John Doyle
Ansys Employee

Thanks for the confirmation.

Perhaps your first instinct was right (i.e. localized buckling).  Could you run an linear eignevalue buckling analysis to get an approximate idea as to what physical anomoly (perterbation) would be needed to induce local buckling and then introduce that perturbation into the geometry for the structural nonlinear analysis?  Also, try a displacement based load (for stability).