Health monitoring of beam structures using traveling waves induced by ambient loads

In this paper, we develop a damage identification method for beam structures based on the measurement of propagating waves excited by ambient loads. First, the ambient vibration data acquired by arrayed sensors are separated into the forward-going and the backward-going wave components utilizing the dispersion relation in the frequency domain. Then, the transfer function between an in-coming and out-going pair of the wave components is identified, whose inverse Fourier transform represents the out-going wave packet from a particular region of the structure in response to an impulsive incident. If there exists a crack at a certain location, additional echoes are observed in the identified impulse response, and the arrival time of the echoes would indicate the location of the crack. Experiments show that the proposed method is capable to detect the existence and the position of a crack only using a couple of sensors.

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