<p>The presence of damage can significantly decrease the performance of a structure and lead to a potential failure, repairs, and downtimes. Therefore, it is important and desirable to identify the damage at an early stage.&nbsp; This work proposes a damage detection method using beamforming acoustic source localization. This approach introduces an active acoustic source inside a structure and measures sound radiation using a microphone array. The measured sound pressures are processed using the delay and sum beamforming (DASBF) algorithm to identify the damage location. In the DASBF algorithm, the damage location is considered as the unique sound source, based on an assumption that the sound radiation from the damage location has a much higher amplitude than those from other intact locations on the structure. To investigate effectiveness, accuracy, and noise-robustness of the proposed method, both numerical and experimental studies were conducted. In the numerical study, a vibro-acoustics simulation system is constructed: a hollow box is modelled with damage in the form of through holes on its front face and a monopole sound source is placed inside the box, providing acoustic excitation for the box. Parametric studies were performed s to understand effects of the damage size and location, microphone array arrangement, excitation frequency and distance between the box and microphone array on damage detection results. In the experimental study, a vibro-acoustic setup was realized in a hemi anechoic chamber. A hollow steel box with front faces with various damage scenarios was prepared, and a speaker was attached to back face of box to generate acoustic excitation, and a microphone array was set up in rectangular pattern facing the box. Robustness of the proposed method was investigated with multiple excitation frequencies ranging from 3000 Hz to 15000 Hz, multiple distances between damage and microphone array, ranging from 204 mm to 806 mm, and multiple input voltages, ranging from 1 V to 25. The damaged samples consisted of holes of different diameters, including 2 mm, 4 mm, and 7 mm, at center and off-center locations. It was found that damage detection results depended on the excitation frequency, distance between the structure and microphone array and size of the damage. The optimum excitation frequency and distance range were discussed based on each studied case. While the damage of diameters of 4 mm and 7 mm could be well identified, the damage of the diameter of 2 mm could not be identified in most studied cases. A future work can be the application and extension of the proposed method for identifying damage in large operating engineering structures, such as wind turbine blades.</p>

Structural Damage Identification Using Beamforming Acoustic Source Localization

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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