Multi-mode Lamb wave signal separation method based on fractional differential

Abstract

The invention discloses a multi-mode Lamb wave signal separation method based on a fractional differential. The method comprises the following steps that: (1) calculating the Fourier transform of a multi-mode signal; (2) calculating the fractional differential of an amplitude spectrum; (3) calculating the multinomial coefficient of the fractional order and the fractional differential maximum valueof the amplitude spectrum of a Gaussian model; (4) calculating an amplitude spectrum parameter; (5) on the basis of the Gaussian model, calculating the amplitude spectrum; (6) calculating a phase spectrum; (7) extracting a single-mode Lamb wave signal by the amplitude spectrum and the phase spectrum; and (8) removing a mixed signal of which the signal is extracted, and repeating the above steps to realize the separation of each mode. Compared with the prior art, the method can extract the single-mode characteristic parameter of a multi-mode mixed signal through the fractional differential soas to more favorably keep the detail characteristic of each mode signal, each-mode characteristic parameter can be effectively extracted, and each-mode amplitude spectrum reconstruction is realized soas to realize the separation of the multi-mode mixing signals.

Description

technical field [0001] The invention relates to the technical field of ultrasonic Lamb wave signal processing in non-destructive testing, in particular to a multi-mode Lamb wave signal separation method based on fractional differentiation. Background technique [0002] Ultrasonic Lamb wave is fast, efficient and accurate, and is very suitable for non-destructive testing of large-area plate structures, pipeline structure safety monitoring systems, etc., but due to the complex theory and detection mechanism of ultrasonic Lamb wave itself, there are various problems in the application, which limits practical industrial applications. [0003] The main characteristics of Lamb wave are dispersion and multi-mode. It is possible to excite two or more mode signals at the same excitation frequency. Due to the dispersion characteristics, the phase velocity of each mode changes with the frequency component of the signal, so that the modes interact with each other. Superposition, cannot...

AI Technical Summary

Problems solved by technology

However, the multi-mode aliasing signal will cause nonlinear changes in amplitude due to the dispersion characteristics, making it difficult for the characteristic parameter extraction value of time-frequency analysis to accurately reflect the real single-mode signal energy distribution, making it difficult to apply to excessive aliasing in both time and frequency in the multimodal separation of

[0004] Due to the multi-mode and dispersion characteristics of the Lamb wave, in the actual detection, under the same excitation frequency, there are often mixed signals of multiple modes, and the signals of each mode have different dispersion trends, so that in the case of time-frequency aliasing The detection of lower Lamb waves becomes very complicated

Images