Prediction of anisotropic strengths of steel plate after prior bending-reverse bending deformation: Application of distortional hardening model

Abstract

In this study, the strengths of a steel pipe in different material orientations are predicted using a distortional anisotropic hardening model, namely, the HAH model, implemented in a finite element simulation. The investigated hardening can capture the transient flow behavior under bending and reverse bending strain paths. In addition, the model reproduces the material behavior under orthogonally applied tension from the prior deformation path. To improve the predictive accuracy of the existing distortional hardening model, we additionally implement the multi-component evolution rule of the Bauschinger effect and transient hardening behavior. Two-step tension tests are used to identify the constitutive parameters related to the loading path changes in the bending and reverse bending (BRB) test, which mimics the common pipe manufacturing process in a practical manner. The predicted strengths along the circumferential and transverse directions to the major bending direction agree well with the experimentally measured strengths when the distortional hardening model is employed. By contrast, the classical isotropic hardening and kinematic hardening model over- and under-estimate the yield strength of the specimens after prior BRB loading. The improved accuracy of the strength prediction with the investigated HAH is attributed to the anisotropic identification of the flow behavior under both load reversal and cross-loading conditions, whereas the isotropic-kinematic hardening only considers the back stress evolution at load reversal. In addition to the strengths, the stagnated flow behavior after BRB loading can be well predicted with the HAH model with a properly calibrated yield point elongation using an inverse identification method.