Problem with non-linear bush

[uribemax2]

Hello all

I was looking for a way to modelize a displacement limiter and I think I can do it through a non-linear bush. There are two parts in my model, one fixed and another one turning around its axis. My idea is to fit a bush element between these two parts and set its stiffness variable with the displacement like this (stiffness in vertical axis and displacement in horizontal one):

[COLOR=#FFFFFF].........[/color] ________
         |
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_________|

I mean, the lower part of the graph extents during the displacement that I allow to the mobile part, while the upper part is when that part has reached the displacement limiter and therefore the stiffness will increase a lot.

I have created a field with these values of stiffness and I've introduced it in bush properties but the non-linear analysis (106) doesn't converge I and don't know why.

I have done a very simplified model to learn how bush elements work: a cantilever beam linked to a bush that is fixed to a wall. I apply a 1N axial force and I am willing to obtain a 5mm displacement by increasing the bush stiffness from 1N/m to 100000N/m but it does not work. I have attached you the .bdf file for an easier comprehension.

Thanks in advance.