Structure surface defect detection method based on high-frequency Lamb wave frequency domain information

Abstract

The invention relates to a structure surface defect detection method based on high-frequency Lamb wave frequency domain information. According to the method, a nonlinear index beta for surface defect detection is provided based on the time domain information change rule of high-frequency Lamb wave, is based on the nonlinear characteristics of the Lamb wave and can be used for detecting damage smaller than the wavelength of an excitation wave, calculation of the index does not depend on excitation and extraction of higher harmonics, and the method has good engineering applicability and stability. According to the invention, surface defects in a component can be detected, and depth information of the surface defects can be represented; when the surface damage exists on the monitoring path, the value of the damage index beta is obviously increased and is obviously distinguished from the index on the non-destructive path, and the value of the damage index beta is increased along with the deepening of the damage depth, so that the depth information of the surface damage can be effectively reflected; and the method has a strong anti-noise capability, and a stable monitoring result can still be obtained in a strong noise environment.

Description

technical field [0001] The invention belongs to the technical field of engineering structure health monitoring, and in particular relates to a method for detecting structural surface defects based on high-frequency Lamb wave frequency domain information. Background technique [0002] Non-destructive testing technology based on ultrasonic guided waves can identify and monitor damage in structures to track and evaluate structural accidents and anomalies. The technology can monitor hidden, coated, underwater or soil structures as well as structures sealed in seals and concrete, such as railway tracks, pipelines and even aircraft casings. In thin-walled structures, this technique is also known as the active Lamb wave-based acoustic emission monitoring method. The theoretical basis of this method is the propagation mechanism of Lamb wave in the waveguide. Therefore, the excitation signal is usually applied by one or more exciters to activate the guided wave in the thin-walled s...

AI Technical Summary

Problems solved by technology

However, detection methods based on the linear characteristics of Lamb waves are often limited to detecting damage of the same magnitude as the wavelength, because small-scale damage does not cause significant changes in the linear characteristics of ultrasonic waves, so this method is effective in detecting tiny cracks. aspect inefficiency

Damage detection methods based on the nonlinear characteristics of Lamb waves are more sensitive to small-scale damage, but most of these methods are based on the excitation phenomenon of guided wave high-order harmonics to extract nonlinear information related to damage. There will be obstacles, because the energy of the high-order harmonic signal source generated by the damage reflection is weak, unless complex signal processing is performed, it is necessary to accurately separate and extract high-order harmonics from many low-frequency signals and interference signals. difficulty

In addition, whether it is linear acoustics or nonlinear acoustics, most of the current research is devoted to the detection of penetrating damage such as holes, and there are relatively few studies on the detection of structural surface defects and the characterization of damage degrees.

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