In Creo 1, PTC implemented important improvements of the nonlinear functionality. The most important of these improvments, is the ability to combine several nonlinear phenomenae in the analysis. In this case I have analyzed post-critical behaviour of an axially loaded column. The analysis includes the effect of large deformations, plastic yield in the steel, and nonlinear collapse of the structure. Since the load can't be increased beyond the critical level, the displacement was prescribed, and the reaction force was measured. The reaction force increases up to the critical level, and then declines, as expected. The nonlinear solver benefits from the new ability to create prismatic elements, such as brick and wedge elements.
/Mats Lindqvist/Econocap AB/
The vertical prescribed displacement is applied to one edge of the L-profile, i.e. the force is not aligned with the centre of gravity of the section. So there will be a small bending moment along the beam, sufficient to initiate the unstable behaviour. If the load (in the form of prescribed displacement) had been aligned with the centre of gravity of the section (neutral axis), then it would have been necessary to model some disturbing force, or geometric imperfection, to initiate the buckling.
Yes, I used elasto-plastic material.
I no longer have this model. I have a new job now, and I normally use the account "email@example.com".
B.R. Mats Lindqvist