Nonlinear wave detection method for underwater gate

Abstract

The invention discloses a nonlinear wave detection method for an underwater gate. The method comprises the following steps of: firstly, determining a relationship between the group velocity of lamb waves and the product of frequency plate thickness through wave velocity calculation; performing coupling optimization to reduce energy of the lamb waves leaking into water and increase energy of the lamb waves in a gate plate; adopting seven transducers to excite waves to reach a focus point at the same time, generating the maximum scattered wave at the focus point, improving the signal-to-noise ratio and obtaining a detection signal; and then extracting integer frequency multiplication components of the excited waves in a frequency spectrum, adding the frequency multiplication components to serve as the damage degree of the focus point, and sequentially changing the focus point to form a damage image of the whole gate. According to the method disclosed by the invention, the linear waves with structural scattering are removed, and the gate is detected by only adopting the nonlinear waves with damage scattering, so that the lamb waves can detect a metal plate with a complicated structure, and detection can be carried out while water retaining of the gate is not influenced; and overall damage visualization of the gate can be realized, and the damage degree of each point is quantitatively represented.

Description

technical field [0001] The invention belongs to the technical field of non-destructive testing, and in particular relates to a nonlinear wave detection method of an underwater gate. Background technique [0002] Hydraulic gate is a thin-walled metal structure, which is easily damaged by aging, freezing and thawing, corrosion and cavitation. Under the condition of not affecting the water retention, regular non-destructive testing of hydraulic gates is the key to ensuring engineering safety and realizing scientific maintenance. Therefore, it is necessary to develop an integral, rapid and non-destructive testing method for underwater gates. [0003] The current hydraulic gate inspection is mainly for coating and corrosion detection, and the safety of the gate is evaluated by the thickness of the gate and the stress calculation. The current detection method can only detect point by point, and cannot evaluate the overall safety of the gate, and there are hidden dangers in the sa...

AI Technical Summary

Problems solved by technology

Therefore, although the Lamb wave can detect smooth metal plates well, it is difficult to apply to the detection of gates with complex structures.

At the same time, the common damage of the gate, such as corrosion, fatigue, loose bolts, etc., is difficult to detect by linear scattered waves

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