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The prime function of crown wheel pinion is to receive the power from transmission & distribute to two-wheel ends. Doing so these members will experience the tremendous bending fatigue. Shot peen is the one of the latest technology used to improve the bending fatigue of the CWP [1]. In this particular case- six CWP are taken for the study to understand the effect of the operations after shot peen process. Three Samples are named as batch A, another 3 samples are named as batch B. Both the batch CWP are shot peened. Then as a regular production practice the batch A CWP are process through hard turning ➔ Abrasive lapping ➔ Hot lubriting (manganese phosphate) ➔ Fully finish ready for assembly. Then both the batch A & batch B samples are taken for residual stress analysis using X-Ray diffraction technique. The measurement location is 50 microns below the surface. The results tabulated, found that batch A samples shows decrease in Residual stress relatively to batch B.

Now a day’s ductile iron spring is becoming common in vehicles. Most OEMs prefer change over from forged spring seat to ductile cast iron spring seat particularly for lower spring seat application as there is weight benefit. The primary function of lower spring seat is to hold the axle and leaf spring together. Lower spring seat would experience pre load generated during U bolt clamping and could undergo permanent deformation when applied stress exceeds the material strength. In ductile cast iron nodularity is the prime factor which is responsible for material ductility characteristics. In this case study two spring seats A & B is compared for U bolt pre load force (Torque) where spring seat A is with nodularity requirement of 80 % min and the spring seat B is with nodularity of the order of 55%. U Bolt preload permanent deformation bench test is carried out and outcome shows that the spring seat A failed at 800 Nm torque and spring seat B failed at 600 Nm.

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.

Crown wheel can experience severe impact load when there is sudden drop in clutch pedal during vehicle operation. The higher core hardness at the pitch circle diameter of the gear teeth could drastically reduce the impact energy absorption characteristic of the material resulting in very fine micro crack on the teeth surface. The optimum core hardness range is very much necessary in order to improve the material impact energy absorption characteristic and subsequent balance between the impact & fatigue strength of the gear. The Brugger sample method is used to select the best core hardness range that exhibits optimum impact energy. The Brugger specimens with various core hardness bands, starts from 30 HRC to 45HRC, are prepared and tested for impact energy absorption capacity. The raw material with appropriate jominy value is used to prepare the specimen. Based on the Brugger test result, the optimum core hardness band is selected.