Reconstruction and extraction method for diffraction echo signals in laser ultrasonic defect detection

Abstract

The invention discloses a reconstruction and extraction method for diffraction echo signals in laser ultrasonic defect detection. The method comprises the steps of firstly inputting a to-be-processedlaser ultrasonic defect detection diffraction echo signal, and sequentially carrying out subtraction and white noise adding to generate a noise-added signal; decomposing the noise-added signal by adopting an EMD (Empirical Mode Decomposition) method to generate a plurality of IMF components, sorting the IMF components according to the frequency, calculating the dispersion degree of each IMF component, and selecting the corresponding IMF component to reconstruct according to the dispersion degree distribution and the IMF component relationship to obtain a reconstructed signal; denoising the reconstructed signal in an exponential weighted average mode, extracting extreme points of the denoised reconstructed signal, and selecting and outputting a certain number of maximum extreme points at intervals of a certain length. Useful signals are prevented from being lost; the decomposition effect of EMD is improved; useful signals are prevented from being submerged in incident signals; useful signals containing defect information are effectively reserved, high-frequency noise signals from the environment are abandoned, and the purposes of accurate output of the useful signals and visual judgment of defects are achieved.

Description

technical field [0001] The invention belongs to the technical field of laser ultrasonic detection, and in particular relates to a method for reconstructing and extracting diffraction echo signals for laser ultrasonic defect detection. Background technique [0002] With the rapid development of the manufacturing industry, people have higher and higher quality requirements for products, especially in strategic fields such as aviation, nuclear energy, and petrochemicals. The service environment of products is relatively harsher, and the reliability requirements are also higher. However, in the process of product manufacturing and processing, the occurrence of defects is often inevitable, and the existence of defects will greatly affect the performance of the product, reduce the reliability of the product, shorten the service life of the product, and bring great potential safety hazards Therefore, it is extremely important to use laser ultrasonic testing technology to test produ...

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Problems solved by technology

[0005] The technical problem to be solved by the present invention is to provide a method for reconstructing and extracting the diffraction echo signal of laser ultrasonic defect detection for the above-mentioned defects of laser ultrasonic detection technology, effectively avoiding the influence of high-amplitude incident signals on EMD decomposition, and ensuring The useful signal is not lost; effectively overcome the endpoint effect that exists when EMD

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