How to generate the .VTK files of local dislocation density for each grain

ripening phenomena, dislocations, grainboundary topology
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Junny
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How to generate the .VTK files of local dislocation density for each grain

Post by Junny » Thu Mar 16, 2017 4:57 pm

Dear Bernd,

I am thinking of simulating the recovery/recrystallization behavior of austenite grains during isothermal/continuous heating. Following one of the example files, I realized that I need a file, which contains the dislocation density (gradient) in the individual grains. Normally one can get from the crystal plasticity simulation output. However, I want to introduce the local dislocation densities manually. Would that be possible? What should be the format, e.g. number of columns, grain numbers etc? Thanks in advance!

With kind regards,
Jun

ralph
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Re: How to generate the .VTK files of local dislocation density for each grain

Post by ralph » Thu Mar 16, 2017 5:14 pm

HI Junny,

see the ReX_local_recovery example for reference.
In this example, the initial grain structure (grain IDs) and the local dislocation densities are read from a VTK file. It is an ASCII file which can examine in a normel editor.

A 'structured points' dataset with 'CELL_DATA' fields are used,
i.e. the number of nodes of the strutured grid is given in the line

DIMENSIONS 410 2 318

and the number of voxel/cells in the line

CELL_DATA 129653
( 129653 = 409 * 317 )

The number of data values in each line of a field is (nearly) arbitrary.

Regards,
Ralph

Junny
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Re: How to generate the .VTK files of local dislocation density for each grain

Post by Junny » Fri Mar 17, 2017 11:15 am

Dear Ralph,

Thank you for your kind quick response and the suggestions.

I have a new question regarding defining the spatial distributions of the dislocation density within a grain. In the .rhoD file for the dislocation density distribution, for the example ReX_local_recovery, the total dimension is 409*317 in XZ plane. While the dislocation densities numbers was listed in the form of 14406 (rows) * 9 (columns). The same format is found in the korn vtk file. How they correlate to the spatial grain distributions.

I want to introduce a higher dislocation density close to the grain boundary than in the center of the grains on purpose. How can I manipulate this while writing the .vtk file?

With kind regards,
Jun

ralph
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Re: How to generate the .VTK files of local dislocation density for each grain

Post by ralph » Fri Mar 17, 2017 11:34 am

The cell data is interpreted in the order X, Y, Z dimension. The number of columns, i.e. line breaks, are ignored in VTK.
That corresponds to the following loop:
for ( z = 0; z < cellsInZDimension; z++ )
for ( y = 0; y < cellsInYDimension; y++ )
for ( x = 0; x < cellsInXDimension; x++ )
grid[x,y,z] = readNextData

If you already have a VTK data field for your grain structure, you can read it in script and write the corresponding rhoD dependent of grain boundaries.

Best,
Ralph

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