Ultrasonic guided-wave based calculation method for separating flexural mode reflected signal

Abstract

The present invention discloses a calculation method for separating symmetric and flexural mode wave packet and extracting weak signal of the bending mode. Based on the wave structure characteristic theory of axisymmetric mode and bending mode, the method uses finite element software to establish correlative model, extracts transient displacement signal of signal acquisition nodes of a guided-wave monitoring surface, and conducts delay superimposing on the collected signals on the frequency domain in accordance with relative formula; then the superimposed frequency domain signal is subjected to the inverse Fourier transform to obtain guided-wave mode wave packet of each order after separation; and Hilbert-Huang envelope is employed to calculate reflection coefficient for each mode. The method uses secondary development function of finite element software to compile the secondary development program, quantitatively analyze the influence degree of the parameters such as characteristics of defect size, location distribution, the number of defects and the center excitation frequency on the amplitude value of the flexural mode reflection echo generated from the defect locations through modal conversion, thereby integrally utilize reflection coefficients of axisymmetric mode and bending mode to evaluate the distribution of defect locations.

Description

technical field

[0001] The invention relates to a calculation method for quantitative analysis of the action mechanism of ultrasonic guided waves propagating in a tubular waveguide and defects, especially using the wave structure characteristics of axisymmetric mode and bending mode to separate symmetrical and bending mode wave packets and extract bending For weak modal signals, the reflection coefficients of each mode are obtained by using the Hilbert yellow envelope, and the reflection coefficients of the axisymmetric mode and the bending mode are comprehensively used to evaluate the defect position distribution Background technique

[0002] Thick-walled pipe refers to a tubular steel structure with a ratio of outer diameter to wall thickness of less than 20. Thick-walled pipes are widely used in the fields of petroleum, chemical industry, and thermal power generation. Since the pipes work in high-temperature and high-pressure environments and the inner and outer walls of ...

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