• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집
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• pp.239-246
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• 2009

The Mode I interlaminar fracture toughness of woven fabric carbon/epoxy and glass/epoxy composites for a train carbody was measured and FEM analysis was conducted. The woven fabric epoxy composite manufactured by hand lay-up, has high stiffness and strength, good resistance for impact, fatigue, corrosion and in-plane failure. The DCB(Double Cantilever Beam) specimen made of woven fabric epoxy composite had the size of 180mm $\times$ 25mm $\times$ 5mm and the insert of 65mm. The Mode I interlaminar toughness of specimen was measured according to ASTM 5528-01. The crack propagation behavior of the DCB specimen was simulated using FEA with cohesive elements that model the adhesive layer between woven fabric plies.

• Journal of Welding and Joining
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• 제27권5호
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• pp.49-54
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• 2009

Recently, a demand of ferritic STS is increasing rapidly in automobile exhaust system. Exhaust manifolds are the part nearest to the engine so that the material is exposed to high temperature exhaust gas. Excellent heat resistant properties, especially high temperature strength, thermal fatigue resistance and high corrosion resistance are necessary for these parts. STS429L contains 15 weight percent of Cr and low Mo, so has good price competitive. And it has excellent high temperature strength and corrosion resistance, so receives attentions as material that applying to exhaust manifold. In tensile test of lap joint welded STS 429L, most of specimens are failed in base metal, but occurs brittle fracture in weld metals at some specimens in the face of good welding conditions. In the process of tensile test, lap joint welded STS429L specimens are transformed locally. The brittle fracture occurs that local transforming area exists in weld metals. But, butt welding specimens made by same materials showed ductile fracture in tensile test and bending test. In this study, suppose the reason of brittle fracture is in the combined local transform and tensile stress, through analysis of bead geometry, evaluate geometrical factor of brittle fracture in lap joint welded STS429L.

• 대한기계학회논문집A
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• 제26권2호
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• pp.308-313
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• 2002

It is known that the composite material shafts using on small boats have various advantages comparing to forged steel shafts, fur examples, specific strength, fatigue strength, corrosion, etc. The analysis of the stresses and strains in the composite material shafts made by filament winding method is presented in this paper. The classical laminated plate theory is applied on the patch cut from the composite material hollow shafts. It is verified that the composite material hollow shafts of diameter 40 mm is the most optimum when the ratio of the inner diameter to the outer is 0.4 and winding angle is 45$^{\circ}$. It is also proven that the shear strain does not change seriously between 30$^{\circ}$and 60$^{\circ}$of winding angles. It is dangerous when the winding angle is over 75$^{\circ}$because the values of shear strain and stress produced on the shaft are too high so it must be avoided to wind the filament by the angle over 75$^{\circ}$.

• 접착 및 계면
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• 제23권4호
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• pp.101-107
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• 2022

Adhesive joints have many advantages such as weight savings, corrosion and fatigue resistance and now developed even withstand of high impact and dynamic loads. However, an adhesion has cumbersome and complicated surface preparation processes. The surface preparation step is critical in adhesive joint manufacturing in order to obtain the prescribed strength for adhesive joints. In this study, it was attempted to simplify and reduce the number of surface preparation steps, and abrasion and rapid adhesive application (ARAA) process is developed for an alternative solution. The abrasion processes are performed only for creating surface roughness in standard procedures (SP), although the abrasion processes cause surface activation itself. The results showed that there is no need the long procedures in laboratory or chemical agents for adhesion. After the abrasion process, the attracted and highly reactive fresh surface layer obtained, and its effect on bonding success is observed and analyzed in this research, in light of the essential physic and adhesion theories. Al 6061 aluminum adherends and epoxy-based adhesives were chosen for bonding processes, which is mostly used in light vehicle parts. The adherends were cleaned, treated and activated only with abrasion, and after the adhesive application the specimens were tested under quasi-static loading. The satisfied ARAA results were compared with that of the specimens fabricated by the standard procedure (SP) of adhesion processes of high impact loads.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2004년도 ISMP Pb-free solders and the PCB technologies related to Pb-free solders
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• pp.233-241
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• 2004

A new alloy definition will be presented concerning increasing demands for the board level reliability of miniaturized interconnections. The damage mechanism for LFBGA components on different board finishes is not quite understood. Further demands from mobile phones are the drop test, characterizing interface performance of different package constructions in relation to decreased pad constructions and therefore interfaces. The paper discusses the characterization of interfaces based on SnPb, SnPbXYZ, SnAgCu and SnAgCuInNd ball materials and SnAgCuInNd as solder paste, the stability after accelerated tests and the description of modified interfaces strictly related to the assembly conditions, dissolution behavior of finishes on board side and the influence of intermetallic formation. The type of intermetallic as well as the quantity of intermetallics are observed, primaliry the hardness, E modules describing the ability of strain/stress compensation. First results of board level reliability are presented after TCT-40/+150. Improvement steps from the ball formulation will be discussed in conjunction to the implementation of lead free materials In order to optimize ball materials for area array devices accelareted aging conditions like TCTs were used to analyze the board level reliability of different ball materials for BGA, LFBGA, CSP, Flip Chip. The paper outlines lead-free ball analysis in comparison to conventional solder balls for BGA and chip size packages. The important points of interest are the description of processability related to existing ball attach procedures, requirements of interconnection properties and the knowledge gained the board level reliability. Both are the primary acceptance criteria for implementation. Knowledge about melting characteristic, surface tension depend on temperature and organic vehicles, wetting behavior, electrical conductivity, thermal conductivity, specific heat, mechanical strength, creep and relaxation properties, interactions to preferred finishes (minor impurities), intermetallic growth, content of IMC, brittleness depend on solved elements/IMC, fatigue resistance, damage mechanism, affinity against oxygen, reduction potential, decontamination efforts, endo-/exothermic reactions, diffusion properties related to finishes or bare materials, isothermal fatigue, thermo-cyclic fatigue, corrosion properties, lifetime prediction based on board level results, compatibility with rework/repair solders, rework temperatures of modified solders (Impurities, change in the melting point or range), compatibility to components and laminates.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2004년도 ISMP Pb-free solders and the PCB technologies related to Pb-free solders
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• pp.211-219
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• 2004

A new alloy definition will be presented concerning increasing demands for the board level reliability of miniaturized interconnections. The damage mechanism for LFBGA components on different board finishes is not quite understood. Further demands from mobile phones are the drop test, characterizing interface performance of different package constructions in relation to decreased pad constructions and therefore interfaces. The paper discusses the characterization of interfaces based on SnPb, SnPbXYZ, SnAgCu and SnAgCuInNd ball materials and SnAgCuInNd as solder paste, the stability after accelerated tests and the description of modified interfaces stric시y related to the assembly conditions, dissolution behavior of finishes on board side and the influence of intermetallic formation. The type of intermetallic as well as the quantity of intermetallics are observed, primaliry the hardness, E modules describing the ability of strain/stress compensation. First results of board level reliability are presented after TCT-40/+150. Improvement steps from the ball formulation will be discussed in conjunction to the implementation of lead free materials. In order to optimize ball materials for area array devices accelareted aging conditions like TCTs were used to analyze the board level reliability of different ball materials for BGA, LFBGA, CSP, Flip Chip. The paper outlines lead-free ball analysis in comparison to conventional solder balls for BGA and chip size packages. The important points of interest are the description of processability related to existing ball attach procedures, requirements of interconnection properties and the knowledge gained the board level reliability. Both are the primary acceptance criteria for implementation. Knowledge about melting characteristic, surface tension depend on temperature and organic vehicles, wetting behavior, electrical conductivity, thermal conductivity, specific heat, mechanical strength, creep and relaxation properties, interactions to preferred finishes (minor impurities), intermetallic growth, content of IMC, brittleness depend on solved elements/IMC, fatigue resistance, damage mechanism, affinity against oxygen, reduction potential, decontamination efforts, endo-/exothermic reactions, diffusion properties related to finishes or bare materials, isothermal fatigue, thermo-cyclic fatigue, corrosion properties, lifetime prediction based on board level results, compatibility with rework/repair solders, rework temperatures of modified solders (Impurities, change in the melting point or range), compatibility to components and laminates.

• 콘크리트학회논문집
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• 제26권4호
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• pp.491-497
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• 2014

철근의 부식은 철근콘크리트 교량 바닥판의 성능 저하에 큰 요인으로 작용한다. FRP는 비부식성 재료이기 때문에 이를 활용하여 보강근을 개발하려는 노력이 이루어지고 있다. 여러 종류의 FRP 보강근이 개발되었으나 아직 활용 실적은 많지 않은 상황이다. 그 이유로는 FRP 보강 콘크리트 구조물에 대한 단/장기 검증 데이터가 부족하기 때문이다. 이 연구에서는 GFRP 보강 바닥판에 대한 피로성능을 관찰하기 위해서 길이 4000 mm, 폭이 3000 mm, 높이 240 mm인 실제 크기의 교량 바닥판을 도로교설계기준을 준용하여 제작한 후 실험을 실시하였다. 하부 보강비를 변수로 설정하였으며 DB-24 하중이 바닥판 중앙에 집중 작용하는 것으로 실험을 실시하였다. 사용하중의 3.5, 4.5, 5.0배에 해당하는 다양한 하중을 2백 만회 이상 반복 재하하여 GFRP 보강 바닥판의 피로성능을 관찰하였다. 실험 결과 거더가 횡구속된 GFRP 보강 바닥판의 최대성능은 보강근비에는 민감하지 않았고, 피로성능은 보강비보다는 적용하중의 크기에 민감하며, 바닥판이 200만회 이상 반복재하에 저항하기 위해서는 재하되는 집중하중의 크기는 최대하중의 58% 수준 이하이어야 하며, 이 연구의 실험 대상 GFRP 보강 바닥판의 피로수명은 철근 콘크리트 바닥판의 수명 예측값보다는 다소 낮은 값을 나타내었고 FRP 보강 콘크리트 바닥판의 기존 예측값보다는 높은 값을 나타내었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.313-316
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• 2008

철근 콘크리트 구조물의 철근 부식은 구조물의 성능 저하의 주요한 원인 중 하나이다. 철근 부식은 구조물의 수명을 단축시켜 막대한 유지 관리 비용을 요구하게 된다. 또한 이러한 철근의 부식은 주기적인 반복하중을 받는 교량이나 도로와 같은 구조물들의 구조적 성능저하를 가중시키는 요인이 되고 있다. 이러한 이유들로 인해 철근을 대체할 수 있는 FRP 보강근의 사용에 대한 관심이 증가하고 있다. 그러나 국내외적으로 FRP 보강근의 피로시험에 대한 연구는 전무한 실정이다. 이에 본 연구에서는 국내외로 상용화된 FRP(GFRP, CFRP) 보강근의 실제 구조물에 대한 적용가능성을 고찰하기위해 휨 보강시험체의 인장부 보강근으로 사용하여 정적 및 피로 성능을 검증하고자 한다. 본 연구에서 사용된 시험체는 ACI 440.1R-06으로 설계되었으며, CFRP 보강근으로 보강된 시험체(CR)와 GFRP 보강근으로 보강된 시험체(GR)는 과보강 단면으로 설계되었다. 정적 휨 실험을 수행한 결과, CR 시험체와 GR 시험체 모두 콘크리트 보의 상단 압축부가 파괴되는 것을 확인할 수 있었다. 피로 실험시 피로응력수준은 정적 휨 강도의 60%, 70%, 80%로 하여 실험을 수행하였다. 대부분의 시험체가 압축 파괴 양상을 보였지만 CR-60과 CR-70 시험체는 인장부 보강근의 파단으로 인한 파괴를 확인할 수 있었다. 피로 실험결과를 바탕으로 회귀분석을 통해 S-N 상관도를 적용하여 S-N 관계식을 얻을 수 있었다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.337-341
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• 2004

Engineering ceramics have superior heat resistance, corrosion resistance, and wear resistance. Consequently, these art significant candidates for hot-section structural components of heat engine and the inner containment of nuclear fusion reactor. Besides, some of them have the ability to heal cracks and great benefit can be anticipated with great benefit the structural engineering field. Especially, law fracture toughness of ceramics supplement with self-healing ability. In the present study, we have been noticed some practically important points for the healing behavior of silicon nitride, alumina, mullite with SiC particle and whisker. The presence of silicon carbide (SiC) in ceramic compound is very important for crack-healing behavior. However, self-healing of SiC has not been investigated well in detail yet. In this study, commercial SiC was selected as sample, which can be anticipated in the excellent crack healing ability. The specimens were produced three-point bending specimen with a critical semi-circular crack of which size that is about $50-700{\mu}m$. Three-point bending test and static fatigue test were performed cracked and healed SiC specimens. A monotonic bending load was applied to cracked specimens by three-point loading at different temperature. The purpose of this paper is to report Strength Properties and Elastic Waves Characteristics of Silicon Carbide with Crack Healing Ability.

• 콘크리트학회지
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• 제8권6호
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• pp.151-161
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• 1996

토목 및 건축재료로써 폴리프로필렌 섬유보강 모르터 및 콘크리트의 사용은 미국, 영국 등지에서 개발되기 시작하여 많은 연구가 진행되어 왔는데, 경제적 이점, 화학적인 안정성과 우수한 내구성으로 인해 국내에서도 그 사용이 점차 증대되고 있는 실정이다. 이러한 폴리프로필렌 섬유의 사용은 모르터 및 콘크리트가 건조나 온도에 의해 수축될 때 , 구속에 의해 발행하는 인장응력 및 균열을 제어하고, 인성의 증가와 충격, 마모, 피로에 대한 저항성을 증대시키며, 콘크리트의 내구성을 증대시키는 등의 장점을 가지는 것으로 보고되고 있다. 본 연구에서는 이러한 폴리프로필렌 섬유보강 모르터 및 콘크리트의 재료적 특성인 유동성, 압축강도, 인장강도, 휨인성뿐만 아니라 균열제어특성, 건조수측특성을 실험을 통하여 규명하고자 하였다. 본 연구 결과. 폴리프로필렌섬유의 혼입으로 인성이 증가되고 건조수축균열 및 건조수축량이 제어되고 있는 것으로 나타났다. 본 연구는 앞으로 건조수축균열제어와 인성증가를 위한 폴리프로필렌 섬유보강 콘크리트의 활용 및 설계에 기초자료를 제시할 수 있을 것으로 사료된다.