Test Data Evaluation of Very High Cycle Fatigue Based on Maximum Likelihood Method

Abstract

The very high cycle fatigue tests of TC4 alloy were accomplished through ultrasonic fatigue experiment which were conducted on the ultrasonic fatigue testing system at frequency range of 20000 ±1000 Hz. In contrast to the commonly used Basquin model, a Maximum Likelihood Method to fit the three-parameter nonlinear model was used to verify the adaptability in very high cycle fatigue regime. These two methods were used to estimate S-N curves of three types of materials which were TC4 alloy, GH4169 alloy and TC17 alloy in the very high cycle fatigue regime and the results were compared with test data. The evaluation result of the MLM model based on the three-parameter nonlinear model shows a good agreement with test data. The mean and variance of relative error of the MLM model are less than those of the Basquin model, providing a suitable evaluation method for predicting very high cycle fatigue limit which often has higher scatter.