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Time-of-flight diffraction ultrasonics

About: Time-of-flight diffraction ultrasonics is a research topic. Over the lifetime, 544 publications have been published within this topic receiving 3189 citations.


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Journal Article
TL;DR: In this article, the development, principles, characteristics and applications of scan ultrasonic imaging are analyzed and the development trend of ultrasonic detection imaging technology is pointed out, which can better guide the practical application of ultrasound imaging technology.
Abstract: The ultrasonic detection imaging technology plays a very important role in many fields of modern industry and has a bright prospect of development.The development,principles,characteristics and applications of scan ultrasonic imaging,ultrasonic image display,ALOK imaging,phased array method,ultrasonic microscope,SAFT imaging,TOFD imaging and ultrasonic CT imaging are analyzed.This article can better guide the practical application of ultrasonic detection imaging technology.The development trend of it is pointed out.

2 citations

Journal ArticleDOI
31 Dec 2019
TL;DR: In this article, the authors have developed a testing procedure to overcome this limitation and to determine the depth of defects in the welds with non-equal wall thickness by TOFD technique using the standard ‘depth calculator’.
Abstract: During construction, reconstruction and technical inspection of vertical steel tanks (VST), all wall butt weld joints are subjected to ultrasonic testing to detect internal defects or flaws. The considerable length of examined welds (it can exceed 3,000 m) necessitates the development and implementation of mechanized and automated inspection systems that can increase the rate of testing and documentation of results. Systems of mechanized and automated ultrasonic echo-testing do not support the detection of all defect types and reliable determination of their geometric parameters. The Time-of-Flight Diffraction (TOFD) technique makes it possible to estimate the height of the defect regardless of its type and orientation. However, the application of TOFD technique for welds with non-equal wall thickness is complicated by the fact that the standard software of flaw detectors (‘depth calculator’) does not consider this non-uniformity. The authors have developed the testing procedure to overcome this limitation and to determine the depth of defects in the welds with non-equal wall thickness by TOFD technique using the standard ‘depth calculator’. An experimental verification of this technology confirmed the correctness of the calculations. The inspection scheme and calculation of the depth of discontinuity boundaries using the TOFD technique were tested using the example of the welded joint of the walls with non-equal thickness of the 10,000-m3 tank under construction. The thickness of the walls was 12 and 14 mm; 8 and 10 mm. The inspection of the real facility has confirmed good detection of defects and high reliability of the results.

2 citations

Journal Article
TL;DR: In this article, a modified testing mode named TOFDW, which employs the three-fold reflected longitudinal wave from the bottom of the piece under testing, is presented based on the conventional TOFD technique.
Abstract: Aims at the problem of near surface dead zone in ultrasonic TOFD(time of flight diffraction) method,a modified testing mode named as TOFDW,which employs the three-fold reflected longitudinal wave from the bottom of the piece under testing,is presented based on the conventional TOFD technique.The characteristic of sound propagation in TOFDW mode is analyzed and its detection principle is illustrated.Through artificial defect testing,the features of tested signal and image are cognized,and the testing sensitivity and accuracy of the testing mode are studied.Weld piece is tested and the result is verified by destructive testing.The experimental results show that TOFDW model can identify the near surface defect that cannot be distinguished by using conventional methods,and the artificial defect with buried depth of 1.0 mm can be effectively detected.The model has a high quantitative accuracy,and the average absolute error of artificial defects location is less than 0.3 mm.

2 citations

Journal Article
TL;DR: An image enhancement method based on synthetic aperture focusing technique (SAFT) that was able to accurately judge for crack defect and can be improved by 6.4% compared to that of traditional detection method.
Abstract: when testing the defect by ultrasonic time of flight diffraction (TOFD), the image signal detected is often re- shaped and resulted in inaccuracy of defect measurements because the probe beam has a limited range. This paper pro- posed an image enhancement method based on synthetic aperture focusing technique (SAFT). A mathematical model of testing image was first established based on the generation process of the image. A method was then designed for detect- ing defects in near surface blind area based on filtering of through waves. Finally, a synthetic aperture focusing algorithm based on peak capture pretreatment was used to enhance the resolution of the image. By applying the above method to test a crack defect of 15mm, the method was able to accurately judge for crack defect. Also, the measuring accuracy can be improved by 6.4% compared to that of traditional detection method.

2 citations

Journal ArticleDOI
TL;DR: In this article, the authors used echo signals reflected from the bottom of the test object, taking into account the change in the wave type, then the combined reflector image can be obtained from the set of partial images reconstructed by the digital antenna focusing (DFA).
Abstract: The TOFD method, widely used in ultrasonic flaw detection, makes it possible to distinguish a crack from a volume reflector by the phase of echo signals and to determine its height with high accuracy. However, the TOFD method without piezoelectric transducers scanning across the welded joint does not allow determining the offset of the reflector from the weld center, which is very important when evaluating the test results. The scanning devices used for this have a complex design, their price is higher than that of one-dimensional scanning devices, and, most importantly, the testing time increases considerably. If we use echo signals reflected from the bottom of the test object, taking into account the change in the wave type, then the combined reflector image can be obtained from the set of partial images reconstructed by the digital antenna focusing (DFA) method. Using the echo signals measured in the combined mode for each piezoelectric transducer, then it is possible to estimate the displacement of the reflector across the welded joint with an accuracy of $$ \pm 1.5$$ mm. Numerical and model experiments have confirmed the efficiency of the proposed approach.

2 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202110
202017
201919
201823
201724
201624