Active Slip Systems (Schmid Factor)

[Camilo Garzón]

Hi,

I was checking the procedure of Schmid Factor, with the objective of obtaining the active slip systems, however, when I use my EBSD data, MTEx shows all grains with a slip plane active, which makes me ask myself if there is a criterium to know which was really activated.

Do you know one?

Thanks for your help

PD: https://mtex-toolbox.github.io/SchmidtFactor.html#18

---

sSAll = slipSystem (show methods, plot)
 mineral: Titanium (Alpha) (622, X||a, Y||b*, Z||c)
 size: 12 x 1
   U    V    T    W  | H    K    I    L CRSS
   1    1   -2    0    0    0    0    1    1
   1   -2    1    0    0    0    0    1    1
  -2    1    1    0    0    0    0    1    1
   2   -1   -1    0    0    1   -1    0    1
   1    1   -2    0   -1    1    0    0    1
   1   -2    1    0   -1    0    1    0    1
   2   -1   -1    0    0    1   -1    1    1
   1    1   -2    0   -1    1    0    1    1
   1   -2    1    0   -1    0    1   -1    1
   1   -2    1    0   -1    0    1    1    1
   1    1   -2    0   -1    1    0   -1    1
   2   -1   -1    0    0   -1    1    1    1

%%Rotation of slipping systems to sample coordinates

sSAllSampleAd = grains_csm(‘Titanium (Alpha)’).meanOrientation * sSAll

%%Stress Tensor

sigma = -1 * stressTensor.uniaxial(vector3d.Z)

%Schmid Factor for all the systems
SF = sSAllSampleAd.SchmidFactor(sigma);

%Max Schimd Factor for each system
[SFMax,active] = max(SF,[],2);

%Vector to identify slipping systems
A = zeros(length(SFMax),1);

%Feeding the A vector
for j=1:length(A)
    for i=1:length(sSAll)
        if SFMax(j) ==  SF(j,i)
        A(j) = i
        end
    end
end

%After processing the data (yellow=basal, orange=prismatic, blue=pyramidal)

[Rüdiger Kilian]

Hi,

the Schmid Factor is a purely geometric concept, using e.g. the assumption that the slip system with the highest resolved shear stress (also considering that different sS may have different CRSS) is the one which slips ("is active"). However, it's totally static and hence "active" means that  - from a purely geometric point of view - it would be the slip system to move. Such a solution can be found for every grain of course while this of course does not mean at all that this sS was active or will be active when the given load is applied to the crystal, since further conditions may exist which are not part of the Schmid factor model.

Hope this helps.

Cheers,

Rüdiger