Low cycle fatigue (LCF) life prediction and critical distance analysis for TC4 alloy notched specimens were conducted.The correlation between the critical distance and fatigue life

load ratio

stress concentration factor and their influence on the fatigue life prediction were studied.The result suggests that the critical distance of TC4 alloy is not only related to the fatigue life

but also to the load ratio and stress concentrate factor.For the same load ratio

the power function can be used to describe the relationship between the critical distance and the fatigue life.For TC4 alloy notched specimens

when the load ratios were -1 and 0.1

the critical distance-fatigue life curves almost coincide;when the load ratios rose up to R=0.5

the critical distance increased obviously.For the same load ratio and fatigue life

the critical distance of TC4 alloy notched specimens was approximately inverse to the stress concentrate factor.Life prediction results show that the correlation between critical distance and fatigue life

load ratio

stress concentration factor must be considered to obtain more accurate fatigue life prediction for notched TC4 alloy using the theory of critical distance.