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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.
전자기법을 이용한 3Cr-lMo-0.25V 강의 물성 평가
남영현,안봉영,이승석,Nam, Young-Hyun,Ahn, Bong-Young,Lee, Seung-Seok 대한기계학회 2003 大韓機械學會論文集A Vol.27 No.2
It is advantageous to use NDE methods to assess the mechanical properties of materials since the conventional method is time-consuming and sometimes requires cutting of sample from the component. The NDE parameters such as ultrasonic velocity and attenuation, electric resistivity, and magnetic coercive force and remanance have been utilized to evaluate changes of material properties due to heat treatment condition. It has been found that changes of materials properties under quenched and tempered/PWHT treatments could not be detected using EMAT and Electrical resistivity methods. However, victors hardness and magnetic hysteresis loop decreased with heat treatment procedures. These results were obtained using 3Cr-lMo-0.25V steel. The magnetic parameters were found to be most sensitive to changes of material properties.
Barkhausen noise를 이용한 1Cr-1Mo-0.25V강의 열화도 평가
이종민,안봉영,남승훈,이승석,이억섭,남영현,Lee, Jong-Min,Ahn, Bong-Young,Nahm, Seung-Hoon,Lee, Seung-Seok,Lee, Ouk-Sub,Nam, Young-Hyun 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.7
It is inevitable to evaluate the life of turbine rotor because the operating periods of power plants need to be extended. For the test, seven kinds of specimens with different degradation levels were prepared by the isothermal heat treatment at $630^{\circ}C$. Magnetic methods utilizing Barkhausen noise coercive force($BN_c$) were applied to detect the degradation caused by thermal aging. Magnetic property of material is related with domain dynamics and that is affected by the microstructure of material. Therefore $BN_c$ is very sensitive to the microstructure change of the material. With the increase of degradation, $BN_c$ was decreased and this phenomenon is considered due to precipitations and grain size. The result was compared with Vickers hardness($H_v$) and coercive force($H_c$) to detect the relative variation, and was related with $H_v$ and YS to estimate the change of the mechanical properties with the degradation.
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.
남영현(Y. H. Nam),안봉영(B. Ahn),이승석(S. S. Lee) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
It is advantageous to use NDE methods to assess the mechanical properties of materials since the<br/> conventional method is time-consuming and sometimes requires cutting of sample from the component. The<br/> NDE parameters such as ultrasonic velocity and attenuation, electric resistivity, and magnetic coercive force<br/> and remanance have been utilized to evaluate changes of material properties due to heat treatment condition.<br/> It has been found that changes of materials properties under quenched and tempered/PWHT treatments could<br/> not be detected using EMAT and Electrical resistivity methods. However, vickers hardness and magnetic<br/> hysteresis loop decreased with heat treatment procedures. These results were obtained using 3Cr-1Mo-0.25V<br/> steel. The magnetism parameters were found to be most sensitive to changes of material properties.