Constitutive Equations Study in Biaxial Stress Experiments

Abstract

An experimental study of high temperature creep constitutive equations is reported. The experiments are performed in uniaxial and biaxial (tension-torsion) state of stress. Stress drop experiments starting from a given plastic state (i.e., fixed creep rates, stresses and temperature) lead to the flow rules. It is so pointed out: that hardening is essentially kinematical (as well as creep induced anisotropy), that in steady creep the components of this hardening are proportional to those of applied stress. Then, constitutive equations can be derived from that, the identification of which is reduced to the determination of three hardening and recovery scalar functions and to the knowledge, easily open to measure, of the relationship between the equivalent strain rate and the effective equivalent stress. In the case of our experiments, this relationship is a power law.