Probabilistic fatigue life model for medium and low cycle fatigue based on plastic strain energy

The fatigue life of turbine disk may show large scatter duo to the variability of parameters such as material properties, geometrical features, load and some other factors. Taking into full account the influence of factors on the fatigue life, such as stress, strain and stress ratio in the loading and unloading process, a probabilistic fatigue life model based on plastic strain energy was proposed for medium and low cycle fatigue. Besides, the factors commonly used to calculate the scatter of fatigue life, like material property, geometry size and load, the randomness of the cyclic stressstrain curve, were also considered. With the method of quadratic interpolation for stress ratio, the relation of plastic strain energy damage parameter and fatigue life under various stress ratios could be obtained. Using the plastic strain energy probabilistic fatigue life model in conjunction with the response surface method and MonteCarlo method, the probabilistic fatigue life of a simulated bolthole specimen of a turbine disk was analyzed. The results showed that the calculated median fatigue life of the simulated specimen was just 022% less than the median test life, while the fatigue life scatter factor was just 581% less than that of the test result, showing high accuracy of the proposed model for probabilistic fatigue life prediction.