Process Analysis Of Radial Forging For Rectangular Cross-Section Billet

Radial forging is an effective technique for bulk forging.Due to its high dimensional accuracy and good mechanical properties,radial forging process has been widely used in industrial production.At present,the investigations on deformation laws and quality of billet of radial forging process are mainly concentrated on round cross-section billet,while that of rectangular cross-section billet is scarce.Because the material flow and deformation law of these two kinds of billets in radial forging process are quite different,investigation results of round billet can not be directly utilized in the forging process of rectangular cross-section billet,whose theoretical study is not yet enough and design of process parameters is not yet mature.Radial forging can produce high three-dimensional compressive stress condition in billet,and its efficiency is larger than traditional flat-tool forging process.Based on the above reasons,the deformation law and mechanism of radial forging process of rectangular cross-section billet,and its application in industry have been studied.Main contents of research are as follows:Firstly,the radial forging experiment for the rectangular cross-section billet was carried out using an equivalent experimental device at room temperature.Strain gauges and data acquisition system were applied to obtain forging force data,which was used to verify finite element model and upper bound model.Then,based on the working principle of radial forging process,a three-dimensional finite element model was established and validated.The dimensionless parameters such as reduction ratio and feed ratio were adopted,combined with quadratic regression orthogonal design.Thus influences of these parameters on forging force,billet spread and strain distribution during one pass forging were analyzed.In addition,influence of different combination of tool width ration and blank width ratio on central stress state of billet was investigated on the condition of one forging stroke.In actual production,the fitting formula of dimensionless forging force can be used to estimate possible maximum forging force and select forging ability of equipment reasonably.The fitting formulas of billet elongation and maximum dimensionless spread can be used to estimate the volume of blank and increase utilization of materials.A combination of critical tool width ratio-blank width ratio was obtained to ensure three-dimensional compressive stress condition of billet in a certain zone along axial direction.Finally,because finite element simulation is time-consuming and it can not explicitly demonstrate the influences of different parameters on radial forging process,an upper bound model was established and verified.A three-dimensional kinematically admissible velocity field was proposed,the dissipative power of the whole system was optimized and assumptions of separate the forging forces of two pairs of hammers were put forward.Therefore,predictions of forging forces and longitudinal flow of material could be acquired.Results show that friction coefficient and parameters of appearances of hammers have different influences on forging force and longitudinal flow of materials.