1. The problem statement, all variables and given/known data Let assume that we have two rectangular prism elements of similar dimensions: e.g. 1.) x0=100.1, y0=100.2, z0=90.4 2.) x0=100.2, y0=100.4, z0=90.0 How can I calculate the stress tensor of each of the two elements if I assembly them by merging their z-y faces together? I'd wanna use the Poisson's ratio(v=0.25)and linear elastic material (E=70GPa). 2. Relevant equations V=x0(1+ε)*y0(1-vε)*z0(1-vε) σ=εE 3. The attempt at a solution The solution is easy If the material is absolutely compressible(v=0). I derived a general formula for the new y dimension(same for both elements) from the condition of mechanical equilibrium ƩFi(in y-direction)=0: y=Ʃ(xi*zi)/Ʃ((xi*zi)/yi) But I can't find any equation of mechanical equilibrium for my case. If you know at least how to calculate the principal stresses neglecting the shear elements of the matrices, that would be a great help too. FEM type of solution is welcomed too.