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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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Proceedings ArticleDOI
08 May 2019
TL;DR: In this article, defect sizing random and systematic errors associated with different calibration technique are assessed, improvements for surface and backwall defect sizing are proposed, and best practices have been recommended.
Abstract: Time Of Flight Diffraction (TOFD) has been widely used for defect sizing and has better defect sizing capability than ultrasonic pulse echo technique if it is used properly and good signal to noise ratio is achieved. By knowing some parameters by calibration, the defect’s time-of-flight is converted to its depth below the scanning surface. The numerical values of these parameters will inevitably be subject to random measurement errors and the time-of-flight of the defect will also be subject to some random errors. All these errors in the “source” parameters will have the knock-on effect that the calculated depth or Through Wall Extent (TWE) of the defect will itself have associated random errors. Commercially available TOFD systems assume a constant probe index point for lateral wave, back wall and defect signals and a flat scanning surface. However, it is not the case resulting in systematic errors. In this study, defect sizing random and systematic errors associated with different calibration technique are assessed, improvements for surface and backwall defect sizing are proposed, and best practices have been recommended.
01 Nov 2008
TL;DR: A failure analysis of ammonia converter which suffered hydrogen attack in two years since its initial operating time was presented in this article, where the repair procedures based on the principle to decrease the residual stress then proposed.
Abstract: A failure analysis of ammonia converter which suffered hydrogen attack in two years since its initial operating time was presented. It is constructed from 2.25 Cr?1 Mo steel. Analysis showed that the failure on closing seam weld joint was due to local improper post weld heat treatment (PWHT). Improper PWHT can introduce high residual stresses in thick-walled pressure vessel. High residual stress level in weld joint is very prone to hydrogen attack for any components which are operating in hydrogen gas environment. The repair procedures based on the principle to decrease the residual stress then proposed. The repair was controlled very carefully by applying several nondestructive tests in the each stage of repair. To assure the successful of the proposed repair, after one year since repair time, high temperature ultrasonic and TOFD methods were applied on-stream to this equipment in order to evaluate its post repair condition. The two methods showed good results on the repaired area.
01 Jan 2006
TL;DR: In this paper, a Neural-Fuzzy classifier is developed to overcome the dimensionality problems associated with Fuzzy logic and to provide the training and learning ability of the neural network s which makes this classifier more powerful and reliable in clustering of each defect class.
Abstract: Ultrasonic Time-Of-Flight Diffraction (TOFD) is rapidly gaining prominence as a reliable non-destructive testing technique for weld inspection in steel structures, providing highly accurate positioning and sizing of flaws with a high probability of detection. Use of TOFD as a rapid non-destructive i nspection tool for steel plates, pipelines and vessels has grown tremendously during recent years, bringing into light the challenge of developing a fast and reliable dat a processing and interpretation platform. This paper presents several innovative procedures d eveloped and implemented to great success for the automation of the classification of weld flaws in TOFD data according to the adopted defect classification standard as an essential stage of a comprehensive TOFD inspection and interpretation aid. A Neural-Fuzzy classifier is developed to overcome the dimensionality problems associated with Fuzzy logic and to provide the training and learning ability of the neural network s which makes this classifier more powerful and reliable in clustering of each defect class. A number of advanced image processing tools have been developed to characteris e TOFD images and extract distinguishable features to be used in defect class ification. Several features have been investigated and selected, which prove to produce a good discrimination between different defect classes. Neural-Fuzzy classificati on is a powerful tool and considered as the key technology for representing knowledge of th e human experience and for constructing adaptive systems. Combining the technologies of Neural-Fuzzy classification with advanced visual scan features e nables the differentiation between different defect classes in a fully automatic and u n-supervised manner.
01 Jan 2016
TL;DR: In this paper, the authors examined the influence of symmetry and asymmetry of the distance between the transducers, the frequency and the angle of propagation of ultrasonic waves in the detection small and large discontinuities in welded joints of carbon steel.
Abstract: The Time of Flight Difraction technique ( TOFD) allows a significant simplification of standards compared to the conventional ultrasound inspection methods. Depending on the use of two transducers (transmitter/receiver) which waves propagate longitudinally, the diffraction of waves permits the characterization of internal defects more quickly and effectively. On the basis of ultrasonic signals are emitted in the longitudinal direction by a given angle, the frequency of the transducer as well as the signals propagating angle influences the sizing of defects. Starting from the use of specimens with pre-sized defects, this paper aims to examine the influence of symmetry and asymmetry of the distance between the transducers, the frequency and the angle of propagation of ultrasonic waves in the detection small and large discontinuities in welded joints of carbon steel. Experiments were carried out and analyzed using statistical techniques under conditions that minimize the measurement error. For a 3 mm defect, results in the best accuracy was obtained for a frequency of 5 MHz and 70 ° angle. On the other hand, for a defect 6 mm, the best accuracy was obtained for the frequency of 5 MHz and 45 ° angle.

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