• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.36 no.1
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• pp.1-11
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• 2000

A low frequency, high power hydroacoustic transducer with 7 tonpilz piston elements assembled in a circular array suitable for marine application, such as the transmission of underwater information and the development of new fisheries resources in the deep sea zone was designed. A modified Mason's model was applied to monitor and to simulate the transducer behavior at each step during the fabrication. The in air, and in water constructed tonpilz transducer was tested experimentally and numerically by changing the size and the type of the material for head, tail and acoustic window. Also, the developed transducer was excited by pulse signals and the received waveform was analyzed. The resonance peaks in the transmitting voltage response(TVR) of a single tonpilz element without housing were observed at 11.33kHz in air and 10.93kHz in air and 10.93 kHz in water, respectively, with the overall electrical-acoustic efficiency of 43.7%. The value of TVR of single tonpilz element with aluminum housing in water was 129.87dB re 1 $\mu$Pa/V at 12.25 kHz with the frequency bandwith of 2.15 kHz and half beam angle of 30.2$^{\circ}$at -3dB.The resonance peaks in the transmitting voltage response of the 7 element circular transducer were observed at 11.50 kHz in air and 11.45 kHz in water, respectively. The value of TVR in water 144.84 dB re 1$\mu$Pa/V at 11.5kHz with the frequency bandwith of 4.25 kHz and the half beam angle of $22.3^{\circ} $ at -3dB.Reasonable agreement between the experimental measurements and the theoretical predictions for the directivity patterns, TVRs and the impedance characteristics of the designed transducer was achieved.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.5
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• pp.475-479
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• 2003

Traditional ultrasonic evaluation to detect micro/small surface cracks is the pulse-echo technique using the normal immersion transducer with high frequency, or the angle beam transducer with surface wave. It is difficult to make the automatic ultrasonic system that is to detect micro and small surface crack and position on the large structure like steel and ceramic rolls, because of the huge data of inspection and the ambiguous position data of transducer. The aim of this study using the high precision scanning acoustic microscope with 10MHz large aperture transducer was to display the real time A, B, C-scan for the automatic ultrasonic system in order to detect the existence and position of surface crack. The ultrasonic method with large aperture transducer was improved the scanning time and speed over 10times faster than traditional methods.

• Smart Structures and Systems
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• v.4 no.3
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• pp.291-304
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• 2008

Piezoelectric materials have been widely used in ultrasonic nondestructive testing (NDT). PZT ceramics can be used to receive and generate surface acoustic waves. It is a common application to attach PZT transducers to the surface of structures for detecting cracks in nondestructive testing. However, not until recently have piezoelectric polymers attracted more and more attention to be the material for interdigitated (IDT) surface and guided-wave transducers. In this paper, an interdigitated gold-on-polyvinylidene fluoride (PVDF) transducer for actuating and sensing Lamb waves has been introduced. A specific etching technology is employed for making the surface electrodes into a certain finger pattern, the spacings of which yield different single mode responses of Lamb waves. Experiments have been performed on steel and carbon fiber composite plates. Results from PVDF IDT sensors have been compared with those from PZT transducers for verification.

• The Journal of the Acoustical Society of Korea
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• v.16 no.2E
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• pp.21-26
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• 1997

We propose to use transverse waves instead of longitudinal waves in a scanning tomographic acoustic microscope (STAM) and new type of multiple-transducer with the functions of muliple-angle and multiple-frequency tomography. Proposed multiple-transducer scheme has three insonification angles and three resonance frequencies in order to operate in the transverse wave mode and multiple-angle and multiple frequency tomography for the STAM. In order to evaluate the performance of proposed transducer scheme we have simulated tomographic reconstruction with back-and-forth propagation(BFP) algorithm. Simulation results showed proposed multiple-transducer scheme is capable of obtaining good resolution with transverse wave mode and multiple-frequency tomography. It is also showed that proposed scheme is an efficient rotation scheme by proportion to the number of projections.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.9
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• pp.532-538
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• 2016

In this paper, a underwater acoustic Tonpilz transducer with the piezoelectric single crystal(72PMN-28PT) is developed. The thickness and the number of piezoelectric elements are theoretically designed with the equivalent circuit analysis to have the desired resonance frequency. In order to compare the performances, a piezoelectric ceramic transducer is also manufactured and their electrical impedance, TVR (transmitting voltage response), RVS (receiving voltage response) and beam pattern are compared.

• Journal of the Korean Society for Heat Treatment
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• v.32 no.3
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• pp.118-123
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• 2019

The aim of this study investigates the feasibility of scanning acoustic microscope (SAM) with high frequency transducer for material degradation. The test specimen was prepared by artificial heat treatment of Co-base superalloy. The high frequency 200 MHz acoustic lens was used to generate the leaky surface acoustic wave (LSAW) on the test specimens. The matrix precipitates coarsened with thermal aging time, and then grow up to several tens of micrometers. The velocity of LSAW decreased with increasing aging time. Also, it has a good correlation between LSAW and hardness. Consequently, V(z) curve methods of SAM using high frequency transducer is useful tool to evaluate the heat treatment effects on microstructure.

• The Journal of the Acoustical Society of Korea
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• v.28 no.4
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• pp.363-369
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• 2009

In this paper, an estimation method is presented to determine the equivalent circuit model of an underwater acoustic piezoelectric transducer with multiple resonant modes. A fitness function that includes the coupled resonant effects is proposed to minimize an error between the measured impedance of the transducer and the calculated impedance of the equivalent model. Unknown parameters of the equivalent circuit are estimated by using PSO algorithm. The proposed method is applied to an example transducer of the sandwich type with 3 resonances in the frequency band of interest. The analytical impedance of the estimated equivalent circuit model is compared with the measured impedance of the transducer and the validity of proposed method is verified.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.1
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• pp.1-6
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• 2012

This study is damage evaluation for CNG fuel tank during the burst test through the analysis of acoustic emission signals. Kaiser effect until the pressure 420 bar appears, but More than 420 bar by the creep effect appears significantly damaged vessels, and 480 bar pressure, the Kaiser effect of the rising phase was missing. Resonant transducer at 540 bar than 480 bar decreased activity such as energy and count Continually, but increased wideband transducer. In addition, through the rise time or frequency analysis of composite pressure vessels in order to observe the damage mechanisms wideband transducer is more effective than resonant transducer.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.2
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• pp.944-951
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• 2011

This paper reports results of a joint experimental and numerical investigation of the causes of near-transducer errors due to the combined effect of acoustic and ADCP-induced flow disturbance near the ADCP transducer. The laboratory study focused on an isolated ADCP (deployment without boat). Measurements of the flow disturbance produced by the ADCP in vertical and horizontal planes were obtained acquiring measurements with an Acoustic Doppler Velocimeter (ADV). Concurrent measurements with ADCP and ADV were made to infer additional near-transducer effects in the ADCP measurements. The numerical investigation was designed to extend the inquiry on the near-transducer potential errors when the ADCP is deployed from a boat. Large Eddy Simulation (LES) was conducted to obtain the extent and magnitude of the disturbances induced by the drag acting on a boat-mounted ADCP and by the blockage effect of the instrument and boat. It is found the velocities measured by the ADCP are biased low and differ substantially from the undisturbed channel flow solution within a limited layer beneath the instrument.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.370.2-370
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• 2002

Magnetostrictive materials are used low-frequency sonar transmitter instead of piezoelectric materials. But it is difficult to analyze due to the nonlinearity and hysteresis of magnetostrictive materials. This paper deals with the program development based on finite element method to model the magnetostrictive tonpilz transducers and to analyze their acoustic characteristics. (omitted)