Bezier Interpolation-type Anisotropic Yield Loci And Evolution Model

In order to describe the complex hardening behavior of materials in plastic forming,a novel discrete interpolation-type yield loci description method based on Bezier curves and the subsequent evolution model are proposed,which are suitable on two-dimensional stress space.The main research contents are summarized as follows:（1）Based on the results of tensile-torsional combined loading tests on Al6061-T6511 aluminum alloy from Khan et.al.,which showing extremely strong size,center point and shape change of the yield loci on two-dimensional stress space,caused by very small yield strain threshold,10^-5,the corresponding discrete interpolation yield loci were constructed,with the interpolation parameters determined by fitting the experimental results under each pre-strain condition.The fitting models considering size,center point and shape change of the subsequent yield loci were proposed to describe the isotropic,kinematic and distortional hardening behavior.（2）Taking the DP590 steel sheet as an example,the pre-stretched specimens were cut at different angles to the rolling direction,including 0°,45°and 90°.Three different pre-strains were applied by uniaxial tension,and lamination,plane strain,uniaxial tension,uniaxial compression and shear specimens were cut from the homogeneous deformation zone,and the subsequent loading tests were implemented.According to the experimental results,the anisotropic yield behavior and the evolution law of the subsequent yield loci of the material were studied.（3）The evolution law of the subsequent yield loci of DP590 steel sheet on the quasi-Πplane was studied.The experimental results were modeled,predicted and analyzed by using the Bezier curve-based subsequent yield loci evolution model.The model is simple to construct and contains clear geometric meaning,which directly reflects the anisotropic hardening behavior.