Test method for residual stress analysis of the inner surface of small caliber Ti-3Al-2.5V tubing by X-ray diffraction

摘要

The residual stresses of Ti-3Al-2.5V tubing have effects on both fatigue performance and stress corrosion resistance. The inner surface, which directly contacts the hydraulic fluid of the aircraft, is the working surface of Ti3Al-2.5V aerospace hydraulic tubing and fatigue cracks probably initiate on the inner surface. However, measuring residual stresses on the inner surface of small caliber tubing is difficult using X-ray diffraction at diffraction angles (2.) of higher than 120. because the X-rays would be shaded by the outer surface. In this work, the as-received Ti-3Al-2.5V tubing was transversely cut using an electric discharge machine to obtain a sample having a length that was suitable for subsequent measurements and as long as possible to avoid stress relief. Then a diffractometer with Cu K alpha radiations was used to scan the lattice planes {103} at the 2 theta of 70.631 degrees for the inner surface stresses of the sample. In particular, to avoid shading effects, we let the incident X-rays enter from one end of the sample and let the diffracted radiations exit from the other end. This work is of theoretical significance and application value for optimizing stress relief annealing process and for X-ray stress analysis of titanium and other metallic tubing.