Ultrasonic stress measurement is based on the acoustoelasticity law which presents the relationship between the stress and acoustic wave velocity in engineering materials. The technique uses longitudinaLCRitically refracted (LCR) waves that travel parallel to the material surface. The LCR wave is a bulk longitudinal wave that propagates within an effective depth underneath the surface while the penetration depth of a L CR wave depends on its frequency. It is possible to measure the residual stress in different depths by employing different frequencies of the LCR waves. This paper evaluates welding residual stresses in different depths of a plate made of austenitic stainless steel (304L). The penetration depths are accurately measured for the LCR waves produced by 1 MHz, 2 MHz, 4 MHz, and 5 MHz transducers. Residual stresses through the thickness of the plate are then evaluated by employing four different series of transducers. It has been concluded that the LCR method is nondestructive, easy and fast, portable, readily available, and low cost and bulk measuring technique which can be accurately employed in through-thickness stress measurement of austenitic stainless steels.
- ultrasonic stress measurement
- acoustic wave velocity
- LCR waves