EFFECT OF INITIAL STRESS ON THE PROPAGATION BEHAVIOR OF GENERALIZED RAYLEIGH WAVES IN LAYERED PIEZOELECTRIC STRUCTURES
初应力对压电层状结构声表面波传播性能的影响

Surface acoustic wave devices are applied extensively to many technical fields. Such as television, telecommunication, nondestructive evaluation, radar and health monitoring systems.Rayleigh waves are the most commonly used wave modes in surface acoustic wave devices, which is related to the concentration of the energy at the sensitive surface. The basic structure supporting the propagation of Rayleigh waves is a piezoelectric substrate or a layered piezoelectric structure with a piezoelectric thin film deposited on a nonpiezoelectric substrate. Great efforts have been devoted by many researchers to study the propagation behavior of Rayleigh waves on the basic structures. For the layered piezoelectric structures, it is well known that due to the mismatch of the material properties of the layer and the substrate, there exists residuaJ stress during the manufacture process of piezoelectric surface acoustic wave devices. On the other hand, to prevent the piezoelectric material from brittle fracture, the layered piezoelectric structure is usually prestressed during the manufacture process, where the initial stress is negative with the magnitude of 100 MPa. To the author's knowledge, no work has been carried out so far to discuss the effect of initial stress on the propagation behavior of generalized Rayleigh waves in layered piezoelectric structures. In this paper we are concerned with the propagation behavior of generalized Rayleigh wave in pre-stressed layered piezoelectric half-space, where a thin piezoelectric layer is perfectly bonded to a non-piezoelectric elastic half-space substrate. Solutions of the mechanical displacement and electrical potential function are obtained for the piezoelectric layer and elastic substrate,respectively, by solving the electromechanically coupled field equations. The phase velocity equations of generalized Rayleigh wave propagation are obtained for electrically open and shorted cases on the free surface, respectively. Effect of the initial stress on the phase velocity of generalized Rayleigh wave propagation and the electromechanical coupling factor of the layered piezoelectric structure are respectively discussed, where one set of the piezoelectric layer on elastic substrate system, i.e., PZT-5H ceramic layer~SiO2 glass substrate is considered. It is seen that the phase velocity of generalized Rayleigh wave propagation decreases and the electromechanical coupling factor increases remarkably as the absolute value of initial stress is greater than 100 MPa. These results are very useful for the design of surface acoustic wave devices.