Introduction to Nonlinear Finite Element Analysis using Optistruct

About This Book......Page 7
1 Introduction to Nonlinearity......Page 13
1.1 Sources of Nonlinearity......Page 14
1.2 Features of Nonlinear Problems......Page 15
1.3 When to Choose a Nonlinear Analysis?......Page 17
1.4 Small vs Large Displacement Nonlinear Analysis......Page 18
2 Solution Techniques......Page 21
2.1 Incremental-Iterative Procedure......Page 22
2.2 Automatic Increment Size Control......Page 23
2.4 Analysis Controls......Page 24
2.4.1 Main Parameters - NLPARM......Page 25
2.4.2 Additional Time Step and Convergence Controls – NLADAPT......Page 26
2.4.3 Request for Intermediate Results with NLOUT......Page 27
2.4.5 Loadsteps Sequence......Page 28
2.4.5.1 Boundary Fixing for CNTNLSUB......Page 30
2.5 Path Dependent Loading......Page 31
2.5.1 Path Dependent Load Setup in OptiStruct......Page 32
2.6 Restarting a Nonlinear Analysis......Page 33
2.8 On the Fly Output of Displacement Results for Nonlinear Analysis......Page 34
3 Material Nonlinearity......Page 38
3.1 Elastic-Plastic Material......Page 39
3.1.1 Engineering vs True Stress and Strain......Page 40
3.1.2 Hardening Models......Page 42
3.1.3 Plasticity Setup in OptiStruct – MATS1......Page 44
3.1.4 Plasticity Results......Page 47
3.1.5 Tutorial: Small-Strain and Large-Strain Plasticity in a Test Coupon......Page 48
3.2 Hyperelastic Material......Page 55
3.2.1 Hyperelastic Material Models in OptiStruct......Page 56
3.2.2 Defining Hyperelastic Material Properties......Page 57
3.2.3 General Remarks for Hyperelastic Models......Page 58
3.2.4 Tutorial: Compression of a Hyperelastic Part......Page 59
4.1 Large Deflection......Page 64
4.2 Large Strain......Page 66
4.2.1 Large Strain in Shells......Page 67
4.3 Non-Uniqueness of the Solution: Snap-Through......Page 68
4.4 Follower Forces......Page 69
4.4.1 Follower Forces Setup......Page 70
4.4.2 Tutorial: Follower Forces on a Curved Rod......Page 72
5.1 Contact Discretization......Page 77
5.1.1 Node-to-Surface Contact......Page 78
5.1.2 Surface-to-Surface Contact......Page 79
5.1.3 Which One to Choose – N2S or S2S?......Page 80
5.1.5 Continuous, Finite vs Small Sliding Contact......Page 81
5.1.7 Tutorial: N2S and S2S Contact......Page 83
5.2.1 Contact Types......Page 90
5.2.2 Contact Stiffness (Penalty)......Page 92
5.2.3 Friction Modelling......Page 94
5.2.4 Alternative Approach – MPC-based TIE Contact......Page 97
5.2.5 Fast Contact......Page 98
5.3 Contact Utilities......Page 99
5.3.1 Tutorial: Using ADJUST Option in Contact Analysis......Page 108
5.3.2 Tutorial: Utilizing CLEARANCE with a Variable Gap......Page 112
5.4.1 Via Contact Browser – Manually......Page 117
5.4.1.1 Contact Surface Setup......Page 119
5.4.2 In Model Browser – Manually......Page 120
5.4.3 Via Contact Browser – AutoContact......Page 121
5.5 Analysis Controls for Contacts......Page 123
5.6 Contact Output......Page 124
5.6.1 Print Contact info Prior to Analysis......Page 125
5.8 Tutorial : Nonlinear Analysis of an Interference Fit......Page 127
5.9 Capstone Tutorial Part 1: Setting Up Frictional Contact in a Bolted Pipe Flange Model......Page 140
6.1 Pretensioning Process......Page 145
6.2 Bolt Pretension in OptiStruct......Page 146
6.2.1 1D Bolt Pretensioning......Page 147
6.2.3 Bolt Pretension Setup......Page 148
6.3 Capstone Tutorial Part 2: Creating Pretensioned 3D Bolts in the Bolted Pipe Flange Model......Page 151
7.1 Loading/Unloading Data Setup......Page 156
7.2 Gasket Material & Property Cards......Page 158
7.3 Gasket Elements Setup......Page 160
7.4 Capstone Tutorial Part 3: Creating Gaskets for the Bolted Pipe Flange Model......Page 161
8 Nonlinear Direct Transient Analysis......Page 167
8.1 Solution Method......Page 168
8.2 Nonlinear Transient Analysis Setup......Page 169
8.3 Tutorial: Nonlinear Transient Analysis of a Plate with a Hole......Page 171
9.1 Essential Steps To Start With Nonlinear FEA......Page 178
9.2 Debugging......Page 179
9.3 Useful Tutorials and Industry Examples......Page 181
10 Appendix......Page 185