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Lamb wave group velocity and frequency domain measurement method for complex structure

A wave group velocity and frequency domain measurement technology, which is used in measurement devices, measurement of propagation velocity, measurement of ultrasonic/sonic/infrasonic waves, etc. It can solve the problems of complex engineering structure, inaccurate group velocity values, and time domain expansion of signal wave packets. , to achieve the effect of high measurement efficiency, improved accuracy and reduced impact

Active Publication Date: 2018-04-06
NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
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Problems solved by technology

However, the dispersion of Lamb waves can easily cause time-domain expansion and deformation of the signal wave packet, which makes it difficult to accurately extract the arrival time of the direct Lamb wave packet, and ultimately reduces the accuracy of the group velocity measurement results
The more severe the Lamb wave dispersion, the less accurate the group velocity value measured based on the traditional time-domain measurement method above
In addition, the actual engineering structure is relatively complex, and the boundary reflection is serious. The direct wave packet of the selected mode in the Lamb wave sensing signal is easily aliased with the boundary reflection wave packet, and it is difficult to extract the pure direct wave packet for this mode. group velocity measurement

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  • Lamb wave group velocity and frequency domain measurement method for complex structure
  • Lamb wave group velocity and frequency domain measurement method for complex structure
  • Lamb wave group velocity and frequency domain measurement method for complex structure

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[0040] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described through implementation with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are the embodiment of the present invention. Some, but not all, embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0041] For the convenience of verification, this embodiment adopts the structure of LY21 aluminum plate, the size is 800mm×800mm×4mm, and the material parameters are shown in Table 1.

[0042] Table 1. Aluminum plate material parameters

[0043] Thickness d(mm)

Density ρ(kg / m 3 )

Poisson's ratio μ

Elastic modulus E(GPa)

4

278...

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Abstract

The invention proposes a Lamb wave group velocity and frequency domain measurement method for a complex structure, and belongs to the field of Lamb wave structure health monitoring. The method comprises the following steps: (1), arranging a piezoelectric patch in the structure, and collecting a structure Lamb wave reference signal; (2), introducing a scatterer to the structure, and collecting a Lamb wave sensing signal in a current structure state; (3), solving a Lamb wave scattering signal according to the Lamb wave sensing signal and the reference signal thereof; (4), extracting a scatteredwave packet in a selected mode from the Lamb wave scattering signal; (5), calculating the frequency spectrum of an Lamb wave excitation signal and the frequency spectrum of the scattered wave packet;(6), solving the phase difference spectrum of the Lamb wave excitation signal and the scattered wave packet; (7), calculating and obtaining the group velocity of the selected mode of the Lamb wave through the phase difference spectrum. The method avoids the impact of Lamb wave scattering in a conventional time domain measurement method, and improves the measurement accuracy.

Description

technical field [0001] The invention relates to a frequency-domain measurement method for Lamb wave group velocity of a complex structure, which belongs to the field of Lamb wave structure health monitoring. Background technique [0002] Structural health monitoring technology is of great significance for improving the safety of engineering structures and reducing maintenance costs. As a kind of ultrasonic guided wave in thin-plate structures, Lamb wave has a long propagation distance and is sensitive to both internal and surface damage of the structure, so it is widely used in structural health monitoring. Lamb waves have multimode and dispersion properties. Multimodality refers to the existence of at least two Lamb wave modes in the structure. According to whether the particle vibration of the structure is symmetric or antisymmetric with respect to the interface in the structure when the Lamb wave propagates, the Lamb wave modes are divided into two types: symmetric mode...

Claims

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Application Information

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IPC IPC(8): G01H5/00G01H11/08
CPCG01H5/00G01H11/08
Inventor 蔡建袁慎芳汪晓鹏
Owner NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
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