Investigation on the effect of imperfect interface on the properties of Love wave propagation

Surface waves can be found many practical applications in MEMS and ultrasonic transducers. Love wave devices/sensors are high sensitive devices which can be found much engineering significance in many signal transmission, signal processing and information storage applications. For the piezoelectric film/elastic substrate layered system, in practical applications, piezoelectric ceramics often inherently have a much higher mechanical strength under compressive stresses in order to improve the reliability of transducers. On the other hand, due to the thermal mismatch, intrinsic stress and the brittleness nature of piezoelectric ceramics, there exists unavoidable initial stress in above-mentioned piezoelectric layered structures and imperfection occurs between the interfaces of the structures. These imperfections may influence the propagation behavior of Love waves. Effects of imperfections on the dispersion relations of Love wave in piezoelectric layered structures are taken into account theoretically and experimentally. A new kind of contact-type line-focused transducer is developed for the Love wave to be excited and detected. Experiments concerning the propagation of Love waves in piezoelectric layered structure are carried out to investigate the imperfect interface effect. Results obtained in our research indicate that imperfect interface can greatly influence the propagation properties of Love waves under some certain conditions. Experimental results agree well with the theoretical prediction, which also indicate that the novel Love wave transducer developed by us is effective.