A critical evaluation and extension of internal state variables constitutive models

• Published in: International journal of plasticity Vol. 11; no. 4; pp. 331 - 345
• Main Authors: HUI LI, SUNIL SAIGAL, WANG, P. T, PIEHLER, H. R
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Science 1995
• Subjects: Applied sciences; Condensed matter: structure, mechanical and thermal properties; Deformation and plasticity (including yield, ductility, and superplasticity); Exact sciences and technology; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Metals. Metallurgy; Physics; Hot deformation; Constitutive equation; Aluminium base alloys; Plasticity; Theoretical study; Mechanical properties; Stress-strain relation; Forming; Plastic deformation; Modeling; Strain rate
• ISSN: 0749-6419; 1879-2154
• DOI: 10.1016/S0749-6419(95)00002-X

This study provides a critical comparison of the internal state variables constitutive models proposed recently in the literature for metals at elevated temperatures and deformed over a wide range of strain rates. As a result of the observations from this comparative evaluation, a set of modified constitutive relations is also presented. The experimental data available in the literature for 1100 aluminum and a fully dense high purity aluminum were used along with a nonlinear least squares fitting procedure to estimate the material constants. A nonlinear functional dependence of the effective stress with respect to the internal state variable in the evolution relationship was determined to model more effectively, compared to previous models, the case where a material may exhibit both hardening and softening behaviors, respectively, corresponding to different applied strain rates at the same temperature. The modified relations presented here propose a simple form of this nonlinear function, which accurately models the material response and which allows a more robust implementation in numerical simulations. (Author)