Research And Parameter Optimization Of The Rotary Forging Of Wheel Bearing Riveted Assembly

Wheel bearings are key safety components and functional components for automobiles.Generally,the axial fixing of the inner ring of wheel bearings is achieved by the nut-fixed method,and this structure has the defect that nut looseness causes a reduction in clamping force.Inner rings are fixed by the plastic deformation of flange shaft ends after rotary forging,which can not only reduce the weight of wheel bearings and reduce energy consumption,but also provide stable clamping force for wheel bearings.However,the rotary forging of wheel bearing riveted assembly will cause radial deformation of inner rings,resulting in the reduced life of wheel bearings.Fracture failure may occur at the outer fringe of edge curls after rotary forging.There is no research on stress-strain characteristics in the rotary forging process of wheel bearings.There is no research on the mechanism of forming defects in rotary forging from microstructure.A new elastoplastic numerical model for the rotary forging of wheel bearing riveted assembly was established.The part which touches flange shaft ends of punches was set as an analytical rigid body,and the other part was set as a discrete rigid body.This method not only improves the calculation accuracy,but also shortens the calculation time.The strain change of the inner ring was measured by a quarter bridge connection circuit in rotary forging,and the accuracy of the numerical model is verified.The wrinkle area of edge curls is dominated by PE13,and the outer fringes of edge curls is dominated by PE22 and PE13,which proves that rotary forging can reduce clinching force.Clamping force and inner ring outside diameter variation increase with the increase of feeding displacement,and clamping force increases with the increase of the tempering temperature of flange shafts.The influences of four loading trajectories on rotary forging were compared and analyzed by numerical model.The springback of inner rings and edge curls was analyzed by ABAQUS implicit module.Critical feeding displacement occurs in the springback of inner rings and edge curls for circle and serration trajectories,and the springback of inner rings and edge curls increases with the increase of feeding displacement.Clinching peaks under the same clamping force for four trajectories are sorted from large to small: serration,chrysanthemum shape,plum blossom shape,circle.Inner ring outside diameter variations under the same clamping force for four trajectories are sorted from large to small: chrysanthemum shape,circle,plum blossom shape,serration.The influence of the speed of autorotation and feeding speed on rotary forging were studied by numerical model.When the upper surface center of punches moves to the outermost position of trajectories,the peak value of clinching force appears.In the same time,clinching force peaks once at the speed of autorotation of 300 r/min,and clinching force peaks twice at the speed of autorotation of 600 r/min.Under the same feeding displacement,clinching force peaks once at the feeding speed of 4 mm/s,and clinching force peaks twice at the feeding speed of 2 mm/s.Increasing the speed of autorotation or decreasing feeding speed can reduce clinching force.The evolution of grain orientation in rotary forging processes was analyzed by optical microscope,and the microhardness of large deformation areas after rotary forging was measured by microhardness tester.The initial grain size of flange shafts varies from approximately 3 ?m to 10 ?m.The length direction of the slender grains formed is perpendicular to the boundary line of wrinkle areas after rotary forging.Under different feeding displacement and speeds of autorotation,there is a peak in microhardness and PEEQ at the wrinkle area and the outer fringe of edge curls.It is confirmed that wrinkle defects are prone to occur in the inside corner of edge curls and fracture failure may occur at the outer fringe of edge curls.Three important parameters were selected as optimization variables,including the central angle between two successively appeared outermost points of plum blossom shape loading trajectories,speeds of autorotation,and tilted angles.Response surface methodology(RSM)was used to optimize the ratio of the inner ring outside diameter variation to the clamping force.The central angle is the most sensitive factor.The interaction effect of the central angle and the speed of autorotation is the most significant.The minimum value 1.41 ?m/k N(the ratio of the inner ring outside diameter variation to the clamping force)occurs in the speed of autorotation of 410 r/min,the central angle of 40°,and the tilted angle of 7°.The error is 2.1% between the RSM forecasted and actual results,which verifies the accuracy of the proposed response surface model.The research results of this thesis provide a reference for the rotary forging process design of wheel bearing riveted assembly.Rotary forging parameters can be reasonably formulated according to product design requirements,which is of great significance for expanding the application field of rotary forging.