This document provides a step-by-step tutorial on generating Abaqus input files from realistic microstructures for finite element method simulations, specifically focusing on magnesium alloy AZ31. It outlines methods to characterize microstructures using EBSD data, format the data with StatGenerator, and create the microstructure with DREAM. Finally, it explains how to extract the data into an Abaqus-compatible format using Python scripting.

1. Building Abaqus Input Files
with Realistic Microstructures
Matthew W. Priddy
Georgia Institute of Technology
August 12, 2013

2. 2
Outline
• Introduction
• Mg AZ31 Abaqus Input file generation
– Step 1: EBSD
– Step 2: StatsGenerator
– Step 3: Dream3D
– Step 4: Python
• Summary

3. 3
Crystal Plasticity Finite Element Method
CPFEM Results
Polycrystalline MeshUMAT
Material
Input
Mesh
Generator
Loading Conditions
Boundary Conditions
Abaqus/Standard
Kinematic
Equations
Constitutive
Equations

4. 4
Crystal Plasticity Finite Element Method
CPFEM Results
Polycrystalline MeshUMAT
Material
Input
Mesh
Generator
Loading Conditions
Boundary Conditions
Abaqus/Standard
Kinematic
Equations
Constitutive
Equations
The focus of
this presentation

5. 5
Creating a Realistic Microstructure
• If we know polycrystalline metals look like:
• How do we recreate the microstructure for FEM simulations?
– There are open-source tools to help us do this!
Ti-6Al-4V β-annealedMg AZ31

6. 6
Creating a Realistic Microstructure
• If we know polycrystalline metals look like:
• How do we recreate the microstructure for FEM simulations?
– There are open-source tools to help us do this!
Ti-6Al-4V β-annealedMg AZ31
The goal of this tutorial is to illustrate, step-
by-step, how to generate a microstructure for
a specific material set.

7. 7
Misorientation Angle
Distribution
Example: Mg AZ31 Microstructure
• EBSD analysis:
• Data acquired:
Pole Figures Grain Size
Distribution

8. 8
Steps to Generate Mesh
Step 1:
Quantify Microstructure

9. 9
Steps to Generate Mesh
Step 1:
Quantify Microstructure
Step 2:
StatsGenerator

10. 10
Dream3D
• Allows for integrated processing, characterization, and
manipulation of digital microstructures.
– Open-source software
– http://dream3d.bluequartz.net/

11. 11
Step 2: StatsGenerator | Introduction
• The information found in Step 1 needs to be in a format that
Dream3D can use, so they also created StatsGenerator.
• StatsGenerator can be used to either:
– Format and organize the data you possess for a particular material, or
– To generate fictitious data, based on some input parameters

12. 12
Step 2: StatsGenerator | Phase Definition
• Phase Properties
– Crystal Structure: Hexagonal
– Fraction: 1.0 (single phase material)

13. 13
Step 2: StatsGenerator | Grain Size
• Lognormal Distribution
• Use SigmaPlot to fit the
data
( )( )
2
2
ln
21
( )
2
scale parameter
shape parameter
x
f x e
x
µ
σ
σ π
µ
σ
 − −
 ÷
 ÷
 
=
=
=
24.272
0.985
0.555
R
µ
σ
= 
→ =
= 
2D Graph 1
f= if(x<=0, 0,a*exp(-0.5*(ln(x/x0)/b)^2)/x)
Grain Size (microns)
0 20 40 60 80 100 120 140 160
AreaFraction
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
EBSD Data
Lognormal Distribution

14. 14
Step 2: StatsGenerator | Grain Size
• Size Distribution
– μ = 4.272
– σ = 0.555
– Min cutoff = 4
• 5μm grain diameter
– Max cutoff = 1.33
• 150μm grain diameter
– Bin size = 4.5
– Equiaxed
Note: Vertical axis values are incorrect.
2D Graph 1
f= if(x<=0, 0,a*exp(-0.5*(ln(x/x0)/b)^2)/x)
Grain Size (microns)
0 20 40 60 80 100 120 140 160
AreaFraction
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
EBSD Data
Lognormal Distribution

15. 15
Step 2: StatsGenerator | ODF
• ODF
– Strong basal
texture
– Approximated
with:
• Euler 1: 0
• Euler 2: 0
• Euler 3: 0
• Weight: 50
• Sigma: 10

16. 16
Step 2: StatsGenerator | MDF
• MDF
– Used the data
from the plot
below

17. 17
Steps to Generate Mesh
Step 1:
Quantify Microstructure
Step 2:
StatsGenerator
Step 3:
Dream3D

18. 18
Step 3: Dream3D | Introduction
• The data created in Step 2 is used to inform the synthetic
microstructure generator, Dream3D
• Dream3D has a large database of routines they call filters
• A grouping of filters is referred to as a pipeline
Performed with:Dream3D-4.0.638-Win64(Released July 2013)
Performed with:Dream3D-4.0.638-Win64(Released July 2013)

19. 19
Step 3: Dream3D | Pipeline
• The pipeline we will
use is made up of the
following filters:
• Inputs:
– StatsGenerator data
• Outputs:
– Rectilinear Grid (Vtk)
– Dream3D Data File
Input
Output
Microstructure
Generation

20. 20
Step 3: Dream3D | Input
• Initialize Synthetic Volume
– Creates an empty volume
– Parameters
• Number and spacing of voxels in each direction
• The shape type for each phase
• Location of file generated by StatsGenerator

21. 21
Step 3: Dream3D | Generation
• Pack Primary Phases
– Place primary phases corresponding to goal
statistics
– Parameters
• Periodic boundary conditions for the volume?
• Goal attribute file, if chosen to be written

22. 22
Step 3: Dream3D | Generation
• Find Number of Fields
– Calculates the size of each grain, including the
equivalent diameter, volume, and number of cells in
each grain
• Find Field Neighbors
– Determines the neighboring grains for each grain

23. 23
Step 3: Dream3D | Generation
• Match Crystallography
– Swap or replace the orientation of a grain to reduce
the error of the current ODF and/or MDF
– Parameter: Number of iterations
• Generate IPF Colors
– Generate the inverse pole figure color for each grain
– Parameter: The reference direction of the IPF

24. 24
Step 3: Dream3D | Output
• Write Vtk File
– Open-source 3D computer graphics software
– http://www.vtk.org/
• Write Dream3D File
– Writes data in HDF5 format
– Can also specify the creation of an Xdmf file (http://www.xdmf.org/)

25. 25
Visualization of Dream3D output
• We can view the Dream3D output with Paraview
– http://www.paraview.org/
– Version 3.98 worked successfully, version 4.0.1 did not work
• Open the Xdmf file, select surface with edges and choose
GrainIds

26. 26
Microstructure Comparison
• StatsGenerator Input: • Dream3D Output:

27. 27
Steps to Generate Mesh
Step 1:
Quantify Microstructure
Step 2:
StatsGenerator
Step 3:
Dream3D
Step 4:
Abaqus Input File

28. 28
Sidenote: Abaqus Input File
• An Abaqus input file is generally setup with the following
information, in the following order:
Parameters
Nodes
Elements
Element Sets
Section Definitions
Node Sets
Material Definitions
Boundary Conditions
Loading Conditions
Output Request
Parameters
Nodes
Elements
Element Sets
Section Definitions
Node Sets
Material Definitions
Boundary Conditions
Loading Conditions
Output Request

29. 29
Sidenote: Abaqus Input File
• An Abaqus input file is generally setup with the following
information, in the following order:
• Unfortunately, Dream3D does not currently have an output
filter that writes the data in the above format.
• But, we have a Python script for that!
Parameters
Nodes
Elements
Element Sets
Section Definitions
Node Sets
Material Definitions
Boundary Conditions
Loading Conditions
Output Request
Parameters
Nodes
Elements
Element Sets
Section Definitions
Node Sets
Material Definitions
Boundary Conditions
Loading Conditions
Output Request
Data Created
by Dream3D

30. 30
Step 4: Python | Introduction
• The Vtk file from Step 3 is used to generate the data written in
the Abaqus input file.
• Fortunately, there is a Vtk plugin for python
• Python is an open-source programming language, sometimes
compared to Perl or Java
– http://www.python.org/

31. 31
Step 4: Python | Vtk Extraction
• Information read from Vtk file by the
python script:
– 3D coordinates for each node
– Grain number for each element
– Euler angles for each element
• Information written in the Abaqus
input file:
– 3D coordinates for each node
– Nodes that comprise each element
– Element sets, which are composed of
elements with identical grain numbers
– Euler angles for each element sets

32. 32
Summary
• The purpose of this tutorial was to generate an Abaqus input
file from a digital microstructure.
• The steps needed to complete this task:
– Characterize the microstructure from EBSD data
– Convert the data, using StatsGenerator, into a useful form for Dream3D
– Use Dream3D to generate the microstructure
– Use an in-house python script to convert the Dream3D data into an
acceptable format for Abaqus
• If you have any question about this tutorial or about
microstructure generation, Abaqus, etc., please contact me:
– Matthew W. Priddy
– mwpriddy@gatech.edu

33. 33
Additional Resources
• Dream3D
– http://dream3d.bluequartz.net/resources/DREAM3D_TMS2013.pdf
– http://www.lem3.fr/FIB/docs/DREAM3D_ShortCourse_LEM3.pdf
• Paraview
– http://paraview.org/Wiki/ParaView/Users_Guide/Introduction

34. 34
Supplementary Slide –
Lognormal Distribution
• From StatsGenerator:
( ) ( )
2
0ln ln1
2
0
( )
, , parameters
x x
BA
f x e
x
A B x
 −
−  ÷
 
=
=
( )( )
2
2
ln
21
( )
2
scale parameter
shape parameter
x
f x e
x
µ
σ
σ π
µ
σ
 − −
 ÷
 ÷
 
=
=
=
• From SigmaPlot:
• From inspection:
( )( ) ( ) ( ) ( )
2 2
0 0
2
ln ln ln ln1
2 2 B
x x x x
B
µ µ
σ σ
 − − −   =
 ÷= − →  ÷
 ÷ =  
1 1 1
12 2 2
A A
A
xx B Bσ π π π

= → = → =
