scispace - formally typeset
Search or ask a question
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.


Papers
More filters
Proceedings ArticleDOI
25 Jul 2013
TL;DR: Analysis of the restored image indicate that the Symlets family with the suitable thresholding has Higher Peak Signal to Noise Ratio(PSNR) value than the Coiflets wavelet family.
Abstract: Time-of-Flight Diffraction (TOFD) is an advanced ultrasonic inspection technique best suited for inspection especially inservice wherein the focus is on detection of cracks and linear indications which can propagate during service. The technique is widely used in process industries and also in strategic sector like nuclear. In the case of ISI in nuclear industry, the main difficulties likely to arise during such inspection are the high temperature (during shut down) and the background radiation. With the advent of high temperature probes, this limitation can be overcome. However, a fundamental factor which still is a cause for concern is the degradation of the signal to noise ratio due to thermal noise. Experiments conducted by the authors reveal that the contrast of acquired TOFD Images reduces progressively with increasing temperatures. As the temperature increases beyond 373K, the noise makes interpretation of images difficult and thus possibility of linear defects getting missed out arise. It is well known that the wavelets can be effectively employed for denoising. Wavelets have also been applied in general for denoising UT signals. However, its application for UT signals from stainless steel and which is at high temperature has not been attempted so far. In this paper, we explore the innovative application of wavelet thresholding for denoising applications due to its greater flexibility. Analysis of the restored image indicate that the Symlets family with the suitable thresholding has Higher Peak Signal to Noise Ratio(PSNR) value than the Coiflets wavelet family.

2 citations

Proceedings ArticleDOI
01 Jan 2010
TL;DR: In this article, a coupling focusing ultrasonic technique is used for testing PE butt fusion joints, which has a good testing ability for defects of typical lack of fusion, gas holes with 1mm in diameter and crack with 1 mm in height.
Abstract: The butt fusion process is a widely used method for connecting Polyethylene (PE) pipes. Conventional ultrasonic test is unable to detect defects due to heavy ultrasonic attenuation, disturbance by the structure of the joint, and the weak acoustic response caused by lack of fusion. A new technique named coupling focusing ultrasonic technique used for testing PE butt fusion joints is developed in this paper. The key of the technique is to get a special couplant, which is a mixture of glycerinum, sodium silicate, water, and defoamer, with almost the same sound velocity and acoustic impedance of PE. Through the couplant, sound beam is converged by spherical lens, entering the PE material with focusing zone overlapping the fusion area of the joint. It is proved that the technique has a good testing ability for defects of typical lack of fusion, gas holes with 1mm in diameter and crack with 1mm in height, based on the results of detection experiments of test sample accompanied with typical defect. It is also proved that its sensitivity is better than TOFD technique and traditional contact angle wave ultrasonic technique as well.Copyright © 2010 by ASME

2 citations

Journal Article
TL;DR: In this paper, the results for detectability and depth sizing using phased array ultrasonic technique for thick body were compared with those of conventional TOFD technique for various types of defects.
Abstract: The techniques in order to measure the depth of defect in weldment and structure accurately have been developed. Many researches have made efforts to develop the methods for the accurate depth sizing of defect. TOFD is known as the most accurate method of various methods for measuring depth sizing. However, there is a possibility to miss defects because of the limitation of beam coverage for the ultrasound incident angle. In this study, the results for detectability and depth sizing using phased array ultrasonic technique for thick body were compared with those of conventional TOFD technique. It was experimentally confirmed that the phased array ultrasonic TOFD technique gives good detectability and accurate depth measurement for the various types of defects. The phased array ultrasonic TOFD technique developed in this study will contribute to increase the inspection reliability in thick component such as the pressure vessel of power generation industry.

2 citations

01 Mar 1989
TL;DR: In this article, the accuracy of several ultrasonic flaw sizing techniques was measured using thick-walled mock-ups simulating typical reactor pressure vessel weld and clad configurations, which contained intentional flaws representing three major classes of defects: cracks under the cladding, embedded defects in welds, and lack-of-fusion defects in nozzle-to-shell welds.
Abstract: The accuracy of several ultrasonic flaw sizing techniques was measured using thick-walled mock-ups simulating typical reactor pressure vessel weld and clad configurations. The evaluated techniques were: backward-scattering tip-diffraction, time-of-flight diffraction (TOFD), dB-drop (with three different amplitude thresholds), and large-diameter focused probes. For the amplitude-based dB-drop technique, amplitude thresholds of 6 dB below peak, 50 percent DAC, and 20 percent DAC were used, and the effect of correcting for the spreading of the ultrasonic beam was also evaluated. The mock-ups contained intentional flaws representing three major classes of defects: cracks under the cladding, embedded defects in welds, and lack-of-fusion defects in nozzle-to-shell welds. Approximately 200 measurements were made. The results showed that for sizing near-surface and embedded defects in thick welds, TOFD and the backward-scattering tip-diffraction techniques were far more accurate than the amplitude-based techniques. Beam-spread corrections reduced the mean sizing errors for the 20 percent DAC sizing method, but made negligible reduction in the scatter of the data. Even after beam-spread corrections were made, the sizing errors of the amplitude-based method remained much greater than the tip-diffraction measurement error. For small-bore nozzles, focused probe measurements were substantially more accurate than unfocused probe measurements. 21 refs., 43 figs., 2 tabs.

2 citations


Network Information
Related Topics (5)
Fracture mechanics
58.3K papers, 1.3M citations
67% related
Welding
206.5K papers, 1.1M citations
67% related
Alloy
171.8K papers, 1.7M citations
67% related
Microstructure
148.6K papers, 2.2M citations
66% related
Ultimate tensile strength
129.2K papers, 2.1M citations
65% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202110
202017
201919
201823
201724
201624