Unexpected Force-Displacement plot
Hi everyone,
I am simulating a tensile test of a homogeneous isotropic material, according to the coupon bar example in 'Introduction of Non Linear Finite Element Analysis using Optistruct'.
I imported a different material and the coupon bar geometry is a bit different. I do not understand why the numerical force -displacement curve decreases after the yielding point, while, for example in the ebook, it follows the input trend.
I though the possible problems could be the definition of the true stress-strain curve, or the NLQS parameters NINC and NLOUT, the chosen finite elements (tetrahedral; I used this type because I have to calibrate the material to perform analyses on more complex geometries).
Can anyone find the problem?
I attach the .fem file (ModelB_prova_NLQS).
In additiion I attach a model that behaves as expected (Model2_surf_prova10_NLQS