Research On Integral Mechanical Thermal Expansion Forming Process Of Heavy Duty Vehicle Rear Axle Housing

In the background of the rapid development of automobile lightweight technology,application of new materials, development of new technology, and the new optimizationmethod is becoming a key technology for the automotive industry. As the most importantcomponent of vehicle, heavy–duty vehicle rear axle housing directly affects some importantperformance, for instance carrying capacity, transport capacity, security and so on. Currently,forming of heavy vehicles rear axle housing mainly uses casting and stamping weldingprocess in domestic. Casting process has some serious drawbacks, for instance, lowutilization rate of material, low productivity, and high rejection rate. However stampingwelding process is cumbersome, and the investment in equipment and tooling is large, inaddition, welding deformation will lead to reduced fatigue resistance and less service life. Inorder to overcome the disadvantage of existing technology, domestic manufacturers of heavyvehicles rear are in urgent need of developing advanced manufacturing technology toimprove product performance, reduce production costs and improve market competitiveness.Therefore, research and development of manufacturing heavy vehicle rear axle housingusing seamless steel tube through the integral mechanical thermal dilation forming has beenreferred to the agenda.According to the existing research about mechanical thermal forming technology ofdriving axle housing, this paper presents an in–depth development and puts forward to a newkind of technology which is called heavy vehicle driving axle housing mechanical integralthermal expansion forming technology. The technology uses seamless steel pipe as a rawmaterial and completes the manufacture of axle housing through multi–pass gradual thermalexpansion forming. This will completely eliminate the welding process in the production ofdriving axle housing especially eliminate the process of welding triangle inserts in thestamping and welding process. It can save resources, reduce production costs and at the same time significantly improve the fatigue life of the axle housing and other importantperformance.Firstly, based on the theory of tube bulging and analysis of the structure andgeometrical features of the rear axle housing, the program is developed by using seamlesssteel pipe with reasonable diameter as a blank and multi–pass gradual thermal expansionforming process under the premise of expanding ratio. The process includes the preformingof tube blank and the opening prefabricated hole, then conducts the research of the firstexpansion, radial expansion and correction process.Secondly, research has been conducted on integral Mechanical Thermal ExpansionForming Process specific to the485driving axle housing with Capacity of13tons, which isprovided by the manufacture combined with the scientific production project “Research onIntegral Mechanical Thermal Expansion Forming Process of Vehicle Rear Axle Housing”.During the study process of forming test, due to the shortage of tube specification providedby the manufacturer, the max bulging size located in middle of final forming axle housingcouldn’t be guaranteed, what’s more there would be serious wall thinning defects around thelocal region of pipa hole. Accordingly, after the study the problems discovered in theforming test, the forming parameters, mould structure and tube specification were improvedusing the finite element software to ensure the success of this research.Finally, bulging rate was guaranteed by choosing reasonable tube diameter, then reducethe diameter of both ends，square middle part and optimizing prefabricated hole size. Thekey point of the study is simulation analysis and optimization of metal complementary todeformation regions. Tests done after the process improvement received the good result. Theserious wall thinning defects around the local region of pipa hole was overcame, so that theproduct requirements were met.