I am currently trying to model the buckling behaviour of a cylinder using sol 400 nonlinear static analysis using Nastran. I am using the arc-length (modified Riks) method as apparently it can increment load and displacement in both positive and negative directions, as opposed to Newtons method which only increases the load or displacement increment. However, my problem is that the analysis always stops after a certain load due to convergence problems.
I have tried changing many of the parameters such as MINALR/MAXALR ( min/max arc-length ratio between increments) and MXINC(max increments), however I still don't get any good results.
I feel like I am missing a parameter that enables the load to decrease after a maximum load has been reached.
I am aware that load control and displacement control is possible, but my understanding is that arc-length method uses neither of these, and is sort of a combination of the two. My model has a force applied without any enforced displacement. Is this maybe the problem?
Any other ideas which might help me?
Thanks in advance.