The calculation formula of KAM is based on the following figure, which comes from this paper----W. Fu, Y. Li, S. Hu, P. Sushko, and S. Mathaudhu. Effect of loading path on grain misorientation and geometrically necessary dislocation density in polycrystalline aluminum under reciprocating shear Computational Materials Science, 2022. cited By 0.doi:10.1016/j.commatsci.2022.111221.
Since the output data of damask is output by node or element, I can't know which nodes correspond to which grains? How can I get the node orientation data grouped by grain, or do you have a script for calculating KAMfor me to use for reference?
I would try to load the DAMASK output, i.e. the crystal orientations in the deformed configuration, into the Mtex toolbox (https://mtex-toolbox.github.io). Then you can use Mtex functions to calculate KAM.
See here documentation how to make an EBSD variable. https://mtex-toolbox.github.io/EBSD.EBSD.html
If you can get the Euler angles from Damask (e.g. as EU1, EU2, EU3 and positions X and Y), after deformation, you could try to import it like this:
%crystral symmetry (example for FCC/BCC)
CS = crystalSymmetry('m-3m');
%orientations
orientations = rotation.byEuler(EU1, EU2, EU3);
%phase
phase = ones(size(orientations));
%position fields
prop.x = X;
prop.y = Y;
ebsd = EBSD(orientations,phase,CS,prop);
Alternatively, I'm sure there are ways to export the Damask data into some variable that can be imported into Mtex.
Creating a EBSD-like file from a DAMASK grid solver simulation is rather simple if the deformation of the grid is small and can be ignored. The following commands are given for the undeformed configuration.
r = damask.Result('20grains16x16x16_tensionX.hdf5').view(increment=0)
c = r.coordinates0_point
e = damask.Rotation(r.get('O')).as_Euler_angles()
damask.Table({'coordinates':(3,),'eulers':(3,)},np.hstack(c,e)).save('coordinates_euler.txt')
I assume that MTEX can import the 3D file, if not small manual modifications for naming the columns can be done in any text editor. For large deformation, one would need to map the deformed configuration onto a regular grid that MTEX expects.
Martin Diehl 1. Excuse me, this command-----damask.Table({'coordinates':(3,),'eulers':(3,)},np.hstack(c,e)).save('coordinates_euler.txt')， always reports errors：_vhstack_dispatcher() takes 1 positional argument but 2 were given, so I added parentheses like that np.hstack((c,e)) , but it still reports errors: 'numpy.ndarray' object has no attribute 'items'. How can I solve this problem?
@
2.And so sorry, there is another question. I am not familiar with damask instructions. For large deformation, suppose the incremental step is 50 at this time. How can I get the coordinates after deformation? I see that there is 'u_p' data(displacement of the materialpoints) in the HDF5 file. Do I have to add the initial coordinates and the corresponding incremental 'u_p' to get the deformed grid coordinates I want?
sorry for the typo, adding the brackets is indeed required. In addition, the argument to 'view' is 'increments', not 'increment'. With these changes, it works for me.
u_p are the displacements of the cell centers/point. Adding them to the undeformed points is the correct approach.
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