I would like to be able to predict when a part will fail. I define a failure for this case as a complete fracture of the part which allows the component to separate into two pieces. I have looked at some of the non-linear static examples and set up a simple problem but don't really see how to get there from here.

If I model a cylindrical hollow aluminum tube that is 48" long x 4" dia. X .25" thick I can restrain one end and apply a load to the other end. I can also depict this problem on paper and solve for the bending stress and displacement which matches the SolidWorks solution very closely. That's the good news. How do I use the simulation to predict when the part will actually fracture? Can I do that? Obviously stress in excess of the tensile strength is a problem but I would like to quantify what value is required to fail the part.

When i vary loads on the example described above I seem to continue to get linear results even as the stress in the part goes well above the tensile strength. Shouldn't the displacement and stress be non-linear by definition?

I picture is attached. Any insight would be appreciated.