8.11.3. Problem Sketch ... 8–73 8.11.3.1. Set the Analysis Title and Jobname ... 8–73 8.11.3.2. Define the Element Types ... 8–73 8.11.3.3. Define Material Properties ... 8–74 8.11.3.4. Specify the Kinematic Hardening material model (KINH) ... 8–74 8.11.3.5. Label Graph Axes and Plot Data Tables ... 8–74 8.11.3.6. Create Rectangle ... 8–74 8.11.3.7. Set Element Size ... 8–75 8.11.3.8. Mesh the Rectangle ... 8–75 8.11.3.9. Assign Analysis and Load Step Options ... 8–75 8.11.3.10. Monitor the Displacement ... 8–75 8.11.3.11. Apply Constraints ... 8–76 8.11.3.12. Solve the First Load Step ... 8–76 8.11.3.13. Solve the Next Six Load Steps ... 8–77 8.11.3.14. Review the Monitor File ... 8–77 8.11.3.15. Use the General Postprocessor to Plot Results. ... 8–77 8.11.3.16. Define Variables for Time-History Postprocessing ... 8–78 8.11.3.17. Plot Time-History Results ... 8–78 8.11.3.18. Exit ANSYS ... 8–79 8.12. Sample Nonlinear Analysis (Command or Batch Method) ... 8–79 8.13. Where to Find Other Examples ... 8–82 9. Material Curve Fitting ... 9–1 9.1. Applicable Material Behavior Types ... 9–1 9.2. Hyperelastic Material Curve Fitting ... 9–1 9.2.1. Using Curve Fitting to Determine Your Hyperelastic Material Behavior ... 9–1 9.2.1.1. Prepare Experimental Data ... 9–2 9.2.1.2. Input the Data into ANSYS ... 9–3 9.2.1.2.1. Batch ... 9–3 9.2.1.2.2. GUI ... 9–3 9.2.1.3. Select a Material Model Option ... 9–3 9.2.1.3.1. Batch ... 9–4 9.2.1.3.2. GUI ... 9–4 9.2.1.4. Initialize the Coefficients ... 9–4 9.2.1.4.1. Batch ... 9–4 9.2.1.4.2. GUI ... 9–5 9.2.1.5. Specify Control Parameters and Solve ... 9–5 9.2.1.5.1. Batch ... 9–5 9.2.1.5.2. GUI ... 9–5 9.2.1.6. Plot Your Experimental Data and Analyze ... 9–6 9.2.1.6.1. Batch ... 9–6 9.2.1.6.2. GUI ... 9–6 9.2.1.6.3. Review/Verify ... 9–6 9.2.1.7. Write Data to TB Command ... 9–6 9.2.1.7.1. Batch ... 9–6 9.2.1.7.2. GUI ... 9–7 Structural Analysis Guide

9.3. Creep Material Curve Fitting ... 9–7 9.3.1. Using Curve Fitting to Determine Your Creep Material Behavior ... 9–7 9.3.1.1. Prepare Experimental Data ... 9–7 9.3.1.2. Input the Data into ANSYS ... 9–9 9.3.1.2.1. Batch ... 9–9 9.3.1.2.2. GUI ... 9–9 9.3.1.3. Select a Material Model Option ... 9–9 9.3.1.3.1. Batch ... 9–9 9.3.1.3.2. GUI ... 9–10 9.3.1.4. Initialize the Coefficients ... 9–10 9.3.1.4.1. Batch ... 9–10 9.3.1.4.2. GUI ... 9–11 9.3.1.5. Specify Control Parameters and Solve ... 9–11 9.3.1.5.1. Batch ... 9–11 9.3.1.5.2. GUI ... 9–11 9.3.1.6. Plot the Experimental Data and Analyze ... 9–11 9.3.1.6.1. Batch ... 9–12 9.3.1.6.2. GUI ... 9–12 9.3.1.6.3. Analyze Your Curves for Proper Fit ... 9–12 9.3.1.7. Write Data to TB Command ... 9–12 9.3.1.7.1. Batch ... 9–12 9.3.1.7.2. GUI ... 9–12 9.3.2. Tips For Curve Fitting Creep Models ... 9–12 9.4. Viscoelastic Material Curve Fitting ... 9–14 9.4.1. Using Curve Fitting to Determine the Coefficients of Viscoelastic Material Model ... 9–14 9.4.1.1. Prepare Experimental Data ... 9–15 9.4.1.2. Input the Data into ANSYS ... 9–16 9.4.1.2.1. Batch ... 9–16 9.4.1.2.2. GUI ... 9–16 9.4.1.3. Select a Material Model Option ... 9–16 9.4.1.3.1. Batch ... 9–17 9.4.1.3.2. GUI ... 9–17 9.4.1.4. Initialize the Coefficients ... 9–17 9.4.1.4.1. Batch ... 9–18 9.4.1.4.2. GUI ... 9–18 9.4.1.5. Specify Control Parameters and Solve ... 9–18 9.4.1.5.1. Batch ... 9–19 9.4.1.5.2. GUI ... 9–20 9.4.1.6. Plot the Experimental Data and Analyze ... 9–20 9.4.1.6.1. Batch ... 9–20 9.4.1.6.2. GUI ... 9–20 9.4.1.6.3. Analyze Your Curves for Proper Fit ... 9–20 9.4.1.7. Write Data to TB Command ... 9–20 9.4.1.7.1. Batch ... 9–20 9.4.1.7.2. GUI ... 9–21 10. Gasket Joints Simulation ... 10–1 10.1. Overview of Gasket Joints ... 10–1 10.2. Performing a Gasket Joint Analysis ... 10–1 10.3. Finite Element Formulation ... 10–2 10.3.1. Element Topologies ... 10–2 10.3.2. Thickness Direction ... 10–2 10.4. ANSYS Family of Interface Elements ... 10–3

10.4.1. Element Selection ... 10–3 10.4.2. Applications ... 10–3 10.5. Material Definition ... 10–4 10.5.1. Material Characteristics ... 10–4 10.5.2. Input Format ... 10–5 10.5.2.1. Define General Parameters ... 10–6 10.5.2.2. Define Compression Load Closure Curve ... 10–6 10.5.2.3. Define Linear Unloading Data ... 10–6 10.5.2.4. Define Nonlinear Unloading Data ... 10–7 10.5.3. Temperature Dependencies ... 10–8 10.5.4. Plotting Gasket Data ... 10–11 10.6. Meshing Interface Elements ... 10–12 10.7. Solution Procedure and Result Output ... 10–16 10.7.1. Typical Gasket Solution Output Listing ... 10–17 10.8. Reviewing the Results ... 10–19 10.8.1. Points to Remember ... 10–19 10.8.2. Reviewing Results in POST1 ... 10–19 10.8.3. Reviewing Results in POST26 ... 10–20 10.9. Sample Gasket Element Verification Analysis (Command or Batch Method) ... 10–20 11. Contact ... 11–1 11.1. Contact Overview ... 11–1 11.1.1. Explicit Dynamics Contact Capabilities ... 11–1 11.2. General Contact Classification ... 11–1 11.3. ANSYS Contact Capabilities ... 11–2 11.3.1. Surface-to-Surface Contact Elements ... 11–3 11.3.2. Node-to-Surface Contact Elements ... 11–3 11.3.3. Node-to-Node Contact Elements ... 11–4 11.4. Performing a Surface-to-Surface Contact Analysis ... 11–4 11.4.1. Using Surface-to-Surface Contact Elements ... 11–4 11.4.2. Steps in a Contact Analysis ... 11–5 11.4.3. Creating the Model Geometry and Mesh ... 11–5 11.4.4. Identifying Contact Pairs ... 11–5 11.4.5. Designating Contact and Target Surfaces ... 11–6 11.4.5.1. Asymmetric Contact vs. Symmetric Contact ... 11–7 11.4.5.1.1. Background ... 11–7 11.4.5.1.2. Using KEYOPT(8) ... 11–7 11.4.6. Defining the Target Surface ... 11–7 11.4.6.1. Pilot Nodes ... 11–8 11.4.6.2. Primitives ... 11–8 11.4.6.3. Element Types and Real Constants ... 11–8 11.4.6.3.1. Defining Target Element Geometry ... 11–8 11.4.6.4. Using Direct Generation to Create Rigid Target Elements ... 11–9 11.4.6.5. Using ANSYS Meshing Tools to Create Rigid Target Elements ... 11–10 11.4.6.5.1. Some Modeling and Meshing Tips ... 11–12 11.4.6.5.2. Verifying Nodal Number Ordering (Contact Direction) of Target Surface ... 11–13 11.4.7. Defining the Deformable Contact Surface ... 11–14 11.4.7.1. Element Type ... 11–14 11.4.7.2. Real Constants and Material Properties ... 11–15 11.4.7.3. Generating Contact Elements ... 11–16 11.4.8. Set the Real Constants and Element KEYOPTS ... 11–17 11.4.8.1. Real Constants ... 11–17 11.4.8.1.1. Positive and Negative Real Constant Values ... 11–19 Structural Analysis Guide

11.4.8.2. Element KEYOPTS ... 11–20 11.4.8.3. Selecting a Contact Algorithm (KEYOPT(2)) ... 11–21 11.4.8.3.1. Background ... 11–21 11.4.8.4. Determining Contact Stiffness and Allowable Penetration ... 11–22 11.4.8.4.1. Background ... 11–22 11.4.8.4.2. Using FKN and FTOLN ... 11–23 11.4.8.4.3. Using FKT and SLTO ... 11–23 11.4.8.4.4. Using KEYOPT(10) ... 11–24 11.4.8.4.5. Chattering Control Parameters ... 11–25 11.4.8.5. Choosing a Friction Model ... 11–25 11.4.8.5.1. Background ... 11–25 11.4.8.5.2. Using TAUMAX, FACT, DC, and COHE ... 11–26 11.4.8.5.3. Static and Dynamic Friction Coefficients ... 11–26 11.4.8.6. Selecting Location of Contact Detection ... 11–28 11.4.8.6.1. Background ... 11–28 11.4.8.6.2. Using KEYOPT(4) and TOLS ... 11–28 11.4.8.7. Adjusting Initial Contact Conditions ... 11–30 11.4.8.7.1. Background ... 11–30 11.4.8.7.2. Using PMIN, PMAX, CNOF, ICONT, KEYOPT(5), and KEYOPT(9) ... 11–30 11.4.8.8. Physically Moving Contact Nodes Towards the Target Surface ... 11–37 11.4.8.9. Determining Contact Status and the Pinball Region ... 11–38 11.4.8.9.1. Background ... 11–38 11.4.8.9.2. Using PINB ... 11–39 11.4.8.10. Avoiding Spurious Contact in Self Contact Problems ... 11–39 11.4.8.11. Selecting Surface Interaction Models ... 11–40 11.4.8.11.1. Background ... 11–40 11.4.8.11.2. Using KEYOPT(12) and FKOP ... 11–40 11.4.8.12. Modeling Contact with Superelements ... 11–41 11.4.8.12.1. Background ... 11–41 11.4.8.12.2. Using KEYOPT(3) ... 11–41 11.4.8.13. Accounting for Thickness Effect ... 11–42 11.4.8.13.1. Background ... 11–42 11.4.8.13.2. Using KEYOPT(11) ... 11–42 11.4.8.14. Using Time Step Control ... 11–42 11.4.8.14.1. Background ... 11–42 11.4.8.14.2. Using KEYOPT(7) ... 11–42 11.4.8.15. Using the Birth and Death Option ... 11–42 11.4.9. Controlling the Motion of the Rigid Target Surface (Rigid-to-Flexible Contact) ... 11–43 11.4.10. Modeling Thermal Contact ... 11–44 11.4.10.1. Thermal Contact Behavior vs. Contact Status ... 11–44 11.4.10.2. Free Thermal Surface ... 11–44 11.4.10.3. Temperature on Target Surface ... 11–45 11.4.10.4. Modeling Conduction ... 11–45 11.4.10.4.1. Using TCC ... 11–45 11.4.10.4.2. Using the Quasi Solver Option ... 11–46 11.4.10.5. Modeling Convection ... 11–46 11.4.10.6. Modeling Radiation ... 11–46 11.4.10.6.1. Background ... 11–46 11.4.10.6.2. Using SBCT and RDVF ... 11–47 11.4.10.7. Modeling Heat Generation Due to Friction ... 11–47 11.4.10.7.1. Background ... 11–47 11.4.10.7.2. Using FHTG and FWGT ... 11–47

11.4.10.8. Modeling External Heat Flux ... 11–48 11.4.11. Modeling Electric Contact ... 11–48 11.4.11.1. Modeling Surface Interaction ... 11–48 11.4.11.1.1. Background ... 11–48 11.4.11.1.2. Using ECC ... 11–49 11.4.11.2. Modeling Heat Generation Due to Electric Current ... 11–49 11.4.12. Modeling Magnetic Contact ... 11–50 11.4.12.1. Using MCC ... 11–50 11.4.12.2. Modeling Perfect Magnetic Contact ... 11–51 11.4.13. Applying Necessary Boundary Conditions to the Deformable Elements ... 11–51 11.4.14. Defining Solution and Load Step Options ... 11–51 11.4.15. Solving the Problem ... 11–52 11.4.16. Reviewing the Results ... 11–53 11.4.16.1. Points to Remember ... 11–53 11.4.16.2. Reviewing Results in POST1 ... 11–53 11.4.16.3. Reviewing Results in POST26 ... 11–54 11.5. GUI Aids for Contact Analyses ... 11–54 11.5.1. The Contact Manager ... 11–54 11.5.2. The Contact Wizard ... 11–55 11.5.3. Managing Contact Pairs ... 11–56 11.6. Performing a Node-to-Surface Contact Analysis ... 11–57 11.6.1. Using the Node-to-Surface Contact Elements ... 11–57 11.6.1.1. CONTA175 KEYOPTS ... 11–59 11.6.1.1.1. KEYOPT(3) ... 11–59 11.6.1.1.2. KEYOPT(4) ... 11–59 11.6.1.2. CONTA175 Real Constants ... 11–60 11.6.1.3. Multiphysics Contact ... 11–60 11.7. Using the Internal MPC Approach for Assemblies and Kinematic Constraints ... 11–60 11.7.1. Modeling Solid-solid and Shell-shell Assemblies ... 11–61 11.7.2. Modeling a Shell-solid Assembly ... 11–62 11.7.3. Surface-based Constraints ... 11–66 11.7.3.1. Defining Surface-based Constraints ... 11–67 11.7.3.2. Modeling a Beam-solid Assembly ... 11–68 11.7.4. Restrictions and Recommendations for Internal MPC ... 11–69 11.8. Performing a Node-to-Node Contact Analysis ... 11–70 11.8.1. Creating Geometry and Meshing the Model ... 11–71 11.8.2. Generating Contact Elements ... 11–71 11.8.2.1. Generating Contact Elements Automatically at Coincident Nodes ... 11–72 11.8.2.2. Generating Contact Elements Automatically at Offset Nodes ... 11–72 11.8.2.3. Node Ordering ... 11–72 11.8.3. Defining the Contact Normal ... 11–73 11.8.4. Defining the Initial Interference or Gap ... 11–74 11.8.5. Selecting the Contact Algorithm ... 11–74 11.8.6. Applying Necessary Boundary Conditions ... 11–74 11.8.7. Defining the Solution Options ... 11–75 11.8.8. Solving the Problem ... 11–76 11.8.9. Reviewing the Results ... 11–76 12. Fracture Mechanics ... 12–1 12.1. Definition of Fracture Mechanics ... 12–1 12.2. Solving Fracture Mechanics Problems ... 12–1 12.2.1. Modeling the Crack Region ... 12–1 12.2.1.1. 2-D Fracture Models ... 12–3 Structural Analysis Guide

12.2.1.2. 3-D Fracture Models ... 12–4 12.2.2. Calculating Fracture Parameters ... 12–5 12.2.2.1. Stress Intensity Factors ... 12–5 12.2.2.2. J-Integral ... 12–6 12.2.2.3. Energy Release Rate ... 12–8 13. Composites ... 13–1 13.1. Definition of Composites ... 13–1 13.2. Modeling Composites ... 13–1 13.2.1. Choosing the Proper Element Type ... 13–1 13.2.2. Defining the Layered Configuration ... 13–2 13.2.2.1. Specifying Individual Layer Properties ... 13–3 13.2.2.2. Defining the Constitutive Matrices ... 13–4 13.2.2.3. Sandwich and Multiple-Layered Structures ... 13–4 13.2.2.4. Node Offset ... 13–5 13.2.3. Specifying Failure Criteria ... 13–5 13.2.4. Additional Modeling and Postprocessing Guidelines ... 13–6 14. Fatigue ... 14–1 14.1. Definition of Fatigue ... 14–1 14.1.1. What the ANSYS Program Does ... 14–1 14.1.2. Basic Terminology ... 14–1 14.2. Doing a Fatigue Evaluation ... 14–2 14.2.1. Enter POST1 and Resume Your Database ... 14–2 14.2.2. Establish the Size, Fatigue Material Properties, and Locations ... 14–2 14.2.3. Store Stresses and Assign Event Repetitions and Scale Factors ... 14–4 14.2.3.1. Storing Stresses ... 14–4 14.2.3.1.1. Manually Stored Stresses ... 14–4 14.2.3.1.2. Nodal Stresses from Jobname.RST ... 14–5 14.2.3.1.3. Stresses at a Cross-Section ... 14–5 14.2.3.2. Listing, Plotting, or Deleting Stored Stresses ... 14–6 14.2.3.3. Assigning Event Repetitions and Scale Factors ... 14–6 14.2.3.4. Guidelines for Obtaining Accurate Usage Factors ... 14–7 14.2.4. Activate the Fatigue Calculations ... 14–9 14.2.5. Review the Results ... 14–9 14.2.6. Other Approaches to Range Counting ... 14–9 14.2.7. Sample Input ... 14–9 15. p-Method Structural Static Analysis ... 15–1 15.1. Definition of p-Method Analysis ... 15–1 15.2. Benefits of Using the p-Method ... 15–1 15.3. Using the p-Method ... 15–1 15.3.1. Select the p-Method Procedure ... 15–1 15.3.2. Build the Model ... 15–2 15.3.2.1. Define the Element Types ... 15–2 15.3.2.1.1. Specifying a p-Level Range ... 15–2 15.3.2.2. Specify Material Properties and/or Real Constants ... 15–3 15.3.2.2.1. Material Properties ... 15–3 15.3.2.2.2. Real Constants ... 15–3 15.3.2.3. Define the Model Geometry ... 15–4 15.3.2.4. Mesh the Model into Solid or Shell Elements ... 15–4 15.3.2.4.1. Using Program Defaults ... 15–4 15.3.2.4.2. Specifying Mesh Controls ... 15–4 15.3.2.4.3. Guidelines for Creating a Good Mesh ... 15–5 15.3.3. Additional Information for Building Your Model ... 15–5

15.3.3.1. Viewing your element model ... 15–5 15.3.3.2. Coupling ... 15–6 15.3.3.2.1. Coupling of Corner Nodes ... 15–6 15.3.3.2.2. Midside Node Coupling ... 15–7 15.3.4. Apply Loads and Obtain the Solution ... 15–7 15.3.5. Helpful Hints for Common Problems ... 15–12 15.3.6. Review the Results ... 15–12 15.3.6.1. The p-Element Subgrid ... 15–13 15.3.7. Querying Subgrid Results ... 15–13 15.3.8. Printing and Plotting Node and Element Results ... 15–14 15.3.8.1. Specialized p-Method Displays and Listings ... 15–14 15.4. Sample p-Method Analysis (GUI Method) ... 15–14 15.4.1. Problem Description ... 15–15 15.4.2. Problem Specifications ... 15–15 15.4.3. Problem Diagram ... 15–15 15.4.3.1. Set the Analysis Title ... 15–15 15.4.3.2. Select p-Method ... 15–15 15.4.3.3. Define the Element Type and Options ... 15–15 15.4.3.4. Define the Real Constants ... 15–16 15.4.3.5. Define Material Properties ... 15–16 15.4.3.6. Create Plate with Hole ... 15–16 15.4.3.7. Mesh the Areas ... 15–16 15.4.3.8. Define Symmetry Boundary Conditions ... 15–17 15.4.3.9. Define Pressure Load along Right Edge. ... 15–17 15.4.3.10. Define Convergence Criteria ... 15–17 15.4.3.11. Solve the Problem ... 15–17 15.4.3.12. Review the Results and Exit ANSYS ... 15–18 15.5. Sample p-Method Analysis (Command or Batch Method) ... 15–18 16. Beam Analysis and Cross Sections ... 16–1 16.1. An Overview of Beams ... 16–1 16.2. What Are Cross Sections? ... 16–1 16.3. How to Create Cross Sections ... 16–2 16.3.1. Defining a Section and Associating a Section ID Number ... 16–3 16.3.2. Defining Cross Section Geometry and Setting the Section Attribute Pointer ... 16–3 16.3.2.1. Determining the Number of Cells to Define ... 16–4 16.3.3. Meshing a Line Model with BEAM44, BEAM188, or BEAM189 Elements ... 16–4 16.4. Creating Cross Sections ... 16–5 16.4.1. Using the Beam Tool to Create Common Cross Sections ... 16–5 16.4.2. Creating Custom Cross Sections with a User-defined Mesh ... 16–6 16.4.3. Creating Custom Cross Sections with Mesh Refinement and Multiple Materials ... 16–7 16.4.4. Defining Composite Cross Sections ... 16–8 16.4.5. Defining a Tapered Beam ... 16–8 16.5. Managing Cross Section and User Mesh Libraries ... 16–9 16.6. Sample Lateral Torsional Buckling Analysis (GUI Method) ... 16–9 16.6.1. Problem Description ... 16–10 16.6.2. Problem Specifications ... 16–10 16.6.3. Problem Sketch ... 16–11 16.6.4. Eigenvalue Buckling and Nonlinear Collapse ... 16–11 16.6.5. Set the Analysis Title and Define Model Geometry ... 16–12 16.6.6. Define Element Type and Cross Section Information ... 16–12 16.6.7. Define the Material Properties and Orientation Node ... 16–12 16.6.8. Mesh the Line and Verify Beam Orientation ... 16–13 Structural Analysis Guide

16.6.9. Define the Boundary Conditions ... 16–13 16.6.10. Solve the Eigenvalue Buckling Analysis ... 16–14 16.6.11. Solve the Nonlinear Buckling Analysis ... 16–15 16.6.12. Plot and Review the Results ... 16–15 16.7. Sample Problem with Cantilever Beams, Command Method ... 16–16 16.8. Where to Find Other Examples ... 16–17 17. Shell Analysis and Cross Sections ... 17–1 17.1. An Overview of Shells ... 17–1 17.2. What Are Cross Sections? ... 17–1 17.3. How to Create Cross Sections ... 17–1 17.3.1. Defining a Section and Associating a Section ID Number ... 17–2 17.3.2. Defining Layer Data ... 17–2 17.3.3. Overriding Program Calculated Section Properties ... 17–3 17.3.4. Specifying a Shell Thickness Variation (Tapered Shells) ... 17–3 17.3.5. Setting the Section Attribute Pointer ... 17–3 17.3.6. Associating an Area with a Section ... 17–3 17.3.7. Using the Shell Tool to Create Sections ... 17–3 17.3.8. Managing Cross Section Libraries ... 17–5 Index ... Index–1

List of Figures

2.1. Diagram of Allen Wrench ... 2–14 3.1. Diagram of a Model Airplane Wing ... 3–12 3.2. Choose Master DOF ... 3–20 3.3. Choosing Master DOFs ... 3–20 3.4. Choosing Masters in an Axisymmetric Shell Model ... 3–21 4.1. Harmonic Response Systems ... 4–1 4.2. Relationship Between Real/Imaginary Components and Amplitude/Phase Angle ... 4–6 4.3. An Unbalanced Rotating Antenna ... 4–7 4.4. Two-Mass-Spring-System ... 4–14 5.1. Examples of Load-Versus-Time Curves ... 5–4 5.2. Examples of Gap Conditions ... 5–21 5.3. Model of a Steel Beam Supporting a Concentrated Mass ... 5–27 5.4. Effect of Integration Time Step on Period Elongation ... 5–34 5.5. Transient Input vs. Transient Response ... 5–35 5.6. Rayleigh Damping ... 5–38 6.1. Single-Point and Multi-Point Response Spectra ... 6–2 6.2. Simply Supported Beam with Vertical Motion of Both Supports ... 6–11 7.1. Buckling Curves ... 7–1 7.2. Adjusting Variable Loads to Find an Eigenvalue of 1.0 ... 7–4 7.3. Bar with Hinged Ends ... 7–9 8.1. Common Examples of Nonlinear Structural Behavior ... 8–1 8.2. A Fishing Rod Demonstrates Geometric Nonlinearity ... 8–2 8.3. Newton-Raphson Approach ... 8–3 8.4. Traditional Newton-Raphson Method vs. Arc-Length Method ... 8–4 8.5. Load Steps, Substeps, and Time ... 8–4 8.6. Nonconservative (Path-Dependent) Behavior ... 8–5 8.7. Load Directions Before and After Deflection ... 8–6 8.8. Stress-Stiffened Beams ... 8–8 8.9. Elastoplastic Stress-Strain Curve ... 8–9

8.10. Kinematic Hardening ... 8–10 8.11. Bauschinger Effect ... 8–11 8.12. NLISO Stress-Strain Curve ... 8–14 8.13. Cast Iron Plasticity ... 8–16 8.14. Hyperelastic Structure ... 8–17 8.15. Typical Hyperelastic Stress-Strain Curves ... 8–23 8.16. Data Locations in Stress and Strain Input Arrays ... 8–25 8.17. Typical Evaluated Hyperelastic Stress-Strain Curve ... 8–27 8.18. Stress Relaxation and Creep ... 8–29 8.19. Time Hardening Creep Analysis ... 8–30 8.20. Shape Memory Alloy Phases ... 8–32 8.21. Viscoplastic Behavior in a Rolling Operation ... 8–33 8.22. Viscoelastic Behavior (Maxwell Model) ... 8–34 8.23. Linear Interpolation of Nonlinear Results Can Introduce Some Error ... 8–58 8.24. Convergence Norms Displayed By the Graphical Solution Tracking (GST) Feature ... 8–67 8.25. Typical Nonlinear Output Listing ... 8–70 8.26. Cyclic Point Load History ... 8–73 10.1. Element Topology of a 3-D 8-Node Interface Element ... 10–2 10.2. Pressure vs. Closure Behavior of a Gasket Material ... 10–5 10.3. Gasket Material Input: Linear Unloading Curves ... 10–7 10.4. Gasket Material Input: Nonlinear Unloading Curves ... 10–8 10.5. Gasket Compression and Unloading Curves at Two Temperatures ... 10–11 10.6. Gasket Finite Element Model Geometry ... 10–14 10.7. Whole Model Mesh with Brick Element ... 10–14 10.8. Interface Layer Mesh ... 10–15 10.9. Whole Model Tetrahedral Mesh ... 10–15 10.10. Interface Layer Mesh with Degenerated Wedge Elements ... 10–16 11.1. Localized Contact Zones ... 11–6 11.2. ANSYS Geometric Entities and Their Corresponding Rigid Target Elements ... 11–10 11.3. A Single Circular Target Segment Created From Arc Line Segments ... 11–11 11.4. Meshing Patterns for Arbitrary Target Surfaces ... 11–12 11.5. Smoothing Convex Corner ... 11–13 11.6. Correct Node Ordering ... 11–13 11.7. Contact Element Types ... 11–15 11.8. Specification of the Contact Surface's Outward Normal ... 11–17 11.9. Depth of the Underlying Element ... 11–20 11.10. Sliding Contact Resistance ... 11–26 11.11. Friction Decay ... 11–27 11.12. Contact Detection Located at Gauss Point ... 11–28 11.13. Contact Detection Point Location at Nodal Point ... 11–29 11.14. Node Slippage Using Nodal Integration KEYOPT(4) = 1 or 2 ... 11–29 11.15. Contact Surface Adjustment With ICONT ... 11–32 11.16. Contact Surface Adjustment (PMIN, PMAX) ... 11–33 11.17. A Scenario in Which Initial Adjustment Will Fail ... 11–34 11.18. Ignoring Initial Penetration, KEYOPT(9) = 1 ... 11–35 11.19. Components of True Penetration ... 11–36 11.20. Ramping Initial Interference ... 11–37 11.21. Effect of Moving Contact Nodes ... 11–38 11.22. Auto Spurious Prevention ... 11–39 11.23. Target Temperature ... 11–45 11.24. Contact Manager Toolbar ... 11–54 11.25. Example of a Contact Wizard Dialog ... 11–56 Structural Analysis Guide

11.26. Node-to-Surface Contact Elements ... 11–58 11.27. Example of Shell-solid Assembly ... 11–62 11.28. Shell-solid Assembly (Original Mesh) ... 11–63 11.29. Shell-solid Assembly with Solid-solid Constraint Option ... 11–64 11.30. Shell-solid Assembly with Shell-shell Constraint Option ... 11–64 11.31. Shell-solid Assembly with Shell-solid Constraint Option ... 11–65 11.32. Rigid Constraint Surface ... 11–66 11.33. Force-distributed Surface ... 11–67 11.34. Beam-solid Assembly Defined by Rigid Constraint Surface ... 11–69 11.35. Beam-solid Assembly Defined by Force-distributed Surface ... 11–69 11.36. Node-to-Node Contact Elements ... 11–70 11.37. Contact Between Two Concentric Pipes ... 11–72 11.38. Two Concentric Pipes, Normals Rotated Properly ... 11–73 11.39. Example of Overconstrained Contact Problem ... 11–75 12.1. Crack Tip and Crack Front ... 12–2 12.2. Examples of Singular Elements ... 12–3 12.3. A Fracture Specimen and 2-D FE Model ... 12–4 12.4. Taking Advantage of Symmetry ... 12–4 12.5. Crack Coordinate Systems ... 12–5 12.6. Typical Path Definitions ... 12–6 12.7. J-Integral Contour Path Surrounding a Crack-Tip ... 12–7 12.8. Examples of Paths for J-integral Calculation ... 12–7 13.1. Layered Model Showing Dropped Layer ... 13–3 13.2. Sandwich Construction ... 13–4 13.3. Layered Shell With Nodes at Midplane ... 13–5 13.4. Layered Shell With Nodes at Bottom Surface ... 13–5 13.5. Example of an Element Display ... 13–7 13.6. Sample LAYPLOT Display for [45/-45/ - 45/45] Sequence ... 13–8 14.1. Cylinder Wall with Stress Concentration Factors (SCFs) ... 14–4 14.2. Three Loadings in One Event ... 14–5 14.3. Surface Nodes are Identified by PPATH Prior to Executing FSSECT ... 14–6 15.1. Fan Model Showing p-Element vs. h-Element Meshes ... 15–5 15.2. Coupled Nodes on One Element ... 15–6 15.3. Nodes Coupled Between Adjacent Elements ... 15–6 15.4. Both Corner Nodes are Coupled ... 15–7 15.5. All Coupled Nodes are Midside Nodes ... 15–7 15.6. Constraints on Rotated Nodes ... 15–9 15.7. p-Element Subgrids for Quadrilateral Elements ... 15–13 15.8. Steel Plate With a Hole ... 15–15 16.1. Plot of a Z Cross Section ... 16–2 16.2. Types of Solid Section Cell Mesh ... 16–4 16.3. BeamTool with Subtypes Drop Down List Displayed ... 16–6 16.4. Lateral-Torsional Buckling of a Cantilever I-Beam ... 16–10 16.5. Diagram of a Beam With Deformation Indicated ... 16–11 17.1. Plot of a Shell Section ... 17–2 17.2. Shell Tool With Layup Page Displayed ... 17–4 17.3. Shell Tool With Section Controls Page Displayed ... 17–4 17.4. Shell Tool With Summary Page Displayed ... 17–5

List of Tables

1.1. Structural Element Types ... 1–2 2.1. Basic Tab Options ... 2–3 2.2. Sol'n Options Tab Options ... 2–4 2.3. Nonlinear Tab Options ... 2–4 2.4. Advanced NL Tab Options ... 2–5 2.5. Loads Applicable in a Static Analysis ... 2–8 3.1. Analysis Types and Options ... 3–2 3.2. Loads Applicable in a Modal Analysis ... 3–5 3.3. Load Commands for a Modal Analysis ... 3–5 3.4. Load Step Options ... 3–6 3.5. Expansion Pass Options ... 3–8 3.6. Symmetric System Eigensolver Choices ... 3–17 4.1. Analysis Types and Options ... 4–4 4.2. Applicable Loads in a Harmonic Response Analysis ... 4–7 4.3. Load Commands for a Harmonic Response Analysis ... 4–8 4.4. Load Step Options ... 4–9 4.5. Expansion Pass Options ... 4–22 5.1. Transient Tab Options ... 5–8 5.2. Options for the First Load Step-Mode Superposition Analysis ... 5–15 5.3. Options for the First Load Step-Reduced Analysis ... 5–22 5.4. Expansion Pass Options ... 5–24 5.5. Damping for Different Analysis Types ... 5–36 5.6. Damping Matrix Formulation with Different Damping Coefficients ... 5–39 6.1. Analysis Types and Options ... 6–4 6.2. Load Step Options ... 6–4 6.3. Solution Items Available in a PSD Analysis ... 6–21 6.4. Organization of Results Data from a PSD Analysis ... 6–22 8.1. Suggested Mooney-Rivlin Constants ... 8–23 8.2. Data Locations in Stress and Strain Input Arrays ... 8–24 9.1. Experimental Details for Case 1 and 2 Models and Blatz-Ko ... 9–2 9.2. Experimental Details for Case 3 Models ... 9–2 9.3. Hyperelastic Curve Fitting Model Types ... 9–3 9.4. Creep Data Types and Abbreviations ... 9–8 9.5. Creep Model and Data/Type Attribute ... 9–8 9.6. Creep Models and Abbreviations ... 9–10 9.7. Viscoelastic Data Types and Abbreviations ... 9–15 11.1. ANSYS Contact Capabilities ... 11–2 11.2. Summary of Real Constant Defaults in Different Environments ... 11–18 11.3. Summary of KEYOPT Defaults in Different Environments ... 11–21 16.1. ANSYS Cross Section Commands ... 16–2 17.1. ANSYS Cross Section Commands ... 17–1 Structural Analysis Guide

Chapter 1: Overview of Structural Analyses

1.1. Definition of Structural Analysis

Structural analysis is probably the most common application of the finite element method. The term structural (or structure) implies not only civil engineering structures such as bridges and buildings, but also naval, aeronaut-ical, and mechanical structures such as ship hulls, aircraft bodies, and machine housings, as well as mechanical components such as pistons, machine parts, and tools.

1.2. Types of Structural Analysis

The seven types of structural analyses available in the ANSYS family of products are explained below. The primary unknowns (nodal degrees of freedom) calculated in a structural analysis are displacements. Other quantities, such as strains, stresses, and reaction forces, are then derived from the nodal displacements.

Structural analyses are available in the ANSYS Multiphysics, ANSYS Mechanical, ANSYS Structural, and ANSYS Professional programs only.

You can perform the following types of structural analyses. Each of these analysis types are discussed in detail in this manual.

Static Analysis--Used to determine displacements, stresses, etc. under static loading conditions. Both linear and

nonlinear static analyses. Nonlinearities can include plasticity, stress stiffening, large deflection, large strain, hy-perelasticity, contact surfaces, and creep.

Modal Analysis--Used to calculate the natural frequencies and mode shapes of a structure. Different mode

extrac-tion methods are available.

Harmonic Analysis--Used to determine the response of a structure to harmonically time-varying loads.

Transient Dynamic Analysis--Used to determine the response of a structure to arbitrarily time-varying loads. All

nonlinearities mentioned under Static Analysis above are allowed.

Spectrum Analysis--An extension of the modal analysis, used to calculate stresses and strains due to a response

spectrum or a PSD input (random vibrations).

Buckling Analysis--Used to calculate the buckling loads and determine the buckling mode shape. Both linear

(eigenvalue) buckling and nonlinear buckling analyses are possible.

Explicit Dynamic Analysis--This type of structural analysis is only available in the ANSYS LS-DYNA program. ANSYS

LS-DYNA provides an interface to the LS-DYNA explicit finite element program. Explicit dynamic analysis is used to calculate fast solutions for large deformation dynamics and complex contact problems. Explicit dynamic analysis is described in the ANSYS LS-DYNA User's Guide.

In addition to the above analysis types, several special-purpose features are available: • Fracture mechanics

• Composites • Fatigue • p-Method • Beam Analyses

1.3. Elements Used in Structural Analyses

Most ANSYS element types are structural elements, ranging from simple spars and beams to more complex layered shells and large strain solids. Most types of structural analyses can use any of these elements.

Note — Explicit dynamics analysis can use only the explicit dynamic elements (LINK160, BEAM161,

PLANE162, SHELL163, SOLID164, COMBI165, MASS166, LINK167, and SOLID168).

Table 1.1 Structural Element Types

Element Name(s) Category

LINK1, LINK8, LINK10, LINK180 Spars

BEAM3, BEAM4, BEAM23, BEAM24, BEAM44, BEAM54, BEAM188, BEAM189 Beams

PIPE16, PIPE17, PIPE18, PIPE20, PIPE59, PIPE60 Pipes

PLANE2, PLANE25, PLANE42, HYPER56, HYPER74, PLANE82, PLANE83, HYPER84, VISCO88, VISCO106, VISCO108, PLANE145, PLANE146, PLANE182, PLANE183

2-D Solids

SOLID45, SOLID46, HYPER58, SOLID64, SOLID65, HYPER86, VISCO89, SOLID92, SOLID95, VISCO107, SOLID147, SOLID148, HYPER158, SOLID185, SOLID186, SOLID187, SOLID191 3-D Solids

SHELL28, SHELL41, SHELL43, SHELL51, SHELL61, SHELL63, SHELL91, SHELL93, SHELL99, SHELL150, SHELL181

Shells

INTER192, INTER193, INTER194, INTER195 Interface

CONTAC12, CONTAC52, TARGE169, TARGE170, CONTA171, CONTA172, CONTA173, CON-TA174, CONTA175

Contact

SOLID5, PLANE13, FLUID29, FLUID30, FLUID38, SOLID62, FLUID79, FLUID80, FLUID81, SOLID98, FLUID129, INFIN110, INFIN111, FLUID116, FLUID130

Coupled-Field

COMBIN7, LINK11, COMBIN14, MASS21, MATRIX27, COMBIN37, COMBIN39, COMBIN40, MATRIX50, SURF153, SURF154

Specialty

LINK160, BEAM161, PLANE162, SHELL163, SOLID164, COMBI165, MASS166, LINK167, SOLID168 Explicit Dynamics

1.4. Material Model Interface

For analyses described in this guide, if you are using the GUI, you must specify the material you will be simulating using an intuitive material model interface. This interface uses a hierarchical tree structure of material categories, which is intended to assist you in choosing the appropriate model for your analysis. See Section 1.2.4.4: Material Model Interface in the ANSYS Basic Analysis Guide for details on the material model interface.

1.5. Types of Solution Methods

Two solution methods are available for solving structural problems in the ANSYS family of products: the h-method and the p-h-method. The h-h-method can be used for any type of analysis, but the p-h-method can be used only for linear structural static analyses. Depending on the problem to be solved, the h-method usually requires a finer mesh than the p-method. The p-method provides an excellent way to solve a problem to a desired level of accuracy while using a coarse mesh. In general, the discussions in this manual focus on the procedures required for the h-method of solution. Chapter 15, “p-Method Structural Static Analysis” discusses procedures specific to the p-method.

Chapter 2: Structural Static Analysis

2.1. Definition of Static Analysis

A static analysis calculates the effects of steady loading conditions on a structure, while ignoring inertia and damping effects, such as those caused by time-varying loads. A static analysis can, however, include steady inertia loads (such as gravity and rotational velocity), and time-varying loads that can be approximated as static equi-valent loads (such as the static equiequi-valent wind and seismic loads commonly defined in many building codes). Static analysis is used to determine the displacements, stresses, strains, and forces in structures or components caused by loads that do not induce significant inertia and damping effects. Steady loading and response conditions are assumed; that is, the loads and the structure's response are assumed to vary slowly with respect to time. The kinds of loading that can be applied in a static analysis include:

• Externally applied forces and pressures

• Steady-state inertial forces (such as gravity or rotational velocity) • Imposed (nonzero) displacements

• Temperatures (for thermal strain) • Fluences (for nuclear swelling)

More information about the loads that you can apply in a static analysis appears in Section 2.3.4: Apply the Loads.

2.2. Linear vs. Nonlinear Static Analyses

A static analysis can be either linear or nonlinear. All types of nonlinearities are allowed - large deformations, plasticity, creep, stress stiffening, contact (gap) elements, hyperelastic elements, and so on. This chapter focuses on linear static analyses, with brief references to nonlinearities. Details of how to handle nonlinearities are described in Chapter 8, “Nonlinear Structural Analysis”.

2.3. Performing a Static Analysis

The procedure for a static analysis consists of these tasks: 1. Section 2.3.1: Build the Model

2. Section 2.3.2: Set Solution Controls

3. Section 2.3.3: Set Additional Solution Options 4. Section 2.3.4: Apply the Loads

5. Section 2.3.5: Solve the Analysis 6. Section 2.3.6: Review the Results

2.3.1. Build the Model

See Section 1.2: Building a Model in the ANSYS Basic Analysis Guide. For further details, see the ANSYS Modeling

and Meshing Guide.

2.3.1.1. Points to Remember

• You can use both linear and nonlinear structural elements.

• Material properties can be linear or nonlinear, isotropic or orthotropic, and constant or temperature-de-pendent.

– You must define stiffness in some form (for example, Young's modulus (EX), hyperelastic coefficients, and so on).

– For inertia loads (such as gravity), you must define the data required for mass calculations, such as density (DENS).

– For thermal loads (temperatures), you must define the coefficient of thermal expansion (ALPX). Note the following information about mesh density:

• Regions where stresses or strains vary rapidly (usually areas of interest) require a relatively finer mesh than regions where stresses or strains are nearly constant (within an element).

• While considering the influence of nonlinearities, remember that the mesh should be able to capture the effects of the nonlinearities. For example, plasticity requires a reasonable integration point density (and therefore a fine element mesh) in areas with high plastic deformation gradients.

2.3.2. Set Solution Controls

Setting solution controls involves defining the analysis type and common analysis options for an analysis, as well as specifying load step options for it. When you are doing a structural static analysis, you can take advantage of a streamlined solution interface (called the Solution Controls dialog box) for setting these options. The Solution

Controls dialog box provides default settings that will work well for many structural static analyses, which means

that you may need to set only a few, if any, of the options. Because the streamlined solution interface is the

re-commended tool for setting solution controls in a structural static analysis, it is the method that is presented in

this chapter.

If you prefer not to use the Solution Controls dialog box (Main Menu> Solution> Analysis Type> Sol'n Controls), you can set solution controls for your analysis using the standard set of ANSYS solution commands and the standard corresponding menu paths (Main Menu> Solution> Unabridged Menu> option). For a general

overview of the Solution Controls dialog box, see Section 3.11: Using Special Solution Controls for Certain Types of Structural Analyses in the ANSYS Basic Analysis Guide.

2.3.2.1. Access the Solution Controls Dialog Box

To access the Solution Controls dialog box, choose menu path Main Menu> Solution> Analysis Type> Sol'n

Controls. The following sections provide brief descriptions of the options that appear on each tab of the dialog

box. For details about how to set these options, select the tab that you are interested in (from within the ANSYS program),

and then click the Help button. Chapter 8, “Nonlinear Structural Analysis” also contains details about the nonlinear

options introduced in this chapter.

2.3.2.2. Using the Basic Tab

The Basic tab is active when you access the dialog box.

The controls that appear on the Basic tab provide the minimum amount of data that ANSYS needs for the ana-lysis. Once you are satisfied with the settings on the Basic tab, you do not need to progress through the remaining tabs unless you want to adjust the default settings for the more advanced controls. As soon as you click OK on any tab of the dialog box, the settings are applied to the ANSYS database and the dialog box closes.

You can use the Basic tab to set the options listed in Table 2.1: “Basic Tab Options”. For specific information about using the Solution Controls dialog box to set these options, access the dialog box, select the Basic tab, and click the Help button.

Table 2.1 Basic Tab Options

For more information on this option, see: Option

• Section 1.2.6.1: Defining the Analysis Type and Analysis Options in the ANSYS Basic Analysis Guide

• Chapter 8, “Nonlinear Structural Analysis” in the ANSYS

Structural Analysis Guide

• Section 3.16: Restarting an Analysis in the ANSYS Basic

Analysis Guide

Specify analysis type [ANTYPE, NLGEOM]

• Section 2.4: The Role of Time in Tracking in the ANSYS

Basic Analysis Guide

• Section 2.7.1: General Options in the ANSYS Basic

Analysis Guide

Control time settings, including: time at end of load step [TIME], automatic time step-ping [AUTOTS], and number of substeps to be taken in a load step [NSUBST or

DELTIM]

• Section 2.7.4: Output Controls in the ANSYS Basic

Analysis Guide

Specify solution data to write to database [OUTRES]

Special considerations for setting these options in a static analysis include:

• When setting ANTYPE and NLGEOM, choose Small Displacement Static if you are performing a new analysis and you want to ignore large deformation effects such as large deflection, large rotation, and large strain. Choose Large Displacement Static if you expect large deflections (as in the case of a long, slender bar under bending) or large strains (as in a metal-forming problem). Choose Restart Current

Analysis if you want to restart a failed nonlinear analysis, or you have previously completed a static

ana-lysis, and you want to specify additional loads.

• When setting TIME, remember that this load step option specifies time at the end of the load step. The default value is 1.0 for the first load step. For subsequent load steps, the default is 1.0 plus the time specified for the previous load step. Although time has no physical meaning in a static analysis (except in the case of creep, viscoplasticity, or other rate-dependent material behavior), it is used as a convenient way of re-ferring to load steps and substeps (see Chapter 2, “Loading” in the ANSYS Basic Analysis Guide).

• When setting OUTRES, keep this caution in mind:

Caution: By default, only 1000 results sets can be written to the results file (Jobname.RST). If this

number is exceeded (based on your OUTRES specification), the program will terminate with an error. Use the command /CONFIG,NRES to increase the limit (see Chapter 19, “Memory Management and Configuration” in the ANSYS Basic Analysis Guide).

2.3.2.3. The Transient Tab

The Transient tab contains transient analysis controls; it is available only if you choose a transient analysis and remains grayed out when you choose a static analysis. For these reasons, it is not described here.

2.3.2.4. Using the Sol'n Options Tab

You can use the Sol'n Options tab to set the options listed in Table 2.2: “Sol'n Options Tab Options”. For specific information about using the Solution Controls dialog box to set these options, access the dialog box, select the Sol'n Options tab, and click the Help button.

Table 2.2 Sol'n Options Tab Options

For more information about this option, see the following section(s) in the ANSYS Basic Analysis Guide:

Option

• Section 3.2: Selecting a Solver through Section 3.10: Using the Automatic Iterative (Fast) Solver Option Specify equation solver [EQSLV]

• Section 3.16.2: Multiframe Restart Specify parameters for multiframe restart

[RESCONTROL]

Special considerations for setting these options in a static analysis include: • When setting EQSLV, specify one of these solvers:

– Program chosen solver (ANSYS selects a solver for you, based on the physics of the problem) – Sparse direct solver (default for linear and nonlinear, static and full transient analyses)

– Preconditioned Conjugate Gradient (PCG) solver (recommended for large models/high wavefronts, bulky structures)

– Algebraic Multigrid (AMG) solver (applicable in the same situations as the PCG solver, but provides parallel processing; for faster turnaround times when used in a multiprocessor environment) – Distributed Domain Solver (DDS) provides parallel processing on multiple systems across a network – Iterative solver (auto-select; for linear static/full transient structural or steady-state thermal analyses

only; recommended) – Frontal direct solver

Note — The AMG and DDS solvers are part of Parallel Performance for ANSYS, which is a separately-licensed

product. See Chapter 13, “Improving ANSYS Performance and Parallel Performance for ANSYS” in the

ANSYS Advanced Analysis Techniques Guide for more information about these solvers.

2.3.2.5. Using the Nonlinear Tab

You can use the Nonlinear tab to set the options listed in Table 2.3: “Nonlinear Tab Options”. For specific inform-ation about using the Solution Controls dialog box to set these options, access the dialog box, select the

Non-linear tab, and click the Help button.

Table 2.3 Nonlinear Tab Options

For more information about this option, see the following section(s) in the ANSYS Structural Analysis Guide:

Option

• Section 8.5.2.3.5: Line Search Option • Section 8.10.2.4: Using Line Search Activate line search [LNSRCH]