Research On Cold Ring Rolling Simulation Based On Macro-Micro Constitutive Relation

Cold ring rolling is an advanced plastic forming technology with continuous revolving local deformation, which has significant advantages in labor saving, energy conservation, material saving, high efficient and low cost. The technology has received an increasing application in the fields of aerospace, automobile, train and energy etc. To consistent with the development of cold ring rolling theory and technology, the research on the effect of material properties as well as their evolution in processing on the forming technology is becoming an important issue. So this paper pays more emphasis on the study of macro-micro constitutive relations. Then user's material subroutines were developed based on ABAQUS/Explicit platform, and further 3D-FEM simulation of cold ring rolling was fulfilled. The main achievements in this paper are as follows:J2 plastic theory was employed with isotropic hardening coefficient introduced. A stress offset updating algorithm was put forward on the basis of elasticity tensor, and the results demonstrate the improved computational accuracy and efficient of constitutive equation. Based on the algorithm, the subroutine of elastic-plastic constitutive relation with hybrid hardening was developed on ABAQUS/Explicit platform. It fulfills the macroscopic description of anisotropic behavior in strain-hardening in ABAQUS.Time incremental formulas of crystal plastic constitutive relation were employed, and optimization for the key problems as the simplifying and solving of nonlinear equations set and even the iterative initial values' confirming was treated. Based on the homotopy auto changing discrete-type continuation method, the subroutine of crystal plastic constitutive relation was developed. It enables the description of material's microscopic responses during macroscopic deforming process from the point of view of dislocation slip. Further the accuracy of the subroutine was evaluated by the results of single element compression simulation. Thus it expands the application of crystal microscopic plastic anisotropic property in ABAQUS/Explicit.To study the effect of material parameters on the deforming process, 3D-FEM simulation of cold ring rolling was performed on ABQUS/Explicit platform with user's materials subroutines developed. The results show that: â‘ The metal flows difficultly, the material deforming becomes uniform, and the cross-section of ring becomes smooth, as well as the draught pressure and roll torque augment, associated trackslip between the ring and the driver arises and turns severer with increasing isotropic hardening coefficient, hardenability value and initial yield stress; Young's modulus mainly affects metal's plastic flow. The metal flows easier as Young'smodulus turns larger. (2) On the basis of virtual orthogonal test, the effect of material parameters on draught pressure and fishtail coefficient obeys the following order: initial yield stress, hardenability value, isotropic hardening coefficient and Young's modulus. These results obtained above will provide a valuable reference for choosing ring material.