Metal plate micro-defect detection method based on nonlinear Lamb waves

Abstract

The invention provides a metal plate micro-defect detection method based on nonlinear Lamb waves. The metal plate micro-defect detection method comprises the following steps of: S1, acquiring a phasevelocity frequency dispersion curve and a group velocity frequency dispersion curve of a metal plate; S2, acquiring an excitation frequency, Lamb waves of a specific mode and an incident angle of theLamb waves of the specific mode as model parameters according to the phase velocity frequency dispersion curve and the group velocity frequency dispersion curve; S3, deriving a relative nonlinear coefficient beta' according to the Lamb waves of the specific mode in the S2, wherein the relative nonlinear coefficient beta' is used for representing the depth of a defect; S4, establishing a nonlinearultrasonic test system according to the model parameters; and S5, testing the metal plate according to the nonlinear ultrasonic test system established in the step S4, judging whether the relative nonlinear coefficient beta' is reliable or not, and if so, representing the defects of the tested metal plate by utilizing the relative nonlinear coefficient beta'. According to the metal plate micro-defect detection method, the relative nonlinear coefficient beta' represents the defects of the tested metal plate, the defects of the metal plate can be effectively represented, and the detection precision is improved.

Description

technical field [0001] The invention relates to the field of non-destructive testing, in particular to a method for detecting micro-defects in aluminum alloy plates based on nonlinear Lamb waves. Background technique [0002] Compared with traditional ultrasonic technology, the technology of using the propagation characteristics of ultrasonic guided waves in solid media to detect materials and structures is faster, more economical, and more sensitive. It is an important research in the field of non-destructive testing (Non Destructive Testing, NDT) hotspot. [0003] Lamb wave is a commonly used guided wave mode in ultrasonic nondestructive testing. Because of its advantages of small attenuation, long detection distance and fast propagation speed, it is very suitable for defect detection of large-area metal plates. During the propagation of the Lamb wave in the plate, there will be dispersion phenomenon, and multiple modes will be generated. Due to the mutual interference be...

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Problems solved by technology

During the propagation of the Lamb wave in the plate, there will be dispersion phenomenon, and multiple modes will be generated. Due to the mutual interference between the wave packets of multiple modes, the reception and signal processing are very complicated.

[0004] When there are defects in the plate, the propagation of the Lamb wave will be more variable and complex. The selection of the Lamb wave mode is directly related to the accuracy of the detection. In the prior art, the selection of the Lamb wave mode often does not have a single Therefore, based on Lamb wave, a more accurate method of detecting metal plates is required by the industry

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