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Ultrasonic turbine shaft inspection using the synthetic aperture focussing technique (SAFT)
ND T Abstracts effects of the sound field for different particle velocity distributions, the transducer is subdivided into strip-like elementary transducers. The fields of the elementary transducers are obtained by means of the impulse response method proposed by Lockwood and Willette. The errors arising due to the transducer subdivision into elementary strips are discussed. The results of numerical modelling are presented in terms of three- dimensional plots, it turned out that in the case of harmonic excitation the ultrasonic waves are effectively focussed only in one plane and spread into the perpendicular plane. The side lobes can be effectively reduced using non-uniform particle velocity distributions on the radiating surface. The results are of particular significance for acoustic imaging applications. 47942 Reibold, R.; Kazys, R. Radiation of a rectangular strip-like focussing transducer Part 2: transient excitation Ultrasonics, Vol. 30, No. 1, pp. 56-59 (1992) The transient radiation of an ultrasonic transducer intended for use in synthesized aperture focussing technique (SAFT) applications is analysed. The transducer is a narrow rectangular strip (15 x 3 ram) with a radiating surface cylindrical concave along its side length. The pulsed sound fields are calculated using the impulse response method according to Lockwood and Willette. The influence of various particle velocity distributions on the spatial-temporal structure of the sound field is evaluated as in Part 1 of this paper. The results obtained show that due to the strip-like shape of the transducer in the transient mode focussing is observed only in one plane. In the perpendicular plane the ultrasonic beams spreads, rather as it does in the case of harmonic excitation. The shortest duration of an impulse is obtained in the focal region. The spurious side lobe impulses can be suppressed effectively using a non-uniform particle velocity distribution monotonously decreasing to zero toward the rim. 47936 Muller, W.; Kreutter, T.; Thumser, D.; Schmitz, V. Ultrasonic turbine shaft inspection using the synthetic aperture focussing technique ( S A F T ) , Nuclear Engineering and Design, Vol. 130, No. 3, pp. 339-346 (1991) Ultrasonic imaging techniques developed for turbine shaft inspection result in a two-dimensional image of the defect distribution inside the specimen. It is shown, how the effect of reflectors outside of the image plane lead to misinterpretation of the reflector positions. The expansion of two-dimensional imaging technique to three-dimensions will help to overcome these problems. 47886 Behravesh, M. Application of electromagnetic acoustic transducers to coarsegrained material Electric Power Research Institute, Palo Alto, California (United States), EPRI NP-7438, Final Report, 32 pp. (Jul. 1991) Investigators conducted research to determine which ultrasonic wave mode has the lowest attenuation and the least scattering from grains at a given frequency. After determining that the shear horizontal mode met that criteria, they designed a 500-H-Iz EMAT to focus the wave into the interior of centrifugally cast stainless steel. Because EMATs require no couplant fluid, investigators demonstrated the ease of scanning over the surface of a part by using synthetic aperture focusing techniques t o enhance the detectability of small defects. Finally they conducted laboratory tests on fine-grained material to test EMAT theory and on coarse-grained material to determine EMAT effectiveness
Doctor, S.R.; Bowey, R.E.; Hutton, P.H.; Kurtz, R.I.; Schuster, G.I. 46917
Advanced NDE technologies and characterization of RPV flaw distribution Proceedings of the 18th Water Reactor Safety Information Meeting, Rockville, Maryland (United States), 22-24 Oct. 1990. NUREG/CP-0114. Vol. 3, pp. 137-155. Office of Nuclear Regulatory Commission, Washington, DC 20555 (Apr. 1991) This paper is a review of several NRC programs. The fast program involves the final stages of the development and acceptance of two advanced NDE technologies: acoustic emission (AE) for continuous monitoring of light water reactor components and synthetic aperture focusing technique for ultrasonic testing (SAFT-UT). The second program involves the development of a program for the characterization of fabrication defects in U.S. reactor pressure vessels (RPVs).
46885 Grating lobe reduction in ultrasonic synthetic focusing Electronic Letters, Vol. 27, No. 14, pp. 1225-1227 (4 Jul. 1991)
Two novel schemes of data acquisition in synthetic aperture ultrasonic imaging systems using a linear array transducer are presented to solve the troublesome grating lobe problem. Simulation and experimental results show that in both schemes the grating lobes are significantly reduced without appreciable degradation of the main lobe characteristics.
46160 Mayer, K.; Marklein, R.; Langenberg, K.I.; Kreutter, T. An ultrasonic imaging system for three-dimensional highresolution defect imaging Review of Progress in Quantitative Nondestructive Evaluation, Brunswick, Maine (United States), 23-28 Jul. 1989. Vol. 9A, pp. 967- 974. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (I990) A quantitative ultrasonic imaging system is described which utilizes a diffraction tx~nography nondestructive testing technique. This technique is known as Fourier Transform Synthetic Aperture Focusing (FT-SAFT) and uses an army processor complementary Golay sequences to improve the signal-to-noise ratio and vice deconvolution, the axial resolution. A personnel computer is used for data acquisition, storage, processing and sophisticated graphics display. 45902 MacDonald, D.E. Images of flaws in generator retaining rings using S A F T reconstruction of T O F D data Review of Progress in Quantitative Nondestructive Evaluation, Brunswick, Maine (United States), 23-28 Jul. 1989. Vol. 9A, pp. 765- 772. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1990) Retaining rings are assembles onto each end of electric generator rotors to support the rotor end-turn windings against rotational forces. These same geometric features to discriminate form real damage. The capability of SAFr processing of TOFD data to discriminate IGSCC from geometric reflectors was investigated using several retired retaining rings assembled to mandrelssimulating the generatorrotor. 45404 Hutchins, D.A.; Kramer, S.M.; Saleh, C. S A F T processing of non-contact ultrasonic N D E data IF_,BE 1989 Ultrasonics Symposium, Montreal, Quebec (Canada), 3-6 Oct. 1989 Vol. 1, pp. 661-664 Edited by B.R. McAvoy. (1989) Ultrasonic data has been obtained by scanning a pulsed laser source and EMAT detector over the surface of an aluminium sample containing artificial defects. The annular EMAT was concentric with the source to imitate pulse-echo systems. Reflected data was processed using SAFr methods, to give images of the defects. Details are given for modifications to the usual SAFr approach, to compensate for the finite EMAT aperture.
45400 Kovalev, A.V.; Kozlov, V.N.; Samokrutov, A.A.; Shevaldykin, V.G.: Yakovlev, N.N. Pulse echo in concrete monitoring: interference and spectral selection Soviet Journal of Nondestructive Testing, Vol. 26, No. 2, pp. 110-118 (Oct. 1990) The physical basis is given for focusing aperture synthesis for spatial selection of reflectors in inhomogeneous materials in ultrasonic echo monitoring. The conclusions and recommendations are based on acoustic studies on concrete as the ~nost characteristic representative of such materials. Estimates have been made on the signal/noise ratios for initial realizations in the presence of spatial correlation for the structural noise, simulation, and experiments on a visualisation system with a focusing synthetic aperture and combined probing.
45183 Silk,M.G. The capabilities and limitations of N D T : Part 5 - Ultrasonic testing special techniques British Instituteof NDT, 31 pp (1989), ISBN 0903132109 In early 1970'sthe common criticismof ultrasonics,which was voiced regularly, was of the poor accuracy of ultrasonic techniques when used to size defects. The accuracy and reliability of ultrasonic defect location and sizing has been improved substantially for the majority of inspection tasks. The initial work concentrated on improvement of the accuracy of estimating defect length or width (e.g. in C-scans), followed later by techniques to estimate defect height. Most recently the problems raised by materials characterisation" the inspection of difficult materials and the determination of stress have been considered. Some of the results of these developments in ultrasonics are described in the following sections.
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Doctor, S.R.; Bowey, R.E.; Hutton, P.H.; Kurtz, R.I.; Schuster, G.I. 46917
Advanced NDE technologies and characterization of RPV flaw distribution Proceedings of the 18th Water Reactor Safety Information Meeting, Rockville, Maryland (United States), 22-24 Oct. 1990. NUREG/CP-0114. Vol. 3, pp. 137-155. Office of Nuclear Regulatory Commission, Washington, DC 20555 (Apr. 1991) This paper is a review of several NRC programs. The fast program involves the final stages of the development and acceptance of two advanced NDE technologies: acoustic emission (AE) for continuous monitoring of light water reactor components and synthetic aperture focusing technique for ultrasonic testing (SAFT-UT). The second program involves the development of a program for the characterization of fabrication defects in U.S. reactor pressure vessels (RPVs).
46885 Grating lobe reduction in ultrasonic synthetic focusing Electronic Letters, Vol. 27, No. 14, pp. 1225-1227 (4 Jul. 1991)
Two novel schemes of data acquisition in synthetic aperture ultrasonic imaging systems using a linear array transducer are presented to solve the troublesome grating lobe problem. Simulation and experimental results show that in both schemes the grating lobes are significantly reduced without appreciable degradation of the main lobe characteristics.
46160 Mayer, K.; Marklein, R.; Langenberg, K.I.; Kreutter, T. An ultrasonic imaging system for three-dimensional highresolution defect imaging Review of Progress in Quantitative Nondestructive Evaluation, Brunswick, Maine (United States), 23-28 Jul. 1989. Vol. 9A, pp. 967- 974. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (I990) A quantitative ultrasonic imaging system is described which utilizes a diffraction tx~nography nondestructive testing technique. This technique is known as Fourier Transform Synthetic Aperture Focusing (FT-SAFT) and uses an army processor complementary Golay sequences to improve the signal-to-noise ratio and vice deconvolution, the axial resolution. A personnel computer is used for data acquisition, storage, processing and sophisticated graphics display. 45902 MacDonald, D.E. Images of flaws in generator retaining rings using S A F T reconstruction of T O F D data Review of Progress in Quantitative Nondestructive Evaluation, Brunswick, Maine (United States), 23-28 Jul. 1989. Vol. 9A, pp. 765- 772. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1990) Retaining rings are assembles onto each end of electric generator rotors to support the rotor end-turn windings against rotational forces. These same geometric features to discriminate form real damage. The capability of SAFr processing of TOFD data to discriminate IGSCC from geometric reflectors was investigated using several retired retaining rings assembled to mandrelssimulating the generatorrotor. 45404 Hutchins, D.A.; Kramer, S.M.; Saleh, C. S A F T processing of non-contact ultrasonic N D E data IF_,BE 1989 Ultrasonics Symposium, Montreal, Quebec (Canada), 3-6 Oct. 1989 Vol. 1, pp. 661-664 Edited by B.R. McAvoy. (1989) Ultrasonic data has been obtained by scanning a pulsed laser source and EMAT detector over the surface of an aluminium sample containing artificial defects. The annular EMAT was concentric with the source to imitate pulse-echo systems. Reflected data was processed using SAFr methods, to give images of the defects. Details are given for modifications to the usual SAFr approach, to compensate for the finite EMAT aperture.
45400 Kovalev, A.V.; Kozlov, V.N.; Samokrutov, A.A.; Shevaldykin, V.G.: Yakovlev, N.N. Pulse echo in concrete monitoring: interference and spectral selection Soviet Journal of Nondestructive Testing, Vol. 26, No. 2, pp. 110-118 (Oct. 1990) The physical basis is given for focusing aperture synthesis for spatial selection of reflectors in inhomogeneous materials in ultrasonic echo monitoring. The conclusions and recommendations are based on acoustic studies on concrete as the ~nost characteristic representative of such materials. Estimates have been made on the signal/noise ratios for initial realizations in the presence of spatial correlation for the structural noise, simulation, and experiments on a visualisation system with a focusing synthetic aperture and combined probing.
45183 Silk,M.G. The capabilities and limitations of N D T : Part 5 - Ultrasonic testing special techniques British Instituteof NDT, 31 pp (1989), ISBN 0903132109 In early 1970'sthe common criticismof ultrasonics,which was voiced regularly, was of the poor accuracy of ultrasonic techniques when used to size defects. The accuracy and reliability of ultrasonic defect location and sizing has been improved substantially for the majority of inspection tasks. The initial work concentrated on improvement of the accuracy of estimating defect length or width (e.g. in C-scans), followed later by techniques to estimate defect height. Most recently the problems raised by materials characterisation" the inspection of difficult materials and the determination of stress have been considered. Some of the results of these developments in ultrasonics are described in the following sections.
N D T & E International Volume 26 Number 3 1993
159