PPT Slide
Note that each slip plane contains three slip directions and that 12 values (4 x 3) have to be obtained.
Schmid and coworkers used the variation in the resolved shear stress to explain the great differences in the yield stresses of monocrystals of certain metals.
They proposed the following rationalization, known as the Schmid law: Metals flows plastically when the resolved shear stress acting in the plane and along the direction of slip reaches the critical value
where the factor M is usually known as the Schmid factor