Dear All,

     In ABAQUS manual, it is said for hyperelastic material, it is better to define it by stretch tensor U. But if I need to use deformation gradient F in the material model directly, I need to rotate the stress back to corotational frame. How should I do that?  Should I make a polar decomposition of F=R*U first, and then apply Rt*S*R? or I can use the relative spin increment already provided to do that? If so, how?

     Also, an alternative method I think is that I can rotate the deformation gradient to corotational frame  first, and then calculate the stress based on tranformed deformation gradient. Is that right?