DETERMINATION OF NEAR-SURFACE RESIDUAL-STRESSES ON WELDED-JOINTS USING ULTRASONIC METHODS

Ultrasonic velocity measurements are used to determine residual stresses induced by welding processes. A welded stainless steel pipe and aluminium alloy plate are analysed in their near surface residual stress distribution by using subsurface longitudinal waves and Rayleigh waves. The experimental procedure is presented: measurement of time of flight, calibration of the acoustoelastic effect, methods for residual stress measurements. The effects of a slightly orthotropic symmetry on wave velocities are investigated in the case of the aluminium alloy plate, which exhibits a texture due to rolling processes. Special calibration, performed on two test specimens, allows the effect of this texture to be taken into account. The acoustic birefringence technique is also used in the case of the aluminium plate to verify the stress distribution in the thickness. The results of surface residual stress distribution are compared with those obtained with an X-ray diffraction technique.