The mechanical response of the reference microstructure is compared to the modified microstructures. For that the microstructures are deformed using the Spectral solver and the differences in equivalent stress and strain are calculated between reference simulation and modified microstructure. A detailed description of this work is presented in the following.

> seeds_fromRandom -N 50 -g 128 128 128 > orientation.seedsgeom_fromVoronoiTessellation enables to create a microstructure with random orientations fron an existing the created seed file. Every grid point is assigned to a grain identification number with

> geom_fromVoronoiTessellation < orientation.seeds > 50grains128x128x128_00.geomThe notation "_00" here in the output file stands for the value of ϕ

> geom_check 50grains128x128x128_00.geom

Figure 1: 3D microstructure containing 50 grains generated by using a Voronoi tessellation and discretized into a grid of 128 × 128 × 128 points. |

Figure 1 shows the geometry of the generated microstructure. Figure 2 shows the different crystallographic orientations of the central grain starting with the reference structure followed by modified microstructures for ϕ

Figure 2: IPF of the central grain for the reference microstructure and the variants |

- Load definition: Contains all information about the loadcase. Here, the applied strain rate and the stress conditions are shown in tensor form. Components denoted with ``*'' are prescribed with complementary conditions. In this simulation the material is strained in x-direction.
> fdot 1.0e-3 0 0 0 * 0 0 0 * stress * * * * 0 * * * 0 time 10 incs 40 freq 4 > fdot 1.0e-3 0 0 0 * 0 0 0 * stress * * * * 0 * * * 0 time 60 incs 60

- Geometry defintion: The geometry defintion as obtained from seeds_fromRandom and geom_fromVoronoiTessellation.
- Microstructure configuration and Texture configuration are taken from the header of the generated geometry file (including the changes to the Euler angles of the central grain).
- Homogenization configuration In the presented simulations the spectral solver is used with a dummy homogenization of type
*none*. - Crystallite configuration In this file the output at the crystallite level is requested. For this simulation the parameters texture, stress, strain gradient, and Euler angles are considered.
- Phase configuration Contains all information about the deformation behavior of the material, examples are found in the examples folder of DAMASK.

> DAMASK_spectral --geometry 50grains128x128x128_00.geom --load tension.load00 is the notation for ϕ

> postResults 50grains128x128x128_00_tensionX.spectralOut \ > --cr fp,f,p,orientation,grainrotation,texture \ > --co shearrate_slip,shearrate_slip \ > --separation x,y,z \ > --increments --range 60 60 1 --splitwhere

`--split`

indicates splitting of the results per time increment, `--separation x,y,z`

separates the data spatially (instead of averaging over the whole volume), `--increments`

turns on incremental counting and `--range 60 60 1`

selects the last increment written out.
To derive further quantities from these basic results, other tools are included in DAMASK.
The commands addStrainTensors that appends to the ASCIItable strain columns derived from the given stretches and addMises for the equivalent values of stress and strain are important for this simulation.
> addStrainTensors -0 -v 50grains128x128x128_00_tensionX_inc60.txt > addCauchy 50grains128x128x128_00_tensionX_inc60.txt > addMises -e 'ln(V)' -s Cauchy 50grains128x128x128_00_tensionX_inc60.txtThe labels of the variables in all ASCIItables are the same, hence they need to be renamed before the data is merged in order to compute the differences. reLabel enables to rename a scalar, vectorial, or tensorial data in the ASCIItable.

> reLabel -l fp,f,p,'ln(V)',Cauchy,'Mises(ln(V))','Mises(Cauchy)',texture -s fp-00,f-00,p-00,'ln(V)-00',Cauchy-00,'Mises(ln(V))-00','Mises(Cauchy)-00',texture-00 50grains128x128x128_00_tensionX_inc60.txt

> paste -d ' ' 50grains128x128x128_10_tensionX_inc60.txt 50grains128x128x128_00_tensionX_inc60.txt >temp.txt > mv temp.txt 50grains128x128x128_10_tensionX_inc60.txt128 stands for the resolution, 60 for the increment, 00 and 10 for the values of ϕ

> addCalculation -l "Delta(Cauchy)","Delta(ln(V))","Delta(Mises(Cauchy))","Delta(Mises(ln(V)))" -f "Cauchy-00#-#Cauchy-10#","#ln(V)-00#-#ln(V)-10#","#Mises(Cauchy)-00#-#Mises(Cauchy)-10#","#Mises(ln(V))-00#-#Mises(ln(V))-10#" 50grains128x128x128_00_tensionX_inc60.txtThe last operation is the visualization of the results, in particular the calculated differences. This can be done using vtk_rectilinearGrid and vtk_addRectilinearGridData as outlined in Generate a file for visualization. These files can be visualized in programs such as ParaView or visit.

Both videos show that differences in distributions of equivalent stress and strain are widespread over the closest neighboring grains and not just restricted to the grains next to the rotated one. Strong local variations in their magnitude reveal the effect of microstructure on deformation processes in this simulation. These variations strongly depend on the orientation relationship between the rotated grain and its neighbors.

Copyright by the contributing authors. All material on this collaboration platform is the property of the contributing authors.

Ideas, requests, problems regarding DAMASK? Send feedback

§ Imprint § Data Protection

Ideas, requests, problems regarding DAMASK? Send feedback

§ Imprint § Data Protection