• 대한치과보철학회지
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• 제36권2호
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• pp.336-354
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• 1998

Traditionally, many kinds of mechanical bonding techniques were used for bonding resins to the surface of the metal alloys. If there is a seperation between resin and metal junction by stress accumulation and temperature change of oral cavity, the cracks or crazing may occur, accompanied by failure of resin bonding to metal. This study was designed to compare the shear bond strength of the type IV gold alloy and Cr-Co alloy surfaces treated with various methods and thermocycling. Universal Instron (Model 1000) and scanning electron microscope (JEOL, Japan) was used to record the shear bond strength of 5 groups. Forty specimens were made for each group ; group 1 was treated with sandblasting only, group 2 was coated with V-primer after sandblasting, group 3 was coated with Metal primer, group 4 wase coated with MR Bond and group 5 was coated with silane. After treated with various methods, thermocycling was done for half of the each group. The surfaces of failed pattern were observed with SEM. The results were as follows : 1. Shear bond strength of the group 1 was lower than that of another groups in type IV gold alloys and bond strength of the group 1, 2 were lower than that of group 3, 4, 5 in Cr-Co alloys. 2. Shear bond strength of the gold alloy with resin was higher than that of Cr-Co alloy when specimens were coated with V-primer. 3. Shear bond strength of the Co-Cr alloys with resin was higher than that of gold alloys when specimens were coated with Metal primer. 4. The bond strength of all specimens did not decreased significantly after thermocycling. 5. Adhesive failures were found in group 1 and Cr-Co alloy in group 2, but adhesive and cohesive failures were found in another groups.

• 대한전기학회논문지
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• 제36권6호
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• pp.418-423
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• 1987

In the course of the investigation to the field dependent electrical conducation mechanism in polypropylene, an abnormal conduction phenomena such as voltage controlled negative resistance charateristics has been observed at the junction of two regions charateriged by schottky effect and space charge effect respectively. This abnormal characteristics was observed initially about 110MV / m of the field strength and at 25 , however, the field strength where it observed was decreased and the apparent feature of negative charateristics was less pronounced as increasing ambient temperature. Although the observations of analogous characteristics in other materials such as polyethylene, polymethylemethactylate, and polystyrene have already been reported together with plausible explanation by Toureille and others, however, it was found that the proposed concept by those authors was little use to the present observations for quantitative discussions. Accordingly we tried to adapt another conceptual discussion based on Gibbons's formulation pertaing to the saturatio trend of the field dependent drift velocity of carriers towards the thermal velocity corresponding to the ambient temperature so that the quantitative explanatio on the observed facts has been succeeded to some estent of reasonable acceptance.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1604-1613
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• 2008

지오그리드란 토목합성보강재의 한 종류이며, 지반의 보강 처리를 위해 주로 사용된다. 본 연구에서는 유한 요소해석프로그램에 의한 지오그리드의 접점강도, 응력분산효과해석과 광폭인장강도 평가 개선을 위한 방법에 관한 연구를 주목적으로 하였다. 이 때 범용 유한요소 해석 프로그램인 VisualFEA/Edu를 사용하였으며, 실제 실험값과 프로그램의 결과 값의 비교를 통하여 해석모델의 타당성을 검증하였다.

• Journal of Welding and Joining
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• 제5권3호
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• pp.19-27
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• 1987

This paper presents the weldability for cold pressure but welding method in junction of dissimilar metals each other. Although the weldability between the same aluminium metal plate welding has been studied, the study of itthe rod of aluminium and coper has not fully been investigated. The purpose is to suggest the optimal conditions on the rod of those under above method. To obtain the optimal conditions, associated experiments were performed in a various welding parameters. Consequently, it was proved that the mechanical properties such as tensile strength, hardness and bending strength could be obtained excellent particularly under the welding conditions; pressure is $(32~39) {\times} 10^3/kg/cm^2$, time is beyond 70 seconds, stage is higher than fifth stage.

• 폴리머
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• 제39권3호
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• pp.514-521
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• 2015

본 연구는 자동차, 건축, 디스플레이 부품 접합 등에 사용되는 다층구조형 양면 점착테이프에 대한 것으로 UV 경화에 의해 제조된 아크릴폼 기재에 용제 건조형 점착제(AD)를 양면에 붙이고 피착제 종류에 따른 박리강도와 전단접착강도를 고찰하였다. AD 종류와 기재 조성에 따른 접착력 변화 및 피착재로 사용한 플라스틱에 대한 접착력을 고찰한 결과, AD의 분자량(MW)이 증가할수록 박리강도 및 전단접착강도가 증가하였으나 약 65만 이상의 MW를 가진 AD는 접착력이 감소하는 거동을 보였다. 양면 점착테이프에 사용된 AD층 두께가 얇을수록 온도감소와 함께 높은 물성 값을 보였다. 기재와 AD와의 계면접합 특성은 MW 615000(AD-4)을 사용한 것이 가장 우수하였으며, MW가 615000보다 낮으면 기재인 아크릴 폼과의 계면이 분리되는 결과를 보였다. 따라서 본 연구에서 검토한 다층구조형 양면 점착테이프는 표면에너지가 낮은 플라스틱 부품 및 곡면 부위에 적용가능한 산업분야에 유용하게 사용될 수 있을 것으로 판단된다.

• 대한기계학회논문집B
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• 제27권10호
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• pp.1464-1471
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• 2003

In order to investigate the flows with shock wave in branch, 108$^{\circ}$ elbow and T-junction of the IRWST system of standard Korean nuclear reactor, detail time dependent behaviors of unsteady flow with shock wave, vortex and so on are obtained by numerical method using compressible three-dimensional Navier-Stokes equations. At first, the complex flow including the incident and reflected shock waves, vortex and expansion waves which are generated at the corner of T-junction is calculated by the commercial code of FLUENT6 and is compared with the experimental result to obtain the validation of numerical method. Then the flow fields in above mentioned units are analyzed by numerical method of [mite volume method. In numerical analysis, the distributions of flow properties with the moving of shock wave and the forces acting on the wall of each unit which can be used to calculate the size of supporting structure in future are calculated specially. It is found that the initial shock wave of normal type is re-established its type from an oblique one having the same strength of the initial shock wave at the 4 times hydraulic diameters of downstream from the branch point of each unit. Finally, it is turned out that the maximum force acting on the pipe wall becomes in order of the T-junction, 108$^{\circ}$ elbow and branch in magnitude, respectively.

• 폴리머
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• 제37권2호
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• pp.184-195
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• 2013

아크릴 점착테이프는 자동차, 전기전자 및 디스플레이 모듈 접합에 사용된다. 본 연구는 이러한 모듈 접합에 사용되는 고강도 준구조형 점착테이프 제조를 위해 2-ethylhexylacrylate(2-EHA)와 acrylic acid(AAC)를 사용하여 UV 조사에 의한 광중합 및 점착테이프 제조를 위해 광경화를 진행하였고, AAC의 함량 및 무기물 충전제 $SiO_2$ 함량에 따라 아크릴 점착테이프의 물성에 미치는 영향을 고찰하였다. 공단량체로 사용된 AAC의 함량이 많을수록 아크릴고분자 사슬의 강직성이 증가하여 초기 점착력이 낮았고, 시간경과에 따라 점착력이 증가하였으며 테이프의 젖음성, 접촉각 및 SEM 이미지를 통해 확인할 수 있었다. 충전제를 첨가하지 않은 점착테이프의 박리강도와 전단접착강도는 반비례 관계였으나 충전제를 첨가하면 함량 증가에 따라 박리강도 증가와 함께 전단접착강도가 증가하는 비례관계를 보였다. 이러한 상관관계로부터 고강도 준구조형 접착물성을 필요로 하는 용도에 최적화된 아크릴 점착테이프를 제시할 수 있었다.

• 한국기계가공학회지
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• 제14권2호
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• pp.25-30
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• 2015

This study involved the fabrication of precision machine tools using a polycrystalline diamond tip [sintered PCD and cemented carbide (WC-Co) tip] and WC-Co shanks via diffusion bonding with a paste-type nickel alloy filler metal. Diffusion bonding is a process whereby two materials are pressed together at high temperature and high pressure for a sufficient period of time to allow significant atomic diffusion to occur. For smooth progress, a filler metal of nickel alloy was used at the interface. Optical microscopy images were used to observe the copula of the bonded layer. It was confirmed that cracks occurred near the junction in all cases. The tensile strength of the bond was measured using a universal testing machine (UTM) with WC-Co proportional test specimens.

• 한국공간구조학회논문집
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• 제16권4호
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• pp.45-52
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• 2016

The single layer latticed domes have attracted many designers and researchers's attention all of the world, because these structures as spatial structure are of great advantage in not only mechanical rationality but also function, fabrication, construction and economic aspect. But single layer latticed domes are apt to occur the unstable phenomena that are called "buckling" because of the lack of strength of members, instability of structural shape, etc. In the case of latticed dome, there are several types of buckling mode such as overall buckling, local buckling, and member buckling according to the shape of dome, section type of member, the size of member, junction's condition of member and so on. There are many methods to increase the buckling strength of the single layer latticed dome, that is, with the change of geometrical shape of dome, the reinforcement of buckled member, etc. Therefore, the purpose of this study is to verify the reinforcement effect of buckled member when designers reinforce the buckled member to increase the buckling strength of single layer latticed dome with 3-way grid.

• 대한조선학회논문집
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• 제28권1호
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• pp.189-196
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• 1991

본 논문에서는 SWATH선의 횡 구조물에 신뢰성 해석법을 적용하였다. cross-structure와 strut의 윗부분에 있는 판부재를 선정하여 그 압축 최종강도에 대한 신뢰성해석을 수행하였고, 또한 cross-structure와 strut, sponson과 strut의 연결부에 대한 피로 신뢰성해석을 수행하였다. 피로손상의 허용수준의 설정에 대한 일례를 보여주었으며, 최종강도와 피로강도를 동시에 고려한 일종의 series system에 대한 신뢰성해석을 포함하였다. 이는 구조의 안전성 평가시 보다 정확한 결과를 얻을 수 있다는 점에서 바람직하다고 하겠다.