SEDL / STP / STP765-EB / STP28893S

A Kinetics Approach to the Derivation and Measurement of the Constitutive Equations of Time-Dependent Deformation

Krausz, AS
Professor and Chairman, University of Ottawa, Ontario

Faucher, B
Research Associate, Industrial Material Research Institute, Division of National Research Council of Canada, Montreal, Quebec

Pages: 14    Published: Jan 1982

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Abstract

The approach is based on a model that is an intermediate between the specific micromechanics models of the structural theory of plasticity and the phenomenological continuum-mechanics models of anelasticity. It is considered that the fundamental physical processes, producing the deformation of any solid, are the breaking and mending of atomic bonds, and that plastic flow occurs by the movement of flow units that very often have to overcome a series of energy barriers. Therefore the constitutive relations are derived from the kinetics analysis of the energy barriers and the deformation rate is determined from rate theory. The constitutive equations obtained in the study are in the form of ordinary differential equations and are based on a rigorously defined physical model. Numerical solutions of the equations applied to a system of two consecutive energy barriers show excellent agreement with experimental results obtained under various testing conditions. Furthermore, calculations show that the stiffness of the testing machine can have a considerable influence on the observed behavior during stress relaxation experiments.