Tutorial for ABAQUS Users

200 Pages·2016·12.88 MB·English

ABAQUS
Tutorial

Version 7

Fracture Analysis Consultants, Inc

www.fracanalysis.com

Revised: July 2016
Table of Contents:

1.0 Introduction .......................................................................................................................... 6
2.0 Tutorial 1: Crack Insertion and Growth in a Cube .............................................................. 6
2.1 Step 1: Create the ABAQUS FE Model .......................................................................... 6
2.2 Step 2: Reading ABAQUS FE Model into FRANC3D .................................................. 8
Step 2.1: Importing ABAQUS FE Model ............................................................................... 8
Step 2.2: Select the Retained Items in the FE Model ........................................................... 10
Step 2.3: Displaying the FE Model ....................................................................................... 12
2.3 Step 3: Importing as a Sub-Model ................................................................................... 13
2.4 Step 4: Insert a Crack ..................................................................................................... 18
Step 4.1: Define a new Crack from FRANC3D Menu ......................................................... 18
Step 4.2: Insert Cracks from Files......................................................................................... 24
2.5 Step 5: Static Crack Analysis ........................................................................................ 26
Step 5.1: Select Static Crack Analysis .................................................................................. 26
Step 5.2: Select FE Solver .................................................................................................... 27
Step 5.3: Select ABAQUS Analysis Options ....................................................................... 28
2.6 Step 6: Compute Stress Intensity Factors ...................................................................... 30
2.7 Step 7: Manual Crack Growth ....................................................................................... 31
Step 7.1: Select Grow Crack ................................................................................................. 32
Step 7.2: Specify Growth Rate.............................................................................................. 33
Step 7.3: Specify Fitting and Extrapolation .......................................................................... 33
Step 7.4: Specify Crack Front Template ............................................................................... 35
2.8 Step 8: Automatic Crack Growth .................................................................................. 36
Step 8.1: Open FRANC3D Restart File ................................................................................ 36
Step 8.2: Select Crack Growth Analysis ............................................................................... 36
Step 8.3: Specify Growth Parameters ................................................................................... 37
Step 8.4: Specify Growth Model Data .................................................................................. 38
Step 8.5: Specify Fitting and Template Parameters .............................................................. 39
Step 8.6: Specify Extension or Cycle Data ........................................................................... 40
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Step 8.7: Specify Analysis Code ........................................................................................... 41
Step 8.8: Specify Analysis Options ...................................................................................... 42
2.9 Step 9: SIF History ........................................................................................................ 44
Step 9.1: Select SIFs Along a Path ....................................................................................... 44
Step 9.2: Select SIFs For All Fronts ..................................................................................... 45
Step 9.3: Select Fatigue Life Predictions .............................................................................. 46
3.0 Tutorial 2: Multiple Load Cases and Crack Face Tractions .............................................. 51
3.1 Step 1: Reading ABAQUS FE Model into FRANC3D ................................................ 52
Step 1.1: Importing ABAQUS FE Model ............................................................................. 52
Step 1.2: Select the Retained Items in the FE Model ........................................................... 54
Step 1.3: Displaying the FE Model ....................................................................................... 56
3.2 Step 2: Insert Crack From File ...................................................................................... 56
3.3 Step 3: Apply Crack Surface Traction .......................................................................... 60
3.4 Step 4: Static Analysis................................................................................................... 61
Step 4.1: Run ABAQUS static crack analysis ...................................................................... 61
Step 4.2: Compute SIFs ........................................................................................................ 63
Step 4.3: Re-Run ABAQUS static crack analysis with crack face contact .......................... 65
Step 4.4: Compute SIFs with crack face contact .................................................................. 67
3.5 Step 5: Apply Surface Treatment Residual Stress ........................................................ 70
3.6 Step 6: Apply Tractions from Mesh-Based Stress ........................................................ 76
Step 6.1: Create Mesh-Based Stress Field ............................................................................ 76
Step 6.2: Apply Mesh-Based Stress as Crack Face Traction ................................................ 78
Step 6.3: ABAQUS Mesh-Based Stress ............................................................................... 82
4.0 Tutorial 3: Two Cubes Glued Together ............................................................................ 84
4.1 Step 1: Create the ABAQUS FE Model ........................................................................ 84
4.2 Step 2: Import ABAQUS FE Model into FRANC3D ................................................... 86
Step 2.1: Importing ABAQUS FE Model ............................................................................. 86
Step 2.2: Insert a Crack ......................................................................................................... 87
Step 2.3: Static Crack Analysis ............................................................................................. 88
Step 2.4: Compute SIFs ........................................................................................................ 89
Step 2.5: Plot Deformed Shape ............................................................................................. 90
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Step 2.6: Contact surface mesh not retained ......................................................................... 90
Step 2.7: Specify No Crack Material Region........................................................................ 92
5.0 Tutorial 4: Disk with Rotation and Temperature .............................................................. 93
5.1 Step 1: Create the ABAQUS Disk Model ..................................................................... 93
5.2 Step 2: Run ABAQUS Thermal Analysis ..................................................................... 96
5.3 Step 3: Run ABAQUS Structural Analysis ................................................................... 97
5.4 Step 4: Import Disk into FRANC3D ............................................................................. 98
5.5 Step 5: Insert Initial Crack .......................................................................................... 100
5.6 Step 6: Static Crack Analysis ...................................................................................... 102
5.6 Step 6: Compute SIFs .................................................................................................. 104
5.7 Step 7: Crack Growth .................................................................................................. 106
5.8 Step 8: Automatic Crack Growth ................................................................................ 110
5.9 Step 9: Analysis Results .............................................................................................. 112
6.0 Tutorial 5: Multiple Cracks in a Plate ............................................................................. 115
6.1 Step 1: Create the ABAQUS Plate Model .................................................................. 115
6.2 Step 2: Import Plate Model into FRANC3D ............................................................... 116
6.3 Step 3: Insert Multiple Cracks ..................................................................................... 118
6.4 Step 4: Static Crack Analysis ...................................................................................... 128
6.5 Step 5: Compute SIFs for Multiple Crack Fronts ....................................................... 130
6.6 Step 6: Grow Multiple Cracks ..................................................................................... 130
6.7 Step 7: Grow Crack around a Corner .......................................................................... 133
6.8 Step 8: Grow Crack through a Back Surface .............................................................. 138
7.0 Tutorial 6: Computing Fatigue Life Cycles .................................................................... 142
7.1 Step 1: Perform Crack Growth .................................................................................... 145
7.2 Step 2: Compute Fatigue Crack Growth Cycles ......................................................... 147
7.3 Step 3: Crack Growth and Fatigue Options ................................................................ 149
7.3.1 Variable Amplitude Loading ..................................................................................... 151
7.3.2 Spectrum Loading for Manu Model .......................................................................... 152
7.4 Step 3: Sequence Crack Growth ................................................................................. 154
7.5 Step 4: Spectrum Crack Growth ................................................................................. 154
7.6 Step 5: Transient Crack Growth .................................................................................. 154
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8.0 Tutorial 7: Resume Growth with Larger Submodel ....................................................... 155
8.1 Step 1: Extract and Save Crack Geometry .................................................................. 155
8.2 Step 2: Restart from Saved Crack Geometry .............................................................. 156
8.3 Step 3: Combine SIF Histories .................................................................................... 161
9.0 Tutorial 8: Fretting Fatigue ............................................................................................. 168
9.1 Step 1: Saving ABAQUS Data.................................................................................... 168
9.2 Step 2: Fretting Model Import ..................................................................................... 170
9.3 Step 3: Fretting Crack Nucleation ............................................................................... 173
9.3 Step 3: Discrete Crack Nucleation .............................................................................. 177
10.0 Tutorial 9: Multiple Submodel Portions ......................................................................... 185
10.1 Step 1: Import Plate Model into FRANC3D ........................................................... 186
10.2 Step 2: Insert Multiple Cracks ................................................................................. 189
10.3 Step 3: Crack Analysis ............................................................................................ 194
11.0 Tutorial 10: Session Log Playback ................................................................................. 196
12.0 Tutorial 11: Python Interface .......................................................................................... 199

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1.0 Introduction

This manual contains tutorials that introduce the fracture simulation capabilities of FRANC3D
Version 7 and ABAQUS Version 6.14 (earlier or later versions should work). The FRANC3D
software is introduced by first analyzing a simple surface crack in a cube. Subsequent tutorial
examples build on this first example and describe additional capabilities and features of the
software. It is intended that the user perform the operations as they are presented, but you should
feel free to experiment, and you should consult the other reference documentation whenever
necessary.

Menu and dialog box button selections are indicated by bold text, such as File. Window regions
and dialog options, fields and labels will be underlined. Model names and file names will be
indicated by italic text.

2.0 Tutorial 1: Crack Insertion and Growth in a Cube

The first tutorial simulates a surface crack in a cube under far-field tension. It is assumed that
the user is familiar with a pre-processor for ABAQUS; we use ABAQUS CAE. Once the model
is created, the FRANC3D steps necessary to read the mesh information, insert a crack, rebuild
the mesh, perform the ABAQUS analysis, and compute stress intensity factors are all described.

2.1 Step 1: Create the ABAQUS FE Model

First, create a cube model using any pre-processor for ABAQUS. Here we simply outline the
necessary steps to create the model and boundary conditions to ensure that we have a complete
model that can be used with FRANC3D.

1. Create a 10x10x10 cube geometry; assume units of length are mm.
2. Subdivide the edges for meshing using 10 to 20 subdivisions.
3. Define the element type as quadratic elements; use brick or tetrahedral elements.
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4. Define the material properties as 10000 for the elastic modulus and 0.3 for the Poisson’s
ratio; assume the units for E are MPa.
5. Mesh the volume.
6. Boundary conditions consist of displacement constraints on the bottom surface and
uniform traction (a negative pressure) on the top surface of 10 MPa. The bottom surface
is constrained in the y-direction, the bottom left edge is also constrained in the x-
direction, and the point at the origin is also constrained in the z-direction. Note that you
should use unique set and surface names when defining boundary conditions.
7. Save the model as an .inp file (Abaqus_Cube.inp).

The resulting model should appear as in Fig 2.1. The symbols for the boundary conditions are
displayed attached to the model; the brick mesh is displayed in the lower right corner.

Figure 2.1: ABAQUS cube with boundary conditions; meshed with brick elements.
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Note that ABAQUS CAE tends to use default set and surface names such as SET-1 at both the
Part and the Instance levels, Fig 2.1b. FRANC3D currently cannot differentiate between the Part
SET-1 and Instance SET-1; the Instance SET-1 can be both a node and element set. If boundary
conditions are applied in CAE using the Instance SET-1 (right side image), then FRANC3D will
apply the boundary conditions to both Part and Instance SET-1 nodes. The solution is to name
the sets and surfaces in CAE with unique names, especially when defining boundary conditions.

Figure 2.1b: ABAQUS CAE set-1 at both Part and Instance levels.

2.2 Step 2: Reading ABAQUS FE Model into FRANC3D

Start by importing an existing volume element mesh into FRANC3D. We use the model written
in the previous step.

Now you can choose to do either Step 2 or Step 3 (Section 2.3); we describe both Steps here, but
we use Step 3 for subsequent steps of this tutorial.

Step 2.1: Importing ABAQUS FE Model

Start with the FRANC3D graphical user interface, Fig 2.2, and select File and Import. In the
window shown in Fig 2.3, choose Complete Model. Switch the Mesh File Type radio button in
the Select Import Mesh File window, Fig 2.4, to ABAQUS and select the file name for the
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model, called Abaqus_Cube.inp here, Fig, 2.4. Select Next. The mesh file type can be set in the
Preferences so that you do not have to change the radio button if you always use ABAQUS.

Figure 2.2: FRANC3D graphical user interface

Figure 2.3 Import type

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Figure 2.4: Select Input Mesh File dialog box

Step 2.2: Select the Retained Items in the FE Model

The next panel, Fig 2.5, allows you to choose the mesh surface facets that are retained from the
ABAQUS .inp file. Surfaces with boundary conditions appear in blue as shown in Fig 2.6, and
turn red when selected, Fig 2.7. We can retain the surfaces with boundary conditions (top and
bottom of the cube) by choosing Select All. The boundary conditions will be transferred
automatically to the new mesh when a crack is inserted. Select Finish.

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