Influence Of Hollow Divided Flow On Filling Behavior Of Bulk Forming And Its Application In Synchronous Ring Forging

Hollow divided flow forging is a new precision forging process,which is developed on the basis of traditional closed die forging.Previous studies have shown that hollow divided forging can effectively reduce the forming load,but there is still a lack of in-depth research on how relief-hole affect the filling performance and the internal mechanism of the sharp corner cavity.In industrial production,improving the filling performance of tooth cavity is an important target for precision die forging.Therefore,it is necessary to study the effect of hollow divided flow forging on the filling of the sharp tooth cavity and its internal mechanism.This paper combines experiments and finite element simulation,from the aspects of hydrostatic pressure,equivalent stress,surface friction and metal flow characteristics,etc.studied the influence of hollow divided flow forging on the filling property of the sharp cavity,and the inherent mechanism is analyzed combining with the theory of plastic forming.At the same time,the hollow divided flow is applied to the forging of 20CrMnTi synchronous ring,and the structure of the die is designed and optimized.The influence of the die on the forming process is analyzed by numerical simulation.The main conclusions are as follows:(1)Research shows that,the influence of hollow divided flow forging on the sharp corner filling is related to the filling rate ? of the tooth cavity and initial relieve-hole diameter d0 of the billet.For sharp corner parts,when the filling rate ? is relatively small,hollow divided flow forging is in favor of cavity filling.The larger initial relieve-hole diameter d0,the better corner filling;When the filling rate ? is relatively large,hollow divided flow forging is in detrimental to cavity filling.The larger initial relieve-hole diameter d0,the worse corner filling.(2)The relief-hole will affect the hydrostatic pressure ?m and the equivalent stress ? of the tooth in the hollow diverting forging.When ? is smaller,hydrostatic pressure ?m and effective stress ? of the tooth increases with the increase of d0,but when ? is larger,hydrostatic pressure ?m and effective stress ? of the tooth decreases with the increase of d0.(3)The physical experiment results are in good agreement with the simulation results of DEFORM-3D under the constant shear friction model,and the error of the simulation results under Coulomb Friction Model is relatively large.This indicates that the friction boundary condition is much closer to the normal shear friction model when the hollow diverting forging is applied.(4)By adding a 1mm high convex platform between the top circle of synchronizer ring involute spline and the resistance wall,which helps to change the direction of metal flow,improve the filling of the tooth,and reduce the overall load at the same time.In the non-critical parts of the forgings,the divided flow groove is set in the corresponding mold.When the divided flow groove width ?d is large,the divided flow groove has been full filled up when the tooth cavity is not filled up.When the divided flow groove width ?d is small,though the forming load can be reduced properly,but the effect is not obvious.