Research On Rotary Forging Process For Hub Bearing Shaft End And Optimization Of Its Structural Parameters

Hub bearing is to carry and provide steering guidance and plays an important role in the safety,comfort and economy of automobile.The shaft end rotary forging is one of the most critical processes in hub bearing manufacturing.Compared with the international advanced level,the rotary forging assembly process in China has a big gap in process accuracy,product consistency and others due to the lack of systematic research on this technology.Starting from the basic theory of rotary forging,with combination of theoretical analysis,numerical simulation and experimental research,the study focus on the forging force,materials deformation,structure parameters,error influence,and process related issues in the dissertation.The main work of the dissertation is as follows:1)The forging force and clamping force are studied.Based on the basic principle of rotary forging,the analytical expressions of contact area and unit pressure are deduced and a simply expression on forging force is obtained.According to the test data of material properties and the basic theory of simulation,the simulation model of rotary forging process with implicit-explicit-implicit data interchange is established.The change rule of forging force from rapid increase,slow increase,sharp increase to sharp decrease is revealed during the process by simulation and experiment.The mechanism and characteristics of the clamping force are analyzed,and the measurement method of the clamping force is proposed,which is based on the strain measurement,riveting released by turning and simulation correction.2)The deformation characteristics during forming process are studied in detail.The deformation flow law of the metal at the shaft end is analyzed,and the strain law and microstructure of the material in the large deformation area are revealed.The dissertation reveals the deformation law in radial and axial directions of the inner ring from three aspects of interference expansion,forming expansion and springback shrinking.The main cause of the inner ring deformation is radial extrusion pressure produced by upsetting the flange and the secondary cause is axial pressure produced at the later stage of forming.Based on the influence of inner ring deformation and clamping force on bearing clearance,the control standard that inner ring expansion is established.With the combination of theory,simulation and experiment,the radial expansion produced by interference fit,and the influence of forming process on interference are studied,and the design principles of interference are given.The conclusion is drawn that the spline deformation is mainly observed on the top of the shoulder of the flange shaft after analyzing the spline deformation characteristics of the flange.3)Many process parameters and structure parameters are studied.The influence of feed displacement,feed per revolution,the inner ring parameters such as the round corner,wall thickness,chamfering angle and the height of quenching zone are analyzed.A bevel angle structure of the inner ring is proposed which can reduce its expansion.The influences of friction coefficient and initial interference volume on forming process are also studied.The suspended structure without contact between the small surface of the inner ring and the shoulder of inner flange shaft is discussed with a conclusion reducing the groove diameter to form positive clearance before forming is benefit to bearing performance.After studying error factors on forming process,it is revealed that the shaft end height error is the most important influence factor and the improvment method is also proposed.The performance evaluation methods of fatigue life,riveting reliability,rigidity and static strength of the riveted products are improved.4)The influences of dressing methods of the die and profile parameters of the die,and the wear character of the die are analyzed.Based on Archard model,the wear character and stress distribution of the die are analyzed,the influence of process parameters on the wear depth is revealed.With quantitative analysis of two methods of die dressing and profile parameters of the die,the suitable dressing methods,times and profile parameters are obtained,which provide the basis for the design,manufacture and use of the die.