I tried plotting maximum equivalent stress vs maximum equivalent strain considering only 1 element. The result again is linear.
Also, to add to your point of getting non-linear reaction force. I too am getting non-linear reaction force if I plot versus time and not versus strain. I think here is the problem.
Equivalent stress, Equivalent strain and force everything is nonlinear versus time. But if I plot stress vs strain they shows linearity.
what to do in such situations?
Thanks in advance