Mr. NickFL, thanks for your suggestions. I was trying your approach and have some follow up issues. First of all, I can assign different X,Y,Z values, but there is column for force or pressure (but no option to specify Fx, Fy, and Fz separetely). Then when I apply that external force (imported load), I can only select a face (not the whole volume). Now my question is the force applied normal to that selected force? 



Then I tried to apply stress in place of force, in this case, I can select the whole volume. But what does this stress means? Is it an input as von-mises stress or any of the principal stresses?