Failure analysis of rear axle shaft of a heavy vehicle

Failure of the rear axle shaft of a heavy vehicle was thoroughly investigated. It was noticed that the axle shaft had failed during service and broken into two pieces. Different types of investigations were carried out on the failed axle shaft which includes visual examination, chemical analysis, Mechanical testing, Fractography and ultrasonic testing. Several cleavages were noticed in the Fractography, which depicted a sign of brittle fracture. Fatigue striations were observed in scanning electron microscopic analysis of the as received failed axle, which a typical indispensible characteristics of fatigue failure. The tensile fracture surface revealed mixed component of dimple as well as cleavage facet. Results indicated that failure occurred due to sudden loading on the axle shaft. The shear stress in the weak portion of the axle was not sufficient to counter the stress imposed by sudden loading.