Method for analyzing depth of crack of thin plate based on ultrasonic lamb waves and time-reversal theory

Abstract

The invention discloses a method for analyzing the depth of the crack of a thin plate based on ultrasonic lamb waves and a time-reversal theory. The method comprises the following steps: selecting a thin plate with a crack, and stimulating single-mode Lamb waves IA(t) in the excitation point A of the thin plate; carrying out a sectioning technology to obtain a multi-mode domain signal received by a reception point B, carrying out the time-reversal technology to obtain a reconstructed signal I'A(t) at the point A, and calculating the waveform damage index DI of the reconstructed signal I'A(t) and an excitation signal IA(t); selecting thin plates having different crack depths L, repeating above steps to obtain corresponding waveform damage indexes DI, and carrying out data fitting through a least square technology to obtain a relation between the crack depth L and the waveform damage index DI; and detecting a thin plate with the crack having an unknown depth to obtain the DI value in order to determine the crack depth L. The sectional calculation technology is adopted to effectively solve the problem of propagation of the Lamb waves in a sheet having defects; and the r time-reversal theory is adopted to reconstruct the signal waveform in order to solve the multi-mode problem and the unable identification problem of the reception point, caused by long distance transmission.

Description

technical field [0001] The invention belongs to the technical field of non-destructive testing, and in particular relates to a thin plate crack depth analysis method based on ultrasonic Lamb wave and time reversal theory. Background technique [0002] With the rapid development of material science and mechanized manufacturing, plates are widely used in the aviation industry, automobile industry, shipbuilding industry, pressure boilers and large chemical containers. For specific application introductions, please refer to the literature: HanhuiXu, Chunguang Xu, Shiyuan Zhou, Study of Lamb Wave Propagation in Plate for UNDE by 2-D FEM Model[J].IEE,2010:556-559. However, since the cracks generated during the forming and use of the plate will pose a threat to the safety of the product, rapid and comprehensive quality and safety testing of the material is an indispensable link (see literature: Percival W.J, E.A.Birt . Insight: Non-Destructive Testing and Condition Monitoring [J],...

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Problems solved by technology

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art, and provide a thin plate crack depth analysis method based on ultrasonic Lamb wave and time reversal theory, and effectively solve the propagation of Lamb wave in the plate with defects by adopting the segmented calculation method Analyze and solve the problem that the Lamb wave cannot propagate at the plate defect and the multi-mode characteristics of the signal waveform distortion and dispersion make it difficult to identify the received signal

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