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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.
이승석 ( Lee Seung-seok ),안봉영 ( Ahn Bong-young ) 한국구조물진단유지관리공학회 1997 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.1 No.1
Welding residual stress was measured by ultrasonic birefringence technique and Barkhausen noise method. Acoustoelastic constant was taken by averaging the values in the literatures. The EM AT transducers were used to remove couplant effect. The results show that the distribution and magnitude of welding residual stress from ultrasonic measurement and Barkhausen noise method are in good agreement with those from blind hole method.
Yunri Piao,조윤호(Younho Cho),Lianji Jin,안봉영(Bong-Young Ahn),김노유(Nohyu Kim),조승현(Seung Hyun Cho) 한국비파괴검사학회 2009 한국비파괴검사학회지 Vol.29 No.4
토모그래피는 다중 빔을 이용하여 단면을 영상화하는 기법으로서 주로 의료진단 분야에서 인체의 단면 영상획득을 위해 응용되어지는 기법이다. 비파괴검사 분야에서도 단순한 시간영역 신호의 제시에서 탈피하여 검사자에게 영상을 제공함으로써 진단의 효율성을 높이고자 하는 추세이므로 이 기법은 많은 의미를 갖는다. 최근, 유도초음파를 이용한 평판 구조물의 진단 기법이 많은 주목을 받고 있어, 본 논문에서는 컴퓨터 기반 유도초음파 해석 기법과 토모그래피 영상화 기법을 기반으로 2차원 평판에 존재하는 결함 위치를 영상화하는 연구를 수행하였다. 이를 위해 경계요소법을 이용하여 판 구조물에 존재하는 결함이 유도초음파의 전파 양상에 미치는 영향을 해석하고 그 결과를 토모그래피 영상화 기법에 적용하여 평판의 결함 위치를 판별하고자 하였다. 그 결과, 토모그래피를 위해 사용되는 센서의 개수가 결함 검출 성능에 많은 영향을 미침을 확인할 수 있다. Tomography is the imaging method of cross sectional area using multi beam signals and is mainly applied to the medical diagnosis to acquire the image of the inside human body. This method is pretty meaningful in nondestructive evaluation field since the imaging of the inspection region can enhance the comprehension of the inspector. Recently, much attention has been paid to the guided wave for the diagnosis of platelike structures. So, in this work, a study on the imaging of the damage location in a plate was carried out on the basis of computer aided analysis of guided waves and tomographic imaging. To this end, boundary element method was employed to analyze the effect of the damage in plate on the propagation of the guided waves and the analytic results were applied to the tomographic imaging method to identify the damage location. Consequently, it was shown that the number of sensors heavily affect the inspection performance of the damage location.
적외선열화상 비파괴측정에 의한 고속회전바퀴의 결함검출 기술연구
최만용(Choi, Man-Yong),김수언(Kim, Su-Un),박정학(Park, Jeong-Hak),안봉영(Ahn, Bong-young),신성용(Shin, Seong-Yong) 한국구조물진단유지관리학회 2010 한국구조물진단학회 학술발표회논문집 Vol.2010 No.2
In this study, we performed a dynamic simulation on the roller-coaster vehicle model and we determined the driving behavior. And we suggested a method of real time detection and evaluation by using the infrared thermography NDT.
조승현(Cho, Seung-Hyun),박재하(Park, Jae-Ha),안봉영(Ahn, Bong-Young),김기복(Kim, Ki-Bok) 한국소음진동공학회 2010 한국소음진동공학회 논문집 Vol.20 No.1
Micro particles in fluid can be manipulated by using ultrasonic standing wave since the ultrasound makes particles move by means of its acoustic radiation force. This work concerns the micro particle manipulation system using ultrasonic standing wave which consists of a microchannel, a reflector, and an ultrasonic transduer. In the present system, the effects of the structural elements should be carefully considered to comprehend the system and find the optimal operational condition. In this investigation, finite element analysis was employed to analyze the system. Some interesting characteristics on the reflector thickness, the channel width, and the operational frequency were observed. Several experimental results were compared with the analytic results. Consequently, this work solidifies the importance of those system parameters and reveals the possibility of various applications of the particle manipulation using ultrasonic standing wave.
이동진(Dong-Jin Lee),조윤호(Younho Cho),장강원(Kang-Won Jang),조승현(Seung-Hyun Cho),안봉영(Bong-Young Ahn) 한국비파괴검사학회 2012 한국비파괴검사학회지 Vol.32 No.1
MEMS/NEMS 구조체의 개발과 응용기술의 발달로 박판 및 박막의 기계적 물성 평가에 대한 요구가 점차 늘어나고 있다. 기계적 물성은 주로 인장시험이나 초음파의 속도 측정으로 평가되어 왔으나, 박판/박막 구조의 경우 기존의 기술로는 측정에 한계가 있어 나노압입시험법, 유도초음파법 등의 새로운 기술이 개발되고 있다. 본 연구에서는 박판 구조의 금속재료의 탄성계수를 평가하기 위하여 EMAT으로 송수신된 박판내에서의 유도초음파 진행 속도를 측정하였으며, 이론적으로 계산된 유도초음파 군속도와 실험적인 군속도의 최적화 과정을 통해 최종적으로 박판의 탄성계수를 평가하였다. 두께 50 μm의 니켈 박판에서 측정된 영률은 201.6 GPa이었으며, 나노압입시험법으로 측정된 207 GPa, 참고문헌의 203.7 GPa과 비교하면 약 3% 내에서 일치하는 결과이다. As the development of MEMS/NEMS structure and application technology the demand for an assessment of the mechanical properties have increased. The mechanical properties are mainly evaluated by using tensile test or ultrasonic wave measurement. However, the new technology have been developed such as nano-indentation, guided wave method because they have a limitation in case of a thin plate and thin film. In the study, the guided wave velocities are measured by electromagnetic-acoustic transducer(EMAT), the material properties of thin metallic foils are obtained using optimization process of the theoretical and experimental group velocity of guided wave. The Young"s modulus obtained by the optimization process(201.6 GPa), nano-indentation(207.0 GPa) and literature value(203.7 GPa) of a 50 μm thick nickel thin plate shows good agreement within 3%.
김준수(J . S . Kim),변재원(J . W . Byeon),권숙인(S . I . Kwun),이승석(Seung Seok Lee),안봉영(Bong Young Ahn) 한국열처리공학회 2001 熱處理工學會誌 Vol.14 No.1
N/A The microstructural changes with pearlite formation heat treatment in eutectoid steel(railway steel) consisting of only pearlite structure were evaluated by the ultrasonic attenuation and velocity measurements. The result of this investigation showed a strong linear dependence of ultrasonic attenuation on pearlite interlamellar spacing, and accordingly on fracture strength of the pearlite.
안봉영,김영주,김영길,이승석 한국비파괴검사학회 2000 한국비파괴검사학회지 Vol.20 No.1
석유화학 설비 등과 같은 노출 배관의 결함을 검출하는데 효율적으로 이용될 수 있는 자왜형 초음파 센서를 제작하였다. 최대의 초음파 발생 효율을 얻기 위한 최적 조건을 설정하였으며, 실험에 사용된 배관의 경우 250~350Oe의 정자기장이 최적이었으며, 180kHz의 주파수를 갖는 초음파를 발생시키기 위해서는 15mm 폭의 코일을 사용하는 것이 가장 좋았다. 최적의 조건에서 발생된 초음파는 50m 이상을 충분히 진행할 수 있으며, 결함의 단면적이 증가함에 따라 수신된 결함 신호는 직선적으로 증가함을 확인하였다. Magnetostrictive sensors which can be used effectively to detect flaws in pipe were fabricated. The optimal conditions to obtain the maximum generation efficiency of the ultrasonic wave were established. In case of the used steel pipe the optimal magnetic field was 250~350Oe and the coil width of 15mm showed the best efficiency for generating a wave with the frequency of 180 kHz. In the best condition, the wave can propagate further than 50m without serious attenuation. The amplitude of the ultrasonic wave reflected from artificial flaw had a good linear relationship to the cross-sectional area of the flaw.