Total fatigue life prediction for titanium alloys structure

Based on the longer life of fatigue crack initiation and small crack propagation, considering the crack inspection technique, the total fatigue lives of titanium alloys were divided into three stages: crack initiation life (crack grow form 0 mm to 0.3 mm), small crack propagation life(crack propagation form 0.3 mm to 2 mm), large crack propagation life(crack propagation form 2 mm to a_C). The different fatigue life prediction methods were adopted for these three stages due to their different damage mechanisms. That improved the prediction accuracy of total fatigue life. The predicted and tested results of the TC4ELI and TA15ELI Titanium alloys under constant amplitude and spectrum loads indicated that: Crack initiation life occupied the most proportion of the total fatigue life and had the poorest prediction accuracy; Correspondingly the large crack propagation life exhibited the least proportion and predicted error; Small crack propagation life revealed longer life and poorer predicted error than the large crack propagation stage. The predicted errors of the Titanium alloy fatigue total life under both constant amplitude and spectrum loads were within the acceptable engineering life prediction requirement.