Hi everybody,

Im trying to develop a VUMat routine and thus Im just learning its features.

There is a question that I would mostly appreciate if anyone hemp me to find the answer.

As you know in a VUMat routine the stresses are updated according the input strain increment and the calculated stiffness matrix. As far as I realized, at the beginning of the analysis, stepTime = 0, the routine is called but the updated stresses at this call are not considered. I want to know what the use of this very first call is. As this call is usually treated as a pure elastic I assumed that this is done in order to find a reasonable step time dt for the analysis or maybe to find and estimation of stiffness matrix to present reasonable strain increment in the following increments. Well, if my guess is right, suppose that we have a bunch of steps in our model. Is it possible to have such first calls at the beginning of each step or this is just for the very first increment which is totalTime = 0

Thanks a lot