Prediction of combined cycle fatigue life of TC11 alloy based on modified nonlinear cumulative damage model

The nonlinear cumulative damage model is modified to have high prediction accuracy when the high-low cycle stress frequency ratio m is large (m >= 500). The low cycle fatigue (LCF) tests, high cycle fatigue (HCF) tests and combined high and low cycle fatigue (CCF) tests of TC11 titanium alloy were carried out, and the influencing factors of CCF life were analysed. The CCF life declines with the decrease of the ratio of high-low cycle stress frequency m. Both linear and nonlinear cumulative damage models are used to predict the CCF life. The CCF life prediction error of the linear cumulative damage model is great and the predictions tend to be overestimated, which is dangerous for engineering application. The accuracy is relatively high when the high-low cycle stress frequency ratio m <= 500. The accuracy of nonlinear cumulative damage model is higher than that of linear model when the high-low cycle stress frequency ratio m >= 500. Based on the relationship between high cycle average stress sigma(major) and material yield limit sigma(p,0.2), a correction term is added to the nonlinear cumulative damage model and verified, which made the modified model more accurate when m >= 500. (C) 2021 Chinese Society of Aeronautics and Astronautics. Production and hosting by Elsevier Ltd.

Automated summary

The study conducted fatigue tests on TC11 titanium alloy and found that the CCF life varies with the high-low cycle stress frequency ratio m. The linear cumulative damage model has higher accuracy when m <= 500, while the nonlinear model has higher accuracy when m >= 500.