ELASTIC WAVE PROPAGATION INDUCED BY PIEZOELECTRIC ACTUATORS FOR HEALTH MONITORING OF STRUCTURES Xiaodong Wang and Guoliang Huang Department of Mechanical Engineering, University of Alberta Edmonton, Alberta, Canada T6G 2G8 email: xiaodong.wang@ualberta.ca SUMMARY Piezoelectric actuator-induced wave propagation is now being considered for use in health monitoring of structures. The current study provides a comprehensive analysis of the elastic wave propagation generated by surface bonded and embedded thin-sheet piezoelectric actuators. A one-dimensional actuator model is used to simulate the actuation process and the dynamic load transfer between the actuators and the host medium. The resulting wave propagation due to multi- ple actuators is determined using a Pseudo-incident wave method. Detailed numerical simulation is conducted to study the electroelastic behaviour of this composite system. KEYWORDS : Wave propagation, Actuator, Smart Structures, Health monitoring INTRODUCTION Piezoelectric actuators and sensors are being integrated with conventional structural element to form intelligent systems [1-2]. Recent developments in exploring this technology include active noise control and vibration suppression of structures, position control of flexible robot arms, smart skin systems for submarines and shape control of advanced structures [3-6]. Due to the presence of the material discontinuity between the actuators and the host medium, a complicated stress field is generated when external electric fields are applied to the actuators. It is difficult to simulate this actuation process using analytical solutions based on the original bounary/interface conditions. As the result, simplified actuator models have been used to estimate the static load transfer between piezoelectric actuators and host structures [7-11]. The dynamic load transfer between thin-sheet actuators and an elastic host medium was recently studied using a one-dimensional actuator model [12], in which the transverse deformation of the actuator was ignored based on the assumption that the actuator has a high length-to-thickness ratio and the typical wave length is much larger than its thickness. Piezoelectric actuator/sensor systems are being considered to use in online health monitoring of structures. Rogers [13] developed a method for identifying structure damages by measuring the mechanical impedance of structures. This method provided an effective technique for monitoring damages, which may result in measurable impedance change. System identification techniques based on modal frequency and mode shape data have also been used to identify damages [14]. To determine precisely the properties of possible damages in structures, reflected/scattering waves from damages can be used, which carry the information on the location and nature of the damages and can be measured using the attached piezoelectric sensors. This method has been used to detect cracks based on wave energy in geotechnical and geoenvironmental applications [15]. To monitor damages in structures, which are usually small in size, detailed understanding of the wave propagation is necessary. In addition, since an array of actuators/sensors are usually used, accurate estimation of the interaction between actuators/sensors becomes an important issue in the design of health monitoring systems. The object of the present paper is to provide a comprehensive analytical study and numerical simulation of the wave propagation resulting from piezoelectric actuators bonded to or embedded in an elastic medium subjected to high frequency electric loads, based on the use of a generalized actuator model and a Pseudo-incident wave method. 1