ND T Abstracts Tmmvene matrix cracks in [O.9O], [O.9O]and [+-451, gmphi*e/epoxy laminatm were imsed wima 15 MHz ~ y fecused Ummdua~which was oriented at 27 from the normul to the plane of the laminate and ~ to tbe fiber din~tion of the cracimi ply. Tbe t E k s c s t m ~ sisml Iironithe micron wide oracks was two to five times m~nf~r than the beckscatm~ signal from the fil~rs. Polar tecksmner C-tc~s of the coupon shaped specimens showed the cracks clearly enough to be counted up to a crack density of 8 per centimeter. 47436 Birring, A.S.; Kawano, K. Detection of hydrogen attack in petrochemical plants Petroleum Industry Inspection Technology, Houston, Texas (United States), 20-22 Jun. 1989. pp. 91-95. ASNT (1989) Three ultrasonic techniques based on velocity change, attenuation, and back_,¢,___~=rthat can be applied to detect hydrogen I ~ t ~ are diso_,__~__= Actual hydmsun-damased samples we~ examined from vessels and piping. It was found that the ultrasm~¢ backscatter technique could detect usdy stages of hydrogen attack. 47052 Fang,J.; Bond, L.I. Reconstruction of volumetric flaws using ultrasonic backseattering d a t a colloquium on Measurements, Modelling and Imaging for NonDestructive Testing, London (United Kingdom), 27 Mar. 1991. pp. 2/I-2/4. IEE (1991) Digest No. 1991/054. We present a simple technique to extract the radii of spherical voids in sWactmulmaterials by the invecsion of Imckscattemdultrasonic sigmd using the area function formula based on the Born approximation. The Born approximation is a weak _scJ_~_~ingapproximation, however, it is shown that the technique works well for voids which are strong scattere~. 46916 Mihara,T.; Obata, M. Carburtzed case depth estimation by Rayleigh.wave backscattering Materials Evaluation, Vol. 49, No. 6, pp. 696-700 (Jun. 1991) This paper investigates the possibility of nondestructive depth estimation of carburized case by Usingultrasonic backscatte~g of Rayleigh waves in low-alloy steel. Before the experintental work. the theoretical relation betwean backJcattured Rayleigh-wave amplitude and caxbudT~ depth was investigated. These investigations depended on the simple assumption that a transmitted wave is attenuated by micrustructoral ullrason/c scattering according to a simple law of mixtures between the scattering coefficient in carborized case and that in uncarimrized base rnamiaL To confirm the reliability of the theomicul investigation, both and transmission of Raylulgh waves were measured for eight of carburized steels. Tbe~ measurements indicmd that beckscJ_~_,~dampfitude decreased according to the amount of cs~ourizing, as expected from the theoretical investigation. This relation allows
monitoringof cerburizndcase depth by Rayleigh-wavebedacatter~.
46407 Amurwabumi, K. A study of ultrasound backscatter techniques for monitoring stresses and simulated crack month opening in niuminium alloys and steel used for offshore oil platforms Ph.D. Thesis, Department of Physics, Brunel University, 194 pp. (Jni. 1989) A non-contact method of ultrasound backscat~ technique for monitoring stress and simulated crack mouth opening in uluminium ~oys and steel used for offshore oil platfomm is described. The Imckscauexsignal was rewusanted as a frequency spectrum in the frequency domain. The stress dependence of the Imckscst~ ~ is assumed to be related to the stress dependence of ultrasound attenuation due to dislocation damping. A sudden change of backscatter energy, which is considered to he linked with the onset of plastic defonnation, was observed prior to the stress reaching the ultimate tensile strength of the ulumim'umalloys. The stress at which this sudden change occurred is about 20% higbex than the elastic limit measured using a strain gauge. An ultrasound beam was directed at the Rayleigh angle, with the beam axis passing in close proximity to the crack. The backtu~___~_rechoes from the cracks were obtained by means of leaky Rayleigh wave propagation. The peak of the frequency spectrum of the bac~___~_r echoes shifted to lower freqnencies linearly with the crack mouth opening. The maximum dimmq~ency of the crack mouth opening calculated from the spectrum shift with those obtained using a strain gauge, is about 17¢£ and 70% for uluminium alloys and offshore steel respectively.
46406 MerrY, g. Nondestructive evaluation of the affect of heat treatment on subsurface measurement of chromium.nickel stainless steel ( . ~ r M A ~ 316"H) by t m r a s o n k bsckscetter M.Sc. Thetis, Department of Physics, Bnmel University, 168 pp. Oun. 1988) The use of ultrasonic b~k~__'~=r technique to monitor nondestructively the effect of heat treatment of ~ u m
nickel stainless steel
is investigated. The amplitude of 5MHz ultrasound pulse backscattered at the Raykigh angle found to vary systematically with annealing temperature but was relatively independent of the cooling history. Both grain size and hardness change dramatic~y over a smull range of annealing temperature around I050C and this sudden change in physical properties is accurately identified by corresponding pronounced changes in backscatter amplitude. The dependence of the normalised back_,c~m~_amplitude on the first power of D (grain size) rather than third power suggests attenuation mechanisms other than Rayleigh scattering, with a dependerge on d, are present. Referring to American national standard (page 109) (1987), part 3, where cold working is involved in processing prior to annealing, the minimum solution annealing tempetatme for type A240 316H must be 1900F (1840). The results obtained in the present study seem to corLqrm the above staten~nL
46124 Vergara-Dominguez,L.; Paez-Borrallo, J.M. BackscatteHng grain noise modelling in ultrasonic nondestructive testing Waves in Random Media, Vol. 1. No. 1, pp. 81-92 (1991) This paper is devoted to the modelling of the probability density and the spacetime correlation functions of the grain noise complex envelope. Assuming statistical independence between any pair of grains, we derive
analytical expcessions for the above functions. The analytical expressions are verified by means of real data measured in anstenitic stainless steel
45934 Xu, ¥.; Achenbach, J.D. Numerical analysis of scattering by interface flaws Review of Progress in Quantitative Nondestructive Evaluation, Brunswick, Maine (United S!a!e=s), 23-28 Jul. 1989. Vol. 9A, pp. 93- 100. Edited by D.O. Thompson and D.E. Chimenti. Plenum Press (1990) Scattering by inhomngeueities in homogeneous media can he analyzed in an elegant harmer by reducing the woblem statement to the solution of a system of singular in~gral equations over the surface of the scatterer. An inhomnganeity is an interface betwean two sofids of different mechanical proportins prnsents some additional complications to the numerical analyst. These complications are discussed in this paper. Specific results are presented for backscaUefingby a spherical cavity in the interface of solids of different elastic mnduli and mass densitius. 45879 Mittlemann, J.; Mohr,D.W. Correlations between micrestructure and backscattered ultrasonic energy Review of Progress in Quantitative Nondestructive Evaluation, Brunswick, Maine (United States), 23-28 Jul. 1989. Vol. 9B, pp. 1715- 1722. Edited by D.O. Thompson and D.E. Chimenti. Plenum
Press (1990) The study examines the application of ultrasonic testing to materials characterization. Correlations are established between metallurgical mictustmctore and the beckscat~ng observed when high fieqneacy ultrasonic energy interacts with crystalline grain structures during inunenion tests. Samples used were prepared through a cold-rolling and annealing process to produce surfaces with minimal defects and a wide range of grain sires within the material. A variety of signal processing techniques were used to analyze the results.
45649 Kreshna, A. A study of ultrasound backscatter techniques for monitoring
stresses and simulated crack month opening in aluminium alloys and steel used for offshore oil platforms Dissertation AbsWacts International Vol. 51, No. 5, pp. 2586-B (Nov. 1990) (BRDX90192) A non-contact method of ultrasound backscanter technique for monitoring stress and simulated crack mouth opening in uluminium alloys and steel used for offshore oil platforms is described. The beckscatier signal was represented as a frequency spectnun in the f~uoncy domain. The stress dependence of the becksc,attor unergy is assumed to he related to the s t n ~ dependence of ultrasound attenuation due to dislocation damping. The
maximum calculated value of attenuation due to the presence of dislocations N D T & E International Volume 26 Number 5 1993