Wrong slip direction when calculating Schmid Factor?

[MTEXNewbie]

I have a sample that was imported using this specimen reference system - https://i.imgur.com/ahtAbFT.jpg

The sample was pulled in tension to the left (negative x-axis). When I calculate the Schmid factor using the below code, I get slip direction to the left. How can I rectify this?

%% Schmid Factor

csSF = ebsd('Iron fcc').CS;

% consider fcc slip

sS = slipSystem.fcc(csSF);

% and all symmetrically equivalent variants

sS = sS.symmetrise;

sigma = stressTensor.uniaxial(xvector); % anyway to define neagtive xvector?

% compute Schmid factor for all slip systems

SF = sS.SchmidFactor(inv(grains('Iron fcc').meanOrientation) * sigma);

% find the maximum Schmidt factor (along the rows)

[SFmax,active] = max(SF,[],2);

% plot the maximum Schmid factor (for each grain)

figure

plot(grains('Iron fcc'),SFmax,'micronbar','off');

mtexColorbar

% take the active slip system and rotate it in specimen coordinates

sSGrain = grains('Iron fcc').meanOrientation .* sS(active);

% plot then the plane normal and the Burgers vectors into the centers

% of the grains

hold on

% visualize the trace of the slip plane (plane normal)

quiver(grains('Iron fcc'),cross(sSGrain.n,zvector),'displayName','slip plane','color','k');

% and the slip direction (Burgers vectors)

quiver(grains('Iron fcc'),sSGrain.b,'displayName','slip direction','color','r');

hold off

[ruediger Kilian]

H,
I do not see how "pulling to the left" should be different from "pulling to the right" ?
What would you expect to get a a result?
Cheers,
Rüdiger

[MTEXNewbie]

Hi Rüdiger,

These are the slip directions with the above code - [image removed]

But if I use the below code then all the slip directions are opposite to the pulling direction (left) - [image removed]

%% Schmid Factor

csSF = ebsd('Iron fcc').CS;

% consider fcc slip

sS = slipSystem.fcc(csSF);

% and all symmetrically equivalent variants

sS = sS.symmetrise;

% compute Schmid factor for all slip systems

SF = sS.SchmidFactor(inv(grains('Iron fcc').meanOrientation)*xvector);

% find the maximum Schmidt factor (along the rows)

[SFmax,active] = max(SF,[],2);

% plot the maximum Schmid factor (for each grain)

figure

plot(grains('Iron fcc'),SFmax,'micronbar','off');

mtexColorbar

setColorRange([0.43 0.48])

axis off

% The variable active contains now for each grain the id of the slip system

% with the largest Schmidt factor. In order to visualize it, we first

% rotate for each grain the slip system with largest Schmid factor in

% specimen coordinates

sSGrain = grains('Iron fcc').meanOrientation .* sS(active);

% plot then the plane normal and the Burgers vectors into the centers

% of the grains

hold on

% visualize the trace of the slip plane (plane normal)

quiver(grains('Iron fcc'),cross(sSGrain.n,zvector),'displayName','slip plane','color','k');

% and the slip direction (Burgers vectors)

quiver(grains('Iron fcc'),sSGrain.b,'displayName','slip direction','color','r');

hold off

1. Which one of these codes is correctly showing the slip direction?

2. What is the reason these two codes are showing different slip directions? I have reused these two codes from MTEX documentation.

[MTEXNewbie]

Hi,

I was wondering if anyone could explain the difference in slip direction of the above two codes.

[ruediger Kilian]

Hi,
have a look here: https://github.com/mtex-toolbox/mtex/issues/374
I guess f you make the relevant changes, results should be identical.


Cheers,
Rüdiger

[MTEXNewbie]

Hi Rüdiger,

Thank you for pointing out the issue, which approach is giving the correct result (sign or direction of SF)?