I would like to dissuss the difficulties in modeling the softening behaviour of softening materials (eg. soils, few polycarbonates etc)
1) The mathematical explanation of softening or post bifurcation period.
2)The approach to correctly model the softening part which include the mechanics of the materials . I know there is one model developed by Dr C S Desai and his group.
3) and, Numerical technique to predict the post bifurcation period.
Amit