Nonlinear Kinematic Hardening Constitutive Model Based On Hill48 Yield Criterion And Its Application

During sheet metal forming, deformation which is induced by compression after stretching or bending back after bending, will not only produces the Bauschinger effect, but also enhances sheet metal’s directional characteristics. As a result, the isotropic theory is no longer held. In view of such problems, by studying the behavior of materials under cyclic loading condition, a nonlinear kinematic hardening model was developed and applied on numerical analysis of reinforcement for deep drawing.In theory, based on the plane stress assumption, Hill48 anisotropic yield criteria and A-F nonlinear kinematic hardening model, a non-linear material model was established considering the Bauschinger effect. The method to calculate the materials parameters of the model was given and the constitutive matrix was derived.According to the stress algorithm in finite elements theory and Taylor expansions, the numerical constitutive model was completed. Using Fortran language program, through the ABAQUS software UMAT interface achieving the interface of the constitutive model of the secondary development. The correctness of the subroutines was demonstrated by example.Using the above nonlinear kinematic hardening model, based on finite element nu-merical simulation method, drawbead process was analyzed. Obtained were mechanical properties of hot-dip galvanizing deep drawing steel sheet DC54D+ZF by the tensile test and the finite element numerical simulation of material constants. Established was a unit of drawbead model, using the developed material model and ABAQUS models in analysis of the deformation of the sheet through the drawbead. Compared with experiments, the influence of the structure parameters of the drawing model on the resistance and the strain state of the sheet metal was discussed. Results showed that the developed material model based on Hill48 criteria was closer to the experimental results than ABAQUS isotropic model.