Experimental failure analysis of a reconditioned heavy crankshaft by welding process

The reconditioning of a diesel-engine crankshaft by welding process and its influence on premature failure of the crankshaft was experimentally investigated. The fracture occurred between the web and the first crankpin where a repair welding process was previously carried out on the crankpin. Macroscopic features of the fracture surface indicated that fatigue damage was the governing failure mechanism. The chemical composition, mechanical properties, hardness, and microstructure of the crankshaft material at two locations, the fractured region and an intact section, were determined. Comparison of the results revealed a substantial difference between the repaired and sound sections. The premature failure of the crankshaft was attributed to an uncontrolled change in microstructure of the repaired section assisted by a high level of stress concentration.