A Numerical Simulation of Probability Study on Fatigue Fracture of Heavy Machinery

The construction of heavy machinery is giant, of which the propagation process of fatigue crack is complex, there is big difference when different model of fatigue crack growth was selected in estimating its residual life. For this problem, a three stages method of assessment for crack propagation process is divided which include surface cracks, center penetrate cracks and edge through crack. and the characteristics what the stress intensity factor is changing with crack size is considered, based on probability fracture theory, the model in three stages fatigue crack growth which is used to estimate remaining life is established under constant amplitude loading. By the numerical simulations of Monte-Carlo, the survival line of 50-97% probability or P-S-N curve were obtained, also the sensitivity analysis about which the initial size of surface crack effects to the total life was given. It was shown that the time of surface crack propagation which has a closer relationship with the thickness of the plate occupies a large proportion of the total life, and the effect of the center and edge cracks can be ignored when the thickness of the plate is more than 12×10−3 finally, the experience range of the stress correction factor was given. the results can be regarded as theoretical foundation for estimation of fatigue residual life under about heavy machinery in amplitude and random load.