Constitutive equations optimized for determining strengths of metallic alloys

• We examine the suitability of three constitutive equations for metallic alloys.
• Hollomon equation does not describe material with linear-work-hardening well.
• The Swift equation generally describes yield strengths correctly.
• The Voce equation predicts yield strengths more accurately.

We investigate compatibilities of three constitutive equations, the Hollomon, the Swift, and the Voce equations for determination of yield and ultimate tensile strengths based on tensile true stress–strain curves of 27 metal alloys including those with power-law type and linear-type strain-hardening. We analyze each constitutive equation in terms of yield strength determined by the intercept of the linear elastic loading curve and plastic flow curve and ultimate tensile strength evaluated by the concept of instability in tension. We found that the describing plastic flow is very sensitive in determination of the yield strength and tensile strength from parameters of constitutive equation. Voce equation gives estimate yield strength and tensile strength better than Hollomon and Swift equations.