Influence Of Process Parameters On Residual Stress And Parameter Optimization Of High-speed Cold Rolling

High-speed cold roll-beating forming technology is a precise plastic formingtechnology, and contains many advantages which are high material utilization, lowproduction costs, high dimensional accuracy of forming workpiece and stable surfacequality, etc. During high-speed cold roll-beating forming process, the residual stress isan important factor affecting the quality of the molding surface, and differentprocessing parameters in turn affect the magnitude and nature of the residual stress.Therefore, it has important theoretical significance to deeply study the distribution ofworkpiece surface residual stress and optimization program of process parameters.Through static and dynamic compression experiment of40Cr tempered steel,constitutive equation has been established, and parameters of constitutive equationhave been obtained by data fitting. Finite element model of high-speed cold roll-beating forming process has been established by using ABAQUS software. The threestages of the forming process have also been analyzed, and conclusion has beenobtained. The middle depression and both sides of the projections of workpiece surfaceis completed by two laws which are constant volume of plastic forming and the leastresistance of metal tissue flow.The cause of residual stresses classified during high-speed cold rolling has beenanalyzed, and above lead to a conclusion that residual stresses were caused byslippaging of grains inside. Silhouette and residual stresses distribution on surface ofworkpiece have been analyzed by matching forming parameters including revolvingspeed, feed rate and radius of rolling wheel, and disciplines of forming parametersaffecting silhouette and residual stresses on surface of workpiece have been obtained.Finite element modeling of the second strike was carried out after the first strike. Anddisciplines of the second strike affecting residual stresses on machining surface havebeen acquired.Experiment on residual stresses on surface of workpiece caused by high-speed cold rolling has been proceed after experiment platform of crack compliance method builtalready. The experiment leads to residual stresses being under compressive stress statewhen distance of residual stresses and surface is0to0.8mm and under tensile stressstate when distance of residual stresses and surface is0.8to1.8mm. By comparingsimulation result and experimental result, the cause of error has been analyzed andveracity of experimental result has been verified.Using the scheme of single factor experiment, matching the curve of the changetechnological parameter of residual stress with the rolling wheel speed, the workpiecefeeding and rolling wheel radius etc by taking advantage of least square method,obtained the line corresponding to the matching formula and the decision coefficient offitting curve, prediction the influence of various process parameters. Matchedmultiple-unit process parameters and using orthogonal test plan, analyzed theinfluence of the surface residual stress under the multiple-unit form parameters.Obtained the influence of the primary and secondary order of the residual stress inworkpiece, optimized the technological parameter of the process of high cold rolling.