ND T Abstracts

44730 Badalyan, V.G. Coherent imaging methods in ultrasonic defectoscopy (review) Industrial Laboratory, Vol. 55, No. 1 I, pp. 1290-1299, (May 1990)

In the last 15 years, methods for visualization of defects have become increasingly widely used in the area of ultrasonic nondestructive monitoring, in this case, information about the defect is represented on the monitor as a visual form, using which we can judge the type, dimensions. shape, and coordinates of the defects.

44695 van der Wal, L.F.; Lorenz, M.; Berkhout, Ad. A unified approach towards inverse problems in ultrasonic NDT Proceedings of the IUTAM Symposium on Elastic Waves and Ultrasonic Nondestructive Evaluation, University of Colorado, Boulder, Colorado (United States), 30 Jul. - 3 Aug. 1989. pp. 151-156 Edited by S.K. Datta, J.D. Achenbach and Y.S. Rajapakse. North - Holland, (1990). ISBN 0 444 874 852

At the end of 1988 a research project was started to develop an applicable, high-resolution imaging method for ultrasonic NDT, based on the synthetic aperture focusing technique. This project is initiated by the TNO Institute of Applied Physics and two major companies in The Netherlands. In this paper our proposed approach and the underlying acoustical theory are presented.

44682 Langenberg, Kd.; Kreutter, T.; Mayer, K.; Fellinger, P. Inverse scattering and imaging Proceedings of the IUTAM Symposium on Elastic Waves and Ultrasonic Nondestructive Evaluation, University of Colorado, Boulder, Colorado (United States), 30 Jul. - 3 Aug. 1989. pp. 93-98 Edited by S.K. Datta, J.D. Achenbach and Y.S. Rajapakse. North - Holland, (1990). ISBN 0 444 874 852

Following the guidelines of a recently developed unified theory of scalar inverse scattering within the lin~'izing Born or Kirchhoff approximations - we extent its basic ideas to elastic wave inverse scattering, especially for the case of a scatterer with stress-free boundaries being illuminated by a plane pressure or shear wave. Two inversion schemes, both yielding the same result, i.e. the "visible" part of the singular function of the ~.atteriog surface, are proposed: far-field inversion, provided the data are collected in the remote region of the defect, or, far-field inversion combined with a near- field far-field transformation of the measured data for the case of defects closed to a measurement surface. Our algorithms are checked against simulations and discussed as elastodynamic extensions of the scalar SAFr-algorithm in terms of a mode-matched SAFr.

44666 Mayer, K.; Marklein, R.; Langenberg, KJ.; Kreutter, T. Three-dimensional imaging system based on Fourier t ransform synthetic aper ture focusing technique Ultrasonics, Vol. 28, No. 4, pp. 241-255 (Jul. 1990)

For planar scan surfaces, digitized ultrasonic RF-data can be adequately processed in terms of the Fourier transform synthetic aperture focusing technique algorithm, i.e. in terms of synthetic aperture pulse-echo backpropagation utilizing Fourier transforms only, to yield a quantitative three-dimeusional image of defects residing in the homogeneous and isotropic bulk material. The implementation of this algorithm into an ultrasonic imaging system is described, which mainly comprises an array processor and high-resolution graphics to display the three-dimensional reconstruction volume as a walk-throngh along three orthogonal planes.

A.A.A.93 Kramer, S.L. Imaging defects with laser ul t rasound Nondestructive Testing and Evaluation, Vol. 5, No. 2-3, pp. 85-96 (1990)

A pulsed laser ultrasonic source and an electromagnetic acoustic (EMAT) detector have been used to produce images of artificial defects in aluminium samples. Three different imaging techniques have been investigated: reflection tomography, the synthetic aperture focusing technique (SAFT) and transmission tomography.

44387 Doctor, S.R.; Deffenbaugh, J.D.; Good, M.S.; Green, E.R.; Heasler, P.G.; Reid, L.D.; Simonen, F.A.; Spanner, J.C.; Taylor, T.T.; Vo. T.V. NDE refiability and SAFT-UT final development Nuclear Engineering and Design, Vol. 118, No. 3, pp. 359-374 (1990)

The Evaluation and Improvement of NDE Reliability for Inservic¢ Inspection of Light Water Reactors (NDE Reliability) program at the Pacific Northwest Laboratory (PNL) was established by the US Nuclear Regulatory Commission (NRC) to determine the reliability of current inservice

inspection (ISI) techniques and to develop recommendations that will ensure a suitably high inspection reliability. This is a progress report covering the programmatic work from October 1987 through September 1988. The program for Validation and Technology Transfer for SAFT-UT is designed to accomplish the final step of moving research results into beneficial application. Accomplishments for FY99 in Synthetic Aperture Focusing of Ultrasonic Test data (SAFT-UT) under this program are discussed in this paper.

43902 Kramer, S. Ultrasonic weld defect using the synthetic aper ture focusing technique Proceedings of the 15th Annual Review of Progress in Quantitative Nondestructive Evaluation, La Jolla, California (USA), 31 Jul. - 5 Aug. 1988. Vol. 8B, pp. 1995-2002. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1989). ISBN 0-306-43209-9.

The synthetic aperture focusing technique (SAFT) has been shown to increase lateral resolution of appropriately acquired B-scan images. The requirements of very accm-ate transducer po6ition information and well understood divergent ultrasonic beam can make it difficult to incorporate into conventional inspections or to use it on previously acquired data. By using a reference reflector and an echo locus matching procedure it is possible to ease the latter requirement so that data acquired using conventional focused or flat transducers can be enhanced using the SAFT process.

43356 Li, Y.; Newhouse, V.L.; Shankar, P.M.; Karpur, P. Speckle reduction in ultrasonic SAFT images in coarse grained material through split spectrum p r o c c ~ n g Review of Progress in Quantitative Nondestructive Evaluation, Vol. 8A. Edited by D.C. Thompson and D.E. Chimenti, pp. 727-734. Plenum Press (1989), ISBN 0 306 43209 9

SAFr has been used for the flue grained materials ultrasonic evaluation with excellent results. However, use of SAFT in coarse grained material results in an image which suffers from ultrasonic speckle. The presence of speckle reduces the detectability of targets. This problem is also encountered in ultrasonic A-scan and B-scan coarse grained material testing. Speckle is actually an interference pattern due to the presence of grain noise in each raw A-line signal.

42644 Aidridge, E.E.; Hawker, B.M. Shaping the insonifying pulse to optimise B-scans obtained in austenite United Kingdom Atomic Energy Authority, Harwell, AERE- R--13518, 35pp. (May 1989)

This study examines the dependence of inspection capability for coarse- grained equiaxed cast anstenitic steel on the total transfer function of the ultrasonic system and describes work done to ~,4~pt an inspection system to give it a we-defined idealised transfer function.

42609 Melton, R.B. Knowledged based systems in nondestructive evaluation Signal Processing and Pattern Recognition in Nondestructive Evaluation of Materials, Proceedings of the NATO Advanced Research Workshop, Lac Beauport, Quebec (Canada) 19-22 Aug. 1987, pp. 199-204 Springer Vedag, Berlin Heidelberg (1988)

This paper discusses the application of knowledge based systems technology to problems in nondestructive evaluation (NDE). The Saft Image Interpretation Assistant (SIIA) is used an illustrative example. SIIA is a prototype knowledge based system designed to assist in making the operation of the Synthetic Aperture Focusing Technique (SAFT) Ultrasonic Inspection System more reliable and efficient. The first section of the paper describes the structure of the SAFi" inspection problem. The next section discusses three forms of knowledge: procedural, structural, and inferential as they relate to the SAFT problem. The final section discusses the implications of this type of system in other NDE techniques and applications.

42396 Ozaki, Y.: Sumitani, H. Method for imaging cross section of object by ul t rasound using synthetic aperture technique Journal of the Atomic Energy Society of Japan, Vol. 31, No. 8, pp. 60-71 (Aug. 1989)

The synthetic aperture imaging technique has recently become popular in the field of non-destructive testing (NDT), but its image reconstruction process takes a time too long to be applied practically. We have developed a real-time ulU'asonic imaging system based on the synthetic aperture focusing technique (SAFr). The system provides a cross-sectional image as a

160 N D T & E In te rna t iona l V o l u m e 26 Number 3 1993