Probabilistic fatigue life prediction for crankshaft of marine diesel engine

Diesel engines are the most commonly used power plant of ships in the world. The crankshaft which transforms the translational motion generated by combustion to rotational motion, is the critical components which affects the fatigue life of diesel engine. In this paper, a probabilistic fatigue life prediction method for crankshaft is proposed. A three-dimensional finite element analysis (FEA) is used to analyze the distribution of equivalent von Mises stress of the crankshaft. The S-N/ε-N curve of the material obtained from existing literature is used to evaluate the parameters of Coffin-Manson model. The life model parameters are statistically identified using Bayesian estimation with Markov chain simulations. In addition to simulation examples, an actual case from Shanghai Marine Diesel Engine Research Institute is carried out using this probabilistic fatigue life prediction method. Then the probabilistic life and material dispersion are obtained, which is helpful for the design, replacement and maintenance strategy of the crankshaft.