Dislocation theory of steady state deformation and its approach in creep and dynamic tests

Abstract

A concept of strain hardening in constant strain rate (CSR) tests and creep tests is presented taking into account dislocation production and recovery by slip, climb and concurrent subboundary migration. A master equation is derived to relate the evolution of the dislocation density with strain rate and stress. Transient and steady state equations are developed for various combinations of recovery mechanisms in both types of tests, and are analyzed with respect to material characteristics ( μ, b, D, γ sf ), and test conditions ( T, ⋗3, σ). For steady state equivalent relations between stress and strain rate are obtained for both test modes. The appropriate relations for the approach to steady state and their mutual correlations are elaborated. The derived dependencies are discussed with respect to experimental results in order to elucidate the occurrence and impact of possible recovery mechanisms and to apply proper procedures for a conclusive determination of steady state parameters.