Fatigue Life Analysis of Crankshaft at Various Surface Treatments

The service life of engine crankshaft is closely related to its material characteristics. Without any dimensional modification, one can significantly improve the fatigue life of crankshaft by applying various surface treatments. The objective of this research is to predict and to quantify the fatigue life of crankshaft at different alloy design and surface treatments - microalloyed steel vs. carbon steel as well as nitriding vs. fillet rolling. It is found that nitriding improves more than 60% in fatigue life depends upon matrix hardness. This study also demonstrates a relationship between fatigue life and fillet rolling force. We observed that the fillet rolled specimens with the applied force of 500∼900kgf exhibit 40∼80% improvement in fatigue life compared to non-treated sample. Consequently, methods are proposed to quantify and normalize fatigue life at various treatments to optimize crankshaft design for maximizing the engine performance.