Case Study-Strengthening of Axle Shaft by Heat Treatment to Overcome Twist

An important use of axle shaft is to transmit the power between two parallel planes. Axle shaft can experience severe impact load when there is sudden drop in clutch pedal during the vehicle operation under loaded condition. Insufficient case depth and lower core hardness could cause the low subsurface shear strength of the material. This would result in torsional permanent deformation, phenomenon called Twist in the axle shaft. In order to improve the metallurgical property of the material, the axle shaft is redesigned & strengthened by suitable heat treatment process. The surface of the shaft is induction hardened and the core is toughened (hard & tempered) which would enhance the subsurface & core property of the material particularly shear strength of the material. The correlation between the applied shear stress & material inherent shear strength is used to determine the optimum shaft diameter. The current shaft is modified for increase in case depth, core hardness, shaft diameter & subjected to Ultimate Torsional bench Test. The test result of modified axle shaft shows improvement in average B10 torque carrying capability by 56% with no twist.