Parameter Calibration And Correction Of Cold Roll-beating Johnson-cook Constitutive Model

The cold roll-beating plastic forming technology is based on the characteristics of the metal material in the cold state,using a rolling wheel with a specific profile to continuously strike the outer surface of the working part,and to squeeze the metal part to produce plastic deformation and accumulate gradually by a rolling wheel.It can be widely used in gear,spline and related transmission parts manufacturing field.According to the requirement of numerical simulation analysis of cold roll-beating process,the calibration and correction method of suitable material Johnson-Cook(J-C)constitutive model is studied in this paper.This is of great significance to the establishment of accurate cold roll-beating simulation models.A calibration method for Johnson-Cook constitutive model is established.According to the parameter calibration method of the constitutive model of Johnson-Cook material,the stress and strain curves of the material under static state are obtained by two experimental methods of static compression and separation Hopkinson pressure bar.The J-C constitutive model parameters of three materials of 20 steel,45 steel and 40Cr were obtained by processing the stress and strain results in static and dynamic state.The finite element analysis model of Hopkinson pressure bar experiment was established.The parameters of the J-C constitutive model obtained by the experiment are simulated by the finite element method,and the simulation results consistent with the experimental curves are obtained,and the accuracy of the calibrated J-C constitutive model is verified.The stress strain field and rolling force during cold roll-beating are analyzed by finite element method.Through the analysis of the grain changes between the specimens under cyclic loading,it is found that the grain refinement will affect the stress-strain relationship of the material during the cold roll-beating process.The multivariate function correction method for the parameters of the J-C constitutive model was adopted.According to the experimental results,the 4 parameters of the 20 J-C constitutive models of 20 steel,45 steel and 40Cr are corrected.Comparing the simulation results of the parameters of the unmodified J-C constitutive model,it is found that the modified J-C constitutive model parameters can obtain more accurate results of the cold rolling simulation,thus verifying the validity of the model parameter calibration and the correction method.