An advanced acoustic emission sensor for transient elastic wave measurements

This paper reports the development of an advanced acoustic emission system for transient elastic wave measurements. The goal is to develop an inexpensive but effective acoustic emission system which can simultaneously obtain high-frequency acoustic emission signals at multiple locations. The transient elastic signals can then be used for inversely deducing important characteristics of the acoustic emission event. To achieve this goal, a number of miniature PZT elements are first fabricated using an excimer laser micro-machining technique. The PZT element is in conical shape and with an aperture size around 200 μm. Very similar to the conventional NBS conical transducer but much smaller in size, the miniature PZT element is an excellent acoustic emission transducer with much high bandwidth. A new packaging method of the mini-conical element allows the transducer not only can measure conductive samples but also non-conductive ones. This improvement greatly enhances the applicability of the acoustic emission system. A number of PZT mini-conical transducers have been used to construct the acoustic emission measurement system. The transducer has been tested with standard glass capillary breaking methods. Finally, a mechanical fixture is designed to mount these acoustic emission transducers and to make the acoustic emission measurements much more convenient. To demonstrate the capability of this advanced acoustic emission system, a number of plate samples are used. Acoustic emission signal at multiple locations are obtained and compared with their theoretical counterparts. Good results are obtained. Further improvement and application of this system will be addressed.