Defect visual imaging method for eliminating laser ultrasonic traveling waves
An imaging method and laser ultrasound technology, which are used in the analysis of solids using sonic/ultrasonic/infrasonic waves, material analysis using sonic/ultrasonic/infrasonic waves, and processing response signals of detection. Small steps, etc.
Active Publication Date: 2020-10-30
WUHAN UNIV
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[0004] The purpose of the present invention is to address the deficiencies of the prior art, to provide a defect visualization imaging method that eliminates laser ultrasonic traveling waves, and to solve the defect images caused by small scanning steps, distorted traveling wave shapes, and large dispersion in the prior art Hard-to-obtain problems, enabling laser-ultrasonic defect visualization imaging in advanced manufacturing applications such as metal additive manufacturing
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[0028] In order to better understand the present invention, the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.
[0029] The 316L stainless steel additive manufacturing sample printed by powder spreading, the average surface roughness of the sample is Ra7.5μm. Grooving was performed on the surface of the sample by EDM, and a groove defect with a width and depth of 50 μm and a length of 5 mm was obtained. Based on the above samples, the present invention provides a laser ultrasonic high signal-to-noise ratio imaging method for micro-defects in metal additive manufacturing, which specifically includes the following steps:
[0030] S1. Data acquisition of square scanning excitation and central single-point reception: set an M×M square scanning area on the sample surface, set the receiving laser at the center of the square scanning area, and use the excitation laser to scan in the square according to a cer...
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The invention discloses a defect visual imaging method for eliminating laser ultrasonic traveling waves. The method comprises the steps: collecting data through square scanning excitation and centralsingle-point receiving; preliminarily judging the defect position by reversely drawing an amplitude image in time; obtaining a matching signal S2 of an ultrasonic signal S1 in the defect area by taking the receiving point as a symmetric center; sequentially carrying out noise reduction processing, maximum amplitude equalization processing and waveform translation processing on the paired signals S1 and S2; removing traveling waves by subtracting paired signals; setting a time window and obtaining a maximum amplitude matrix D according to the defect wave position of the subtraction signal; andperforming graphic drawing on the maximum amplitude matrix D to obtain a defect image. According to the method, the problem that traveling waves are difficult to eliminate due to small laser scanningspacing, traveling wave front distortion, symmetrical traveling wave shape dispersion and the like can be solved, and visual imaging of defects is realized, so that laser ultrasonic visualization is expanded to the advanced manufacturing fields of metal additive manufacturing and the like.
Description
technical field [0001] The invention relates to the technical field of laser ultrasonic nondestructive testing, in particular to a laser ultrasonic high signal-to-noise ratio imaging method for micro-defects in metal additive manufacturing. Background technique [0002] Due to its characteristics of non-contact, wide-band and high-efficiency scanning, laser ultrasound has been more and more widely used in the field of engineering inspection. In 2008, Japanese scholars proposed the laser ultrasonic visualization imaging method. Through the acquisition and post-processing of scanning data of a series of position points, the visualization of ultrasonic propagation and the process of interacting with defects was realized, which provided a solution for rapid detection of defects; but this method Because the defect signal and the traveling wave signal are superimposed together, it is difficult to quantify the defect size. In 2012, on the basis of this method, Korean scholars prop...
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IPC IPC(8): G01N29/04G01N29/06G01N29/07G01N29/44
CPCG01N29/045G01N29/069G01N29/07G01N29/4427G01N29/4436G01N2291/0234
Inventor 张俊李晓红徐万里丁辉
Owner WUHAN UNIV