Thermodynamic modeling of creep damage in materials with different properties in tension and compression

A constitutive model is developed to describe the creep response of polycry stalline metals and alloys with different behavior in tension and compressi on. A second-order damage tensor is introduced in order to describe the cre ep damage under nonproportional loading in nonisothermal processes. The the rmodynamic formulation of the creep equation and the damage evolution equat ion is used to study the creep behavior and creep damage in the initially i sotropic materials. The determination of the material parameters in the pro posed equations is demonstrated from a series of basic experiments outlined in this paper. The results generated from the model are compared with thos e obtained from experiments under uniaxial nonproportional and multiaxial n onproportional loading for both isothermal and nonisothermal processes. (C) 2000 Elsevier Science Ltd. All rights reserved.