Strain rotation in MPM

Hello,@kks32,@bodhinandach,@jgiven100
I noticed that there is no strain rotation in the function of “compute_strain” in particle.tcc. I think we need to consider it in mpm simulation. such as maybe a cube rotate 90 degree, and x-y strain turns to y-z strain maybe. Could you please point it in the cb-geo, or how to deal with the strain rotation in the cb-geo?
Thanks all.

Hi @fengzk the strain assumption that is used in the main branch is the infinitesimal strain, so it does not split the stretch and rotation and is not objective. We found it to work OK for a small time increment. However, for such a large rotation, i.e. a cube rotates 90 degrees, you might want to use finite strain assumption instead.