• 소성∙가공
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• 제13권5호
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• pp.455-460
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• 2004

The deformation and annealing behaviors of a 1050 Al alloy deformed at cryogenic temperature were investigated, focusing on the evolution of microstructures and mechanical properties. Especially, the effects of annealing temperature, $150~300^{\circ}C$, on microstructures and mechanical properties of the sheets received reduction of 88% at cryogenic temperature were investigated. The significant change in mechanical properties with the annealing temperatures of $200~300^{\circ}C$ would be attributed to the variations in the volume fraction of recrystallized grains and coarse equiaxed grains.

• Tribology and Lubricants
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• 제27권1호
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• pp.25-33
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• 2011

Rolling contact ball bearings are utilized almost exclusively for liquid propellant rocket engine turbopump. Turbopump ball bearings are required to endure high speed and high load for a poor lubricated condition in cryogenic environment. To evaluate bearing heat generation performance, friction torque is investigated as a function of rotation speed, bearing load and cooling flow rate through an experimental study using water coolants. Radial and axial loads are simultaneously applied to the test bearing by gas pressurized cylinder rod. Endurance performance of bearing has been also verified under the bearing required load for operating condition during total accumulated test time 2,100 sec.

• 소성∙가공
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• 제18권6호
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• pp.471-475
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• 2009

The effect of prior microstructures on mechanical properties in low carbon steels were examined by comparing the behavior of cementite and mechanical properties of cryo-rolled and subsequently annealed steels. Prior microstructures consisted of ferrite + pearlite, banite or martensite. Steels, consisting of bainitic microstructure, exhibited the better combination of strength - ductility than steels with other prior microstructures, such as ferrite + pearlite and martensite.

• 반도체디스플레이기술학회지
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• 제7권4호
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• pp.29-33
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• 2008

Rapid increase of integrity for recent semiconductor industry highly demands the development of removal technology of contaminated particles in the scale of a few microns or even smaller. It is known that the surface cleaning technology using $CO_2$ snow has its own merits of high efficiency. However, the detailed removal mechanism of particles using this technology is not yet fully understood due to the lack of sophisticated research endeavors. The detachment mechanism of particles from the substrates is known to be belonged in four types; rebounding, sliding, rolling and lifting. In this study, a modeling effort is performed to explain the detachment mechanism of a contaminant particle due to the rebounding caused by the vertical collision of the $CO_2$ snow. The Hertz and Johnson-Kendall-Roberts(JKR) theories are employed to describe the contact, adhesion and deformation mechanisms of the particles on a substrate. Numerical simulations are followed for several representative cases, which provide the perspective views on the dynamic characteristics of the particles as functions of the material properties and the initial inter-particle collision velocity.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제29회 추계학술대회논문집
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• pp.114-118
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• 2007

본 연구는 30ton급 액체로켓엔진 지상연소시험용 연소기의 설계 및 제작에 관한 것이다. 본 연소기는 연소압력이 60 bar, 노즐 확대비가 12이며, 헤드부와 연소실부가 용접되는 일체형 재생냉각형 연소기이다. 헤드부는 저온에서 기계적 특성이 좋은 STS316L을 사용하였다. 연소실부는 실린더부, 노즐목부, 1차 노즐부, 2차 노즐부로 구성되어 있다. 연소실부의 내피 재질은 동합금 /STS319J1/STS316L, 외피 재질은 STS329J1을 사용하였다. 선반, 밀링, MCT, 롤링 및 프레싱 등의 기계적 가공을 통하여 단품들을 완성하였다. 이러한 각 단품들을 조립하여 일반 용접 및 전자빔 용접, 브레이징 등을 적용하여 일체형으로 접합하였다.