• Journal of the Korean Society for Nondestructive Testing
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• v.19 no.3
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• pp.207-216
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• 1999

A phased array is a multi-element piezoelectric device whose elements are individually excited by electric pulses at programmed delay time. One of the advantages of using phased array in nondestructive evaluation (NDE) application over conventional ultrasonic transducers is their great maneuverability of ultrasonic beam. There are some parameters such as the number and the size of the piezoelectric elements and the inter-element spacing of the elements to design phased array transducer. In this study, the characteristic of ultrasonic beam for phased array transducer due to the variation of the number of elements has been simulated for ultrasonic SH-wave on the basis of Huygen's principle. Ultrasonic beam directivity and focusing due to the change of time delay of each element were discussed due to the change of the number of piezoelectric elements. It was found that ultrasonic beam was much more spreaded and hence its sound pressure was decreased as steering angle of ultrasonic beam was increased. In addition, the ability of ultrasonic bean focusing decreased gradually with the increase of focal length at the same piezoelectric elements. However, the ability of beam focusing was improved as the number of consisting elements was increased.

• The Journal of the Acoustical Society of Korea
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• v.25 no.4
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• pp.164-171
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• 2006

If the velocities of longitudinal, transverse and leaky surface acoustic waves in an isotropic material are given, the elastic constants and density of the material can be deduced analytically. Those velocities have been measured using three ultrasonic transducers with different vibrational modes so far. In this paper a line-focusing PVDF transducer with divided electrodes was newly proposed and designed for measuring approximate velocities of the three waves. The measurement method established in this study for each waves using the transducer was applied to several isotropic materials including fused quartz. The elastic stiffness constants and densities of the materials were calculated using the measured velocities, and the accuracies were discussed. It was shown that the obtained results are in good accord with the reference values.

• The Journal of the Acoustical Society of Korea
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• v.15 no.5
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• pp.82-89
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• 1996

Application fields of ultrasonic transducers can be divided into two categories, a high ultrasonic resolution required field and a high ultrasonic power required field. This paper is aimed to determine the optimal properties of the matching layers of the transducer for each of the applications. Further, it is aimed to optimize the properties of the matching layers that show satisfactory performances for both of the application fields. Through the direct time domain analysis of the transmission and reflection behavior of the ultrasonic wave, apart from the conventional equivalent circuit analysis, and Fourier transformation of its results, we found the optimum acoustic impedances of the matching layers. The newly determined layers provide much better transducer performance-57% at most-than those obtained with conventional design methods. Based on the results, we also found the optimal acoustic impedances of the layers good for both of the application fields. For te optimization, we developed a new transducer performance evaluation parameter that can be applied to any type of ultrasonic transducers.

• Journal of the Korean Society for Nondestructive Testing
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• v.16 no.2
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• pp.95-108
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• 1996

In ultrasonic testing, flaw signal from which quantitative information on flaws is determined is influenced by 3 factors : (1) the incident wavefield.produced by the transducer, (2) the scattered waves produced by flaws, and (3) the reception of the scattered waves back at the transducer. So even small changes in transducer performance due to aging or unexpected damages can produce the changes in the characteristics of flaw signal and finally the changes in the quantitative information on flaws. Thus a reliable calibration method of transducer performance is desired. Recently, theoretical models for ultrasonic testing have been employed as reference standards for the calibration of transducers which are considered as circular planar piston sources in the most of cases. But this simplification cannot be applied to partially damaged transducer which has lost their symmetry in performance, even not in appearance. Unfortunately there has been no reliable practical model which can be used for the calibration of partially damaged transducers. Here a pulse-echo testing model for partially damaged ultrasonic transducers was developed with experimental verification. The experimental responses agree very well with the theoretical prediction. So we expect that this model can be served as a theoretical reference standards for transducer calibration.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.34 no.1
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• pp.85-95
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• 1998

The broadband ultrasonic transducers have been designed to use in obtaining the broadband echo signals from fish schools in relation to the identification of fish species. The broadening of bandwidth was achieved by attaching double acoustic matching layers on the front face of a Tonpilz transducer consisted of an aluminum head, a piezoelectric ring, a brass tail and to evaluate the performance characteristics, such as the transmitting voltage response(TVR) of transducers. The constructed transducers were tested experimentally and numerically by changing the parameters such as impedances and thicknesses of the head, tail and matching layers, in the water tank. Also, the developed transducer was excited by a chirp signal and the received chirp waveforms were analyzed. According to the measured TVR results, the available 3 dB bandwidth of the transducer with double matching layers of an $Al_O_3/epoxy$ composite of 7 mm thick and a polyurethane window of 18 mm thick was 7.3 kHz with a center frequency of 38.8 kHz, and the maximum and the minimum values of the TVR in this frequency region were 135.7 dB and 132.7 dB re $1\;{\mu}Pa/V$ at 1 m, respectively. Also, the available 3 dB bandwidth of the transducer with double matching layers of an $Al_O_3/epoxy$ composite of 11 mm thick and a polyurethane window of 15 mm thick was 6.2 kHz with a center frequency of 38.6 kHz, and the maximum TVR value in the frequency region was 136.3 dB re $1\;{\mu}Pa/V$ at 1 m. Reasonable agreement between the experimental results and the numerical results for the TVR of the developed transducers was achieved. The frequency dependant characteristics of experimentally observed chirp signals closely matched to the measured TVR results. These results suggest that there is potential for increasing the bandwidth by varying other parameters in the transducer design and the material of the acoustic matching layers.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1149-1150
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• 2013

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.05a
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• pp.258-259
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• 2010

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.42-43
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• 2011

• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.289-292
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• 1996

The 2-way beam simulation for the diagnostic ultrasound is performed with simplified computation by approximating the transducer and the system. The results show that the simulation program can be used as a good system design tool.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.265-271
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• 1997

A bond graph modeling approach which is equivalent to a finite element method is formulated in the case of the piezoelectric thickness vibrator. This formulation suggests a new definition of the generalized displacements for a continuous system as well as the piezoelectric thickness vibrator. The newly defined coordinates are illustrated to be easily interpreted physically and easily used in analysis of the system performance. Compared to the Mason equivalent circuit model, the bond graph model offers the primary advantage of physical realizability. Compared to circuit models based on standard discrete electrical elements, the main advantage of the bond graph model is a greater physical accuracy because of the use of multiport energic elements. While results are presented here for the thickness vibrator, the modeling method presented is general in scope and can be applied to arbitrary physical systems.