Multiplicative decomposition of Defgrad

[Stephen_K]

Hi all,

I've begun work on a viscoelastic-plastic VUMAT for Abaqus/Explicit and want to work from the multiplicative decomposition of F into Fe and Fp, but I havn't found any literature that says how to calculate Fe or Fp! Is there a method that explicitly calculates these from the deformation gradient or are they chosen based on ones own initial assumptions?

[sq]

Think back to your elasticity class- that part of a strain which is considered elastic and what part is plastic will depend entirely on the plasticity model.

One cannot simply be given a value for F and determine a priori the elastic/plastic components of deformation.

[matsgd]

What's really going to confuse you once you start digging, is what to do with the rotational indeterminacy of the decomposition. Remember -- each of these "deformation gradients" can be decomposed into rotations and stretches... 8O