Constitutive Model Parameter Identification And Its Application To Bending Spingback Prediction Of High Strength Sheet Metal

Springback is a common phenomenon in sheet metal forming,and the springback of high strength steel sheet is especially prominent.The springback prediction accuracy depends on many aspects,including the forming conditions,sheet and die geometry,material parameters and constitutive model,numerical method,and the selection of constitutive model is reasonable or not is the key to improve the accuracy of springback prediction.The purpose of this paper is to compare the effects of different constitutive models on the springback prediction of high strength sheet metal bending process.The main contents of this paper are as follows:1)the mechanical properties test and the parameter calibration of the constitutive model are completed.DIC method was used for tensile test of specimens with different orientation,obtain yield stress,thickness anisotropy coefficient and parameters for stress strain curves of mechanical properties;developed anisotropic yield function parameter calibration system parameters to achieve the Hill48,Hill90,Barlat91,Barlat96,Barlat2000-2d,BBC2000,BBC2005 anisotropic yield function fast calibration;design of cyclic shear test fixture,combined with Abaqus,Matlab and optimization software Modefrontier,using the cyclic shear stress and strain data to complete the parameters' calibration of Y-U and HAH hardening model.2)based on the backward Euler method has general projection algorithm,deduces the stress integral formula of different constitutive models;through the Abaqus subroutine interface,complete the preparation of Hill48/ Barlat2000-2d + Y-U/HAH constitutive model of VUMAT/UMAT material subroutine,and mechanical response process under uniaxial tension and compression under cyclic tension was verified,verification shows that the simulation results and the experimental results are consistent,the subroutine can be used to simulate bending case.3)The developed material constitutive model is applied to the U type stretch bending process(Numisheet 2011)of DP780 material and the springback prediction of L type bending process of DP980 material.The simulation results of different constitutive models were systematically compared and analyzed,focusing on hardening model,yield criterion and elastic modulus of high strength steel bending springback finite element simulation the influence of the analysis shows that both the simple loading and complex loading,the prediction error of Y-U and HAH hardening model are smaller than IH hardening model,especially in complex loading conditions using Y-U and HAH hardening model can significantly improve the prediction accuracy of springback;variable elastic modulus coupled into the hardening model can effectively improve the prediction accuracy of springback;using anisotropic yield criterion can effectively simulate the anisotropic samples in different orientations of springback in bending,the theoretical prediction of different the orientation of springback simulation results and anisotropic yield criteria in different orientation on the positive correlation.