Date of Graduation
This study is to develop acoustic waveguides for Acoustic Emission (A.E.) monitoring of concrete structures, in order to overcome the difficulty of high acoustic attenuation in concrete. Solid embedded waveguides, liquid-filled embedded waveguides and solid surface waveguides have been developed in this study. An analytical model of a waveguide with infinitely thick cladding was used to study the wave propagation in an embedded solid waveguide. The analysis revealed the guideline to construct an ideal embedded waveguide with efficient acoustic transmission, that is the existence of a real wavenumber. An embedded waveguide fulfilling the above criterion has not been constructed physically in this study because of the unavailability of materials. However, some experimental proofs of the theory have been obtained. Also, experimental studies on the attenuation measurement of waveguides and AE monitoring of concrete beams indicated that embedded waveguides could improve AE monitoring range, compared with the conventional surface-mounted sensors. Embedded liquid-core waveguides were also studied. A complete theory for wave propagation in a liquid-core waveguide surrounded by an infinitely thick cladding has been developed. An embedded liquid-core waveguide, unlike embedded solid waveguides, always has stable propagation mode. This is a very advantageous characteristic for AE monitoring. Another contribution of this study is the development of surface waveguides. Surface waveguides have been studied both theoretically and experimentally. A theory to simulate wave motions propagating through a surface waveguide has been developed. The design method of surface waveguides, based on both theoretical and experimental results, was established. Experimental results of AE monitoring of three concrete beams using surface waveguides are very promising. Surface waveguides increase the AE monitoring range significantly and appear to be a practical method for AE monitoring of concrete structures. In summary, both theoretical and experimental investigations on various acoustic waveguides have been conducted in this study. Results indicate that acoustic waveguides provide feasible solutions to overcome the high acoustic attenuation in concrete. The use of acoustic waveguides is a very promising solution for AE monitoring of concrete structures.
He, Yidong Eddie, "Acoustic emission monitoring of concrete structures using waveguides." (1996). Graduate Theses, Dissertations, and Problem Reports. 9013.