Distortion stress, distortion strain and their physical concept

A new concept of stress and strain is introduced, in which the regarding stress and strain are named distortion stress and distortion strain that are concerned the type of deformation models. The stress and strain reveal an intrinsic characteristic of the 3rd invariants of the deviatoric stress tensor and the deviatoric strain tensor that shows the deformation histories of a deformation part during different forming processes. This new concept should help in the understanding of basic physical meanings of stress and strain parameters and further to propose associated plastic theories.