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 |  موضوع: كتاب Troubleshooting Finite-Element Modeling with Abaqus السبت 04 يوليو 2020, 12:05 am | |
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أخوانى فى الله
أحضرت لكم كتاب
Troubleshooting Finite-Element Modeling with Abaqus
With Application in Structural Engineering Analysis
Raphael Jean Boulbes
و المحتوى كما يلي :
Contents
Part I Methodology to Start Debugging Model Issues
1 Introduction 3
1.1 Global Mindset 3
1.2 The Four Absolutes of Quality in Analysis 8
1.3 Checklist for Performing Analysis 9
1.4 A Heuristic Analysis Confidence Ratio 9
References 15
2 Analysis Convergence Guidelines 17
2.1 Symptoms of Convergence Problems 17
2.2 Causes of Convergence Problems 18
2.3 Helping Abaqus Find a Converged Solution . 18
2.4 General Tools . 19
2.5 Tools for Contact Stabilization 21
2.6 Tools for Contact Related Convergence Problems . 21
Reference . 23
3 Method to Debug a Model . 25
3.1 Debugging Flowchart . 25
3.2 Job Diagnostic 25
3.2.1 Making a Test Model 25
3.2.2 Output Check 29
3.2.3 Syntax Check 30
3.2.4 Data Check . 31
3.2.5 Loading and Boundary Conditions Check . 34
3.2.6 Materials Check 36
3.2.7 Constraints Check 38
3.2.8 Elements Check 39
3.2.9 Interference Fits Check . 40
3.2.10 Contact Check . 41
xix3.2.11 Initial Rigid Body Motion and Over Constraints
Check . 43
3.2.12 Static Stabilization Check . 47
3.2.13 Dynamics Check . 49
3.3 Causality Energy Method 54
3.3.1 Basic Energy Approaches, Assumptions
and Limitations 55
3.3.2 The Energy Method . 56
3.3.3 Energy Method Example to Scale Analyses 57
3.3.4 Causality and Energy Derivatives . 58
References 59
4 General Prerequisites . 61
4.1 Vocabularies 61
4.1.1 Interpreting Error Messages 63
4.1.2 Interpreting Warning Messages . 64
4.2 An Identified Unconnected Region in the Model . 65
4.3 Correction of Errors During the Data Check Phase
of an Abaqus/Standard Analysis . 67
4.4 Tips and Tricks for Diagnostic Error Messages . 69
4.5 Trying to Recover a Corrupted Database . 70
4.5.1 Procedure 1 . 70
4.5.2 Procedure 2 . 71
4.6 Kinematic Distributing Couplings in Abaqus 72
4.6.1 Nature of the Constraint Enforcement 72
4.6.2 Defining Constraints in Abaqus/CAE . 75
4.7 Abaqus Geometric Nonlinearity 75
4.8 Differences Between Implicit and Explicit Schemes . 78
4.8.1 Equations for Dynamic Problems . 79
4.8.2 Time Integration of the Equations of Motion . 79
4.8.3 Automatic Time Incrementation with Abaqus
Standard . 81
4.8.4 Automatic Time Incrementation with Abaqus
Explicit 86
4.8.5 Dynamic Contact . 88
4.8.6 Material Damping . 88
4.8.7 Half-Increment Residual Tolerance 89
4.8.8 Comparing Abaqus/Standard and Abaqus/Explicit . 90
4.9 Unstable Collapse and Post-buckling Analysis . 91
4.10 Low-Cycle Fatigue Analysis Using the Direct Cyclic
Approach 93
xx Contents4.11 Steady-State Transport Analysis 94
4.11.1 Convergence Issues in a Steady-State Transport
Analysis 95
4.12 Heat Transfer Analysis 97
4.12.1 Transient Analysis 98
4.13 Fluid Dynamic Analysis . 102
4.13.1 Convergence Criteria and Diagnostics 102
4.13.2 Time Increment Size Control . 104
4.14 Introduction to the User Subroutines 105
4.14.1 Installation of a Fortran Compiler . 107
4.14.2 Run a Model Which Uses a User Subroutine . 109
4.14.3 Debugging Techniques and Proper Programming
Habits . 109
4.14.4 Examples of User Subroutine with Abaqus
Standard . 112
4.14.5 Examples of User Subroutine with Abaqus
Explicit 114
4.14.6 Examples of User Subroutine with Abaqus CFD 116
References 116
Part II Stop Struggling with Specific Issues
5 Materials . 119
5.1 Generalities 119
5.2 The Current Strain Increment Exceeds the Strain to First
Yield . 121
5.3 Convergence Behavior of Models Using Hyperelastic
Materials 122
5.4 Models Using Incompressible or Nearly Incompressible
Materials 123
5.5 Equivalence of Uniaxial Tension and Compression
Hyperelastic Test Data 124
5.5.1 Uniaxial Compression Test Data for a Rubber
Material 125
5.5.2 Specifying Tension or Compression Test Data
for the Marlow Hyperelasticity Model 126
5.5.3 Using Simple Shear Experimental Data for
Hyperelastic Materials 127
5.6 Path Dependence of Nonlinear Results Using an Elastic
Material . 129
5.7 User Material Subroutine . 131
5.7.1 Guideline to Write a UMAT or a VMAT 132
5.8 UMAT Subroutine Examples 133
Contents xxi5.8.1 UMAT Subroutine for Isotropic Isothermal
Elasticity . 136
5.8.2 UMAT Subroutine for Non-isothermal Elasticity 138
5.8.3 UMAT Subroutine for Neo-Hookean
Hyperelasticity . 140
5.8.4 UMAT Subroutine for Kinematic Hardening
Plasticity . 145
5.8.5 UMAT Subroutine for Isotropic Hardening
Plasticity . 151
5.8.6 UMAT Subroutine for Simple Linear Viscoelastic
Material 157
5.9 VUMAT Subroutine Examples 160
5.9.1 VUMAT Subroutine for Kinematic Hardening
Plasticity . 162
5.9.2 VUMAT Subroutine for Isotropic Hardening
Plasticity . 165
References 169
6 Mesher and Meshing 171
6.1 Generalities 171
6.1.1 Mesh Control Options . 172
6.1.2 Mesh Controls for a 2D Structure . 172
6.1.3 Mesh Controls for a 3D Structure . 172
6.1.4 Understanding a Mesher 174
6.1.5 Mesh as Grid Generation . 179
6.2 The Abaqus Model Meshed Has Changed into
a Nonphysical Shape with a Regular Pattern 190
6.3 Excessive Element Distortion Warnings 191
6.4 Compatibility Errors Printed to the Message File
for a Model with Hybrid Elements 191
6.5 User Element Subroutine . 192
6.5.1 Guideline to Write a UEL . 193
6.6 UEL Subroutine Examples . 201
6.6.1 UEL Subroutine for Planar Beam with Nonlinear
Cross Section 202
6.6.2 Generalized Constitutive Behavior . 207
6.6.3 UEL Subroutine for a Horizontal Truss
and Heat Transfer Element 209
6.6.4 UELMAT Subroutine for 4 Nodes in Plane
Strain 214
6.7 Using Nonlinear User Elements in Various Analysis
Procedures . 222
References 226
xxii Contents7 Contact 227
7.1 Generalities 227
7.1.1 Understandings . 230
7.1.2 Define Contact Pairs . 234
7.1.3 Define General Contact . 234
7.1.4 Representation of Curved Surfaces 236
7.1.5 Contact Formulation Aspects . 237
7.2 Friction . 262
7.2.1 Static and Kinetic Friction . 263
7.2.2 Change Friction Properties During an Analysis . 266
7.2.3 Classic Friction Values . 266
7.3 Hard or Soft Contact 267
7.3.1 Identification of the Mathematical Stiffness
Function . 270
7.3.2 Exponential Contact Stiffness 274
7.3.3 From Hard Contact to Exponential 276
7.4 Obtain a Converged Contact Solution . 278
7.5 Convergence Difficulty in the First Increment 280
7.6 Causes and Resolutions of Contact Chattering . 281
7.7 Understand Finite Sliding with Surface-to-Surface Contact 283
7.8 Using Penalty Contact . 286
7.9 Using Augmented Lagrangian Contact . 290
7.10 Using Stiffness-Based Contact Stabilization . 292
7.11 Modeling Contact with Second-Order Tetrahedral Elements . 294
References 295
Part III A Toolbox to Do the Job
8 Troubleshooting in Job Diagnostics . 299
8.1 Guidelines with Abaqus Standard 299
8.2 Job with Abaqus Standard Completes, But the Results
Look Suspicious . 301
8.3 Model a Structure Undergoing a Global Instability 304
8.4 Correct Convergence Difficulties Caused by Local
Instabilities . 305
8.5 Correcting Errors During the Data-Check Phase
of an Analysis 306
8.6 Analysis Ends Prematurely, Even Though All the Increments
Have Converged . 308
8.7 Debugging Divergence with Too Many Cutbacks
in the Last Attempted Increment . 309
8.8 Using Follower Loads in Nonlinear Analyses 310
8.9 Understanding Negative Eigenvalue Messages . 311
Contents xxiii8.10 Divergence with Numerical Singularity Warnings . 313
8.11 Zero Pivot Warnings in the Message File . 314
8.12 Convergence Difficulty in the First Increment of a Contact
Analysis . 315
8.13 Explicit Stable Time Increments When Using the Marlow
Model with Noisy Test Data 317
8.14 Cause of an Analysis Ending in a Core Dump . 318
8.15 Debugging User Subroutines and Post Processing
Programs 318
8.16 No Free Memory Available on Linux at the End
of an Analysis 323
Reference . 326
9 Numerical Acceptance Criteria 327
9.1 Generalities 327
9.1.1 Commonly Used Control Parameters . 327
9.1.2 Controlling the Time Incrementation Scheme . 329
9.1.3 Activate the Line Search Algorithm 331
9.1.4 Controlling the Solution Accuracy in Direct
Cyclic Analysis 331
9.1.5 Controlling the Solution Accuracy and Mesh
Quality in a Deforming Mesh Analysis
with Abaqus CFD 332
9.1.6 Convergence Criteria for Nonlinear Problems . 334
9.1.7 Time Integration Accuracy in Transient Problems 343
9.1.8 Avoid Small Changes to the Time Increment
Size During Implicit Integration Procedures 344
9.2 How Much Hourglass Energy Is Acceptable . 345
9.2.1 Enhanced Hourglass Control and Elastic Bending
Moment 346
9.2.2 Enhanced Hourglass Control and Plastic Bending
Moment 346
9.2.3 Kelvin Viscoelastic Hourglass Control 346
9.3 Errors Printed to the Message File for a Model with Hybrid
Elements 347
Reference . 348
10 Need Some Help? 349
10.1 Retrieving Files Referred to Examples in the Abaqus
Documentation 349
10.2 Using the Abaqus Verification, Benchmarks, and Example
Problems Guides . 349
10.3 Excessive Memory Usage with Cavity Radiation Problems 357
xxiv Contents10.4 Perform a Sub-model Analysis 358
10.4.1 Implementation . 359
10.4.2 Loading Conditions . 360
10.4.3 Sub-model Boundary Conditions 360
10.4.4 Interpolation . 361
10.4.5 Step-by-Step Procedure for a Sub-model 361
10.4.6 Setting Options 364
10.4.7 Shell to Solid 365
10.4.8 Changing Procedures 367
10.4.9 Frequency Domain 367
10.4.10 Thermal and Stress Analysis . 368
10.4.11 Dynamic Analysis 369
10.4.12 Limitations of Sub-modeling . 370
10.5 Perform a Restart Analysis . 371
10.5.1 Step-by-Step Procedure for a Restart . 373
10.6 Generate a Shell Part from a Solid Part 376
10.6.1 Benefits for Using Shell Structures 376
10.6.2 Applications to Model Shell Structures . 377
10.6.3 Step-by-Step Procedure to Convert Solid Model
to Shell Model . 378
10.7 Compile and Link a Post-processing Program Using
the Standalone Abaqus ODB API 385
10.8 Create Executables Using the C++ ODB API Libraries
Outside of Abaqus/Make . 387
11 Hardware or Software Issues . 391
11.1 Solving File System Error 1073741819 391
11.2 Interpreting Error Codes . 391
11.3 Obtaining a Traceback from a UNIX/Linux Core Dump 393
11.4 Windows HPC Compute Clusters 397
11.4.1 Classics Troubleshooting with HPC Cluster 402
Reference . 405
Appendix: Guidelines and Good Practices Examples 407
Index .
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