Import from VPSC

A VPSC simulation can record how a polycrystal's orientations and slip activity change with strain. This page imports both histories and shows how to compare their deformation steps in MTEX.

VPSC is a crystal-plasticity code originally written by Ricardo Lebensohn and Carlos Tomé at Los Alamos National Laboratory. The original code can be requested from lebenso@lanl.gov.

Import the texture history

A VPSC run usually writes TEX_PH1.OUT for phase 1. The file contains one block of weighted orientations for each recorded strain level. It does not contain crystal symmetry, so supply that information first.

cs = crystalSymmetry('222',[4.762 10.225 5.994],...
  'mineral','olivine');

SO3Fun.load reads each block and estimates an orientation distribution function (ODF) from its weighted orientations. The 'halfwidth' is the smoothing width of that estimate; it is not a parameter read from VPSC.

path2file = fullfile(mtexDataPath,'VPSC');
odf = SO3Fun.load(fullfile(path2file,'TEX_PH1.OUT'),...
  'halfwidth',10*degree,'CS',cs);

A file with several blocks returns a cell array with one ODF per block. This sample contains nine ODFs. Its first eight steps run from strain 0.25 to 2.00, and the final block is another result at strain 2.00.

strain = cellfun(@(f) f.opt.strain,odf)

strain =
  Columns 1 through 7
    0.2500    0.5000    0.7500    1.0000    1.2500    1.5000    1.7500
  Columns 8 through 9
    2.0000    2.0000

Inspect one deformation step

Use braces to select one ODF. A sigma-section plot exposes the three-dimensional orientation density as a sequence of two-dimensional sections.

plotSection(odf{2},'sigma','figSize','normal')

The section maxima identify the preferred orientations at strain 0.50. Their unequal intensities show that this simulated texture is already far from a uniform orientation distribution.

VPSC header values and the original orientation table remain available in opt. The fields below contain the strain, the phase-ellipsoid axes and angles, the 1000 imported orientations, and the three extra numeric columns from this file.

odf{1}.opt

ans = 
  struct with fields:

                   strain: 0.2500
          strainEllipsoid: [1.1230 1.1270 0.7500]
    strainEllipsoidAngles: [-180 90 -180]
             orientations: [1000×1 orientation]
                     data: [1000×3 double]

File conventions and input weight files

The same command reads weight files with the .wts extension that are handed to VPSC. It also reads files written by export_VPSC. Those files carry neither strain nor a phase ellipsoid, so the corresponding odf.opt entries are NaN.

The fourth header line names the Euler-angle convention. VPSC uses B for Bunge, K for Kocks, and R for Roe, and MTEX follows the convention announced by each file.

Compare pole figures during deformation

A pole figure plots where selected crystal directions lie in the specimen. Plotting the same directions at successive strain levels makes the texture evolution visible without comparing full ODF section plots.

h = Miller({1,0,0},{0,1,0},{0,0,1},cs,'uvw');

fig = newMtexFigure('layout',[4,3],'figSize','huge');
subSet = 1:4;

for n = subSet
  nextAxis
  plotPDF(odf{n},h,'lower','contourf','doNotDraw');
  ylabel(fig.children(end-2),...
    ['\epsilon = ',xnum2str(odf{n}.opt.strain)]);
end
setColorRange('equal')
mtexColorbar

Read the rows from top to bottom as strain increases from 0.25 to 1.00. The shared colour range makes intensities comparable between rows; the changing peak positions and strengths are therefore texture evolution, not independent plot scaling.

Visualize slip-system activity

VPSC also writes ACT_PH1.OUT alongside the orientation data. It contains the activity of the different slip modes during deformation. Read it as a MATLAB table so its STRAIN and MODE1 through MODE9 columns retain their names.

ACT = readtable(fullfile(path2file,'ACT_PH1.OUT'),'FileType','text')

ACT =
  9×11 table
    STRAIN    AVACS    MODE1    MODE2    MODE3    MODE4    MODE5    MODE6    MODE7    MODE8    MODE9
    ______    _____    _____    _____    _____    _____    _____    _____    _____    _____    _____
        0     2.835    0.337     0.31    0.309    0.011    0.012    0.007    0.003    0.002    0.009
     0.25     2.766    0.312     0.23    0.417    0.009     0.01    0.007    0.005    0.003    0.009
      0.5     2.835    0.317    0.198    0.445    0.007    0.009    0.007    0.007    0.004    0.006
     0.75     2.825     0.31    0.131    0.513    0.005    0.007    0.006    0.015    0.007    0.006
        1     2.759    0.312    0.075    0.554    0.003    0.005    0.006    0.028    0.013    0.005
     1.25     2.746    0.327    0.053    0.546    0.002    0.004    0.005    0.041     0.02    0.002
      1.5     2.736     0.37    0.048    0.521    0.002    0.005    0.005    0.033    0.015    0.002
     1.75     2.739    0.394    0.046    0.503    0.002    0.005    0.005    0.031    0.013    0.003
        2     2.828    0.435    0.048    0.468    0.002    0.005    0.004    0.025    0.009    0.004

Plot every mode against strain. AVACS is the second column and is not a slip mode, so the loop begins at the third table column.

close all
for n = 3:size(ACT,2)
  plot(ACT.STRAIN,table2array(ACT(:,n)),'lineWidth',2,...
    'DisplayName',['Slip mode ',num2str(n-2)])
  hold on
end
hold off

xlabel('Strain')
ylabel('Slip activity')
legend('show','location','NorthEastOutside')
set(gca,'YLim',[-0.005 1])
set(gcf,'MenuBar','none','units','normalized',...
  'position',[0.25 0.25 0.5 0.5])

Modes 1--3 dominate this simulation. Mode 3 rises to its maximum near strain 1, mode 2 steadily weakens, and mode 1 nearly catches mode 3 at the final step. To inspect a single mode as a smooth curve, for example mode 3, one can fit csapi(ACT.STRAIN,ACT.MODE3) and plot it with fnplt.

References

Next

Texture Evolution rotates every orientation by the Taylor-model spin over small strain increments. It provides the next step when the texture path should be computed inside MTEX rather than imported from VPSC.