Prediction of fatigue life of TC4 titanium alloy based on normalized equivalent initial flaw size model

Abstract

Ti-6Al-4 V (TC4) is the primary and most widely used titanium alloy in the aerospace industry, mainly for the manufacture of engines and high temperature load-bearing elements in aircraft structural components. In this study, fatigue life and fatigue crack growth (FCG) rate tests of TC4 were carried out at different temperatures and stress ratios. The effect of temperature on the fatigue mechanical properties of TC4 titanium alloy materials was investigated analyzing the test results. The fatigue limit and FCG threshold were obtained from experiments. By the using equivalent initial flaw size method, the growth behavior of small cracks were incorporates in macroscopic FCG rate and a method to predict the fatigue life of TC4 at different temperatures was established. The parameters in the proposed model have a clear physical meaning and can be determined by experiment. Finally, the fatigue test data of TC4 titanium alloy under different test conditions are used to verify the proposed fatigue life prediction model and the prediction results have reasonable accuracy with the test results.