An Iterative Vibration Sensor for Detecting Local Transfer Path Variations in Mechanical Structures

Abstract

Multipath problems in complex structures continue to place limitations on local damage detection among common vibration-based nondestructive detection methods. An interactive vibration sensor based on time reversal (TR) technique for mechanical fatigue detection is proposed. The vibration sensor consists of an exciter for vibration generating and a receiver for picking-up the multipath transferred vibration signal. The exciter initially generates vibration with a chirp signal on the object structure and the receiver captures the reverberated signal. The time-reversed signal is then reconstructed and reemitted by the exciter to complete one iterative sensing cycle. It is found that the energy focusing effect of the TR technique can be used as an indicator for detecting local damages in mechanical structures. A stainless-steel flat plate and a three-story frame are taken as two typical objects for proof-of-concept experiments. Mechanical fatigues are simulated by attaching a mass block on the flat plate and changing the tighten torque of the connection bolts in the frame. The peak values and the symmetry of the focused waveforms decrease while transfer paths change with the simulated fatigues, suggesting the ability of the proposed technique in detecting the existence of local damages of the structure and its approximate location. In addition, robustness test results show that such a method performs good anti-interference ability against background vibration and weakly coupled loads.