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.

Method for improving longitudinal resolution of TOFD (time of flight diffraction) detection with Burg algorithm based autoregressive spectrum extrapolation technology

Abstract: The invention discloses a method for improving longitudinal resolution of TOFD (time of flight diffraction) detection with a Burg algorithm based autoregressive spectrum extrapolation technology, and belongs to the technical field of ultrasonic non-destructive detection. The method adopts an ultrasonic detection system comprising a TOFD ultrasonic detection instrument, TOFD probes, a scanning device, software integrating TOFD conventional analysis functions and a computer. According to the method, TOFD scanning is performed on defects, collected time-domain aliasing signals containing upper-end and lower-end diffraction waves of the defects are subjected to autoregressive spectrum extrapolation processing; the -6dB frequency bandwidth is taken as the benchmark, defect signals in the frequency band range are selected, defect signals outside the frequency band range are estimated with the Burg algorithm, so that the frequency bandwidth is broadened, the longitudinal resolution of defect detection is improved, and the defect height quantification is realized. Compared with other methods for improving the longitudinal resolution of TOFD detection, the method does not have additional requirements for a hardware system, is not limited by exciting pulse time width of the detecting probes, and has higher engineering application value.

Performing of ultrasonic inspection using TOFD technique in terms of the requirements of related standards

Abstract: Rafał Kaczmarek, Karol Kaczmarek, Jacek Słania, Ryszard Krawczyk 2017.05.17 by Marek Dragan The article concerns the time of flight diffraction testing technique (TOFD), which is, next to the simultaneous TOFD + Phased Array testing, one of the most effective methods of volumetric non-destructive tests. The article discusses the advantages of the TOFD technique as well as the basis of diffraction phenomenon and the formation of imaging signals. In addition, the article presents a TOFD image of a welded joint and describes its characteristic elements. Also, the article discusses the TOFD-related testing standards and analyses their requirements related to welded joints and their acceptance criterion, i.e. the quality level according to PN-EN ISO 5817. The target readers of the article include NDT personnel, inspectors, welding engineers and welding equipment manufacturers wishing to implement an effective tool enabling the detection of welding imperfections.

A Novel Method for Ultrasonic Evaluation of Horizontal Defects Using Time-of-Flight Diffraction

Abstract: Time-of-flight diffraction method (ToFD) is an amplitude-independent sizing method which is based on the measurement of time-of-flight of defect tip diffracted waves. Although ToFD can measure through-wall length of defect accurately, this method is not capable of measuring horizontal defect size. In this paper, a new ToFD method for evaluating horizontal planar defects is presented. The finite element method (FEM), using the ABAQUS software package, is employed to simulate the ultrasonic wave behavior in the test blocks and its interaction with the embedded planar defects. The phased array technology is also used to model the ultrasonic inspection system parameters. FEM simulation of the new ToFD method for different crack sizes shows that, compared to the conventional ToFD method, the accuracy of results is within acceptable range to use the novel technique for measuring the horizontal planar defects.