Papers by Keyword: Piezoceramic Sensors

Abstract: A piezoelectric ultrasonic sensing system based on an optical fiber has been developed for detection of various damages. The ultrasonic wave generated from a piezoelectric actuator is guided and propagated in the optical fiber and then sensed by a piezoelectric sensor located at the other end of the fiber. The sensed signal can be influenced by environmental and physical changes around the optical fiber. In this study, the sensitivity of the optical fiber sensor is experimentally studied. Various patterns of damage, such as cracks, loosen bolts, holes, are more common forms in real structures. In particular, detection method of the damage with respect to various depths of the crack is presented in this paper.

Abstract: We present a study on the development of a practical and quantitative technique for the assessment of the structural health condition with using piezoceramic (PZT) sensors. The electroimpedance- based technique with the PZT patches is very sensitive for evaluation of the incipient and small damage in a high frequency range, and however the commonly traditional modal analysis method is effective only for considerably larger damages in low frequency range. The paper presents the performance of the performance of the electro-impedance-based technique in detecting and characterizing real-time damage on the specimen that is an aluminum plate fastened with bolts and nuts by different torques. By using the special arrangement of the PZT sensors, the required longitudinal wave is generated through the specimen. A large number of experiments are conducted and the different conditions of the specimen, i.e. the location of loosening bolts and the loosening extent of bolts are simulated, respectively. Since fixing and loosening the loosened bolt is controlled by a torque wrench, we can control exactly the experiment of the different torques. Compared with the simulated healthy condition, we can find whether or not there is a damage in the specimen with using an impedance analyzer with the PZT sensors. Several indices are discussed and used for assessing the different simulated damages. As for the location of bolt loosening, the RMSD is found to be the most appropriate index for numerical assessment and as well the RMSD shows strongly linear relationship for assessing the extent of the bolt loosening. The possibility of repeatability of the pristine condition signatures is also presented and the appropriate frequency range and interval are uniquely selected through large numbers of experiments. The analytical results strongly show the sensibility and reliability of the electro-impedance based technique.

Abstract: Smart structures needs lots of sensor installation to sense their status and also the external environmental change. Wireless technique can give a good solution to install sensors without heavy cables. So, in this work, a wireless device was developed to transmit static strain and elastic wave propagation of structures. The specification of this device was as follows: 2.4 GHz of transmitted frequency, 8 channels, 57,600 bps of the transmitted speed, and 10 mW of the transmitted power. In order to confirm the wireless device’s feasibility, a beam test was performed with five optical fiber strain sensors and two piezo-ceramic sensors with the wireless instrumentation.