return map algorithm
Dear all,
I am trying to code a UMAT subroutine for perfect plasticity with a Tsai-Wu failure surface. I follow the procedure of the closest point projection in Simo & Hughes, Box 3.5, which is quite straight forward. At least I thought so
The algorithm converges but unfortunately not to the correct point in the (plane-stress) stress space. At first I used an yield surface wich gives a unit sphere in the stress space. It is easy to control the normality of the plastic strain increment and the return-map algorithm is implified to a radial return algorithm.
