SEDL / STP / STP681-EB / STP36689S

A Microstructure-Based Constitutive Relation for Dilute Alloys of α-Zirconium

Hartley, CS
University of Florida, Gainesville, Fla.

Lee, J-J
University of Florida, Gainesville, Fla.

Garde, A
Agronne National Laboratory, Argonne, Ill.

Chung, HM
Agronne National Laboratory, Argonne, Ill.

Kassner, TF
Agronne National Laboratory, Argonne, Ill.

Pages: 12    Published: Jan 1979

Download this paper for $25 PDF (156K)          View License Agreement
Abstract

The microstructural basis for a particular form of constitutive equation relating true stress to true plastic strain in Zircaloy is examined. It is shown that simple physical assumptions about the work-hardening mechanism can lead to an equation of the form τ=τi+Kγn(γ˙/γ˙0)m relating the true stress τ to true plastic strain γ at a constant true strain rate γ˙. The parameters τⁱ, K, n and γ˙0 are dependent on material parameters such as the shear modulus and the Burgers vector of slip dislocations. The strain-rate sensitivity m is shown to be strain dependent in this model. Analysis of experimental data obtained on Zircaloy-4 at two strain rates over a temperature range from 473 to 1073 K demonstrates that the equation provides an excellent fit to experimental data. However, the temperature and strain-rate dependence of the material parameters are not in accordance with the theory. It is concluded that accuracy of fit to stress-strain data cannot be used as a criterion for the validity of a microstructural model and that more accurate microstructural models are required to permit predictions of the variations of phenomenological coefficients with test conditions.