Abstract
Considering the cross effect in the evolution of subsequent yield surfaces for metals, an anisotropic distortional yield surface constitutive model is developed. By introducing an anisotropic distortional hardening function into the isotropic hardening part of the classical Chaboche rate-dependent constitutive model, the plastic-deformation-induced distortional and anisotropic hardening behaviors of subsequent yield surfaces are characterized. The experimental data of distortional yield surfaces for T2 pure copper under three different loading paths, including pre-tension, pre-torsion, and pre-tension-torsion proportional loading of 45-degree, are simulated by implementing the models into a numerical user defined material (UMAT) procedure based on the ABAQUS finite element package. To validate the anisotropic plastic model, the simulated yield surfaces are compared with experimental observations and predicted results for a crystal plasticity model and good agreement are noted. The simulations demonstrate that the proposed model can accurately capture the characteristics of the distortional yield surface and the anisotropic hardening process of the yield surface. Moreover, the distortional shapes of experimental subsequent yield surfaces in loading direction and opposite direction can be better revealed by the anisotropic plastic constitutive model than the crystal plastic constitutive model.
Highlights
It has been long observed that plastic deformations induce anisotropy in initially isotropic materials [1,2], which has been a challenge for the traditional plastic constitutive theory to describe.The study of the evolution law of yield surface relies on the establishment of a plastic constitutive model, which serves as a basis for the analysis of macroscopic test data and verification of the applicability and validity of the model by multiaxial tests
Compared with the experimental data and the simulated results of crystal plastic model, the anisotropic distortional yield surface model proposed in this paper can better exhibit the anisotropic yield characteristic after preloading and the cross effect of subsequent yield surface
The predicted accuracy of the anisotropic model is higher than the crystal plastic model, with the mean error and the standard deviation as
Summary
It has been long observed that plastic deformations induce anisotropy in initially isotropic materials [1,2], which has been a challenge for the traditional plastic constitutive theory to describe. Since the initial and subsequent yield surfaces described by the von Mises theory are cylindrical surfaces in the principal stress space, theyield traditional models cannot the cross effect sharp. Since initial and subsequent surfaces described by describe the von Mises theory are Since the initial and subsequent yield surfaces described by the von Mises theory are cylindrical surfaces in principal stress space, the traditional models cannot describe the cross effect (the sharp point in pre-deformation direction and the relatively flat bottom at its opposite direction) of a yield surface accurately. Taking the subsequent yield of T2 pure copper behavior into account, a macroscopic constitutive model reflecting the distortional yield surface induced by plastic deformation is put forward under the hypothesis of continuous uniform in material. The model parameters are calibrated and the reasonability of the anisotropic model is verified
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