Abstract
Lamb wave inspection provides a promising method to assess the structural health status. However, Lamb wave modes exhibit different characteristics which vary with frequency significantly. The best excitation frequency usually cannot be determined in specific applications. This work proposes a multifrequency exploitation and identification method. Lamb waves of multiple frequencies are excitated simultaneously to utilize diverse attributes of Lamb waves in different frequency ranges. This paper firstly analyzes the detectability and sensitivity of Lamb wave. Then the multifrequency exploitation scheme and corresponding post-processing method are introduced. Relevant simulations by finite element method are conducted to verify its effectiveness. Experiments of single-frequency and multifrequency excitations are implemented. The investigations indicate that the proposed method can avoid the missing of defects compared with single-frequency excitation. In addition, a post-processing method is suggested and the results demonstrate that the multifrequency excitation also provides high accuracy in defect location.
Highlights
The ultrasonic guided wave inspection has the potential of longer distance and higher effeciency than traditional structural health monitoring methods [1]–[4]
In this work, a novel method of multifrequency exploitation and identification is proposed aimed at detecting all defects simultaneously in Lamb wave inspection
The best excitation frequency of Lamb wave is nearly impossible to determine in certain applications due to the complicated relation between the detection sensitivity and frequency of Lamb wave
Summary
The ultrasonic guided wave inspection has the potential of longer distance and higher effeciency than traditional structural health monitoring methods [1]–[4]. One type of guided wave propagating in plate-like structure, have been utilized widely in material inspections [5], [6]. It can be generated by piezoelectric transducer or electromagnetic ultrasonic transducer (EMAT) [7], [8]. Through extracting and interpreting the received Lamb wave signal, the location and quantification of defects, even the imaging of inspected structures can be accomplished. The information used to diagnose the structure includes time, amplitude and phase of the Lamb wave signal. To address the diverse features in specific applications and avoid the problem of undetected flaws when utilizing Lamb wave, a multifrequency exploitation scheme and corresponding signal processing method are proposed.
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