Failure Analysis of Front Axle Wheel Studs in Small Commercial Vehicles

Irrespective of specific applications, the Small Commercial Vehicles (SCV) are always subjected to severe working conditions, especially the front wheels experience higher loads than design intended due to higher overloading by customers, driver abuse and frequent brake applications. The front axle wheels fasten system plays a key role for safety of the vehicle and pedestrian. The wheel separation can lead to serious injuries to passengers of the vehicle and pedestrian or from another vehicle maneuvering including fatalities. In this project investigation, the causes that promote failure of front axle wheels fasten system and subsequent wheels separation of SCV is analyzed carefully. Metallurgical analysis of the failed fasten system shows that it is characterized by a series of synergetic steps that include plastic deformation of nuts and studs caused due to disproportionate torque tightening practices. Also, the effect of other external factors that lead to deterioration of stud fatigue life such as road camber and driver abuse are analyzed. Based on this promise, the present investigation deals with detailed analysis of the root causes contributing such failures are analyzed and discussed in this paper. This study would help the fellow designers to select optimized fastening system considering all the parameters influencing wheel separation due to stud failures for SCV, passenger vehicles and heavy duty trucks.