The Analysis of Light-duty Truck Diesel Engine Crankshaft Failure

In this study, crankshaft failure of four-cylinder light-duty truck diesel engine was examined. The failure occurred by fatigue crack growth which was initiated from a surface defect after about 95000 km on the second crankpin from the crankpin-web llet where the stress concentration was at the highest level. To evaluate the mechanical properties, some hardness and tensile tests were conducted and spectrometry analysis was used for studying the chemical composition of the crankshaft material. Additionally, for considering and evaluating the microstructure, microcracks, fracture surface, and the cause of failure, optical microscopy (OM) and scanning electron microscopy (SEM) equipped with energy dispersive spectrometry (EDS) were used. The morphology of the fracture surface showed a smooth and at crack initiation with the beach marks and ratchet marks and second crack propagation zone with beach marks and fast nal fracture zone near the end. The results of EDS observations indicated that inclusions of non-metallic aren t distributed throughout on the steel and in some places leads to the formation of the microcrack clusters.