Roulette Stress Life Reliability Analysis Method And Its Application

The traditional Stress-Life method uses "point-criterion", namely uses the maximum stress or stress amplitude of critical point directly with the Stress-Life curve to predict the fatigue life of structure. But Stress-Life curve with specific theory stress concentration factor reflects the relations between the mean stress of notched bar dangerous section and the fatigue life, it is essentially not according with "point-criterion". Therefore it is difficult to use traditional Stress-Life method to predict the fatigue life of complicated structures such as the aeroengine fan disk.In view of the above question, a new kind of method was proposed in this paper for calculating Stress Concentration Factor of a complicated structure. And the traditional Stress-Life method was improved by introducing the concept of Correction Coefficient of Stress. Then the effect of Stress Concentration and the Stress Gradient were introduced into the prediction of fatigue life through Correction Coefficient of Stress with the wider suitable life scope. And the Stress-Life probability model was built for the purpose of reliability analysis.The improved Stress-Life method and the Strain-Life method were used to analyze the fatigue life and its reliability of an aeroengine fan disk. The response surfaces of the maximum stress and strain amplitude at the critical point were established. With the uses of Monte-Carlo simulation and probability model of life, the fatigue life distribution of the fan disk and the life in the given probability were obtained. Then the influence of the random variables on the life was analyzed.At the last, the computed results were compared with the test result. The respective characteristics, the serviceability the accuracy and the feasibility of two methods were discussed.