Research On A Modified Bezier Interpolation-type Anisotropic Yield Loci And Evolution Model

In order to conveniently and effectively describe the complex anisotropic behaviors of the sheet materials under different loading conditions and to make up for the shortcomings of the traditional yield models,some scholars have proposed to use the method of interpolation to construct the yield model.This method is convenient,efficient,and has clear geometric meaning.At the same time,Our research group also did some preliminary work on constructing the interpolation yield model,which was constructed the Bezier interpolation-type anisotropic yield loci and evolution model by defining the geometric characteristic parameters of the yield loci.Therefore,a modified interpolation-type yield loci description based on Bezier curves and subsequent evolution model is proposed.The main research contents are as follows:Make the use of the method of interpolation to build interpolation-type yield loci based on the yield loci data of Khan,who used small yield strain threshold to study on the plastic behaviors of Al6061-T6511 and Al1100aluminum alloys according to different loading,unloading,and varying load tests.The new loading model which can fully describe the geometric characteristics and evolution law of yield loci is presented.The new loading model is a kind of improvement over the original model,according to using?to introduce the concept of tensile-torsional stress ratio to define different loading paths.And then a method similar to the incremental theory is used to construct the evolution model of the subsequent yield loci after unloading and varying load.Taking cold rolled DP590 steel sheet as the research object,cut uniaxial tensile and uniaxial compressional samples at the angles of 0°,45°and 90°along the rolling direction,cut shear samples at the angles of 45°and 135°along the rolling direction,and then carry out the corresponding loading experiments.Yield stresses and plastic strain ratios are obtained from uniaxial tension and uniaxial compression tests,and yield stresses are obtained from uniaxial tension and uniaxial compression tests The experimental results show that even the DP590 steel sheet,which is in the delivery state without predeformation,also has the initial anisotropy and strength-difference.The method of upgrading the order of the Vegter’s interpolation model based on the second order Bezier curve is used.Based on the experimental results,the yield loci and interpolation type of anisotropic yield model of the DP590 steel sheet is constructed based on three order Bezier curves on the principal stress plane.And then use the experimental data to verify the accuracy of the interpolation-type yield model.