• Journal of the Korean Society for Nondestructive Testing
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• 제22권6호
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• pp.621-626
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• 2002

The amplitude of a back-wall echo depends on the reflection coefficient of the interface between a transducer and a test material when using contact pulse-echo ultrasonic testing. A couplant is used to transmit ultrasonic energy across the interface, but has an influence on the amplitude of the pulse-echo signal. To investigate the couplant effect on pulse-echo ultrasonic testing, back-wall echoes are measured by using various couplants made of water and glycerine in a carbon and austenitic stainless steel specimens. The amplitude of the first back-wall echo and the apparent attenuation coefficient increases with the acoustic impedance of the couplant. The couplant having a higher value of the transmission coefficient is more effective for flaw detection. The reflection coefficient should be known in order to measure the attenuation coefficient of the test material.

• Composites Research
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• 제29권5호
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• pp.288-292
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• 2016

In this paper, a novel ultrasonic propagation imaging system, called a full-field pulse-echo ultrasonic propagation imaging (FF PE UPI) system is introduced. The system nondestructively inspected targets with two-axis translation stage. The coincident laser beams for ultrasonic sensing and generation are scanned and pulse-echo mode laser ultrasounds are captured. This procedure makes it possible to generate full-field ultrasound in through-the-thickness direction as large as the scan area. Structural inspection results in the form of full-field ultrasonic wave propagation videos are introduced, which are painted sandwich control surfaces. In addition, the inspection results of FF PE UPI system are compared with conventional ultrasonic testing methods such as waterjet and portable C-scan.

• Proceedings of the KSMRM Conference
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• 대한자기공명의과학회 1997년도 춘계학술대회 초록집
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• pp.27-36
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• 1997

• Journal of the Korean Society of Fisheries and Ocean Technology
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• 제26권1호
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• pp.51-56
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• 1990

The authors carried out an experiment to investigate the echo fluctuations from ocean bottom due to ship's motion. The bottom echoes was continuously measured, by using a 50 kHz Echo sounder on board of the ship being at anchor under the sea condition of 15 knots in wind velocity and approximately 2 meters in wave height, to extract the information about the pulse stretching and the ship's motion from the first return and the second return. A data acquisition system was used to record digitally the envelope of the echoes, and the analysis was applied to the echo data collected from the continental shelf in the South China Sea. The results obtained can be summarized as follows: 1. The equivalent pulse width of the second return echoes from ocean bottom was 2.4 times longer than that of the first return echoes. 2. The echo peak values of the first return fluctuated markedly than that of the second return and was shown to be extremely sensitive to small change in ship's motion. 3. Energy target strength and peak target strength of the sandy-mud bottom were -13.4 dB and -14.6 dB, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 1995년도 추계학술대회 논문집
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• pp.205-208
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• 1995

PZT powders were prepared by the molten salt synthesis method. The porous PZT specimens were prepared from a mixture of PZT and Polyvinylalcohol(PVA) powders by BURPS(Burnout Plastic Sphere) technique. The pulse-echo response of PZT-polymer 3-3 type composite transducer with various PVA wt.% were studied, The fall time of pulse-echo response of PZT-polymer 3-3 type composite transducer was shorten to that of solid PZT-maded transducer. Therefore, a good transmitting and receiving properties could be obtained. The distance between transducer and reflector was in good agreement both solid PZT and PZT-polymer 3-3 type composite fabricated transducer.

• Proceedings of the Korean Society For Composite Materials Conference
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• 한국복합재료학회 1999년도 추계학술발표대회 논문집
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• pp.1-4
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• 1999

The attenuation coefficients of SiC particle reinforced low-density polyethylene (LDPE) matrix composites were measured by pulse echo method and dynamic elastic measure method with varying the volume fraction of SiC particle ranged from 0% to 40% and the size of SiC particles ranged from 0.8$\mu$m to 48$\mu$m. The SiCp/LDPE composites were fabricated with the melt injection process and the fabricated composites showed almost full density above 99% up to 40vo1% SiCp reinforcements. The attenuation constant of LDPE measured by dynamic elastic constant had same result with that measured by pulse echo method, but the attenuation constant of SiCp/LDPE measured by dynamic elastic constant did not have same result with that measured by pulse echo method.

• Proceedings of the KIEE Conference
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• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
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• pp.358-360
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• 1995

PZT powders were prepared by the molten salt synthesis method. The porous PZT specimens were prepared from a mixture of PZT and polyvinylalcohol(PVA) powders by BURPS(Burnout Plastic Sphere) technique. The pulse-echo response of porous PZT transducer with various PVA wt.% were studied. The fall time of pulse-echo response of porous PZT transducer was shorten to that of solid PZT-maded transducer. Therefore, a good transmitting and receiving properties could be obtained. The distance between transducer and reflector was in good agreement both solid PZT and porous PZT fabricated transducer.

• Electrical & Electronic Materials
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• 제8권2호
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• pp.211-216
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• 1995

In this study, the piezoelectric ceramics/polymer composite transducers with 1-3 connectivity have been studied. A piezoelectric ceramics PZT prepared by Wet-Dry Combination method was used as a filler in polymer matrix Eccogel. We've got the pulse-echo response for 1-3 type piezc-electric composite transducers in water. It was shown that the transmitting and receiving sensitivity of 1-3 type piezoelectric composite transducers could be improved in comparison with that- of solid PZT transducers. The reason is for that 1-3 type Piezoelectric composites have low dielectric constant and density. There was in a good agreement between the resonant frequencies calculated from one period and observed results on the Ultrasonic Transducer Analyzer. According to these results we could be figured out the distance in water by virture of the pulse-echo response.

• Proceedings of the KIEE Conference
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• 대한전기학회 1994년도 하계학술대회 논문집 C
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• pp.1403-1405
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• 1994

In this study, the piezoelectric transducers with 1-3 connectivity have maded. A piezoelectric ceramic PZT prepared by Wet-Dry Combination method is used as a filler in Eccogel polymer matrix. The pulse-echo response for 1-3 type composite transducers were carried out in water. It was observed that the transmitting and receiving sensitivity of 1-3 type composite transducers were improved in comparison with that or solid PZT transducer. The reason is for that 1-3 composites have a hish piezoelectric voltage coefficients, The period of pulse-echo response for the transducer is in a good agreement with the resonant frequency of self-maded composite transducer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.303-306
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• 1999

In this study, the piezoelectric ceramics PZT powder was synthesized by Wet-Dry combination method. The flexible 1-3-0 type composites were fabricated with piezoceramic PZT and Eccogel polymer matrix embedded 3rd phase. This paper represents the acoustic properties with various 3rd phase wt.%. The acoustic impedance of 1-3-0 type composites was lower than that of single phase PZT ceramics. The pulse-echo response of transducer fabricated with 1-3-0 type composites was better than solid PZT transducer.