I am doing non linear analysis of my BCC lattice structure with one surface as fixed conditions and giving displacement on opposite surface with non linear properties of ABS. The problem is yield strength of BCC structure I am using is 29.11 MPa, so in obvious sense my analysis should break the structure i.e my graph of stress and strain should be non linear and should show plasticity after yield point but that's not the case, even after crossing the yield point my graph is linear. Interesting thing was that, When I did analysis in Y direction my graph was perfectly fine with non linear shape, but when I changed the axis of boundary condition and loading condition for same structure i.e in X and Z direction I am getting linear graph even after yield point. So what might have gone wrong with my analysis?
During my analysis type of analysis and boundary conditions and loading conditions were same for all three direction but still I am not getting non linear results in X and Z direction. So can anyone help me with this issue?
Thanks in advance.