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안봉영(Bongyoung Ahn),이승석(Seung Seok Lee) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
Plastic anisotropy is one of important factors which determine the drawability of a<br/> steel sheet. It has been mainly measured by mechanical tensile test. From the<br/> ultrasonic velocities propagating along the relative directions to the rolling direction,<br/> CODF (crystallite orientation distribution function) can be measured and ODC's<br/> (orientation distribution coefficients) has some correlations with the plastic anisotropy.<br/> In this study the correlations between the plastic anisotropy and ODC's of the cold<br/> rolled steel sheet were measured. From the results of ultrasonic velocity measurements<br/> the average normal anisotropy, r and the average planar anisotropy, Δr could be<br/> predicted within the accuracy of ±0.082 and ±0.096, respectively. Acoustic resonance<br/> method was applied to measure the ultrasonic velocities and EMAT's were used for<br/> generating and detecting the ultrasonic waves.
안봉영(Bongyoung Ahn),조승현(Seung Hyun Cho),김영주(Young Joo Kim),김기복(Ki-Bok Kim) 한국비파괴검사학회 2010 한국비파괴검사학회지 Vol.30 No.4
EMAT는 비접촉식 탐촉자인 동시에 모드 선택성이 우수하여 다양한 분야에 적용되고 있으나 근본적으로 에너지 전환효율이 낮아 신호 대 잡음비의 증가에 한계를 보인다. EMAT에 위상배열 기술을 접목하면 초음파의 집속 효과를 얻을 수 있으므로 낮은 전환효율의 문제를 극복하기 위한 하나의 해결방안이 될 수 있을 것으로 판단한다. 본 연구에서는 위상배열 EMAT에 대한 기초연구로 3~4개의 코일로 구성되는 표면파 및 수직횡파 발생용 위상배열 EMAT를 제작하고 각 요소코일에 공급하는 펄스의 지연으로부터 위상배열의 효과를 확인하고 방향특성을 측정하였다. 또한 시험편의 표면에 0.5 mm 깊이의 표면결함과 시험편 내부에 직경 0.5 mm의 측면 드릴 홀을 가공하여 제작된 위상배열 EMAT로 결함 신호를 검출하였으며, 이로부터 제작된 EMAT의 성능을 평가하였다. EMAT has been applied in various fields for flaw detection and material characterization because it has noncontact property in wave generation and a good mode selectivity. Unfortunately, however, EMAT shows low signal to noise ratio relative to commercial contact transducer because of low energy conversion efficiency. If the phase matching through the control of time delay between each coil consisting of the array EMAT is accomplished, it is expected that it will be a solution for the improvement of low signal to noise ratio. In this experiment, the phased array EMATs which consists of 3 or 4 meander coils and one big magnet were fabricated for surface and vertical shear wave generation. Effect of phased delay control on signal directivity and amplitude enhancement was verified. A slit with the depth of 0.5 mm and a side-drill hole of 0.5 mm diameter were clearly detected by fabricated phased array EMATs, respectively.
도일,임현균,안봉영,지영준,이종실,오재훈,Doh, Il,Lim, Hyun Kyoon,Ahn, Bongyoung,Chee, Youngjoon,Lee, Jongshill,OH, Jae Hoon 대한의용생체공학회 2017 의공학회지 Vol.38 No.3
Blood pressure is one of the important vital signs for monitoring the medical condition of a patient. Automated NIBP(non-invasive blood pressure) monitoring devices calculate systolic and diastolic blood pressures from the oscillation in cuff pressure caused by a pulsation of an artery. To validate the NIBP devices, we developed a simulator to supply the oscillometric waveforms obtained from human subjects. The simulator provided pressure pulses to device-under-test and device readings were compared to the auscultatory references. Fully automated simulation system including OCR(optical character recognition) were developed and used for NIBP monitoring devices. The validation results using the simulator agreed well with previous clinical validation. More validation studies using the standardized oscillometric waveforms would be required for the replacement of clinical trials to validate a new automated NIBP monitoring device.
A Medical Ultrasonic Image Quantification Phantom for Measuring Thin Layer Thickness
Yong Tae Kim(김용태),Bongyoung Ahn(안봉영),Wuon-Sik Kim(김원식) 한국비파괴검사학회 2017 한국비파괴검사학회지 Vol.37 No.6
본 논문에서는 초음파 진단 영상으로 얇은 박막의 두께를 정량화하여 측정하는 방법에서 장치들을 교정하는데 필요한 팬텀을 제안하고, 검증을 위한 해석과 실험을 실시하였다. 얇은 박막 내부의 반사 중첩에 의해 검출되는 펄스의 폭이 달라지는 문제를 해결하기 위하여, 중첩된 펄스 신호의 포락선에서 일정 수준(여기서는 -20 dB)의 폭을 수치 연산하여 포락선의 폭과 박막의 두께 사이의 관계 곡선을 얻었다. 이 관계 곡선과 팬텀을 이용하면 정량화 하는 초음파 두께 영상의 보정이 가능하다. 네 개의 서로 다른 두께를 갖는 PDMS 팬텀을 제작하여 실제 펄스 에코 신호의 거동을 수치해석의 결과와 비교하였다. 그 결과 실험과 예측이 유사한 거동을 보였다. 끝으로 이 관계 곡선과 제안된 팬텀을 이용한 정량화 영상의 교정 절차를 제시하였다. In this paper, we propose a phantom for calibrating devices in a method of quantifying and measuring the thickness of a thin film with ultrasonic diagnostic images, and have conducted analysis and experiments for verification. In order to solve the problem associated with variation of the width of the superposed pulse due to internal reflection in the thin layer, the width of a certain level (here, -20 dB) in the envelope of the superposed pulse signal is numerically calculated so that the width of the envelope and the thickness. Using this relation curve and the proposed phantom, it is possible to calibrate the ultrasonic thickness image which is quantified. PDMS phantoms with four different thicknesses were fabricated, and the behavior of the actual pulse echo signal was compared with the numerical results. The experiments and predictions showed similar behavior. Finally, based on these results, we propose a calibration procedure for the quantified image using this relation curve and the proposed phantom.
김기복(Ki-Bok Kim),안봉영(Bongyoung Ahn),박해원(Haewon Park),김영주(Young-ju Kim),이승석(Seung-Seok Lee) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.8
In this study, the capacitive micromachined ultrasonic transducer (cMUT) was developed. Theoretical analysis and finite element analysis of the behavior of membrane (such as resonance frequency, membrane deflection, collapse deflection and collapse voltage) of the cMUT were performed. The design parameters of the cMUT were estimated and are the dimension and thickness of membrane, thickness of sacrificial layer, thickness and size of electrode, size of active element and so on. With the micro-fabrication process, the cMUT was fabricated on the silicon wafer. To measure the membrane displacement of cMUT, the Michelson phase modulation fiber interferometer was constructed. The measured membrane displacement was good agreed with the result of finite element analysis. To estimate the ultrasonic wave generated by the cMUT, the ultrasonic transceiver system was constructed. The developed cMUT shows a good performance and hence will be widely used to the filed of non-contact ultrasonic application.
자기센서에 의한 강재 케이블 장력측정에서 온도특성에 대한 연구
박해원 ( Haewon Park ),안봉영 ( Bongyoung Ahn ),이승석 ( Seungseok Lee ),박정학 ( Jeonghak Park ) 한국구조물진단유지관리공학회 2008 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.12 No.1
교량 지지용으로 사용되는 강재 케이블에 대한 장력측정은 교량의 안전관리에 중요한 측정항목이다. 현재 케이블에 걸린 장력을 주로 진동법으로 장력을 측정하고 있으나 측정 결과가 아직 만족스럽지 못한 상태이다. 또한 선진국에서는 자기적 방식으로 장력측정 방법을 연구하여 이에 대해 여러 가지 결과물을 제공하고 있다. 이에 우리 연구원에서도 자기적 방식에 의한 케이블 장력측정 방법을 연구하고 있으며 이에 대해 이미 논문지에 발표하였으며 자기적 장력측정 시 케이블이 온도에 따라 출력 특성이 크게 변하고 있다. 따라서 재현성이나 정밀도를 높이기 위해서는 강재 케이블의 온도에 따른 정확한 특성식을 산출하고 적용해야 한다. 따라서 금번 논문에서는 강재 케이블의 온도 특성에 대해 시험한 결과를 분석하고 평가하고자 한다. The tension measurement of steel cables that are used to support bridges is a critical element in terms of bridge safety. Today, cable tension at bridge is measured using the vibration method. However, the measurement results have yet been satisfactory. Further, many developed countries have suggested various outcomes of tension measurement through studies on the magnetic method. Our research institute is also studying the cable tensions measurement method using the magnetic sensor and has already published the findings so far as we were able to deduct that the output properties vary greatly according to the temperature of the cable when measuring its tension. Consequently, in order to improve the reproducibility or and precision, we must compute and apply exact coefficients according to steel cable temperatures. Thus, in this study, we intend to analyze and evaluate the results of the test conducted on the temperature properties of steel cables.
유원시설 와이어로프의 단면적 감소 및 국부 결함 진단용 센서 개발
김영주(Kim, Young-Joo),안봉영(Ahn, Bongyoung) 한국구조물진단유지관리학회 2010 한국구조물진단학회 학술발표회논문집 Vol.2010 No.2
This paper presents the development of a magnetic sensor for wire rope inspection. Our sensor is composed of two parts of different sensing mechanism. One part is for such local faults(LF) as wire disconnections, the other is for metallic loss of cross section areas as wire abrasion, corrosion and so on. The sensor structure was designed to be different with existing commercial systems. The LF and LMA in a test wire were detected well by the developed sensor.