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차량용 터빈 하우징의 내구시험에 의한 균열 발생 및 진행에 대한 연구
신상윤,이도훈,원순재,김동혁,예병준,Shin, Sang-Yun,Lee, Do-Hoon,Won, Soon-Jea,Kim, Dong-Hyoung,Ye, Byung-Joon 한국주조공학회 2018 한국주조공학회지 Vol.38 No.2
To improve the durability of the turbocharger, it is important to suppress cracking of the turbine housing; therefore, we investigated the initiation and growth of these cracks. First, we initiated a crack in the turbine housing using endurance experiments. After the endurance test, cracks mainly occurred in the valve seat, the nozzle area, and the scroll part of the turbine housing. The results of a fracture analysis of the cracks showed that cracks in the valve seat were initiated by fatigue fracture. This seems to be caused by the accumulation of mechanical and thermal stresses due to vibration of the turbine wheel and high-temperature exhaust gas. Also, cracks in nozzle and scroll area were initiated by intergranular corrosion due to the exhaust gas. Thus, although there are differences in the cause of initiation according to the site, a concentric waveform was observed in all fracture planes. This phenomenon indicates that cracks gradually grow due to repeated stress changes, and the main causes are the temperature difference of the exhaust gas and the vibration caused by the turbine shaft.
차수-1 신드롬 전송 방식을 적용한 이진 LDPCA 부호의 성능분석
신상윤(Sang-Yun Shin),장민(Min Jang),김상효(Sang-Hyo Kim) 한국방송·미디어공학회 2010 한국방송공학회 학술발표대회 논문집 Vol.2010 No.11
LDPCA 부호는 부호율-적응적인 특성과 함께 뛰어난 압축률을 가지고 있어 분산 소스 부호화 시스템에서 사용되는 오류정정부호로서 많이 사용되고 있다. 하지만 소스와 보조정보 사이의 상관관계가 낮은 영역에서는 급격한 성능열화가 일어나게 된다. 본 논문에서는 기존 LDPCA 부호에 특정 압축률 이상의 단계에서 추가 누적 신드롬 대신 변수노드와 일대일로 연결되어 있는 차수-1 신드롬을 전송하는 방식을 적용하여 이 영역에서 급격하게 발생하는 성능열화를 줄였다. 또한 차수-1 신드롬과 연결할 변수노드 집합을 선택할 때 복호화기에서 사용하는 LDPCA 부호의 검사노드 차수 분포를 집중시키는 알고리즘을 제안하여 성능을 더욱 향상시켰다.
Fe-0.7wt.%C-2.3wt.%Si-0.3wt.%Mn 강의 오스템퍼링 변태 거동
신상윤 ( Sang Yun Shin ),이도훈 ( Do Hoon Lee ),김서은 ( Seo Eun Kim ),예병준 ( Byung Joon Ye ) 한국주조공학회 2014 한국주조공학회지 Vol.34 No.1
The austempering transformation behavior in Fe-0.7wt.%C-2.3wt.%Si-0.3wt.%Mn steel is investigated. Each specimen was aus-tenitized for 60 min at 900℃, and austempered at 380oC for different time periods varying from 2 min to 256 min. After the austempering heat treatment, the Stage I and II evolutions are performed using optical metallography, X-ray diffraction and image analyses. Variations in the X-ray diffraction patterns and lattice parameters of the ferrite and austenite demonstrate that the residual austenite decomposes into ferrite and carbide during the Stage II evolution; moreover the amount of ferrite increases during the Stage I evolution. While the amount of austenite increases during Stage I, it dicreases during Stage II. Overall, the variations in the volume fractions of the microstructure and carbide formation in stages I and II meet high temperature austempering reaction of the ausferrite microstructure.
신상윤 ( Sang Yun Shin ),김범경 ( Beom Kyung Kim ),박병훈 ( Byung Hoon Park ),박선철 ( Seon Cheol Park ),박준철 ( Jun Chul Park ),손명균 ( Myoung Kyun Soon ),이승률 ( Seung Yul Lee ),임의 ( Eui Im ),전한호 ( Han Ho Jeon ),정경수 대한결핵 및 호흡기학회 2007 Tuberculosis and Respiratory Diseases Vol.63 No.4
Fibrosing mediastinitis is a rare disease that is characterized by the proliferation of dense fibrous tissue of the mediastinum. The pathogenesis of fibrosing mediastinitis is unknown in most cases. However, histoplasmosis, tuberculosis, autoimmune disease, radiation therapy, and other idiopathic fibroinflammatory diseases have been implicated in some cases. Most clinical features are related to an obstruction or compression of the mediastinal structure. Fibrosing mediastinitis is often progressive and occurs diffusely throughout the mediastinum. We encountered a case of fibrosing mediastinitis of a very focal lesion without evidence of mediastinal involvement. The condition was confirmed by biopsy and graft bypass surgery was performed because of SVC syndrome. (Tuberc Respir Dis 2007; 63: 387-391)
다결정 Si ingot 응고 시 도가니 열전도도 및 Ar 유입량 변화에 대한 열유체 해석
신상윤 ( Sang Yun Shin ),예병준 ( Byung Joon Ye ) 한국주조공학회 2012 한국주조공학회지 Vol.32 No.6
This study presents the results on the changes of crucible thermal conductivity and inflow of Ar, and constructed the mathematical model about heat transfer into furnace. As process variables, simulation model was designated thermal conductivity of crucible to 0.5 W M-1 K-1, 1 W m-1 K-1, 2 W m-1 K-1, 4 W m-1 K-1, and inflow rate of Ar to 15L/min, 30L/min, 60L/min. Initial condition and boundary condition were set respectively in two terms of process. Each initial conditions were set up by the preceding simulation of heat and fluid flow. The primary goal is the application of unidirectional growth of Si ingot using the result. In the result of the change of heat conductivity of crucible, the higher higher thermal conductivity of crucible shows the shorter solidification time and the bigger temperature difference. And the flow patterns are changed with the inflow rate of Ar. Finally, we found that the lower crucible`s thermal conductivity, the better crucible is at polycrystalline Si ingot growth. But in case of Ar inflow, it is hard to say about good condition. This data will be evaluated as useful reference used in allied study or process variable control of production facilities.
탄소함량 변화에 따른 오스템퍼드 Fe-2.0wt.%Si-0.3wt.%Mn 강의 기계적 성질
하종규 ( Jong Gyu Ha ),신상윤 ( Sang Yun Shin ),이도훈 ( Do Hoon Lee ),예병준 ( Byung Joon Ye ) 한국주조공학회 2015 한국주조공학회지 Vol.35 No.1
In this study, we investigated the effect of carbon on mechanical properties with different austempering conditions of high carbon(0.7~1.3wt.%C)-2.0wt.%Si steels. The specimens were austenitized at 850, 925 and 1020oC, and austempered at 260, 320 and 380oC for the various period of time from 3 min to 300 min. After heat treatment, the evolution of stage I and stage II was identified with optical microscope, XRD and hardness test. When the austempering temperature was 260oC, the microstructure consisted of the lower ausferrite while the upper ausferrite micro-structure was formed at 380oC. As the austempering temperature increases from 260 to 380oC, the tensile strength decreases and elongation increases. In addition, when carbon content increases, tensile strength and elongation decrease.