Stress gradient of anisotropic material

Hi,

I am using the anisotropic Silicon material parameters and was wondering how to apply a stress gradient to this. I've tried some equations manually and I'm not getting the same results from my COMSOL simulation. I am trying to match experimental results: 0.48 m radius of curvature of a 700 um wide, 25 um high rectangular sample. COMSOL 4a is being used and I'm using the initial stress equation '0.176[MPa/um]*y' currently for Sxx and Syy (0.176 is my calculated gradient). Is this equation correct?

Any help would be great, thanks.
Alan