Laser ultrasonic surface defect imaging noise reduction method based on improved wavelet threshold and VMD

A laser ultrasound and wavelet threshold technology, applied in the analysis of solids using sonic/ultrasonic/infrasonic waves, material analysis using sonic/ultrasonic/infrasonic waves, image enhancement, etc. It can solve problems such as unclear imaging and achieve high signal-to-noise ratio. , Optimize the imaging effect, the effect of short signal processing time

Pending Publication Date: 2021-10-22
LASER RES INST OF SHANDONG ACAD OF SCI
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  • Application Information

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Problems solved by technology

[0004] Aiming at the deficiencies of the prior art, the present invention provides a laser ultrasonic surface defect imaging noise reduction method based on improved wavelet threshold and VMD, which solves the existing problem of unclear imaging

Method used

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  • Laser ultrasonic surface defect imaging noise reduction method based on improved wavelet threshold and VMD
  • Laser ultrasonic surface defect imaging noise reduction method based on improved wavelet threshold and VMD
  • Laser ultrasonic surface defect imaging noise reduction method based on improved wavelet threshold and VMD

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Experimental program
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Effect test

Embodiment

[0101] Embodiment: Step 1: Use a laser galvanometer scanning system and a laser interferometer to perform rapid laser ultrasonic surface scanning of the area to be tested on the test piece to obtain the original signal of the laser ultrasonic.

[0102] Step 2: Perform wavelet decomposition on the laser ultrasonic signal obtained in step 1, select the sym7 wavelet as the wavelet base, and decompose the number of layers into 5 layers to obtain detail components and approximate components.

[0103] Step 3: Hard threshold and soft threshold The wavelet threshold function is widely used, but there are certain limitations. The hard threshold function can retain more peak features of the original signal, but the hard threshold function is discontinuous at the threshold ± T, so that in There will be a certain oscillation phenomenon when reconstructing the signal; the soft threshold function is continuous at ±T, but it will cause a constant error between and, making the mean square erro...

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Abstract

The invention provides a laser ultrasonic surface defect imaging noise reduction method based on an improved wavelet threshold and VMD, and aims to solve the problems of more noise components and poor imaging effect when a non-contact laser ultrasonic detection mode is adopted to carry out imaging detection on surface defects of a metal additive manufacturing test piece, and a traditional soft and hard threshold function is improved. The method comprises the following steps: firstly, carrying out improved wavelet threshold function noise reduction on a collected laser ultrasonic signal, then decomposing the denoised signal into intrinsic mode components through a VMD algorithm, and extracting an effective mode component to carry out signal reconstruction by taking the product of the energy density of each component and the average period of the component as a basis; and performing ultrasonic imaging by using the final noise reduction signal. Surface scanning is carried out on an additive manufacturing aluminum plate containing surface defects, the imaging effect is optimized through the method, the result shows that the imaging effect of the method is greatly improved, and a foundation is laid for follow-up ultrasonic imaging detection of smaller-size surface defects.

Description

technical field [0001] The invention relates to the technical field, in particular to a laser ultrasonic surface defect imaging noise reduction method based on improved wavelet threshold and VMD. Background technique [0002] Metal additive manufacturing technology, as a new type of manufacturing technology, has developed rapidly in recent years. At present, the technology is used in a wide range of materials, and it shows great application potential in aerospace, medical and health and other high-tech fields. While the metal additive manufacturing technology is developing rapidly, its own limitations are gradually revealed. Due to the particularity of the metal additive manufacturing process, defects such as holes and cracks are prone to appear in the parts, and the appearance of defects will greatly reduce the quality of the parts. The yield and reliability of these materials have greatly hindered the development of metal additive manufacturing technology. Therefore, defe...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06K9/00G06T5/00G01N29/04
CPCG06T5/002G01N29/048G06T2207/10132G06F2218/04
Inventor 许万卫白雪马健郭忠铭
Owner LASER RES INST OF SHANDONG ACAD OF SCI
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