initial displacment problem

[mech5243]

i would like to apply an initial displacement to my model.
does anyone know how can i do it?

My problem is that i am programming an umat, and for converenge reasons i would like to have an initial strain at the begining of the first iteration of the first increment. I found some ways to overcome the problem by making some tricks in my equetions, but i think i can solve that problem in a more apropiriate way by applying an initial displacement..which it will give me an initial strain..
Anyone know the command?

thanks in advance of every reply

[biofriend]

Hi

One can think of different ideas but I'm not sure which one may be helpful in your case.

disp. is usually defined in B.C module but it does not allow nonzero values for initial. you can define an additional step before your main step of analysis, in which the part is deformed/displaced to your desired degree and then in the succeeding step your analysis begins, in fact this preliminary step plays as your desired initial value.

you may be also do such thing in predefined fields.

as another choice , you may be able to sketch your part in the strained condition and then add forces to express pre-stress on its boundary. If your part is 2D you can do this by extracting 2D solid part from orphan meshes of your initial analysis database and map the nodal solutions including stress, to your new model.

I think however the first one is easiest if reasonable,

Hope these help,
Bio