• 한국추진공학회지
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• 제15권1호
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• pp.29-34
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• 2011

Hydroxyl terminated polyether(HTPE) 추진제는 전술용 모터에 현재까지도 적용되고 있는 HTPB/AP 추진제를 대체할 수 있는 추진제로서 최근에 개발되고 있다. 본 연구에서는 HTPE와 HTPB 추진제에 대한 파쇄성 시험을 수행하고 그 결과를 분석하였다. 추진제의 파쇄성은 바인더함량, 기계적 특성 및 연소속도에 의해 영향을 받았으며 연소속도가 증가할수록 기계적 인성이 낮아질수록 파쇄성은 증가하는 경향을 보였다.

• 한국압력기기공학회 논문집
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• 제11권1호
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• pp.39-44
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• 2015

The fracture toughness of 2.25Cr-1Mo cast steel (SA217-WC9) samples which were taken from the check valves of feed water piping of Korean Standard Nuclear Power Plant(KSNPP) was measured by Master Curve method. The measured $T_0$ reference temperature of SA217-WC9 steel was $-30^{\circ}C$. The obtained $T_0$ was compared to the derived value from Charpy impact test data following to SINTEP procedure. The heat-to-heat variation in fracture toughness of SA217-WC9 steel was observed. It was found that the low toughness of a heat of SA217-WC9 steel was attributed to the coarse MnS inclusion originated by high sulfur content as the results of microanalyses.

• 한국가스학회지
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• 제2권1호
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• pp.99-106
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• 1998

최근 환경오염 문제와 관련하여 청정연료로 수요가 증가하고 있는 액화천연가스(LNG)의 저장탱크 및 운반선 등 연료 저장 설비, 초전도이용 관련 기기와 같은 저온용 설비 및 기기가 증가하고 있고 대형화의 추세를 보이고 있다. 특히 액화천연가스(LNG)의 수요급증에 따라 이의 운송 및 저장에 필요한 재료의 수요가 증가하면서 극저온재료에 대한 관심이 높아지고 있다. LNG저장조의 대형화에 따라, 설계강도상의 검토는 물론, 사용재료의 특성, 가공성 및 용접 둥의 시공법을 비롯하여 품질관리 면까지 충분한 검토가 필요하다. 특히 LNG를 저장하는 내조재료에 대하여는 모재 및 용접부의 제반 특성을 파악하여 저온에서 취성파괴에 대한 안전성을 확인해 둘 필요가 있다. 본 연구는, LNG 저장 탱크의 안전성 평가시 필요한 재료물성 데이터 중 파괴인성의 측정 기반 기술을 확보하고, 현재 국내에서 사용되고 있는 LNG 저장탱크용 재질(SUS304L강, Al합금 및 $9\%$ Ni강)에 대하여 77 K 및 173 K에서 계장화 샬피충격시험을 실시하여 온도에 따른 충격파괴특성 및 파면해석을 실시하여, 안전성 평가에 필요한 기초 자료를 확보하는 것을 주목적으로 한다. 계장화샬피충격파괴시험결과, $9\%$니켈강의 경우 온도저하에 따라 77K까지는 인성의 저하정도가 적어 우수한 파괴저항을 나타내었다. 계장화 장치에 의해 얻어진 하중-처짐 곡선으로부터, 온도가 173 K에서 77 K로 저하함에 따라 최대하중은 증가하였으나 에너지는 오히려 감소하였다. 또한 균열개시에 쓰여진 에너지보다 균열진전에 쓰여진 에너지가 높게 나타났다. A5083의 경우 합금강재에 비해 충격흡수에너지값이 낮고 저온 특유의 갈라짐 현상을 볼 수 있었다. SUS304L재의 경우 균열개시에 쓰여지는 에너지가 높게 나타났고, 균열진전에 따른 에너지는 거의 나타나지 않아 균열개시 후 비교적 평탄한 파단면을 나타내는 파면관찰 결과와 일치하는 거동을 나타내었다.

• Journal of Welding and Joining
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• 제24권6호
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• pp.33-38
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• 2006

Since the 1990's, European shipbuilding industries introduced hybrid welding process in order to decrease thermal distortion of welded joints in passenger shipbuilding. In this study, we investigated effects of hybrid welding parameters on the toughness of weld metal using DH36 steel in order to obtain more sound welds in passenger shipbuilding. Type of leading process, joint gap distance and chemical composition of consumables were considerably correlated with the toughness of weld metal. Especially, the toughness was considerably increased with high-Ti containing consumables. In addition, hybrid welding speed increased by using plasma cut edges, the oxides layer of which increased absorption efficiency of laser beam.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2004년도 추계학술발표대회 개요집
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• pp.123-124
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• 2004

This study was investigated on the impact toughness and microstructure of welded metal and heat affected zone for Hi Nitrogen TiN Steel. With welding procedures, welding heat input applied were 30, 79 and 264 kJ/cm. TiN steel has shown very small prior austenite grain size for all the welding heat input applied, which was considered to result from the effect of TiN particles. In case of single SAW and EGW welding, the dilution rate of base metal into the weld was not high, resulting that there were no significant effects of base metal chemical composition on the mechanical properties of welds. However, TSAW with double Ypreparation carried very high dilution rate so that TiN steel has impaired the toughness of weld metal because N content in the weld was increased through the dilution of base metal.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2004년도 추계학술발표대회 개요집
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• pp.101-102
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• 2004

This study was investigated on the impact toughness and microstructure of welded metal and heat affected zone for B grade steel. With welding procedures, welding heat inputs applied were 30, 79 and 264 kJ/cm, Prior austenite grain size in coarse zone has increased with increasing welding heat input for B grade steel. The toughness of fusion line zone of Bgrade steel has decreased with increasing welding heat input while the toughness fusion line +3 and +5 mm zone increased contrarily.

• 한국주조공학회지
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• 제8권4호
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• pp.459-466
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• 1988

This study was carried out in the austempering temperature and time after Ni, Mo addition in purpose of modification of impact toughness of austempered ductile irons. Addition of alloy element and austempering treatment of $900^{\circ}C$ 60 minutes followed by $300^{\circ}C$, $350^{\circ}C$ and $400^{\circ}C$ for 60 minutes, in this case impact value was increased by ideal mixed structure. But impact value was decreased when holing time is 120minutes, this is attributed to segregation and carbide precipitation from high carbon austenite. Highest impact value was obtained by $350^{\circ}C$ (Mo-addition) and $400^{\circ}C$ (Ni-addition). This phenomena was caused by presence of remained austenite. At all austempering temperature,, Ni-added specimen showed higher impact values than that of Mo-added specimen. And hardness property was affected by austempering temperature and holding time rather than amounts of alloying element.

• 대한기계학회논문집A
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• 제27권6호
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• pp.987-996
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• 2003

The structural integrity of the reactor vessel with the approaching end of life must be assured for pressurized thermal shock. The regulation specifies the screening criteria for this and requires that specific analysis be performed for the reactor vessel which is anticipated to exceed the screening criteria at the end of plant life. In case the screening criteria is exceeded by the deterministic analysis, probabilistic analysis must be performed to show that failure probability Is within the limit. In this study, probabilistic fracture mechanics analysis of the reactor vessel for pressurized thermal shock is performed and the effects of residual stress and master curve on the failure probability are investigated.

• 열처리공학회지
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• 제11권1호
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• pp.62-72
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• 1998

High carbon steel is used for rails due to the excellent wear resistance, however the welding of high carbon steel is more difficult than that of mild steel owing to the high hardenability and sensitivity to cracking at the weldment. In this study, the impact toughness and cracking behavior of a rail weldment were evaluated as function of preheating temperatures. Impact toughness were more excellent in the specimen welded with preheating temperature above $250^{\circ}C$ than that below $100^{\circ}C$, and cracks were not detected in the specimen welded with preheating temperature above $250^{\circ}C$.

• 열처리공학회지
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• 제10권3호
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• pp.159-164
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• 1997

Non-alloyed and 1.0%Ni alloyed ductile cast iron were cast into the sand mold and metal mold, and finer graphite size was obtained in case of metal mold casting. Direct tempering after casting showed the slight increase of absorbed energy, which is largely due to the relieving of residual stress that is developed during casting. After austempering heat treatment, higher impact energy was obtained in case of metal mold casting than sand mold casting, which is due to the finer graphite size.