Controlling the Cut in Contour Residual Stress Measurements of Electron Beam Welded Ti-6Al-4V Alloy Plates

The multiple cut contour method is applied to map longitudinal and transverse components of residual stress in two nominally identical 50 mm thick electron beam welded Ti-6Al-4V alloy plates, one in the as-welded condition and a second welded plate in a post weld heat treated (PWHT) condition. The accuracy and resolution of the contour method results are directly linked to the quality of the electro-discharge machining cut made. Two symmetric surface contour artefacts associated with cutting titanium, surface bowing and a flared edge, are identified and their influence on residual stresses calculated by the contour method is quantified. The former artefact is controlled by undertaking a series of cutting trials with reduced power settings to find optimal cutting conditions. The latter is mitigated by attaching 5 mm thick sacrificial plates to the wire exit side of the test specimen. The low level of noise in the measured stress profiles for both the as-welded and PWHT plates demonstrates the importance of controlling the quality of a contour cut and the added value of undertaking cutting trials.