Many of the material models in COMSOL Multiphysics will compute a stress based on an elastic strain. The elastic strain tensor is obtained after removing any inelastic deformation contribution from the total deformation from the displacements. There are several possible inelastic strain contributions:
In the finite deformation case, the inelastic strain is instead removed using a multiplicative decomposition of the deformation gradient tensor. The elastic deformation gradient tensor is the basis for all strain energy formulations in hyperelastic materials, and also for the elastic strain in linear and nonlinear elasticity. It is derived by removing the inelastic deformation from the total deformation gradient tensor.
and the elastic Green-Lagrange strain tensor is computed as:
The inelastic deformation tensor Finel is derived from inelastic processes, such as thermal expansion or plasticity. When there are several inelastic contributions, they are applied sequentially to obtain the total inelastic deformation tensor
Finel.
The plastic Green-Lagrange strain tensor is computed from the
plastic deformation gradient tensor as