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신경회로망을 이용한 터빈로타 디스크 키웨이의 결함 검출
이병우,이종오,윤운하,이병우,서원찬,이종규 한국비파괴검사학회 2003 한국비파괴검사학회지 Vol.23 No.1
최근 터빈 로타 디스크 키웨이에서 많은 응력부식균열이 발견되었으며, 터빈설비의 중대한 파손을 예방하기 위해 이러한 균열은 조기에 검출 및 평가되어야 한다. 본 연구에서는 초음파탐상의 RF(radio frequency) 신호를 역전파 알고리즘에 근거한 신경회로망에 적용하여 키웨이 주변의 균열에 대한 위치, 크기 및 방향성을 평가하였다. 각 반사영역에서 수신된 여러개의 피크로 나타나는 RF 신호를 각 반사영역에 대해 하나의 최대 피크를 가지도록 처리한 후, 트랜스듀서의 위치 정보와 각 반사파의 도달시간이 들어있는 주사 데이터를 작성하였다. 이 주사 데이터로부터 각 반사영역 사이의 시간차이와 트랜스듀서의 위치 정보를 신경회로망에 적용한 결과 키웨이에서 시작된 균열의 위치, 크기 및 방향성을 평가하는데 유용함을 알 수 있었다. A number of stress corrosion cracks in turbine rotor disk keyway in power plants have been found and the necessity has been raised to detect and evaluate the cracks prior to the catastrophic failure of turbine disk. By ultrasonic RF signal analysis and using a neural network based on back-propagation algorithm, we tried to evaluate the location, size and orientation of cracks around keyway. Because RF signals received from each reflector have a number of peaks, they were processed to have a single peak for each reflector. Using the processed RF signals, scan data that contain the information on the position of transducer and the arrival time of reflected waves from each reflector were obtained. The time difference between each reflector and the position of transducer extracted from the scan data were then applied to the back-propagation neural network. As a result, the neural network was found useful to evaluate the location, size and orientation of cracks initiated from keyway.
Primary Adenocarcinoma of the Rete Testis With Preceding Detection of Unilateral Hydronephrosis
이병우,박민구,조대연,박석산,여정균 대한비뇨의학회 2013 Investigative and Clinical Urology Vol.54 No.6
Primary adenocarcinoma of the rete testis is a rare malignant testicular tumor with a poor prognosis. Here we report the case of a 54-year-old man with right hydronephrosis that was detected before the diagnosis of the primary testicular lesion. During the evaluation of the right hydronephrosis by use of abdominopelvic computed tomography,a painless, hard, solid lesion was found on the right testis. The patient underwent radical orchiectomy, and the pathologic examination revealed an adenocarcinoma of the rete testis. Multiple metastases were present at the time of diagnosis. The patient received combined chemotherapy after the surgery but lived only 8 months after the initial diagnosis.
Enhancement in the thermal oxidation resistance of a Ni-Cr-base superalloy using ceramic coatings
이병우,조현,이동명,이준희,이희수,방광현 한양대학교 세라믹연구소 2007 Journal of Ceramic Processing Research Vol.8 No.6
A comparative study of the thermal oxidation behavior of a Ni-Cr-base superalloy, Inconel 617, with and without a refractory ceramic coating layer has been conducted and a significant enhancement in the thermal oxidation resistance was obtained by employing the refractory ceramic coatings. 2.5-3.0 μm thick TiAlN- or Al2O3-coated Inconel 617 samples showed much lower mass changes than bare Inconel 617 after annealing at 1000oC for up to 48 h by suppressing the inhomogeneous formation of Cr2O3 at the surface region through the reaction between oxygen and grain boundary-diffused Cr.
Thermal properties of TiAlN and Ti-Al-O coated Inconel 617
이병우,Do Wan Kim,Jong Won Choi,Kwang Hyun Bang,Gun Hwan Lee,Hyun Cho 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.6
TiAlN and Ti-Al-O thin films (~3 mm) were deposited on Inconel 617 by an arc-discharge and a RF sputtering method, respectively. The effect of the coatings on the thermal stability and wear properties of the Inconel alloy after heat treatment up to 1000 oC has been studied. The uncoated Inconel 617, heat treated at 1000 oC, showed a poor wear resistance and an inferior thermal stability due to the formation of thick corrosion scales in addition to the distinctive hill-shape crusts, which are both composed of Cr2O3 on the alloy surface. Ti-Al-O coated samples heat treated at 1000 oC also showed a poor wear resistance due to the considerable amount of Cr2O3 scale formation. It has been found that the TiAlN coating layer decomposed at 1000 oC and was oxidized into a TiO2-rich top-layer, followed by an Al2O3-rich layer between the top-layer and the alloy substrate. Since the dense protective oxide layers, which were oxidation products, prevented the formation of thick and brittle Cr2O3 scales (crusts) on the alloy surface, the TiAlN coated Inconel showed an enhanced thermal oxidation resistance and an increased wear resistance. TiAlN and Ti-Al-O thin films (~3 mm) were deposited on Inconel 617 by an arc-discharge and a RF sputtering method, respectively. The effect of the coatings on the thermal stability and wear properties of the Inconel alloy after heat treatment up to 1000 oC has been studied. The uncoated Inconel 617, heat treated at 1000 oC, showed a poor wear resistance and an inferior thermal stability due to the formation of thick corrosion scales in addition to the distinctive hill-shape crusts, which are both composed of Cr2O3 on the alloy surface. Ti-Al-O coated samples heat treated at 1000 oC also showed a poor wear resistance due to the considerable amount of Cr2O3 scale formation. It has been found that the TiAlN coating layer decomposed at 1000 oC and was oxidized into a TiO2-rich top-layer, followed by an Al2O3-rich layer between the top-layer and the alloy substrate. Since the dense protective oxide layers, which were oxidation products, prevented the formation of thick and brittle Cr2O3 scales (crusts) on the alloy surface, the TiAlN coated Inconel showed an enhanced thermal oxidation resistance and an increased wear resistance.
Evolution of High Temperature Stability of Inconel 617 by Surface Modification
이병우,Jin Hee Koo,Jong Cheon Park,조현 대한금속·재료학회 2012 METALS AND MATERIALS International Vol.18 No.4
A comparative study on the high temperature stability of bare Inconel 617 and Inconel 617 surface-modified by TiAlN overlay- and Al diffusion-coating was performed, and a remarkable improvement in high temperature stability was achieved by surface modification. Microstructural analysis revealed that the formation of brittle and unstable Cr2O3 crusts which makes Inconel 617 vulnerable at high temperatures was inhibited both by a TiO2-rich top layer with an Al-containing subsurface layer (TiAlN overlay-coated), and by an AlxNi1-x (x=0.4-0.6) alloy layer (Al diffusion-coated). Both TiAlN overlay- and Al diffusion-coated Inconel 617 also showed enhanced wear resistance before and after heat treatment at 1000 °C.