A PROBABLISTIC MODEL OF FATIGUE STRENGTH CONTROLLED BY POROSITY POPULATION IN CAST ALUMINUM

摘要

The very high cycle fatigue behavior of E319 cast aluminum alloy was investigated using ultrasonic fatigue instrumentation operating at 20 kHz. An endurance limit was demonstrated in the lifetime regime beyond 10~7 cycles. The fatigue strength at 10~8 cycles was associated with both size and location of the initiating pores through a critical stress intensity factor for fatigue crack growth. Based on the experimental observations, a probabilistic model was developed to establish the relationship between the casting porosity population and the fatigue strength of the alloy. Good agreement was obtained between the modeling results and experiments. The effects of porosity population and specimen geometry on fatigue strength at 10~8 cycles were quantified by Monte-Carlo simulation based on this model.