Research Of Press-forming Process Of Bulging-Crushing Forming Medium-sized Truck Axle Housing

Automobile axle housing is a major component carrying and transferring loads in the chassis, it is required to possess sufficient strength and rigidity and fatigue life. Hydroforming research group of Yanshan University has proposed a new technology of bulging-crushing axle housing: first, the seamless steel tube deforms to preformed tube blank after reducing diameter and bulging; then, the preformed tube blank is filled with liquid and press-formed to axle housing with rear cap and additional front cap by dies. The bulging-crushed axle housing is integral formed, has no welding seam and has reasonable thickness distribution. Moreover, the bulging-crushing axle housing is lighter than casting axle housing and has better mechanical properties than stamping-welding axle housing, and is able to reduce materials consume and environmental protection. However, there are some problems in this new technology, for instance, its process theory needs to be further improved, deformation mechanism during press-forming is not clear, and cleft in rear cap and dent at straight arm part still occur in the actual production. For medium-sized bulging-crushed axle housing, this paper further analyzed the process of press-forming and revealed deformation mechanism and the influence of the loading path(match relationship die movement and internal pressure) and the shape of preformed tube blank to improve the process theory of press-forming and formed the key technology of press-forming. thus, this paper provides an important basis for the mass production of bulging-crushed axles.For the bulging-crushed medium-sized truck axle housing, the design criterions of additional front cap and preformed tube blank were proposed, and the 5t truck with rear cap and additional front cap were designed in detail in accordance with the criterions. On this basis, the design criterions of the preformed tube was proposed for the bulging-crushed medium-sized truck axle housing(At first the reference body of revolution was designed, whose length and the circumference of the cross-section ware equal to the axle tube’s, then the dome part was put into non-symmetrical shape with small radius of front cap and large radius of rear cap.). This paper analyzed the stress-strain state and thickness change tendency of typical sections of axle housing during the press-forming, and revealed the mechanism of cleft in rear cap and dent at straight arm. The force condition of straight arm was analyzed, and the relational mathematical expression of die force, material yield strength and structure parameters of tube was deduced. Then crafts condition influencing dent at straight arm was determined.For the bulging-crushed axle housing of a medium-sized 5t truck axle, this paper used ABAQUS finite element software to simulate the forming process of preformed tube blank whose front cap radius was 162 mm and rear cap radius was 175 mm. And then, the press-forming process were simulated under the common press-forming loading path, and the deformation process and thickness distribution tendency of the preformed tube blank were analyzed by measuring the simulated data. This paper simulated bulging-forming process of the same preformed tube blank under five typical press-forming loading paths, and summarized the die loading and internal pressure loading paths on the influence of the press-formed by comparing formability and thickness distribution of the axle housing, final obtained the reasonable loading path.For the bulging-crushed axle housing of a medium-sized 5t truck axle, this paper design axisymmetric preformed tube blank and a series of asymmetric tubes with different radius of front and rear caps. First,The forming process of preformed tube blank was simulated using finite element, initially identified the value range of front cap radius and rear cap radius initially by comparing the simulation results of formability, thickness distribution and the largest cross-sectional wall thinned rate.On this basis, further bulging-forming process was simulated. Comparison of the simulation results by the thickness distribution, caps wall thinned rate and fillet formability finalized the value range of front cap radius and rear cap radius. Finally, the appropriate shape of preformed tube blank was obtained.For the straight arm press-forming process of a medium size truck axle, the influence of preformed tube blank straight arm diameter, loading path and initial tube wall thickness to the arm concave were analyzed by finite element simulation. According to the idea of compensation law, a concave curved in straight arm mold cavity was designed to solve the dent problem, and the proper shape of the concave cavity was determined by finite element simulation.For the bulging-crushed axle housing of a medium-sized 5t truck axle, a experimental scheme of press-forming was designed. Two types of preformed tube blank were got by preforming experiment. One was axisymmetric preformed tube blank whose maximum radius of cross section was 164.5mm, and the other was asymmetric preformed tube blank whose front cap radius was 162 mm and rear cap radius was 175 mm. Then the above tubes were press-formed separately, the results indicated that the formability was poor and cleft existed easily in rear cap about axisymmetric preformed tube blank; formability was good and outline and fillets were clear about asymmetric preformed tube blank. Measuring results of wall thickness of longitudinal section and cross section of the sample indicated that the wall thickness of sample axle housing increased gradually in axial; around circumference, the wall thickness of transitional area between caps and beam was thickest, and the wall thickness of beam was rather thick; the wall thickness of caps was thinnest. The wall thickness distribution of sample axle housing from asymmetric preformed tube blank met the performance requirement of axle housing. The influence of different loading path to press-forming were verified by further press-forming experiments, and proved that the concave surface die can perfect the dent of straight arm part efficiently.