CONSTITUTIVE-EQUATIONS IN NONLINEAR DAMAGE MECHANICS

The classical method of solving problems concerning the delayed fracture of structural materials and elements is based on analysis of their stabilized stress-strain state and the use of parametric relations which include the time or number of cycles to failure. Over the last twenty years, researchers have developed another approach employing the concept of internal variables [1, 2, 22] along with a system of evolutionary equations and failure criteria. Entropy, internal energy, empirical temperature, internal time, strain-hardening, and damage are the quantities most often chosen as the internal variables. In the present study, we examine methods of constructing adequate evolutionary equations for a damage parameter that cannot be measured directly.