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 distinguish 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 welded in the centre to create a residual stress field, and one of the plates was stress relieved. The L(CR) ultrasonic technique sends a critically refracted longitudinal wave travelling beneath the plate surface, and the stresses in the plate affect the travel times through the acoustoelastic relationship. The L(CR) travel-time measurements not only distinguished between residual stress states in the plate, but also gave some information on their distribution and magnitude. Neither texture nor localized residual stresses affect the results. These findings demonstrate the potential usefulness of the technique for evaluating the state of post-weld heat treatment in structural steels.