View source for ICME 2017 HW3

[[ICME 2017|< Back to ICME 2017 Course Overview]]

=Overview=
In this homework, we will bridge information from the [[:Category:Microscale| microscale]] to the [[:Category:Mesoscale| mesoscale]]. You will dislocation dynamics simulations with multiple Frank Read sources to determine parameters for a hardening rule which will be used in a crystal plasticity code (CPFEM). Thus, there are two parts to this assignment:
* Dislocation Dynamics (DD) using Multiscale Dislocation Dynamics Plasticity (MDDP)
* Crystal Plasticity (CPFEM) implemented as a user material routine in <u>[[Code: ABAQUS FEM | ABAQUS]]</u> or <u>[[Code: CALCULIX | Calculix]]</u>

This exercise uses the hardening law parameters obtained from DD 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, DD serves as a "virtual experiment" from which the hardening parameters can be determined.

All necessary input files and scripts are available through the website. Save these files to your own directory (and make a backup copy) before trying to perform any simulations.

Use /scratch/"Your Directory" for best results.

Write a full report that follows a journal article manuscript format (include figures and tables in the text). '''Please double-space your document'''

Upon completion, submit via email a .pdf and .doc(x) file of your report. Be sure to also include the requested files and plots from each section of the homework.



=Part 1 - Dislocation Dynamics Virtual Experiment=

==Objectives==

This exercise uses dislocation dynamics calculations to determine the parameters of the hardening law used in crystal plasticity. The hardening law for the slip systems is a critical aspect of crystal plasticity models and contains material related parameters that are hard to obtain from experiments. Dislocation dynamics can serve as a “virtual experiment” from which the hardening parameters can be determine using a fitting procedure.

==Environment Setup==

The setup for MDDP is the same as in the [[ICME 2017 HW2|previous homework]].

==Dislocation Forest Hardening==

The steps to run and post-process the results from MDDP will be the same as in the [[ICME 2017 HW2|previous homework]]. However, this time you need to create a DDinput file that includes multiple Frank-Read sources. 



===Homework Assignment===
:1. Using the three stress-strain curves from dislocation dynamics and by assuming a linear fit to the work hardening (post-yield portion of stress-strain curve), estimate the slope of the linear hardening regime. How does uncertainty affect the linear assumption? Is there a better assumption than linearity?
:2. Fit dislocation density results to the Voce Hardening Law (Equation 9.9 in ICME textbook).
:3. Report on your results

=Part 2 - Upscale Dislocation Forest Hardening to Crystal Plasticity=

==Objectives==
* Run a one-element finite element simulation using the Voce hardening law with one crystal orientation.
* Plot a stress strain curve for each set of hardening constants. 
* Report on your results.

==Environment Setup==

==Crystal Plasticity==
===Step 1===
* Navigate to [[Code: ABAQUS CPFEM|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 <pre>data  filePath&#10;&    /'/cavs/cmd/data1/users/qma/abaqus_xtalplas/oneelement/'/</pre>
** Replace the file path with the path to the directory that all the crystal plasticity files are saved in.
**In the texture input file, the number of grains needs to be changed<pre> 500&#10;0    0&#10;101.98      145.03      249.44&#10;131.73       86.26      229.29&#10;13.58      153.68      314.40&#10;88.98      124.12      115.16&#10;132.81      105.72      180.69&#10;238.51       61.10      158.50&#10;346.98       88.58      325.61&#10;82.38      144.74      207.65&#10;329.83       45.23      169.92&#10;...&#10;...</pre>
** 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<pre>1    500                                 / crystalID (1:FCC, 2:BCC, 3:HCP), numgrn/&#10;fcc.sx                                  / single crystal input file&#10;&#10;1                                   / ODF code (fODFCode) /&#10;20                                      / multiples of inc to output texture (fODFOutInc) /&#10;texture                                 / filename for I/O texture /&#10;...&#10;...</pre>
** 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".
* '''If you are running the calculation on Raptor'''
** In the ABAQUS input file the material definition needs to be edited<pre>** MATERIALS&#10;**&#10;*Material, name=Material-1&#10;*Depvar&#10;     35000,&#10;*User Material, constants=2&#10;1.,1.</pre>
** 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

===Step 4===
* Change the FCC data to match that of nickel
** In the fcc.sx file the following lines need to be edited 
<pre>108.2e3  61.3e3  28.5e3                 / c11(c1), c12(c2), c44(c3) / # These numbers should match c11, c12, and c44 for nickel
.
.
2.e-5                                / bdrag / # This should match the drag coefficient obtained in HW2
35.5  39.5  1.85  0.0-4  5.0e10    / h0, tausi, taus0, xms, gamss0 / # The first three should match the values obtained in Part 1
.
.
</pre>

==Running the Calculation==
* The finite element simulation can be run either on Raptor or locally (very short simulation)

===Change the permissions===
* As with previous assignments, to avoid errors, open permission on all the files with:<pre>chmod 755 *</pre>

===Run on Raptor===
* Enter the following software setup command in a terminal<pre>swsetup abaqus</pre>
* Use a PBS script to submit to Raptor or enter this command into a local terminal:<pre> abaqus job=tension user=umat_xtal.f</pre>

===Run Locally===
'''Abaqus must be setup to run with Intel Fortran libraries for this method to work!'''
* Open Abaqus CAE and click Open Database
* Navigate to the ''cpfem_decks'' folder and open ''oneelement.cae'' -- You will be prompted to covert the database; click Yes
* For the single grain case a new material will need to be made that has a Depvar = 70 and a User Material with Mechanical Constants 1 = 1, 2 = 1
* For the multiple grain cases a new material will need to be made that has a Depvar = (70*# of grains) and a User Material with Mechanical Constants 1 = 1, 2 = 1
* Do not forget to apply this material to the Section
* Under jobs there are four (4) jobs that have already been created -- To run any of these you will need to edit the job; Under the General tab point the Scratch Directory to a temp folder and the User subroutine file to umat_xtal.for ('''BE SURE THAT THE UMAT EXTENSION IS''' .for)
* You are now able to submit the job and work with the data to produce a stress-strain curve

==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.

=Room for Improvement=
As with the previous homeworks, improve the tutorial(s) by adding/modifying the ICME website for:
:1. Dislocation dynamics (MDDP)
:2. Crystal Plasticity