Real-time synthetic aperture ultrasonic scroll-imaging system and imaging experiment for nuclear power plant NDT

- N D T abstracts N D T A b s t r a c t s are c o m p i l e d b y A E A T e c h n o l o g y N a t i o n a l N D T C e n t r e , H a r w e l l , O x o n , O X 1 1 0RA, U K . T h e entries are d r a w n f r o m o v e r 500 British a n d I n t e r n a t i o n a l p u b l i c a t i o n s . E a c h issue c o n c e n t r a t e s o n o n e o r t w o s u b j e c t areas. T h e subjects c o v e r e d in p r e v i o u s issues f r o m F e b r u a r y 1992 o n w a r d s are: Acoustic e m i s s i o n monitoring of fatigue - 25(6); Acoustic techniques for adhesive bond e v a l u a t i o n - 25(2); Artificial intelligence in N D T - 25(1); C h a r a c t e r i z a t i o n of u l t r a s o n i c t r a n s d u c e r s - 25(3); M a g n e t i c flux l e a k a g e - 26(1); T h e o r y and m o d e l l i n g of r a d i o g r a p h y - 25(4); T h e r m o g r a p h y o f composites - 26(2)

Synthetic aperture signal processing 52704 Schmitz, V.; Muller, W.; Schafer, G. Synthetic aperture focussing technique: state of the art Acoustical Imaging. Vol. 19, pp. 545-551. Edited by H. Ermert and H.P. Harges. Plenum Press (1992) Starting from manual inspection the research and development during the last years lead to modern remote controlled and g-processor controlled equipments with a wide variety of implemented signal processing algorithms. This article is concentrated upon the discussion of one of these signal processing algorithms, the so-called "Synthetic Aperture Focussing Technique = SAFF'. The reason why more and more institutions enter this technique is the capability to get the highest information content on position, inclination, size and shape of single or of multiple scatterers like inclusions, voids or cracks in real industrial components. 52468 Doctor, S.R.; Hall, T.E.; Reid, L.D.; Mart, G.A. Synthetic aperture focusing technique in real-time and tandem operation for thick section steels 9th International Conference on Nondestructive Evaluation in the Nuclear Industry, Tokyo 0apan), 25-28 Apr. 1988, pp. 411-416, Edited by K. Iida, J.E. Doherty and X. Edelmann. ASM (1988) The main problem confronting wide acceptance of SAFT is the ability to perform three-dimensional processing in real time. The program at PNL has focused on this aspect and has successfully accomplished this for pulse-echo and tandem operating modes. The tandem SAFF mode was developed to provide imaging of the strongly forward scattered ultrasonic signal versus the weakly back-scattered signal reflected from vertically oriented defects. A new TSAFI'-3 mode was developed in which the transmitter and the receiver are offset5 and thus can scan past each other to produce the conjugate images needed for most accurate sizing. The performance of the TSAFT-3 mode will be described and quantified. This paper describes how a special purpose processor can be used to achieve processing rates of 10 A-scans/second or larger, and how to effectively implement the tandem mode for thick section materials.

Sumitani, H.; Ozaki, Y.; Tomoda, T.; Tanaka, M. Real.time synthetic aperture ultrasonic scroll-imaging system and imaging experiment for nuclear power plant NDT 52466

9th International Conference on Nondestructive Evaluation in the Nuclear Industry, Tokyo (Japan), 25-28 Apr. 1988, pp. 401-406. Edited by K. Iida, J.E. Doherty and X. Edelmann. ASM (1988) We developed a real-time synthetic aperture imaging system which provides a cross sectional image of an object in real-time. We have carried out imaging experiments with the angle-beam method, it was shown that there were two dominant paths for image reconstruction caused by the dimctivity of the transducer. The images were obtained to be reasonable azimuthal resolutions, from 5.0 to 6.0 ram. Each drilled hole was imaged at each true position within an accuracy of I ram. 52465 Paradis, L.; De Vadder, D.; Samain, E. Ultrasonic large aperture imaging technique 9th International Conference on Nondestructive Evaluation in the Nuclear Industry, Tokyo (Japan), 25-28 Apr. 1988, pp. 397-400. Edited by K. Iida, J.E. Doherty and X. Edelmann. ASM (1988) For the purpose of defect detection, localization and sizing with ultrasound, a large aperture imaging technique has been developed. This method combines a focused transducer as an emitter with N transducers as receivers, regularly spaced in a large aperture. A classical heamforming algorithm is then applied to the N signals in order to obtain the final high

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resolution image. We demonstrate that this configuration ensures both a high signal to noise ratio and a high lateral resolution. This method does not require complex conu'ol system or special purpose processor. 52460 Tsumura,K.; Okano, H.; Kimura, M.; lshikawa, M.; Nagase, K. Development of sophisticated ultrasonic flaw detection system using image processor 9th International Conference on Nondestructive Evaluation in the Nuclear Industry, Tokyo (Japan), 25-28 Apr. 1988. pp. 483-488. Edited by K. lida, J.E. Doherty and X. Edelmann. ASM (1988) Aiming at the development of sophisticated ultrasonic flaw detection system, an application of image processing technique is now in progress. It comprises: (1) Development of algorithm which discriminate flaw echo(flaw image) from the echo signals, applying mainly image processing technique to echo signal. (2) Development of synthetic aperture method by image processing device. 52452 Morimoto,K.; Takeuchi, I.; Miyake, Y.; Doi, T.; Matsuda, K. Development of flaw imaging system with EMAT 9th International Conference on Nondestructive Evaluation in the Nuclear Industry, Tokyo (Japan), 25-28 Apr. 1988. pp. 497-500. Edited by K. Iida, J.E. Doherty and X. Edelmann. ASM (1988) A flaw imaging system for a pipe has been successfully developed by using an electromagnetic acoustic transducer (EMAT).This system uses two small-sized 2 MHz SH wave EMATs as its ultrasonic probes. For signal processing, it employs a signal averaging method to reduce noise, and a synthetic aperture focusing method to obtain flaw cross- sectional images. The newly-developed system was tested by probing artificial flaws on the internal surface of an anstenitic stainless steel pipe. This test has showed that cross-sectional image, C scopes and three-dimensional displays of flaws are possible. 52449 Lurid,S~4.; Nielsen, E.; Kristensen, W.D. Supersaft. ultrasonic image reconstruction for fast a n d accurate flaw locating and sizing 9th International Conference on Nondestructive Evaluation in the Nuclear Industry, Tokyo (Japan), 25-28 Apr. 1988. pp. 505-508. Edited by K. Iida, J.E. Doherty and X. Edelmann. ASM (1988) A new image reconstruction method aimed at fast and accurate flaw locating and sizing analysis has been developed. The method adapts to the ultrasonic P-scan technique developed by the Danish Welding Institute. High accuracy A-scans collected from a scan line are recorded for subsequent image reconstruction with the P-scan Post Processing System. The most pertinent features of the method are high spatial resolution, wide dynamic range and short processing time. 51922 Langenberg, Kd. Elastic wave inverse scattering as applied to nondestructive evaluation Nato Advanced Research Workshop on Inverse Problems in Scattering and Imaging, Cape Cod, Massachusetts (United States), 14-19 Apr. 1991. pp. 246-267. 10pp. Publishing Ltd. (1992) USBN 0750301430 The use of elastic wave inverse scattering as a tool for nondestructive evaluation is discussed. The theoretical basis of elastic wave behaviour in