Application of Non-Contact Laser Impact with Acoustic Emission Analysis and Tomography Technique for Damage Detection in Concrete.

Tomography techniques have been developed based on acoustic emission and elastic-wave propagation to visualize the internal defects in concrete. For instance, the tomography results can reasonably estimate the wave velocity distribution in consideration of P-wave propagation detours, which are supposed to be altered by the disturbance such as internal defects. As for the excitation of elastic waves on the surface of targeted structure, it is generally known that contact time of a steel sphere ball drop depends on the diameter of the ball, and the frequency component generated by the ball impact is derived by the contact time. In this study, to realize remote inspection works, the elastic wave is induced onto the concrete surface by the impact laser system employing high-power pulse, followed by investigating the influence of laser intensity and spot size. To implement the prompt and reasonable laser remote sensing system to damage detection in concrete, high speed scanning of laser pulse irradiation is introduced on the surface of concrete. Amplitude and frequency dependence are analyzed between the ray paths of the propagated elastic waves, calculating P-wave and surface wave propagation time with amplitude attenuation. The applicability of laser-induced elastic wave for the technique is thus investigated when internal defects of concrete is visualized by means of tomography technique. [ABSTRACT FROM AUTHOR]