Determination of residual stress in Z8CDWV12 steel using critically refracted longitudinal waves

Acoustoelasticity, i.e. the stress-dependence of the phase velocity of ultrasonic waves in deformed elastic media, provides a method for determining the stress level. A primary motivation for using the ultrasonic technique is that it allowed to obtain information about stresses in the material. In fact, the velocity shift is proportional to the average stress in the region through which the waves are propagated. This leads to an ultrasonic technique of measure which may be used to determine residual stresses induced by welding processes. In this work, the experiment procedure for the determination of the residual stresses based on the critically refracted longitudinal (L-cr) wave is developed. Different steps of the experiment are presented namely the travel-time measurement, the calibration of the acoustoelastic effect and the residual stress determination. The application of this experimental methodology has been performed on the welded stainless steel plates, for which the residual stresses are determined in different zones and depths using the L-cr waves. The obtained results show that the ultrasonic technique is rather efficient for the evaluation of residual stresses add permit to control the state of the material after thermal and mechanical treatments.