I can't get a simple non linear problem to run. See screenshot below.

Very simple square bar made from a material that has two CTEs, above and below the glass transition temperature. I'm cooling the bar from above Tg to well below Tg over the default time of 1 second.

For some reason at ~0.65s I get the following error message:

Solution failure in a Step>1, it could be due to:

The solution may be at a buckling or limit point, i.e.,

displacements grow large under constant forces. If so,

for force control or contact problems, this is the end

of solution (check out the response graphs).

The solution is set up as follows:

I've restrained the end in different ways in case I was generating very strains but get exactly the same error at exactly the same time.

Any ideas where I'm going wrong?