• 한국전자통신학회논문지
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• 제14권1호
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• pp.137-146
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• 2019

다수의 초음파 트랜스듀서를 이용한 초음파 위상 배열은 초점제어에 의해 인체 내 종양을 치료하는 목적 등으로 사용되고 있다. 초점제어에 의해 결정된 각 초음파 트랜스듀서 표면음압의 크기와 위상은 각 초음파 트랜스듀서에 인가되는 전압의 크기와 위상을 제어하여 구현 가능하다. 본 논문에서는 초음파 트랜스듀서의 인가전압과 표면음압 사이의 관계를 모델링하고, 요구되는 초음파 트랜스듀서의 표면음압을 생성하기 위한 인가전압을 PWM 기법으로 제어하는 방법을 제안한다. 제안한 방법의 타당성은 61개의 초음파 트랜스듀서로 구성된 초음파 위상배열의 초점제어를 예로 들어 시뮬레이션으로 검증하였다.

• 센서학회지
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• 제30권1호
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• pp.25-29
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• 2021

In this study, we successfully developed a highly reliable ultrasonic sediment sensor to detect the sediment levels in sewer pipes in harsh environments. The ultrasonic transducer employed in the ultrasonic sediment sensor was designed so as to possess a simple structure. The developed sensor was carefully optimized by simulating the electromechanical characteristics, radiated sound wave pressures, and directivity via finite element analysis. It was also designed to possess a simple mounting structure minimizing the flow disturbance in a 400-mm sewer pipe; additionally, eight ultrasonic transducers were arranged in a four-channel mode, allowing for measurement of the sediment height in five easy steps. Through experimental evaluations, we verified the performance of the ultrasonic sediment-level sensor and its industrial applicability. The results suggested that although the precision value was notably low at 15 mm, the sediment detection performance was adequate; therefore, the developed sensor can potentially be used in industrial applications.

• 한국음향학회지
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• 제23권4호
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• pp.268-273
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• 2004

본 연구에서는 원호의 내부벽면에 1열로 배열된 어레이 트랜스듀서를 이용한 반사-투과형 생체진단용 역산란 초음파 단층화상법을 제안하였다. 제안된 방법에서는 대상 물체의 배면에 반사판을 배치하여 경면효과를 이용하였고, 유한 대역을 갖는 펄스파를 송신파로 사용하여 다중 주파수 성분을 이용함으로써 데이터 관측 범위를 줄일 수 있었다. 제안된 방법의 성능 평가를 위하여 컴퓨터 시뮬레이션을 이용한 모의 생체 조직에 대한 유효성을 검토한 격과, 트랜스듀서군의 송수신 각도 범위가 30도로 극히 좁은 범위로 제한되었음에도 불구하고 정량적인 화상재현이 가능함을 확인할 수 있다.

• 수산해양기술연구
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• 제35권3호
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• pp.312-322
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• 1999

A ultrasonic transduce with a single acoustic matching layer has been designed as an attempt to increase the bandwidth of underwater transducer. The wideband resonance condition was accomplished by attaching a single matching layer on the front face of a ceramic resonator composed of a piezoelectric bar, a taper part and a head part. A modified Mason's model was used for the performance analysis and the design of transducers, and the constructed transducers were tested experimentally and numerically by changing the impedance and thickness of the matching layer in the water tank.The obtained results are summarized as follows:1. Measured resonant and antiresonant frequencies of the piezoelectric transducer with no matching layer in air were 24.7 kHz and 25.6 kHz, respectively. 2. Two resonant frequencies of the piezoelectric transducer with a single matching layer were 21.7 kHx and 26.9 kHz, respectively, in air and 21.4 kHz and 22.7 kHz, respectively, with a water load.3. Two distinct resonance peaks in the transmitting voltage response(TVR) of the developed transducer were observed at 22.0 kHz and 25.8 kHz, respectively, with center frequency of 24.0 kHz. The values of TVR at these frequencies were 130.1 dB re $1 \muPa$/V at 22.0 kHz and 128.5 dB re $1 \muPa$/V at 25.8 kHz, respectively.Reasonable agreement between the experimental results and the numerical values was achieved.

• 비파괴검사학회지
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• 제28권6호
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• pp.531-537
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• 2008

One of the fundamental features of time reversal acoustic (TRA) techniques is the ability to focus the propagating ultrasonic beam to a specific point within the test material. Therefore, it is important to understand the focusing properties of a TR device in many applications including nondestructive testing. In this paper, we employ an analytical scheme for the analysis of TR beam focusing in a homogeneous medium. More specifically, a nonparaxial multi-Gaussian beam (NMGB) model is used to simulate the focusing behavior of array transducers composed of multiple rectangular elements. The NMGB model is found to generate accurate beam fields beyond the nonparaxial region. Two different simulation cases are considered here for the focal points specified on and off from the central axis of the array transducer. The simulation results show that the focal spot size increases with increasing focal length and focal angle. Furthermore, the maximum velocity amplitude does not always coincide with the specified focal point. Simulation results for the off-axis focusing cases do demonstrate the accurate steering capability of the TR focusing.

• Journal of Mechanical Science and Technology
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• 제16권12호
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• pp.1652-1663
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• 2002

It is desirable to perform nondestructive evaluation to assess material properties and part homogeneity because manufacturing of carbon/carbon (C/C) composites requires complicated and costly processes. In this work several ultrasonic techniques were applied to carbon/carbon composites for the evaluation of spatial variations in material properties that are attributable to the manufacturing process. In a large carbon/carbon composite manufactured by chemical vapor infiltration (CVI) method, the spatial variation of ultrasonic velocity was measured and found to be consistent with the densification behavior in CVI process in order to increase the density of C/C composites. Ultrasonic velocity and attenuation depend on a density variation of materials. Low frequency through-transmission scans based on both amplitude and time-of-flight of the ultrasonic pulse were used for mapping out the material property inhomogeneity These results were compared with that obtained by dry-coupling ultrasonics. Pulse-echo C-scans was used to image near-surface material property anomalies such as the placement of spacers between disks during CVI. Also, optical micrograph had been examined on the surface of C/C composites using a destructive way.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2005년도 동계학술발표대회 논문집
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• pp.591-596
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• 2005

The objectives in the present study are to investigate that the enhancement heat transfer was experimentally measured and was compared with the acoustic pressure obtained by numerical analysis. From the results of the present study, a strong Fluid motion initiated by ultrasonic vibrations can affect heat and mass transfer. This phenomenon. called acoustic streaming, clearly observed by PIV measurement leads to increase in velocity of a Fluid which is a crucial physical concept to explain the enhancement heat transfer. The heat transfer coefficient is increased with increase in the ultrasonic intensities. The largest enhancement heat transfer (about 26%) is measured at the ultrasonic intensity of 300W. Acoustic streaming results from sudden acoustic pressure variations in the liquid. The results of numerical analysis reveal that acoustic pressure is increased by 59.5% at the ultrasonic intensity of 300W. The higher acoustic pressure near four ultrasonic transducers develops more intensive flow destroying the flow instability. Also, the profiles of acoustic pressure variation are consistent with those of enhancement heat transfer.

• 한국음향학회지
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• 제31권4호
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• pp.244-252
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• 2012

본 연구의 목적은 골절 위험도가 높은 대퇴골에서 음속 및 광대역 초음파 감쇠와 같은 음향특성과 골밀도 사이의 상관관계를 조사하는 것이다. 이를 위해 0.5 및 1.0 MHz의 중심주파수를 갖는 두 쌍의 초음파 트랜스듀서와 함께 투과법을 이용하여 생체 외 조건에서 15개의 소 대퇴골 해면질골 샘플의 음속 및 광대역 초음파 감쇠를 측정하였다. 또한 마이크로 컴퓨터 단층촬영법을 이용하여 해면질골 샘플의 단위체적당 골밀도를 측정하였다. 골밀도는 0.5 및 1.0 MHz 초음파 트랜스듀서를 이용하여 측정된 음속 및 광대역 초음파 감쇠와 모두 강한 상관관계를 나타냈으며, 골밀도와 0.5 MHz 초음파 트랜스듀서를 이용하여 측정된 광대역 초음파 감쇠 사이에 가장 높은 상관관계가 존재하였다. 이와 같은 결과는 생체 외 조건의 대퇴골에서 측정된 음향특성이 대퇴골의 골밀도를 예측하기에 충분한 지표라는 것을 의미한다.

• 비파괴검사학회지
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• 제19권5호
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• pp.363-368
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• 1999

시험체의 두께나 초음파 속도를 측정하기 위해서 초음파 펄스-에코법이 널리 사용되고 있다. 초음파 속도를 결정하기 위해서는 초음파 송수신 장치를 포함한 오실로스코우프와 같은 초음파 측정 장치를 사용하여 시험편에서의 초음파진행 시간을 측정하고, 초음파 진행 거리에 해당하는 시험편의 두께를 버어니어 캘리퍼스 또는 마이크로미터와 같은 길이측정 도구를 사용하여 측정한다. 그리고 초음파를 이용하여 시험편의 두께를 측정할 때에는 초음파 속도를 알고 있는 대비 시험편으로 기준을 설정하여야 한다. 본 연구에서는, 대비 시험편 없이 재료의 두께와 초음파 속도를 동시에 구하는 방법을 제시하였다. 재질과 두께를 달리한 여러 시험편에서 측정된 초음파 속도와 두께가 기존의 방법에 의해 측정한 값과 잘 일치하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.634-637
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• 2002

Transducer for linear ultrasonic motor with symmetric and anti-symmetric modes was studied. The transducer was composed of two Langevin-type vibrators. In order to excite two vibration modes, Two Langevin-type vibrators must have 90-degree phase difference with each other. As result, tip of transducers moves in elliptical motion. In this paper, vibration shape of transducer was simulated and The resonant frequency and maximum displacement were calculated using the FEA (Finite Element Analysis).