Experimental study on the effect of reaming on the fatigue life of split-sleeve cold-expanded Ti-6Al-4V alloy components

The split-sleeve cold expansion technique has been widely used in the aerospace industry to improve the fatigue life of metal components with holes. Due to the morphology change after the expansion, a reaming process is necessary to improve the machining accuracy of the hole surface. This final reaming process might change the residual stress distribution around the hole significantly but the effect of the reaming ratio has not been fully explored. This paper investigated the effect of reaming depth on the fatigue life of split-sleeve cold-expanded Ti-6Al-4V alloy components using a series of experiments, including the residual stress measurements, uniaxial fatigue tests, and fracture morphology observations. The expectations of the fatigue cycles were estimated using the 2-parameter Weibull distribution and the S-N curves of different components were acquired. Residual stress measuring results and the fracture surface observations explained the effect of cold expansion and reaming on the components. The experimental results showed that the fatigue life of the components decreased with the increase of the reaming ratio, demonstrating that excessive reaming depth is harmful to the fatigue performance of the cold-expanded components.