Comparison of constitutive relationships of tubes established using uniaxial tensile tests and tube hydroforming experiments

Abstract

The aim of the present paper is to evaluate existing constitutive models and to fitting hardening laws of SS304 tubes for the accurate prediction of the deformation behaviors of the tubes in hydroforming. Uniaxial tensile test (UTT) and free hydro-bugling (FHB) experiments were conducted on SS304 tubes, and a hi-speed three-dimensional (3D) digital image correlation (DIC) system was applied to obtain the deformation data of the samples. Eight constitutive relationships of the tubes were then established by fitting the equivalent stress and strain data with the four existing constitutive models of Hollomon, Ghosh, Voce and Ghosh/Voce, and the fitting accuracy of the obtained constitutive relationships were analyzed and compared. The results show that Ghosh/Voce model holds the highest accuracy in describing the deformation behaviors of the tubes in UTT and FHB, followed by the Ghosh model and then the Hollomon model. The Voce model holds the lowest accuracy. A distinct discrepancy between the constitutive relationships obtained using UTT and FHB experiments are observed in present research conditions.