Examination in Relation to Structural Integrity, Davos, Switzerland, 26-27 August 1987) The results of the round robin trials conducted under the PISC I exercise (1976-1980) showed large discrepancies in the defect detection and sizing capability among different flaws. To identify the causes of such dispersions and quantify the effects, a parametric study was included in the PISC n project, taking into consideration most characteristics of planar flaws. A number of steel specimens containing various artificial defects was made available for the measurements. The defects were ultrasonically scanned by standard methods and by soma advanced techniques, the high performance of which had been established in the PlSC round rnhin tests. This paper deals with the beam focusing technique: 2 MHz, 45sup(0) shear wave transducers have been used in immersion to collect the signals generated by the reference reflectors. The results show that the depth and size of a defect do not significantly affect its detection and sizing, provided that the natural variation of sensitivity and of beam diameter along the propagation axis is taken into account. 39706 Hamilton,N. Frequency characterisation of ultrasonic t r a n s d u c e r s without a spect r u m analyser Non-Destructive Testing - Australia, Vol. 24, No. 6, p. 148 (Nov./Dec. 1987) A new instrument celled a CALPROBE is described which has been developed to provide an economical, effective and easy method for the frequency celibration of ultrasonic probes. Advantages include economy, effectiveness, versatility and accuracy. 39596 Fick,S.E.; Hsu, N3V.; Proctor, T.M. The design a n d calibration of a novel piezoelectric point contact high fidelity ultrasonic t r a n s d u c e r l l t h World Conference on Nondestructive Testing, Las Vegas, Nevada (United States), 3-8 Nov. 1985. Vol. 2, pp. 891-893. Taylor publishing Co., Dallas (1985) The successful use of a specially-designed piezoelectric transducer is reported which generates normal forces of known waveform over small well-defined areas of the surfaces of solid media. Transducer design features, previously verified in tests of the transducer as a receiver, also allow the transducer to he used as a source with performance characteristics superior to those of several other methods of transduction. A discussion follows of one of the techniques by which the tmmducer can be calibrated. 39449 Zhou Tieying; Zhang Jiajun; Xiang Dan; Du Gang. A study of b r o a d b a n d two-dimensional piezoelectric t r a n s d u c e r s International Advances in Nondestructive Testing, Vol. 13, pp. 311-324 (1987). Edited by W.J. McGonnagle. Gordon and Breach Science Publishers. A broadband longitudinal wave - transverse wave piezoelectric transducer has been developed. To fulfil the needs of two-dimensional high resolution NDT and other ultrasonic testing, based on the broadband piezoelectric longitudinal wave transducer and transverse wave transducer. Some characteristics are tested and the results am in good agreement with those from the theoretical analysis. 39269 Brunk, J.A. Performance comparisons of dry coupling with conventional contact ultrasonic transducers, 0.5 - 20 MHz Proceedings of the 16th Symposium on Nondestructive Evaluation, San Antonio, Texas (United States), 21-23 Apr. 1987. pp. 53-62. Nondestructive Testing Information Analysis Center, Texas, USA. Dry coupling (self-coupling) piezoelectric transducers were developed for applications where no liquid could be allowed to contact the test object. Their performance exceeded expectations, and so the use of dry coupling for a wide variety of applicetions was investigated. Initial evaluations led to design changes which improved performance with all types of test objects. Dry coupling is now being used for a diverse assortment of material characterization, flaw detection, and thickness gaging applications. Comparisons of four types of transducers are given: longitudinal wave and zero degree incidence shear wave (direct contact and delay line), dual element, and angle beam. These cover the frequency range 0.5 -20 MHz. The specific examples include some where dry coupling gives quite superior performance, some where there is no significant difference, and others where dry coupling degrades resolution or signal-to-noise ratio. 38714 Kimura, K.: Ohigashi, H. Analysis of impulse response characteristics of polymer ultrasonic transducers Japanese Journal of Applied Physics, Vol. 27, No. 4, pp. 540-546 (Apr. 1988) The impulse response characteristics of polymer ultrasonic transducers were analyzed using the Mason's equivalent circuit. These characteristics strongly depend on material factors of the piezoelectric polymer, the dielectric and mechanical internal loss factors, the electmmechanical couplingfactor and the acoustic impedance. Based on the analytical results, we evaluated the piezoelectric polymers that are presently available as transducing materials. The analytical results were verified experimentally using transducara composed of poly(vinylidene-fiuoride) film and vinylidene fluoride and trifluoroethykna copolymer film. 38710 Ohigashi, H.; Itoh, T.; Kimura, K.; Nakanishi, T.; Suzuki, M. Analysis of frequency response characteristics of polymer ultrasonic transducers
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Japanese Journal of Applied Physics, Vol. 27, No. 3, pp. 354-360 (Mar. 1988) Piezoelectric polymers have large dielectric and mechanical intemal losses. In this study, we introduced internal losses into Mason's equivalent circuit, and analyzed the effects of these losses on the transducer response, mainly in the frequency domain. To prove the validity of the theoretical analysis, we fabricated polymer transducers of several backing load types which are effective for practical use, using vinylidene fluoride and trifluoroethylene copolymer films, and evaluated their frequency and impulse response. The experimental results are in good agreement with the theoretical prediction. We conclude that a consideration of the internal losses is esseotial for the proper design and con-ect evaluation of polymer transducers. 38479 Kojima, T. A ~ v i e w of piezoelectric materials for ultrasonic t r a n s d u c e r s Ultrasonics International 87, Conference Proceedings, London (United Kingdom), 6-9 Jul. 1987. pp. 888-895. Butterworth and Co. (Publishers) Ltd., Guildford, Surrey (1987) Piezoelectric materials of the present state-of-the-art for ultrasonic transducers are classified into seven groups. Each group was reviewed on the relationships between the basic properties of transducer and the intrinsic properties of piezoelectric material and they were discussed through the characteristics obtained with 5 MHz disk transducers of 15 mm in diameter built of the representative materials in the groups, and it is found that the piezoelectric ceramic composite materials will give very much variety in transducer designing. 38471
Kramer,S.M.; Hutchins, D.A.; Mair, H.D.
Use of plane and edge wave components to characterize PVDF transducers Ultrasonics International 87, Conference Proceedings, London (United Kingdom), 6-9 Jul. 1987. pp. 838-843. Butterworth and Co. (Publishers) Ltd., Guildford, Surrey (1987) The transient pressure fields of ultrasonic transducers may be described in terms of plane and edge wave contributions. Based on this concept, a technique is developed which allows characterization of transducers via a single measurement close to the transducer face. This method is examined experimentally for pVDF transducers. 38467 Rodriguez-Corral,G.; San Emeterio, J.L.; Gallego-Juarez, J,4. Focused high-power ultrasonic t r a n s d u c e r with stepped-plate radiator for industrial application in gases Ultrasonics International 87, Conference Proceedings, London (United Kingdom), 6-9 Jul. 1987. pp. 794-799. Butterworth and Co. (Publishers) Ltd., Guildford, Surrey (1987) Flexural axisymmetric vibrating plates with an extensive surface area and stepped profile have shown to be very useful high-power ultrasonic radiators. The stepped profile of these plates provided, together with a rather uniform distribution of displacement, a highly-directional radiation. In addition, if the profile of the non-stepped face is modified, by shifting adequately the different internedal zones, a remarkable focusing effect can be obtained. This paper deals with the characteristics and performance of a high-power transducer constructed with this new stepped-fucused radiator vibrating with seven nodal circles. A similar transducer, but with the previously studied stepped- directional radiator, is also presented. 38442 Gallego-Juarez,J.A.; Sarabia, E.R-.F.; Ramos-Fernandez, A. Performance of ultrasonic composite t r a n s d u c e r s m a d e from scribed. fractured piezoelectric ceramics Ultrasonics International 87, Conference Proceedings, London (United Kingdom), 6-9 Jul. 1987. pp. 471-476. Butterworth and Co. (publishers) Ltd., Guiidford, Surrey (1987) Piezoelectric composites (PZT/polymer) with 1-3 connectivity are well suited to medical ultrasound transducers in the low megahertz range. This paper deals with the characteristics and performance of a new type of composite transducer based on scrihed-fractured piezoelectric ceramics. Results show the good sensitivity and short impulse response of the constructed prototypes. 38433 Sachse, W. T r a n s d u c e r considerations for point-source/point-receiver materials measurements Ultrasonics International 87, Conference Proceedings, London (United Kingdom), 6-9 Jul. 1987. pp. 419-425. Butterworth and Co. (publishers) Ltd., Guildford, Surrey (1987) This paper reviews the requirements and operational characteristics of several sources and receivers which can he used as the basis of a point-source/point-receiver (PS/PR) materials testing system. Considered are sources and receivers whose temporal and spatial characteristics most nearly approximate those needed for making PS/PR measurements directly. Consideration is also given to means for utilizing non-ideal transducers, that is, those whose temporal response is bandllmited or which are not operating as a force source, or as a velocity or displacement receiver and those whose aperture is t-mite. 38360 Hu, J.K.; Zhang, Q.L.; Hutchins, D.A. Directional characteristics of electromagnetic acoustic t r a n s d u c e r s Ultrasonics, Vol.26, No.l, pp. 5-13 (Jan. 1988) The directivity patterns of a wide range of electromagnetic acoustic transducers (EMATs) have been determined experimentally using a second coil EMAT as the detector around a cylindrical surface. A qualitative comparison to theory is presented. together with a discussion of the generation mechanismsinvolved. In addition, the use of a dipolar shear wave EMAT detector with a pulsed laser source is presented and some applications are discussed.