I am trying to simulate a tensile study for bolt displacement under load which is being restrained from a nut. I have performed a prescribed displacement study with a non linear elastic and also tried a plastic von mises material, but cannot get any reasonable results from the study. I have test data in form of force vs displacement which I am trying to assimilate. When I ran a validation in linear static I come close at around 10000 lbf for a .045 deflection, but when ran in non linear its way off. Even the stress values climb into the 6 million psi range which is not physically possible with this load. Any insight on what I am missing ? or how to get this done? I cannot get the bolt to displace from the nut, its all from bolt stretch, at least that how it looks.