Effect of split sleeve cold expansion on cracking behaviors of titanium alloy TC4 holes

The effect of split sleeve cold expansion on fatigue behavior of titanium alloy TC4 open hole was investigated by experiment. After cold expansion, fatigue life of titanium alloy TC4 open hole was increased to 1.5-3.0 times. The residual compressive stress drastically retards the crack propagation rate, especially in the short crack stage. Corner crack initiated at the entrance face for cold expanded holes, while face crack initiated at the mid-plane of non-expanded holes. Finite element results showed that the lowest compression stress occurred at the entrance surface, while the largest one occurred near the middle of the hole wall.