Study of transmitting and receiving in longitudinal stress measurement with the LCR wave

As research in the non-destructive measurement of stress has evolved over the years, it has become clear that the critically refracted longitudinal (L-CR) wave technique offers some distinct advantages over other methods. L-CR wave is a bulk longitudinal mode that travels within an effective depth underneath the surface. It may be used to detect in-plane subsurface stresses in the structures. Ultrasonic transducer is the key element for transmitting and receiving L-CR wave, its performance plays an important role in determining the quality of measurement. Models of transducers for ceramic materials have been proved to be very useful. The Kriniholtz, Leedom and Mathaei (KLM) model using equivalent circuits is employed to analyze the effect of different matching materials to the transducers performance. With carefully choosing the backing layer, coupling medium and a quarter-wave matching layer, the transducers with better performance may be obtained.