ICME 2013 HW3

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Overview

• This exercise uses the hardening law parameters obtained from the previous dislocation dynamics calculations. The hardening law for slip systems is a critical aspect of crystal plasticity models and contains material related parameters which are difficult to obtain from experiments. Thus, dislocation dynamics serves as a "virtual experiment" from which the hardening parameters can be determined through a fitting routine.
• This assignment will make use of the finite element code ABAQUS

Objectives

• Downscale: Obtain hardening constants from dislocation dynamics calculations that were run in the previous homework.
• Run a finite element simulation of a single grain while varying hardening values.
• Run a finite element simulation of 20 and 180 grains while varying hardening values.
• Plot a stress-strain curve for each stress state (tension, compression, torsion).
• Plot pole figures of initial and deformed orientations

Preparation

Step 1

• Navigate to this page and locate the section for crystal plasticity finite element method (CPFEM) for aluminum.
• Copy the all the files listed to a new directory.

Step 2

• In the repository, download the single element input file "tension.inp" for ABAQUS standard. Save the file to the same directory.

Step 3

• Set up inputs for a single grain simulation
  • In the UMAT file the following line needs to be edited

    data  filePath
    &    /'/cavs/cmd/data1/users/qma/abaqus_xtalplas/oneelement/'/

  • Replace the file path with the path to the directory that all the crystal plasticity files are saved in.
  • In the ABAQUS input file the material definition needs to be edited

    ** MATERIALS
    **
    *Material, name=Material-1
    *Depvar
         35000,
    *User Material, constants=2
    1.,1.

  • Change the number of dependent variable to NUMBER_OF_GRAINS * 70
    • For a single grain depvar: 1*70=70. For 200 grains depvar: 200*70=14000
  • In the texture input file, the number of grains needs to be changed

     500
    0    0
    101.98      145.03      249.44
    131.73       86.26      229.29
    13.58      153.68      314.40
    88.98      124.12      115.16
    132.81      105.72      180.69
    238.51       61.10      158.50
    346.98       88.58      325.61
    82.38      144.74      207.65
    329.83       45.23      169.92
    ...
    ...

  • The top number (number of grains) needs to be changed to 1 (for 1 grain)
  • LEAVE THE SECOND LINE IN PLACE
  • Remove all but one set of Euler angles (for the one grain) and set the last number (seed number) to any value greater than the number of grains.
  • Lastly, in the test.xtali input file

    1    500                                 / crystalID (1:FCC, 2:BCC, 3:HCP), numgrn/
    fcc.sx                                  / single crystal input file
    
    1                                   / ODF code (fODFCode) /
    20                                      / multiples of inc to output texture (fODFOutInc) /
    texture                                 / filename for I/O texture /
    ...
    ...

  • The second number in the top most line needs to be changed to the number of grains. If when the texture file was changed (see above), it was given a new name, that new name needs to in the last line shown in place of "texture".

Running the Calculation

Step 1

• As with previous assignments, to avoid errors, open permission on all the files with:

  chmod 755 *

Step 2

• Enter the following software setup command in a terminal

  swsetup abaqus

Step 3

• The finite element simulation can be run either on Raptor or locally (very short simulation)
• Use a PBS script to submit to Raptor or enter this command into a local terminal:

   abaqus job=tension user=umat_xtal.f

Output

• ABAQUS simulation output is stored in an output database file with extension ".odb".
• ODB files can be visualized and post processed in ABAQUS CAE or ABAQUS VIEWER.