The Research For Push And Pull Necking Of Bulging And Pressing Heavy Truck Axle Housing

Axle housing is one of the main load-carrying parts of automobile, and the bulging-pressing deforming process is an advanced technology to manufacture axle housing. This axle-housing has advantages of reasonable thickness distribution, high strength and no welds, etc. This process choose an appropriate seamless steel pipe, and get the pre-forming pipe by necking two ends and bulging the middle area of the pipe, then the axle-housing is made by pressing the pre-forming pipe. The necking process is the main part of the pre-forming process, however, the traditional push necking process has the problem of large increasing thickness and large residual stress in necked area, and the large residual stress not only make the pipe ends crack easily but also weak the axle-housing using performance. The new pushing and drawing necking process, which consist of a pushing necking die and a drawing internal mandrel, can solve the shortcomings of pushing necking process. Now, the necking deformation mechanism, which involves the necking pipe deformation feature, the stress and strain of necking area and the influence of necking parameter on the forming process etc, is not clear. This paper has systematically researched the necking process.The mechanical model of necking pipe is built, and the pipe forming feature,stress and strain of each forming area are analyzed. The relationship of necking force and necking parameter, which includes necking coefficient and friction factor, is given, and the influence rule of the mandrel diameter and its drawing velocity on necking force is analyzed qualitatively.This paper takes a 10 t rated loading axle housing as research object, and the necking model is built by ABAQUS, a finite element analysis software. According to the results of simulation, the state of stress and strain of the push and drawing necking pipe and the freedom push necking pipe is analyzed, and difference of the thickness of necked area, the residual stress and the pipe elongation of two necking processes is obtained. The influence rule of friction factor and necking coefficient on necking force is acquired by changing the simulate parameter. To analyze the effect of mandrel diameter and drawing velocity on necking force, the mandrel diameter and drawing velocity simulating value are adjusted, then the appropriate controlling rate of wall thickness and the minimum critical speed of drawing are given. The simulation model of the axial pressure pipe is built, and the critical axial loading of pipe instability is given. If the necking parameter is not reasonable, the necking force will be too large and necking pipe will wrinkle instability on the front of necking die. Finally, the reasonable necking parameter of the researching axle housing is given, and the theoretical analysis of necking force is corrected by the simulation results.According to the requirements of the axle housing fatigue test, the strength finite element analysis of the necked pipe with the necking residual stress is done, then the fatigue life of the axle housing is analyzed by MSC.FATIGUE software. Compared with the fatigue life of necking and drawing necked pipe, pushing necked pipe and the necked and annealed pipe, the impact of the necking residual stress on fatigue life is revealed.