• Korean Chemical Engineering Research
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• 제49권2호
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• pp.206-210
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• 2011

다양한 방식의 등통로각압축공정으로 생분해성 고분자인 폴리젖산수지 시편을 가공하여 각 공정 방식에 따른 시편들의 열 및 기계적 물성의 변화를 조사하였다. 각각 A, BC, C 세 가지의 시편 재 주입 방식과 1, 2, 4의 가공 횟수를 조합한 7개의 시편들을 제작하고, 각 시편의 녹는점, 열분해온도와 같은 열물성을 시차주사열량분석기와 열무게분석기를 사용하여 측정하였다. 시편의 응력변형의 변화를 경도 시험기를 사용하여 측정하고, 각 시편 절단면의 내부 미세구조를 주사전자현미경을 사용하여 관찰하였다. 관찰된 내부 미세구조는 경도시험결과를 설명하는데 정성적인 뒷받침이 되었다. 그 결과 PLA-P2A의 내부 미세 구조가 가장 치밀하고 촘촘히 겹쳐져 있음으로 인하여 내부 응력변형도 가장 많이 관찰되었다.

• 마이크로전자및패키징학회지
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• 제10권2호
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• pp.55-59
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• 2003

본 연구에서는 RF-Magnetron 스퍼터링 장치를 이용하여 $Al_xTa_{1-x}$(x=0.0∼1.0) 합금박막을 성장하였고, 4탐침법, XRD, AFM, micro-Vickers 미소경도계를 사용하여 시료의 구조적, 기계적, 전기적 특성을 분석하였다. Al조성 x=0.245(Al 24.5 at.%)에서 전기저항이 가장 높게 나타났고, 결정질이 가장 우수하였다. 표면 hillock에 있어서는 낮은 Al 조성영 역에서는 x가 증가할수록 hillock이 감소하다가, x=0.245에서 hillock이 완전히 배제되었고, 이후 x 증가에 따라 hillock 밀도가 다시 급격히 증가하였다. 미소경도의 경우, Al조성 x=0.2∼0.45의 영역에서 가장 높은 경도값이 측정되었다. 본 연구의 모든 결과를 종합적으로 고려할 때, $Al_xTa_{1-x}$ 합금박막의 결정질, 전기저항, 표면형상, 미소경도는 상호 밀접한 관계를 가지고 있었으며, Al 조성 x=0.245에서 가장 우수한 물리적 특성이 나타났다.

• 한국표면공학회지
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• 제36권5호
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• pp.357-363
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• 2003

The aim of this work is the synthesis of a-C:H films from methane gas using surface spark discharge at the atmospheric pressure. Properties of these films have been investigated as functions of energy W delivered per a methane molecule in the discharge. The method enables the coatings to be deposited with high growth rates (up to $100 \mu\textrm{m}$/hour) onto large-area substrates. It is shown that the films consist of spherical granules with diameter of 20∼50 nm formed in the spark channel and then deposited onto the substrate. The best film characteristics such as minimum hydrogen-to-carbon atoms ratio H/C=0.69, maximum hardness $H_{v}$ =3 ㎬, the most dense packing of the granules and highest scratch resistance has been obtained under the condition of highest energy W of 40 eV. The deposited a-C:H coatings were found to be more soft and hydrogenated compared to the diamond-like hydrogenated (a-C:H) films which obtained by traditional plasmaenhanced chemical vapor deposition methods at low pressure (＜10 Torr). Nevertheless, these coatings can be potentially used for scratch protection of soft plastic materials since they are of an order harder than plastics but still transparent (the absorption coefficient is about $10^4$∼$10^{5}$ $m^{-1}$ At the same time the proposed method for fast deposition of a-C:H films makes this process less expensive compared to the conventional techniques. This advantage can widen the application field of. these films substantially.y.

• 한국재료학회지
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• 제10권7호
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• pp.493-498
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• 2000

7050 AI합금을 RRA 처리하였을 때 경도, 전기전도도 및 미세조직의 변화를 조사하였다. 120도씨에서 24시간 동안 1차 시효처리한 후 175도씨에서 2차 퇴화처리하였을 때 경도값의 변화는 초기에 감소하다가 피크 경도를 보인 다음 다시 감소하였으며, 3차 재시효처리재가 2차 시효처리재 보다 큰 경도값을 나타내었다. 2차 퇴화처리시 초기 경도 감소는 T6의 주 강화상인 GP zone의 부분적인 분해에 의한 것이며, 3차 재시효 처리하였을 때 강화상은 GP zone과 파이상이었다. 120도씨에서 24시간 동안 1차 시효처리한 후 175도씨에서 2차 퇴화처리하였을 때 전기전도도 변화는 퇴화 쵤부터 연속적으로 증가혀였으며, 3차 재시효처리에 의해 2차 퇴화처리시 보다 %IACS가 0.5 ~ 2.7 증가하였다. 3단시효에 의해 T6정도의 강도를 유지하면서 38%IACS값 이상의 전기전도도를 얻을 수 있는 최적 퇴화처리 조건은 $175^{\circ}C$ 50분이었다. 이는 퇴화처리 경도곡선의 극소점 또는 극대점과 무관하며 오히려 약간 과시효 조건이다.

• Journal of Welding and Joining
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• 제28권3호
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• pp.92-98
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• 2010

Ferritic stainless steels, which have relatively small thermal expansion coefficient and excellent corrosion resistance, are increasingly being used in vehicle manufacturing, in order to increase the lifetime of exhaust manifold parts. But, there are limits on use because of the problem related to cosmetic resistance, corrosions of condensation and high temperature salt etc. So, Aluminum-coated stainless steel instead of ferritic stainless steel are utilized in these parts due to the improved properties. In this investigation, Al-8wt% Si alloy coated 409L ferritic stainless steel was used as the base metal during Gas Tungsten Arc(GTA) welding. The effects of coated layer on the microstructure and hardness were investigated. Full penetration was obtained, when the welding current was higher than 90A and the welding speed was lower than 0.52m/min. Grain size was the largest in fusion zone and decreased from near HAZ to base metal. As welding speed increased, grain size of fusion zone decreased, and there was no big change in HAZ. Hardness had a peak value in the fusion zone and decreased from the bond line to the base metal. The highest hardness in the fusion zone resulted from the fine re-precipitation of the coarse TiN and Ti(C, N) existed in the base metal during melting and solidification process and the presence of fine $Al_2O_3$ and $SiO_2$ formed by the migration of the elements, Al and Si, from the melted coating layer into the fusion zone.

• 동력기계공학회지
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• 제5권1호
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• pp.97-103
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• 2001

The present study was investigated changes of precipitation behaviour of laves phase in ferrite single phase and ferrite-martensite dual phase and the mechanical properties of 10%Cr ferritic alloys. In the ferrite phase, laves phase was mainly precipitated, whereas in the martensite phase, carbide was preferentially formed during the initial stage of aging and with increasing aging time. Laves phase and carbide were simultaneously precipitated by precipitation of laves phase at around carbide. Strength and toughness were lowered by the disk-type precipitator in the initial stage of aging and toughness was recovered with increasing of aging time and then, decreasing by precipitation of laves phase.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2007년 추계학술발표대회 개요집
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• pp.328-331
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• 2007

It was carried out to evaluate microstructure and mechanical properties of friction stir welded(FSW) on magnesium alloys. Two types magnesium alloy was used in this work, AZ31 wrought and AZ91 cast magnesium alloy. Microstructure near the weld zone showed general weld structures such as stir zone(SZ), thermo-mechanically affected zone(TMAZ) and heat affected zone(HAZ). In the AZ91 alloy, the SZ had a fine grain size and $\beta$ phase particles which were well distributed in matrix. It was characterized to redistribute by partial or full re-solution of the $\beta$ phase which is coarse in base metal during FSW processing. The hardness of the SZ slightly increase than the base metal in AZ31 Mg alloy.

• 자동차안전학회지
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• 제5권2호
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• pp.5-10
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• 2013

The pole side crash caused fatal injury by comparison with other crash impact mode such as frontal and rear crash. EuroNCAP proposed the pole side crash test using WorldSID(World Side Impact Dummy). The objective of this study is to develop the pole side impact sled test using dummy rib deflection between crash and sled test. In the pursuit of this purpose, we fabricated new pole side sled buck and test preliminary pole sled using ES-2re. Through this, we found the sled acceleration pulse scale. Hardness and thickness of the EPP affects the rib deflection. We conducted the pole sled test using WorldSID based on the preliminary results. As a result, rib deflection was shown to correlate well between crash test and pole side sled test.

• 한국식품영양과학회지
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• 제41권8호
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• pp.1151-1157
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• 2012

인삼의 소비촉진과 국민의 건강 증진을 목적으로 인삼을 수삼과 홍삼액의 형태로 첨가하여 인삼 밥을 취반한 후 기호도, 물성 및 사포닌과 유리아미노산의 함량을 분석하였다. 전반적으로 기호도가 가장 좋은 인삼 밥은 마쇄기로 거칠게 간 형태(GRG)의 수삼을 원료 쌀의 10%를 첨가하여 취반한 인삼 밥이었고, 조직감과 밥맛에 대한 기호도는 홍삼액(RGE)을 50% 첨가하였을 때이었다. 인삼 밥의 물성은 쌀알 크기의 1~2배 정도로 잘게 다진 형태의(MRG)의 수삼을 첨가할 경우 10% 이상 첨가 시부터는 hardness와 adhesiveness가 감소하였으며, 홍삼액 형태(RGE)로 밥물 대신 첨가하여 취반하였을 경우는 첨가량이 많아질수록 hardness는 증가하였으며 adhesiveness는 감소하였다. 믹서로 갈은 슬러지 형태의 수삼(GRG)과 잘게 다진 형태(MRG)의 수삼을 첨가하여 인삼 밥을 취반할 경우 취반과정 중 사포닌구조의 변화가 일어나 수삼에서 검출되어진 Re를 포함한 8종의 진세노사이드성분의 함량이 감소되고 홍삼특유의 사포닌인 Rg3, Rh2 및 Rh1 등의 사포닌이 생성되었다. 총 유리아미노산 함량은 수삼 및 홍삼액 모두 첨가량이 증가할수록 인삼밥의 총 유리아미노산 함량이 증가되었다.

• Journal of Advanced Marine Engineering and Technology
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• 제33권1호
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• pp.104-111
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• 2009

This paper shows the behaviors of macro- and micro-structures and mechanical properties for specimen's welding region welded by FSW. according to welding conditions with 5mm thickness aluminum 5083O alloy plate. It apparently results in defect-free weld zone in case traverse speed was changed to 32 mm/min under conditions of anti-clockwise direction and tool rotation speed such as 800 and 1250 rpm with tool's pin diameter of 5 ${\Phi}mm$ and shoulder diameter of 20 ${\Phi}mm$, pin length of 4.5 mm and tilting angle of $2^{\circ}$. The ultimate stress of ${\sigma}_T=331$ MPa and the yield point of 147 MPa are obtained at the condition of the travel speed of 32 mm/min with the tool rotation speed of 1250 rpm. There is neither voids nor cracks on bended surface of $180^{\circ}$ after bending test. The improvement of toughness after impact test was found. The lower rotating and traverse speed became, the higher were yield point, maximum stress and elongation(%) with the stresses and the elongation(%) versus the traverse speed diagram. Vickers hardness for cross section of welding zone were also presented. The typical macro-structures such as dynamically recrystallized zone, thermo-mechanically affected zone and heat affected zone and the micro-structures of the transverse cross-section were also showed. However, the author found out that the region of 6mm far away from shoulder circumference was affected by friction heat comprehensively, that is, hardness softened and that part of micro-structures were re-solid-solution or recrystallized, the author also knew that there is no mechanically deformation on heat affected zone but there are the flow of plastic deformation of $45^{\circ}$ direction on thermo-mechanically affected zone and the segregation of Al-Mg on nugget. The solid solution wt(%) of parent material as compared against of friction stir welded zone was comprehensively changed.