We report a method for describing plasticity in a broad class of amorphous materials. The method is based on nonlinear (geometric) deformation theory allowing the separation of the plastic deformation from the general deformation tensor. This separation allows an adequate pattern of thermodynamical phenomena for plastic deformations in polymers to be constructed. A parameter describing the stress relaxation rate of the material is introduced within the frame of this approach. Additionally, several experimental configurations to measure this parameter are discussed.
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