Double-layer plate Lamb wave non-contact wave speed extraction method

A wave velocity extraction, non-contact technology, applied in the direction of processing the response signal of the detection

Active Publication Date: 2012-07-04
BEIJING UNIV OF TECH
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Problems solved by technology

[0005] The purpose of the present invention is to solve the problem of extracting Lamb wave broadband continuous wave velocity of isotropic double-layer thin plate material, and propose an advanced material wave velocity extraction method

Method used

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  • Double-layer plate Lamb wave non-contact wave speed extraction method
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  • Double-layer plate Lamb wave non-contact wave speed extraction method

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Embodiment Construction

[0041] Below in conjunction with specific example, content of the present invention is described in further detail:

[0042] Step 1): Establish the formula for wave velocity extraction.

[0043] In the case of single frequency excitation / reception, figure 2 In the schematic diagram of Lamb wave propagation shown, the propagation time of direct reflected echo I on the upper surface and the propagation time of Lamb wave L are respectively:

[0044]

[0045]

[0046] Where R is the focus radius, □z is the defocus distance, v w is the ultrasonic velocity of water, θ Lamb is the incident angle for generating Lamb waves, v Lamb is the Lamb wave velocity of the material. So the time difference between the two is:

[0047]

[0048] which is:

[0049]

[0050] Will Snell's Law:

[0051]

[0052] After substituting into (4), we can get:

[0053]

[0054] At this time, if □z is exactly the oscillation period of a V(z) curve, 1 / □t is the excitation frequency f ...

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Abstract

A double-layer plate Lamb wave non-contact wave speed extraction method relates to an ultrasonic measurement method of Rayleigh wave speed and belongs to the technical field of nondestructive testing. Along with progressive development of material science, various functional materials emerge continuously, such as ultrathin glass plates and thin-layer ceramic materials. A testing method adopting traditional destructive mechanical properties cannot meet requirements of novel materials. In nondestructive testing for measuring sound wave speed mainly, a V (z) curve formed by interference of leakyLamb waves and direct reflection waves, namely longitudinal waves, comprises a large amount of information about material properties, such as thickness, density, Young modulus and shear modulus. The double-layer plate Lamb wave non-contact wave speed extraction method is based on a defocusing measurement system, utilizes broadband pulses as an excitation source, receives ultrasonic waves containing various frequency components and obtains the V (z) curve of a material and an oscillation period of the V (z) curve through an improved two-dimensional Fourier transform technique, thereby achieving continuous extraction of broadband of Lamb wave speed. The double-layer plate Lamb wave non-contact wave speed extraction method has the advantages of 1 being capable of performing rapid and accurate wave speed extraction on Lamb waves of different materials; 2 being capable of extracting multi-modality wave speed; and 3 being capable of extracting wave speed in broadband range and replacing a single-frequency pointwise mode.

Description

technical field [0001] The invention belongs to the field of non-destructive testing, and in particular relates to a method for extracting the wave velocity of a double-layer plate Lamb wave. Background technique [0002] With the continuous development of material science, various functional materials are emerging, such as thin film materials and ultra-thin plate materials, which often show brittle characteristics, especially the bonding structure of double-layer ultra-thin plates. Destructive traditional mechanical property testing methods such as stretching and stretching will not be able to meet the needs of new materials. In the non-destructive testing that mainly measures the acoustic wave velocity, the V(z) curve formed by the interference of the leaked Lamb wave and the direct reflected wave contains a lot of information on the microstructure of the material, and the ultrasonic microscope is used as a wave velocity measurement tool. It can be applied to the mechanic...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N29/44
Inventor 何存富吕炎宋国荣柳艳丽高忠阳吴斌
Owner BEIJING UNIV OF TECH
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