A Defect Visualization Imaging Method Eliminating Laser Ultrasonic Traveling Waves
An imaging method, laser ultrasonic technology, is applied in the analysis of solids using sound waves/ultrasonic waves/infrasonic waves, material analysis using sound waves/ultrasonic waves/infrasonic waves, and processing detection response signals. Difficulty obtaining images, etc.
Active Publication Date: 2021-07-23
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 visualization imaging method for eliminating laser ultrasonic traveling waves. The steps include: collecting data through square scanning excitation and central single-point reception; initially determining the defect position by drawing the amplitude image in reverse time; using the receiving point Obtain the ultrasonic signal S of the defect area for the center of symmetry 1 The matching signal S 2 ; will pair signal S 1 and S 2 Perform noise reduction processing, maximum amplitude homogenization processing, and waveform translation processing in sequence; remove the advancing wave by subtracting paired signals; set the time window and obtain the maximum amplitude matrix D according to the defect wave position of the subtraction signal ; Graphically draw the maximum magnitude matrix D to obtain a defect image. The invention can solve the difficulty of eliminating the traveling wave caused by the small laser scanning distance, the distortion of the traveling wave front and the dispersion of the shape of the symmetrical traveling wave, etc., and realize the visual imaging of defects, thereby expanding the visualization of laser ultrasound to advanced manufacturing such as metal additive manufacturing. field.
Description
technical field [0001] The invention relates to the technical field of laser ultrasonic nondestructive testing, in particular to a defect visualization imaging method for eliminating laser ultrasonic traveling waves. 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 proposed the adjacent wave s...
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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