Theory of strains

Usually in the nonlinear theory of elasticity the theory of deformations is based only on geometrical reasons, thus a lot of different strain tensors are considered. It is usually assumed that all of these tensors can be used with identical success. However, this is not correct. It is shown (2001), that the dissipative inequality imposes such restrictions on free energy [1, 2], which at use of Almansi measure of strain appear equivalent to the statement, that the considered material is isotropic. In other words it is shown, that for anisotropic materials free energy cannot be a function of Almansi measure of strain. The definition of the strain measure is given on the base of the equation of balance of energy and the dissipative inequality. It is shown, that according to the given definition the strain measure should be an unimodular tensor.
  1. Zhilin P.A. Basic equations of the theory of non-elastic media // Proc. of the XXVIII Summer School “Actual Problems in Mechanics”. St. Petersburg. 2001. P. 14-58. (In Russian.)
  2. Zhilin P.A. Phase Transitions and General Theory of Elasto-Plastic Bodies // Proceedings of XXIX Summer School - Conference “Advanced Problems in Mechanics”. St. Petersburg, Russia, 2002. P. 36-48.