-ND T abstracts NDT Abstracts is a current awareness service compiled by the National NDT Centre, Harwell Laboratory, Didcot, Oxon, OXll 0RA, UK. The entries are drawn from over 500 British and International publications. Each issue concentrates on one or two subject areas.

The subjects covered in previous issues from February 1990 onwards are: Acoustic microscopy - February 1990; Concrete - April 1990; Eddy currents - December 1990; G a m m a tomography - June 1991; Image processing - June 1990; Magneto-acoustic emission and the Barkhausen effect - February 1991; Radiographic inspection of welds - August 1991; Ultrasonic testing of composites - August 1990; Vibration testing - April 1991; X-ray t o m o g r a p h y - October 1990

Ultrasonic and acoustic testing of concrete

48559 Muravin, G.B.; Merman, A.L; Lezvinskaya, L.M. Acoustic-emission method for estimating the fracture toughness of concrete in large-scale structures and buildings Soviet Journal o f Nondes t ruc t ive Testing, Vol. 27, No. 3, pp. 166-171 (Nov. 1991)

An acoustic-emission technique is developed for estimating the fracture toughness of materials in structures by the calibrated impact method. It is shown that the criteria K lc and J tc can be refined on the basis of data from measurements of the emission parameters. It is established that the reliability of determination of the toughness criteria of heterogeneous materials can be increased up to 30% by acoustic-emission measurements performed with longitudinal mode transducers.

48310 Ouyang, C.; Landis, E.; Shah, S.P. Damage assessment in concrete using quantitative acoustic emission Journal o f Engineer ing Mechanics , Vol. 117, No. 11, pp. 2681-2698 (Nov. 1991)

Quantitative AE techniques were applied to a laboratory study of plain concrete beams under four point loading. Center-notched and off- center-notched beams were loaded in order to produce, respectively, mode I and mixed mode failure. Using AE seismic moment tensor representation, microcracking was characterized as mode I, mode II, or mixed mode. The mode of microcracking was compared to the mode of the visible crack. Most microcrack planes were in a direction normal to the tensile stress for a mode I macrocrack (center-notched), whereas microcrack planes were relatively uniformly distributed for a mixed- mode macrocrack (off-center notched). A large number of mixed-mode microcracks were observed even for the center-notched beam indicating that fracture mechanisms of microcracks may differ from the main macromechanical crack. It is shown that AE measurements can provide a potentially powerful tool in assessing damage.

48286 Chevron Research and Technology Company; (Rutledge, J.M.) Method for cement evaluation using acoustical logs U.S. Patent No. 5 ,036 ,496 (30 Jul. 1991)

The quality of element material in the annular spaces behind casings or in wellbore liners can be measured using the method described here which produces an evaluation using acoustical log keeping. A sonic test cell is used to determine the transit time of a sound wave travelling through a specimen of the cement material. The specimen has a particular length, and is at temperature and pressure curing conditions which are found at the wellbore. Pulse velocity is determined by dividing specimen length by transit time. The slurry density of the specimen is then calculated and the mixing rate at the wellbore recorded. Thus the volume of slurry can be worked out by multiplying the time the slurry remains at that density by the mixing rate. The slurry volume's acoustic impedance is equal to the slurry density multiplied by pulse velocity. The annular displacement volume of the wellbore is determined together with map of its acoustic impedance. Casing and liner thicknesses at various locations are compared to theoretical acoustic impedance to produce a map of the attenuation rate around the wellbore. A voltage map can then be drawn up by comparing attenuation to casing diameter. This data is used to produce measures of calculated acoustic impedance which is compared to theoretical values to predict.

48109 Galan, A. Combined ultrasound methods of concrete testing Elsevier, 350 pp. (1990)

The use of ultrasonic methods for the nondestructive evaluation of concrete has many civil engineer applications. This book aims to contribute to the solution of problems encountered in testing concrete nondestructively. A discussion of new combined ultrasonic-pulse methods developed by the author is included. These methods which combine such parameters as pulse velocity in various propagation modes, elastic constants and ultrasonic attenuation are used to test concrete strength. Certain ultrasonic defectoscopy modes in concrete structure are discussed and an integral system for the quality control of concrete structures and members is proposed.

48040 Naish, C.C.; Buttle, D.; Wallace-Sims, R.; O'Brien, T.M. Acoustic monitoring for corrosion degradation in cemented waste c a n i s t e r s Depar tment o f the Envi ronment , London , (United Kingdom) . D O E - H M I P - RR- 91-024 (Sep. 1990)

This report describes work to investigate acoustic emission as a non- intrusive monitor of corrosion and degradation of cemented wasteforms where the waste is a potentially reactive metal. The acoustic data collected shows good correlation with the corrosion rate as measured by hydrogen gas evolution rates and the electrochemically measured corrosion rates post cement hardening. The technique has been shown to be sensitive in detecting stress caused by expansive corrosion product within the cemented wasteform. The attenuation of the acoustic signal by the wasteform reduced the signal received by the monitoring equipment by a factor of 10 over a distance of approximately 150-400 nun, dependent on the water level in the cement. Full size packages were successfully monitored. It is concluded that the technique offers good potential for monitoring cemented containers of the more reactive metals, for example Magnox and aluminium.

48030 Cent Rech Ind Beton. Non-destructive on-line tester for cast concrete uses continuous monitoring of propagation speed of ultrasonic signals in setting concrete, for quality control European Patent No. 448 ,896 (2 Oct. 1991)

47879 Gaydeck, P.A.; Burdekin, F.M.; Damaj, W.; John, D.G.; Payne, P.A. The propagation and attenuation of medium-frequency ultrasonic waves in concrete: a s igna l a n a l y t i c a l approach Measurement Science and Technology, Vol. 1, No. 3, pp. 126-134 (Jan. 1992)

The manner in which medium-frequency ultrasonic pulses travelling through concrete are generated, received, digitized and analysed is described. Signal analysis was performed by partitioning the signal into discrete windows in the time domain, corresponding to the emergence of individual wave phenomena within the medium. These windows were then transformed to the frequency domain for subsequent filtering and interpretation. Experimentation combined with theoretical modelling has shown that the appearance and decay of discrete frequency bands depends on both the composition of the concrete, termed the resonance phase, and its external geometry, the geometric phase.

47796 Ohtsu, M.; Shigeishi, M.; lwase, H.; Koyanagi, W. Determination of crack location, type and orientation in concrete structures by acoustic emission Magazine o f Concre te Research, Vol. 43, No. 155, pp. 127-134 (Jun. 1991)

In this Paper an advanced AE analysis procedure is proposed. In addition to crack locations, crack types and crack orientation are determined from AE relative amplitudes of the first motions. The procedure classifies cracks into tensile cracks and shear cracks. Based on information of the crack type, the crack orientation is determined; this is the direction of crack opening in the case of tensile cracks, and the direction of sliding motion in the case of shear cracks. The proposed procedure is applied to a pull-out test of an anchor-bolt from a concrete block and a cylinder-tensile test. In the pull out test the opening directions of the tensile cracks is perpendicular to the failure surface, while the directions of sliding motion of the shear cracks are parallel to the failure surface. In the cylinder-tensile test the opening directions of the tensile cracks are perpendicular to the loading direction and all sources are located near the final plane. The proposed procedure is therefore able to determine the microcrack kinematics generated in concrete.

47789 Ohtsu, M. Diagnostic applications of AE to crack inspection in concrete (In Japanese: Eng l i sh A b s t r a c t ) Journal o f the Society o f Materials Science, Japan, Vol. 40, No. 456, pp. 1191-1196 (Sep. 1991)

As a diagnostic application of the acoustic emission (AE) waveform analysis, crack inspection based on the moment tensor analysis is proposed. Because moment tensor components contain information on crack kinematics, the decomposition of eigen- values of the moment tensor is possible and the contributions of shear motion and tensile motion to crack nucleation can be determined from the ratio of eigenvalnes. Thus, cracks are classified into the type of dominant motion. After the crack types are

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determined, crack orientations can be decided from the directions of eigenvectors. The procedure developed was applied to a pull*out test of anchor bolt and a cylindrical tension test. The results confirm the applicability of the procedure to inspecting internal c r acksby the quantitative AE waveform analysis based on the moment tensor inversion.

47640 Limaye, H.S.; Krause, R.J. Nondestructive evaluation of concrete with impact-echo and pulse- velocity techniques Materia ls Evaluat ion, Vol. 49, No. 10, pp. 1312-1315 (Oct. 1991)

The paper describes the applications of two nondestructive techniques, impact echo and pulse velocity, to evaluate the condition of concrete structures. The power plant case histories describe the evaluation of a concrete foundation, a tunnel slab, and turbine pedestal columns. In the impact-echo method, the response of a concrete structure to mechanical impact is monitored and analyzed. The impact induces longitudinal, shear, and surface waves that reflect off internal discontinuities as well as the backs and sides of the concrete members. These reflections, or echoes, can be analyzed with a fast-Fourier transform (FFT) analyzer to determine the condition of the concrete. The pulse-velocity method involves measurement of transit time of an acoustic wave through a concrete structure. Significant changes in transit time are associated with the internal makeup of the structure. This method can be used to determine uniformity of concrete and to detect internal faults such as cracks, voids, or honeycombing.

47627 Gaydecki, P.A.; Burdekin, F.M.; Damaj, W.; John, D.G.; Payne, P.A. An u l t r a s o n i c i n spec t ion system capable of detecting voids and corroded steel components embedded in prestressed concrete structures Col loquium on Measurements , Model l ing and Imag ing for Non-Dest ruct ive Testing, London (United Kingdom) , 27 Mar. 1991. pp. 4/1-4/3. IEE (1991) Digest No. 1991/054

The strength of reinforced prestressed concrete structures critically dependent upon the integrity of the steel reinforcing cables. Catastrophic failure can occur in bridges for examples where cables break, corrosion occurs or defective concrete is present. This article describes an ultrasonic nondestructive inspection system which aids the location and identification of problem regions and can thus be used as a aid to bridge maintenance and repair. The system investigates changes in frequency bands as the signal travels through the concrete as these will change depending upon the size, geometry and acoustic impedance of the defect encountered.

47622 Kim, Y.H.; Lee, S.; Kim, H.C. Attenuation and dispersion of elastic waves in multi-phase m a t e r i a l s Journal o f Physics D. Appl ied Physics , Vol. 24, No. 10, pp. 1722-1728 (14 Oct. 1991)

The attenuation and dispersion of elastic waves in multi-phase materials such as granite, cement, mortar and concrete have been evaluated by the point-source/point- receiver technique with glass capillary breaking as an ideal source and a calibrated pin-type transducer as an ideal detector. The magnitude and phase spectrum from the Fourier analysis of the velocity signal gave attenuation and dispersion of the materials respectively, and the frequency dependence was also obtained in a single experiment. The sequence for attenuation was mortar, cement, granite and concrete; however, that for dispersion was cement, mortar granite and concrete in increasing order. The difference in resonant frequency spectra of mortar and concrete blocks was explained in terms of the measured attenuation and dispersion.

47524 Ohtsu, M. R a t e p roce s s a n a l y s i s of AE activity in u n i a x i a l compression test of core sample Progress in Acoust ic Emiss ion V. The 10th Internat ional Acoust ic Emiss ion Sympos ium, Sendal (Japan), 22-25 Oct. 1990. pp. 311-316. Edited by K. Yamaguchi , H. Takahashi and H. Nii tsuma. The Japanese Society for Non-Dest ruct ive Inspect ion (1990)

A rate process analysis of acoustic emission (AE) during uni-axial compression tests of core samples is proposed to evaluate the deterioration degree of concrete due to microcracking. When concrete contains a number of critical microcracks, AE events occur actively from low stress level. In contrast, AE activity of sound concrete is observed just prior to final failure. The discrepancy of AE generating behaviors is quantitatively evaluated, introducing the rate process analysis. To gauge the applicability of AE rate process analysis, experiments on newly cast concrete and core samples are performed. The correlation with the strength, the age, and the damage levels of concrete is clarified. Thus, AE rate process analysis shows a great promise for providing quantitative information on the deterioration of concrete in the uniaxial compression test of core samples.

47523 Nomura, N.; Mihashi, H.; Suzuki, A.; Izumi, M. Aspects of fracture process zone of concrete Progress in Acoust ic Emiss ion V. The 10th International Acoust ic Emiss ion Sympos ium, Sendal (Japan), 22-25 Oct. 1990. pp. 317-324. Edi ted by K. Yamaguchi , H. Takahashi and H. Nii tsuma. The Japanese Society for Non-Destruct ive Inspect ion (1990)

In this paper, three dimensional acoustic emission technique (3-D AE) is applied to observe the phase of the fracture process zone of concrete. The results show that the fracture process zone is widely created at the peak load and then the zone with active AE events moves towards the bottom of the specimen.

47522 Uomoto, T.; Kato, H. Drying shrinkage of concrete and acoustic emission Progress in Acoust ic Emiss ion V. The 10th International Acoust ic Emiss ion

Sympos ium, Sendal (Japan), 22-25 Oct. 1990. pp. 325-330. Edited by K. Yamaguchi , H. Takahashi and H. Nii tsuma. The Japanese Society for Non-Dest ruct ive Inspect ion (1990)

This paper is aimed to clarify how drying shrinkage starts through experiment, measuring both length change and acoustic emission after concrete prisms are stored in dry atmosphere. The results show that the initiation of drying shrinkage is directly after the concrete is revealed to dry atmosphere, and acoustic emission (AE) monitoring show good correlation with drying shrinkage of concrete.

47521 Niiseki, S.; Satake, M.; Gohke, M. Quick detection of alkali-aggregate reaction by AE monitoring Progress in Acoust ic Emiss ion V. The 10th International Acoust ic Emiss ion Sympos ium, Sendal (Japan), 22-25 Oct. 1990. pp. 331-336. Edi ted by K. Yamaguchi , H. Takahashi and H. Nii tsuma. The Japanese Society for Non-Dest ruct ive Inspect ion (1990)

In the early stage of alkali-aggregate reaction, the expansion pressure of reaction product is considered to give rise to microcracking and AE is extremely sensitive to microcracking in specimens. From such a point of view, in this paper, we propose a new method quickly detecting the alkali-aggregate reaction by monitoring AE in mortar-bar specimens under the same storage condition as the mortar-bar test of JASS.

47520 Muravin, G. Determination of concrete behaviour in structures on the basis of acoustic emission data Progress in Acoust ic Emiss ion V. The 10th International Acoust ic Emiss ion Sympos ium, Sendal (Japan), 22-25 Oct. 1990. pp. 337-344. Edited by K. Yamaguchi , H. Takahashi and H. Nii tsuma. The Japanese Society for Non*Destructive Inspect ion (1990)

We have studied the acoustic emission (AE) nature while concrete deformation and emission parameters are identified with the material structure state characterized by the reference point of the microcrackformation beginning, non-linear creep and develop- ment of main cracks. A method of toughness evaluation of concrete deformation by the way of its hydrodynamic or tared local shot load combined with synchronous AE measuring against microcracks formation in the fracture zone has been worked out for structural engineering exposed to dynamic and impact loads. The data is compared with AE parameters measured at the time of traditional bend test of the samples. The functional connection between mechanic and acoustic energy while concrete samples deformation, in the range of work load, microcrackformation and fracture development is proved.

47519 Yuyama, S.; Nagataki, S.; Okamoto, T.; Soga, T. Several AE sources observed during fracture of repaired reinforced concrete beams Progress in Acoust ic Emiss ion V. The 10th International Acoust ic Emiss ion Sympos ium, Sendal (Japan), 22-25 Oct. 1990. pp. 345-353. Edited by K. Yamaguchi , H. Takahashi and H. Nii tsuma. The Japanese Society for Non-Dest ruct ive Inspect ion (1990)

Bending tests were carried out on large repaired reinforced concrete beams. Fracture process was monitored by AE, visual observation and displacement measurement. It was found that distinctive AE signals were produced by the initiation of early tensile microcracks, local slips, main tensile crack and large-scale slips between the original part and the repaired part. All these different AE sources and their amplitude levels could be clearly discriminated by comparing the AE data with the results of visual observation and displacement measurement. Concrete beam integrity (CBI) ratio, the ratio of the load at onset of AE and the maximum prior load, is proposed as an effective criterion to measure the severity of damages induced in repaired concrete beams.

47484 Taylor, M.; Leaird, J.D. Acoustic emission from concrete NDE: The Next Decade and Beyond. 1990 A S N T Spring Conference, San Antonio, Texas (United States), 19-23 Mar. 1990. pp. 147-149. A S N T (1990)

Evaluation of large amounts of a concrete is obviously a major undertaking and the industry has long felt the need for an accurate in- place test for such qualities as strength and durability (against freeze-thaw, chemical attack, weathering) of concrete. There is no well established nondestructive test (NDT) for any of these qualities. This paper reports the results of three pilot investigations which indicate that acoustic emission (AE) techniques offers real promise as a NDT test for the future.

47350 Mihashi, H.; Nomura, N.; Niiseki, S. Influence of aggregate size on fracture process zone of concrete detected with three dimensional acoustic emission technique Cement and Concre te Research, Vol. 21, No. 5, pp. 737-744 (1991)

Three dimensional acoustic emission technique is applied to observe the phase of the fracture process zone of concrete which is created ahead of the crack tip and significantly influences the tension softening behaviour of concrete. The results show that the fracture process zone is already created at the peak load and then the active AE event zone moves towards the bottom of the specimen. It is also revealed that the fracture process zone may expand as the crack grows and the expanding rate of the process zone is influenced by the aggregate size.

47222 Voiczek, G. Nondestructive testing of concrete in buildings (In German: Eng l i sh Abstract) Mater ia lprufung, Vol. 33, No. 9, pp. 269-271 (1991)

The nondestructive determination of the strength of concrete in buildings becomes as precise as the destructive testing when correction factors are experimentally

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