Micro-defect ultrasonic detection signal processing method considering surface roughness

Abstract

The invention relates to a micro-defect ultrasonic detection signal processing method considering surface roughness. The method comprises the following steps that: S1, a detection system is built to obtain micro-defect ultrasonic detection signals under the influence of a rough surface; S2, a coif4 wavelet generating function is adopted to perform N-layer wavelet decomposition on the micro-defectultrasonic detection signals so as to obtain the approximate component of the Nth layer of a wavelet coefficient as well as the detail components of the first layer to the Nth layer of wavelet coefficients; S3, threshold quantization denoising processing is performed on the detail components of the first layer to the Nth layer; S4, inverse wavelet transformation is adopted to perform reconstruction so as to obtain denoised micro-defect ultrasonic detection signals; and S5, the size and position of a micro-defect are judged according to the amplitude of the denoised micro-defect ultrasonic detection signals and the flying time of the denoised micro-defect ultrasonic detection signals relative to interface waves. According to the micro-defect ultrasonic detection signal processing method considering surface roughness of the invention, a plurality of layers of wavelet coefficients which are obtained based on coif4 wavelet mother generating function-based decomposition can express originalsignal characteristics more accurately and efficiently, and background noises caused by the multi-scattering of the micro-defect detection signals and the sound waves of the rough surface are effectively distinguished.

Description

technical field [0001] The invention relates to the technical field of non-destructive testing, in particular to a method for processing micro-defect ultrasonic testing signals considering surface roughness. Background technique [0002] Ultrasonic detection signal of fine defect is the superposition of background noise signal caused by the rough surface of the workpiece to be tested and the signal of fine defect. The amplitude of the defect echo signal is reduced, the waveform is broadened, and the noise signal is enhanced at the same time, and the signal-to-noise ratio of the final detection signal is reduced. For the detection of micro-defects (such as micro-layered micro-defects and micro-crack micro-defects) inside or on the inner and outer layers of the workpiece to be tested, when the micro-contour size and the size of the micro-defects are in the same order of magnitude, the acoustic wave will produce Mie scattering on the rough surface, The scattering intensity is ...

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Problems solved by technology

[0004] In view of the problem that in the ultrasonic detection process of some micro-defects in the above-mentioned background technology, it is difficult to accurately identify the micro-defect signals caused by the roughness of the workpiece to be tested facing and or facing away from the probe surface, the purpose of the present invention is to use a micro-defect ultrasonic detection method that considers surface roughness. Detection signal processing method to improve the signal-to-noise ratio of the micro-defect echo signal, and then extract the effective detection signal of the micro-defect

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