Topic
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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01 Jan 2004
TL;DR: In this paper, the authors present a review of previous work on pipeline sizing using Time-Of-Flight-Diffraction (TOFD), focusing transducers, zone discrimination, and focused transducers.
Abstract: Pipelines are now using Fitness-For-Service (FFS) for accept/reject of weld defects. FFS requires accurate measurement of defect height for Fracture Mechanics assessments. The standard pipeline weld inspection technique of radiography is incapable of such measurements. However, the newer technique of ultrasonics can measure defect height, in principle. Initially ultrasonic amplitude methods were used for height measurement, but these proved unreliable. Now diffraction methods, especially Time-Of-Flight-Diffraction (TOFD), are being used in conjunction. This paper reviews previous work — mainly large nuclear studies like PISC II — and published pipeline sizing studies. The best nuclear sizing was within a few millimetres, using diffraction. In contrast to nuclear, pipeline AUT uses zone discrimination, focused transducers, much thinner material and simpler analysis techniques. Current accuracies are typically ± 1 mm (terminology undefined), which correlates with the beam spot size and typical weld pass. Requests for accuracies of ± 0.3 mm are probably unachievable, though future R&D should significantly improve pipeline sizing.Copyright © 2004 by ASME
12 citations
Patent•
18 Aug 2010
TL;DR: In this article, the authors proposed a near surface flaw quantification detection method based on an ultrasonic TOFD method, which relates to the field of ultrasonic detection. But the method is limited by the height and width of the welding seam and the detected objects are restricted in the existing flaw locating method using B-scan.
Abstract: The invention discloses a near surface flaw quantification detection method based on an ultrasonic TOFD method, which relates to the field of ultrasonic detection. The invention solves the problems that the B-scan process is greatly influenced by the height and width of the welding seam and the detected objects are restricted in the existing flaw locating method using B-scan. The method comprises the following steps: measuring the time delay of the detection system; marking a three-dimensional detection coordinate system on the detected object, arranging two probes, carrying out A-scan on the welding seam, determining the propagation distance of the flaw wave in the detected object and the positions of the sound incident points of the two ultrasonic probes according to the acquired A-scan signal to acquire an semielliptic equation; moving one of the ultrasonic probes to a new detection point, and repeating the operations above to acquire another semielliptic equation; and solving the two semielliptic equations simultaneously to obtain the coordinates of the intersecting point of the two semielliptic equations, and acquiring the transverse and burial depth position of the flaw end according to the coordinates of the intersecting point. The invention is applicable to the field of ultrasonic detection.
12 citations
TL;DR: In this paper, an alternative TOFD method is presented, capable to detect and size defects in the inspected material with good precision, and it is shown that the diffraction used in this technique is the most relevant signal among the longitudinal backwall and the shear backwall echoes, compared to other TOFD methods.
Abstract: In this work an alternative TOFD method is presented, capable to detect and size defects in the inspected material with good precision. It was shown that the diffraction used in this technique is the most relevant signal among the longitudinal backwall and the shear backwall echoes, compared to other TOFD methods. The proposed technique showed to be particularly efficient in cases where the coventional TOFD method does not perform well; cases include near-surface defects, cracks under compressive stress and bottom tip of defects. The test configuration and a mathematical description referred to the wave path of the signal of interest is described and confirmed by numerical simulations and dynamic and static tests. The proposed method was tested for different defect depth location and find industrial applications such as inspection of cracks in tubes, closed cracks and weld joints. It opens a new possibility for TOFD based inspections.
12 citations
TL;DR: In this article, a modified ultrasonic time-of-flight diffraction testing with double receivers (DR-TOFD) using Barker code excitation is proposed to size the length, depth and orientation of inclined cracks inside material.
12 citations
Patent•
23 Oct 1987
TL;DR: In this article, a time-of-flight diffraction (TOFD) inspection of an under-water object such as an oil-well platform is performed using an ultrasonic transducer.
Abstract: Apparatus (10) is provided for performing time-of-flight diffraction (TOFD) inspection of an under-water object such as an oil-well platform, including means (34, 40, 20) to support two ultrasonic transducers (106, 108) adjacent to the surface of the object but spaced apart from each other, and means (24, 72) to cause one transducer (106) to slide along the surface towards the other transducer (108). A slow speed of about 5 mm/sec is achieved by using the water to damp the sliding motion. The apparatus can be used to size cracks at a welded joint between two members.
11 citations