Hi, sorry for my bad english. PART A I have a cube of 10mm x 10mm x 10mm which is compressed with a stress of 0.5 Mpa on his superior face (σz=-0.6) young modulus=20Mpa, poisson coef=0.5 I have the stress tensor: [ 0 0 0] [ 0 0 0] [ 0 0 -0.6] And then, the deformation tensor is : [0.015 0 0] [ 0 0.015 0] [0 0 -0.3] Why εx+εy+εz =0? is it a question of conservation of the volume ? PART B Well, now i put this cube into an indeformable box of 10.002mm (x) x 10.004 mm (y) x 10 mm (z) and this cube is again compressed with a stress of 0.5MPa; 1) do The face x and y of the cube will touch the faces of the box ? I do ε=ΔL/L and i find εx=0.0002 and εy=0.0004. So I supposed that they will touch if we compared the deformations with the deformation in the first part. 2) Doing an hypothesis that the faces will be in contact with the face of the box, determined the stress and deformation tensor of the cube.... But here i don't know how to do that... If someone can help me.. Thanks a lots PART C IF the box has the same dimension of the cube and if will do a stress of 0.6 MPa again, determined without calculus the deformation tensor.. I think all deformation will be equal 0 is it right ?