I was reading the abaqus theory manual (coz u know.. apparently I have lots of free time ;) ) I realized something interesting and would like to hear your opinions.
in is mentioned in section "1.4.4 The additive strain rate decomposition" that total strain rate can be decomposed into elastic and plastic parts (epsilon_dot = eps_dot_el+eps_dot_pl). This is a correct "estimate" based on assumption that elastic strains (or to be correct deformation) is relatively small. This is a good assumption for many soilds where their elastic modulus is high. I am working with soils. pretty much everyone uses (epsilon_dot = eps_dot_el+eps_dot_pl) in soil mechanics. But is soils elastic strains are not small compared to plastic strains. They are sometimes same magnitude as plastic strains. Any idea theoritically how much this matter?
I can see in equations in same section of the manual that this assumption translates into whether v^2 can be neglected in: F_el = (I+vA) R_el
F_el being elastic part of deformation gradient and R_el is rotation part of deformation gradient