APPLICATION OF THE L(CR) ULTRASONIC TECHNIQUE FOR EVALUATION OF POST-WELD HEAT-TREATMENT IN STEEL PLATES

Ultrasonic travel times obtained with the L(CR) wave are able to disti nguish between stress relieved and non-stress relieved 13 mm (1/2 in) thick, steel plates. Two 1.22 m (48 in) square plates were patch welde d in the centre to create a residual stress field, and one of the plat es was stress relieved. The L(CR) ultrasonic technique sends a critica lly refracted longitudinal wave travelling beneath the plate surface, and the stresses in the plate affect the travel times through the acou stoelastic relationship. The L(CR) travel-time measurements not only d istinguished between residual stress states in the plate, but also gav e some information on their distribution and magnitude. Neither textur e nor localized residual stresses affect the results. These findings d emonstrate the potential usefulness of the technique for evaluating th e state of post-weld heat treatment in structural steels.