2. MSC.Marc/Mentat

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Preamble

Read the General Usage section - it is relevant for use with MSC.Marc as well.

Menu items are printed BOLD.

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Building the model in Mentat

Below we list the points that are specific to DAMASK when setting up your model.

Material definition

In the menu

• MATERIAL PROPERTIES > NEW > FINITE STIFFNESS > STANDARD choose
  • STRUCTURAL and finally
    • TYPE HYPOELASTIC and
    • METHOD USER SUB HYPELA2.

Assign this material to all elements.

State variables

State variables are defined via the menu INITIAL CONDITIONS > NEW (STATE VARIABLE) > GENERAL: STATE VARIABLE

Check the box State Variable and select the material behavior within the geometry as specified in the file material.config.

• State variable ID = 1 temperature (is zero if not set!)
• State variable ID = 2 homogenization scheme
• State variable ID = 3 microstructure

You can use multiple definitions for all three state variables and assign them individually to the respective elements.

Then, you have to tick the predefined state variables you want to use in your model (at least 3) in JOBS > PROPERTIES > INITIAL LOADS > INITIAL CONDITIONS

Additional settings

In the menu JOBS > NEW > STRUCTURAL > PROPERTIES ...

• ... choose ANALYSIS OPTIONS > LARGE STRAIN.

You should not select user defined output manually but rather use the script provided for this purpose, see marc_addUserOutput.

As DAMASK effectively only uses every second iteration you might want to change the MAX # RECYCLES in the menu LOADCASES > PROPERTIES > SOLUTION CONTROL. While you are there it is a good idea to also set MIN # RECYCLES to 1 for the same reason.

In the JOB RUN menu choose

• USER SUBROUTINE FILE and select the interface routine DAMASK_marc.f90.
• SOLVER/PARALLELIZATION > MATRIX SOLVER.
  
  • In the dialog select SOLUTION: NONSYMMETRIC and a TYPE of your choice. (A symmetric solver is required when using DDM!)

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Starting the simulation

You can simply start your simulations from the DAMASK menu to be found in the JOB RUN menu, however, we recommend to use a three step procedure:

1. Start the simulation using the submit script of choice and kill it after step zero is finished.
2. On the command line use the script marc_addUserOutput to add the required user defined output information to the model file(s).
3. Restart the simulation this time using execute instead of submit, so that the input file is not rewritten.

You should repeat this procedure each time you changed your model and afterwards just use execute to start new simulation runs.

marc_addUserOutput

The script marc_addUserOutput can be used to automatically add user defined output to the input file(s):

> marc_addUserOutput inputfile.dat

Optional parameters can be used to specify which exact information to use, see marc_addUserOutput.

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Parallelization

Parallelization can speed up simulations significantly. With DAMASK you can use internal parallelization as well as the Marc domain decomposition feature either separately or combined.

Internally using openMP

DAMASK uses openMP for internal parallelization. You can then set the number of threads to be used by DAMASK via the environment variable DAMASK_NUM_THREADS, e.g.

bash> export DAMASK_NUM_THREADS=8
 csh> setenv DAMASK_NUM_THREADS 8

to use 8 threads.

You need to set the variable before you start Mentat!

Using domain decomposition

Domain decomposition (DDM) is a standard feature of Marc. For compatibility with DAMASK you need to use the following settings for PARALLELIZATION in the RUN JOB menu:

• USE DDM
• DECOMPOSITION IN MENTAT
• MULTIPLE INPUT FILES

Remember that with DDM you have to use a symmetric solver!

Setting up hpmpi

To use DDM you also need to set up MPI. On our systems hpmpi seems to be working better than intelmpi. To set it up you need to

• specify 'MARC_MPI hpmpi' in MSCpathinfo/marc201x/tools/run_marc_defaults
• have a valid RSA key for the loopback device (IP address 127.0.0.2) in your known_hosts file; if you do not have that, one way of getting it in is to make a ssh connection

  > ssh 127.0.0.2
  

• if you encounter problems with obtaining parallel licenses it should help to set the environment variable $MSC_LICENSE_FILE, e.g.

  bash> export MSC_LICENSE_FILE="MSCpathinfo/flexlm/licenses/license.dat"
   csh> setenv MSC_LICENSE_FILE "MSCpathinfo/flexlm/licenses/license.dat"
  

The logic to find the license file seems to be different for parallel jobs than for single jobs.

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Restart

DAMASK does allow restarting a simulation. However, the only mode supported is 'last converged increment'.