Crankshaft failure analysis of a motor vehicle

Abstract

A case study of a crankshaft catastrophic failure of a motor vehicle and its failure analysis is presented. The crankshaft suffered a mechanical seizure on the crankpin no. 2 after 3 years in service. It was repaired and after 30,000 km the vehicle had a damage again, with a catastrophic failure on the same crankpin. A transversal macrograph of the crankpin revealed that the crankpin was rectified and filled with a metal alloy for the same nominal diameter. Two fatigue cracks growing to the center of the crankpin where the final fracture occurred. The symmetric semi-elliptical crack front profile confirms the effect of a pure mode I under alternating bending. The catastrophic failure was a consequence of the inadequate repairing by a non-authorized manufacturer.