Study On Anisotropic Yield Behavior Of DP490 Steel

DP490 dual phase steel has the characteristics of high strength,high toughness and so on.It is a high strength sheet material for automobile.The automobile body structure is mainly made by stamping.However,due to the obvious anisotropy of DP490 dual-phase steel plate,the constitutive model used in the simulation molding prediction before the stamping process formulation does not fully consider the anisotropic characteristics of this material,resulting in the prediction accuracy not meeting the requirements,which cannot well control the generation of defects in the actual stamping production,and directly reduces the production efficiency and economy of the stamping workshop.Therefore,a constitutive model suitable for DP490 dual phase steel is constructed in this artical.Through the calibration of the model,the accuracy and applicability of the model to characterize the yield behavior of DP490 dual phase steel plate are evaluated,so as to improve the accuracy of numerical simulation and provide guidance for the formulation of stamping process.The uniaxial and biaxial yield stress and r value,normal plane and diagonal plane yield loci and plastic strain rate direction of DP490 dual phase steel were obtained by uniaxial tensile test and biaxial tension test.Compared with the traditional evaluation system,the mechanical properties measured at 45°-135° sampling direction were further increased on the basis of RD-TD sampling direction.The anisotropic yield behavior of DP490 dual phase steel plate was characterized by Hill48 and Yld2000-2d.Among them,Hill48 yield criterion uses the anisotropic data of stress and r value to solve the material parameters,and Yld2000-2d yield criterion uses three solving methods,namely,the traditional method(Yld2000-EB),the near-plane strain substitution method(Yld2000-PS)and the global optimization method of uniaxial tension test data(Yld2000-Uni).The uniaxial and equal biaxial yield stress,r value,yield loci and plastic strain rate directions of DP490dual-phase steel were predicted by two yield criteria and different parameter solving methods,and the uniaxial hardening curves with different angles along the rolling direction and the biaxial hardening curves with different loading ratios were deduced to comprehensively evaluate the effectiveness and applicability of the yield criterion.At the same time,the drawing experiment of cylindrical parts was carried out to obtain the earing height of cylindrical parts and the thickness distribution of RD direction,DD direction and TD direction.Based on Yld2000-2d and Hill48 yield criteria,the finite element simulation of cylindrical parts was carried out and compared with the measured results.The results show that compared with Hill48 yield criterion,Yld2000-EB method and Yld2000-PS method show good prediction accuracy in characterizing the anisotropic yield behavior of DP490 dual-phase steel plate.Among them,The yield loci accuracy of Yld2000-EB method is slightly higher than that of Yld2000-PS method in normal plane and diagonal plane,and the accuracy of Yld2000-PS method in predicting biaxial tension hardening cure is slightly higher than that of Yld2000-EB method.The Yld2000-Uni method has the smallest sum difference in the prediction of uniaxial tension,but the prediction error of biaxial tension stress-strain curve is the largest.Yld2000-PS method shows a higher level than the experimental results in predicting the earing height and thickness distribution of cylindrical parts.