Research On Torsion Strength Improving Of The Dual Rear Axle Shaft For Heavy Goods Vehicle And Its Fracture

This paper mainly dealt with the increasing strength parameters and decreasing failure probability of the dual rear axle shaft for heavy good vehicles by means of strictly controlling the composition, hardenability, structure design, rolling and heat treatment processing parameters. The composition uniform, hardenability, improving the thickness of the hardened layer, mechanical properties and the parts structure, decreasing stress concentration and controlling the inner defects of the forged dual rear axle shaft were also studied. With the help of the relationship between the thickness of the hardened layer and the mechanical properties, effectively controlling processes, medium frequency induction quenching, static torsion testing, the fracture analysis by a thermal field emission scanning electronic microscopy, microstructure observation by a metallographic microscopy, the failure reasons and mechanism of torsion fracture of the dual rear axle shaft were comprehensively analyzed. The experimental results showed that there were different torsion fracture ways for the shafts with different shapes and their torsion fractures mainly had the two types of the cross section vertical to the shaft axis and the breaking section and axis 45°angle. The fracture morphology of the vertical fracture shaft was cleavage one and that of the 45°angle fracture shaft was ductile fracture. The reasons for the fractures were relative to raw material quality, heat treatment processing, microstructure and shape. The property and quality of the shafts will obviously be improved and meet the technical requirements of the products through optimizing the material quality and heat treatment processing and also improving the shape design of the shafts. Therefore the safety for the heavy good vehicles running will be ensured and the failure probability of the dual rear axle shaft will be avoided or obviously decreased.