A study on crankshaft failure in diesel engine of wheel loader

Crankshafts are essential parts within internal combustion engines are prone to fatigue failure due to cyclic loading. This paper investigates the failure in a six-cylinder diesel engine crankshaft from a wheel loader, which exhibited an unusual fracture pattern. Unlike common failures where cracks initiate at the crankpin fillet and propagate toward the main journal, this crack originated at the fifth crankpin fillet and terminated at its center. Various analyses were conducted to determine the root cause of failure, including chemical composition testing, microstructural examination, mechanical testing, scanning electron microscopy of the fracture surface, and finite element analysis of stress distribution. The results indicated that a reduction in molybdenum content, low hardness, and inclusions MnS contributed to reduced fatigue resistance. Additionally, the structural stress assessment revealed that the greatest stress concentration occurred at the fillet of the crankpin, corresponding to the crack initiation site. Moreover, features such as beachmarks and striations on fracture surface indicate fatigue. This study provides new insights into influence of material properties and microstructure on heavy-duty crankshaft fatigue behavior, offering recommendations for improved design and manufacturing to enhance fatigue resistance and durability.