Failure analysis of four-cylinder diesel engine crankshaft

In this article, failure analysis was examined in four-cylinder light-duty truck diesel engine crankshaft. The failure happened in service after 95,000km of operation by fatigue crack growth which was initiated from a surface defect on the second crankpin from the crankpin-web fillet. For such objective, standard specimens were cut off from the crankshaft and examined to evaluate the mechanical properties. Some hardness and tensile tests were conducted, and spectrometry analysis was used in order to study the chemical composition of the crankshaft material. Also, for considering and evaluating the microstructure, microcracks, fracture surface and the cause of failure, optical microscopy and scanning electron microscopy equipped with energy-dispersive spectrometry were used. The morphology of the fracture surface shows that the failure happened in the second crankpin at the crankpin-web fillet of crankshaft where the stress concentration was the highest.