This paper describes the failure analysis of a diesel engine crankshaft used in a truck, which is made from ductile cast
iron. The crankshaft was found to break into two pieces at the crankpin portion before completion of warranty period.
The crankshaft was induction hardened. An evaluation of the failed crankshaft was undertaken to assess its integrity that
included a visual examination, photo documentation, chemical analysis, micro-hardness measurement, tensile testing, and
metallographic examination. The failure zones were examined with the help of a scanning electron microscope equipped
with EDX facility. Results indicate that fatigue is the dominant mechanism of failure of the crankshaft. It was observed
that the fatigue cracks initiated from the fillet region of the crankpin-web. The absence of the hardened case in the fillet
region and the presence of free graphite and nonspheroidal graphite in the microstructure of the crankshaft made fatigue
strength decrease to lead to fatigue initiation and propagation in the weaker region and premature fracture.
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