Foreword by Dr. Sonell Shroff	6
	Foreword by Gautam Puri	8
	Foreword by Prof. David Bassir	10
	Preface	11
	Acknowledgements	13
	Contents	16
	Abbreviations	23
	Part I Methodology to Start Debugging Model Issues	24
	1 Introduction	25
	1.1 Global Mindset	25
	1.2 The Four Absolutes of Quality in Analysis	30
	1.3 Checklist for Performing Analysis	31
	1.4 A Heuristic Analysis Confidence Ratio	31
	References	37
	2 Analysis Convergence Guidelines	38
	2.1 Symptoms of Convergence Problems	38
	2.2 Causes of Convergence Problems	39
	2.3 Helping Abaqus Find a Converged Solution	39
	2.4 General Tools	40
	2.5 Tools for Contact Stabilization	42
	2.6 Tools for Contact Related Convergence Problems	42
	Reference	44
	3 Method to Debug a Model	45
	3.1 Debugging Flowchart	45
	3.2 Job Diagnostic	45
	3.2.1 Making a Test Model	45
	3.2.2 Output Check	49
	3.2.3 Syntax Check	50
	3.2.4 Data Check	51
	3.2.5 Loading and Boundary Conditions Check	54
	3.2.6 Materials Check	56
	3.2.7 Constraints Check	58
	3.2.8 Elements Check	59
	3.2.9 Interference Fits Check	60
	3.2.10 Contact Check	61
	3.2.11 Initial Rigid Body Motion and Over Constraints Check	63
	3.2.12 Static Stabilization Check	67
	3.2.13 Dynamics Check	69
	3.3 Causality Energy Method	74
	3.3.1 Basic Energy Approaches, Assumptions and Limitations	75
	3.3.2 The Energy Method	76
	3.3.3 Energy Method Example to Scale Analyses	77
	3.3.4 Causality and Energy Derivatives	78
	References	79
	4 General Prerequisites	80
	4.1 Vocabularies	80
	4.1.1 Interpreting Error Messages	82
	4.1.2 Interpreting Warning Messages	83
	4.2 An Identified Unconnected Region in the Model	84
	4.3 Correction of Errors During the Data Check Phase of an Abaqus/Standard Analysis	86
	4.4 Tips and Tricks for Diagnostic Error Messages	88
	4.5 Trying to Recover a Corrupted Database	89
	4.5.1 Procedure 1	89
	4.5.2 Procedure 2	90
	4.6 Kinematic Distributing Couplings in Abaqus	91
	4.6.1 Nature of the Constraint Enforcement	91
	4.6.2 Defining Constraints in Abaqus/CAE	94
	4.7 Abaqus Geometric Nonlinearity	94
	4.8 Differences Between Implicit and Explicit Schemes	97
	4.8.1 Equations for Dynamic Problems	98
	4.8.2 Time Integration of the Equations of Motion	98
	4.8.3 Automatic Time Incrementation with Abaqus Standard	100
	4.8.4 Automatic Time Incrementation with Abaqus Explicit	105
	4.8.5 Dynamic Contact	107
	4.8.6 Material Damping	107
	4.8.7 Half-Increment Residual Tolerance	108
	4.8.8 Comparing Abaqus/Standard and Abaqus/Explicit	109
	4.9 Unstable Collapse and Post-buckling Analysis	110
	4.10 Low-Cycle Fatigue Analysis Using the Direct Cyclic Approach	112
	4.11 Steady-State Transport Analysis	113
	4.11.1 Convergence Issues in a Steady-State Transport Analysis	114
	4.12 Heat Transfer Analysis	116
	4.12.1 Transient Analysis	117
	4.13 Fluid Dynamic Analysis	121
	4.13.1 Convergence Criteria and Diagnostics	121
	4.13.2 Time Increment Size Control	123
	4.14 Introduction to the User Subroutines	124
	4.14.1 Installation of a Fortran Compiler	126
	4.14.2 Run a Model Which Uses a User Subroutine	128
	4.14.3 Debugging Techniques and Proper Programming Habits	128
	4.14.4 Examples of User Subroutine with Abaqus Standard	131
	4.14.5 Examples of User Subroutine with Abaqus Explicit	133
	4.14.6 Examples of User Subroutine with Abaqus CFD	135
	References	135
	Part II Stop Struggling with Specific Issues	136
	5 Materials	137
	5.1 Generalities	137
	5.2 The Current Strain Increment Exceeds the Strain to First Yield	139
	5.3 Convergence Behavior of Models Using Hyperelastic Materials	140
	5.4 Models Using Incompressible or Nearly Incompressible Materials	141
	5.5 Equivalence of Uniaxial Tension and Compression Hyperelastic Test Data	142
	5.5.1 Uniaxial Compression Test Data for a Rubber Material	143
	5.5.2 Specifying Tension or Compression Test Data for the Marlow Hyperelasticity Model	144
	5.5.3 Using Simple Shear Experimental Data for Hyperelastic Materials	145
	5.6 Path Dependence of Nonlinear Results Using an Elastic Material	147
	5.7 User Material Subroutine	149
	5.7.1 Guideline to Write a UMAT or a VMAT	150
	5.8 UMAT Subroutine Examples	151
	5.8.1 UMAT Subroutine for Isotropic Isothermal Elasticity	154
	5.8.2 UMAT Subroutine for Non-isothermal Elasticity	156
	5.8.3 UMAT Subroutine for Neo-Hookean Hyperelasticity	158
	5.8.4 UMAT Subroutine for Kinematic Hardening Plasticity	163
	5.8.5 UMAT Subroutine for Isotropic Hardening Plasticity	169
	5.8.6 UMAT Subroutine for Simple Linear Viscoelastic Material	175
	5.9 VUMAT Subroutine Examples	178
	5.9.1 VUMAT Subroutine for Kinematic Hardening Plasticity	180
	5.9.2 VUMAT Subroutine for Isotropic Hardening Plasticity	183
	References	187
	6 Mesher and Meshing	189
	6.1 Generalities	189
	6.1.1 Mesh Control Options	190
	6.1.2 Mesh Controls for a 2D Structure	190
	6.1.3 Mesh Controls for a 3D Structure	190
	6.1.4 Understanding a Mesher	192
	6.1.5 Mesh as Grid Generation	197
	6.2 The Abaqus Model Meshed Has Changed into a Nonphysical Shape with a Regular Pattern	208
	6.3 Excessive Element Distortion Warnings	209
	6.4 Compatibility Errors Printed to the Message File for a Model with Hybrid Elements	209
	6.5 User Element Subroutine	210
	6.5.1 Guideline to Write a UEL	211
	6.6 UEL Subroutine Examples	219
	6.6.1 UEL Subroutine for Planar Beam with Nonlinear Cross Section	220
	6.6.2 Generalized Constitutive Behavior	225
	6.6.3 UEL Subroutine for a Horizontal Truss and Heat Transfer Element	227
	6.6.4 UELMAT Subroutine for 4 Nodes in Plane Strain	232
	6.7 Using Nonlinear User Elements in Various Analysis Procedures	240
	References	244
	7 Contact	245
	7.1 Generalities	245
	7.1.1 Understandings	248
	7.1.2 Define Contact Pairs	252
	7.1.3 Define General Contact	252
	7.1.4 Representation of Curved Surfaces	254
	7.1.5 Contact Formulation Aspects	255
	7.2 Friction	280
	7.2.1 Static and Kinetic Friction	281
	7.2.2 Change Friction Properties During an Analysis	284
	7.2.3 Classic Friction Values	284
	7.3 Hard or Soft Contact	285
	7.3.1 Identification of the Mathematical Stiffness Function	288
	7.3.2 Exponential Contact Stiffness	292
	7.3.3 From Hard Contact to Exponential	294
	7.4 Obtain a Converged Contact Solution	296
	7.5 Convergence Difficulty in the First Increment	298
	7.6 Causes and Resolutions of Contact Chattering	299
	7.7 Understand Finite Sliding with Surface-to-Surface Contact	301
	7.8 Using Penalty Contact	304
	7.9 Using Augmented Lagrangian Contact	308
	7.10 Using Stiffness-Based Contact Stabilization	310
	7.11 Modeling Contact with Second-Order Tetrahedral Elements	312
	References	313
	Part III A Toolbox to Do the Job	314
	8 Troubleshooting in Job Diagnostics	315
	8.1 Guidelines with Abaqus Standard	315
	8.2 Job with Abaqus Standard Completes, But the Results Look Suspicious	317
	8.3 Model a Structure Undergoing a Global Instability	320
	8.4 Correct Convergence Difficulties Caused by Local Instabilities	321
	8.5 Correcting Errors During the Data-Check Phase of an Analysis	322
	8.6 Analysis Ends Prematurely, Even Though All the Increments Have Converged	324
	8.7 Debugging Divergence with Too Many Cutbacks in the Last Attempted Increment	325
	8.8 Using Follower Loads in Nonlinear Analyses	326
	8.9 Understanding Negative Eigenvalue Messages	327
	8.10 Divergence with Numerical Singularity Warnings	329
	8.11 Zero Pivot Warnings in the Message File	330
	8.12 Convergence Difficulty in the First Increment of a Contact Analysis	331
	8.13 Explicit Stable Time Increments When Using the Marlow Model with Noisy Test Data	333
	8.14 Cause of an Analysis Ending in a Core Dump	334
	8.15 Debugging User Subroutines and Post Processing Programs	334
	8.16 No Free Memory Available on Linux at the End of an Analysis	339
	Reference	342
	9 Numerical Acceptance Criteria	343
	9.1 Generalities	343
	9.1.1 Commonly Used Control Parameters	343
	9.1.2 Controlling the Time Incrementation Scheme	345
	9.1.3 Activate the Line Search Algorithm	347
	9.1.4 Controlling the Solution Accuracy in Direct Cyclic Analysis	347
	9.1.5 Controlling the Solution Accuracy and Mesh Quality in a Deforming Mesh Analysis with Abaqus CFD	348
	9.1.6 Convergence Criteria for Nonlinear Problems	350
	9.1.7 Time Integration Accuracy in Transient Problems	359
	9.1.8 Avoid Small Changes to the Time Increment Size During Implicit Integration Procedures	360
	9.2 How Much Hourglass Energy Is Acceptable	361
	9.2.1 Enhanced Hourglass Control and Elastic Bending Moment	362
	9.2.2 Enhanced Hourglass Control and Plastic Bending Moment	362
	9.2.3 Kelvin Viscoelastic Hourglass Control	362
	9.3 Errors Printed to the Message File for a Model with Hybrid Elements	363
	Reference	364
	10 Need Some Help?	365
	10.1 Retrieving Files Referred to Examples in the Abaqus Documentation	365
	10.2 Using the Abaqus Verification, Benchmarks, and Example Problems Guides	365
	10.3 Excessive Memory Usage with Cavity Radiation Problems	373
	10.4 Perform a Sub-model Analysis	374
	10.4.1 Implementation	375
	10.4.2 Loading Conditions	376
	10.4.3 Sub-model Boundary Conditions	376
	10.4.4 Interpolation	377
	10.4.5 Step-by-Step Procedure for a Sub-model	377
	10.4.6 Setting Options	380
	10.4.7 Shell to Solid	381
	10.4.8 Changing Procedures	383
	10.4.9 Frequency Domain	383
	10.4.10 Thermal and Stress Analysis	384
	10.4.11 Dynamic Analysis	385
	10.4.12 Limitations of Sub-modeling	386
	10.5 Perform a Restart Analysis	387
	10.5.1 Step-by-Step Procedure for a Restart	389
	10.6 Generate a Shell Part from a Solid Part	392
	10.6.1 Benefits for Using Shell Structures	392
	10.6.2 Applications to Model Shell Structures	393
	10.6.3 Step-by-Step Procedure to Convert Solid Model to Shell Model	394
	10.7 Compile and Link a Post-processing Program Using the Standalone Abaqus ODB API	401
	10.8 Create Executables Using the C++ ODB API Libraries Outside of Abaqus/Make	403
	11 Hardware or Software Issues	407
	11.1 Solving File System Error 1073741819	407
	11.2 Interpreting Error Codes	407
	11.3 Obtaining a Traceback from a UNIX/Linux Core Dump	409
	11.4 Windows HPC Compute Clusters	413
	11.4.1 Classics Troubleshooting with HPC Cluster	418
	Reference	421
	Appendix Guidelines and Good Practices Examples	422
	A.1 Using *COUPLING to Simulate Pure Bending of Thin Walled Pipes	422
	A.2 Available Degrees of Freedom with Kinematic Relation at Coupled Nodes	423
	A.3 Stability and Accuracy of the Trapezoidal Rule	424
	A.4 Accuracy Control in Highly Nonlinear Problems with a Half-Increment Residual Tolerance	431
	A.5 The Art of Meshing	434
	A.5.1 Free Meshing Technique	435
	A.5.2 Model Partitioning with a Strategy Based on Design Symmetry	437
	A.5.3 Model Partitioning with a Strategy Based on the Dominant Geometry	440
	A.5.4 Small Edges and Consequences for the Mesher	444
	A.5.5 Incompatible Mesh	448
	Index	451