• 한국철도학회논문집
• /
• 제8권2호
• /
• pp.188-194
• /
• 2005

Aging characteristics of glass fabric/phenolic composites for tilting train subjected to combined environmental aging factors were investigated. A 2.5KW accelerated aging tester with a xenon-arc lamp was used to provide environmental aging factors such as temperature, moisture, and ultraviolet. A series of aging tests were conducted up to 3000 hours and several types of specimens were prepared along the warp direction and the fill direction. Mechanical degradations for tensile, flexural, and shear properties were evaluated as a function of exposure times through a material testing system. Thermal analysis properties such as storage shear modulus, loss shear modulus, and tan 3 were measured through a dynamic mechanical analyzer. Finally exposed surfaces of the composites were examined using a scanning electron microscope. According to the experimental results, mechanical properties and thermal analysis properties of glass fabric/phenolic composites were found to be slightly degraded as a function of exposure times due to combined environmental effects.

• 비파괴검사학회지
• /
• 제31권2호
• /
• pp.134-138
• /
• 2011

회전기기의 고장 탐지에 있어 기존의 진단법과 달리 동적 하중조건 하에서 비접촉, 비파괴의 적외선 열화상 기법이 제안된다. 본 논문에서는 단열 깊은 홈 볼 베어링을 시편으로 하여, 회전기기의 기존의 고장 진단법 대신 수동형 열화상 기법을 이용한 시험을 수행하였다. 추가적으로, 제안된 방법의 효율성을 평가하기 위해 기존의 진동 스펙트럼 분석법을 적용하여 열화상 시험법을 비교하였다. 시혐의 결과로써, 동적 하중조건 하 볼 베어령의 온도분포 특성이 철저히 분석되었다.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2005년도 춘계학술대회 논문집
• /
• pp.441-445
• /
• 2005

In the resent years, as the research and the development of micro and precision machinery become active, the interest of micro actuators using SMA(Shape Memory Alloy) has been increased. But, no detailed researches between the thermo-dynamic property in Nitinol alloy have been done yet. In this study, the thermal property of high temperature Nitinol shape memory alloy were evaluated using differential scanning calorimeter(DSC). The structure property was investigated using X-ray diffraction(XRD). A dynamic mechanical analyzer(DMA) with three point bending mode was used to study storage and loss modulus of shape memory alloy according to the thirteen frequencies in the temperature range between 30 and $200^{\circ}C$. The effects of the temperature heating/cooling rate, the frequency on the damping capacity have been systematically investigated. Such a frequency and temperature changes also influenced significantly to the damping behavior of the shape memory alloy. It was also found that Nitinol exhibited high damping capacity during phase transformation.

• 공업화학
• /
• 제22권6호
• /
• pp.623-626
• /
• 2011

다양한 조성의 PMDA/BPDA/p-PDA/ODA로 이루어진 폴리아믹산을 합성하여 다양한 조성의 4성분계 폴리이미드 필름을 열적 이미드화 공정을 통해 제조하였다. 제조된 폴리이미드 필름의 화학 구조 및 열적 기계적 특성은 퓨리에 변환 적외선 분광기(FT-IR), 열중량 분석기(TGA), 열 기계 분석기(TMA), 동 역학적 거동 분석기(DMA), 그리고 만능 인장시험기(UTM) 등을 이용하여 조사하였다. 강직한 구조의 PMDA와 p-PDA의 함량이 증가할수록 인장강도, 탄성률 및 열적 특성이 향상되었고, 상대적으로 유연한 구조의 BPDA와 ODA의 함량이 증가할수록 신장률과 흡습률이 각각 증가하였다. 특히, 열팽창계수(CTE)값은 PMDA : BPDA : p-PDA : ODA의 조성이 5 : 5 : 4 : 6 조성일 때 동박의 CTE와 유사한 결과를 나타내었으며, 이와 같은 조성을 갖는 4성분계 폴리이미드 필름의 경우 유연성 회로 기판의 flexible copper clad laminates (FCCL)을 위한 기본 필름으로 적용할 수 있을 것으로 판단된다.

• 폴리머
• /
• 제25권5호
• /
• pp.691-698
• /
• 2001

에폭시 (diglycidyl ether of bisphenol A: DGEBA), 경화제 (dicyandiamide; DICY), 촉매 (benzyl dimethyl amine : BDMA), 그리고 유기치환된 실리케이트 (organically modified mica type silicate: OMTS)를 용융법 및 용액법을 이용해 나노복합체를 제조하였고, $170^{\circ}C$에서 시간에 따라 경화 반응을 진행하면서 X선 회절분석기 (XRD)와 소각 X선 산란장치 (SAXS)를 이용하여 구조 변화를 관찰하였다. 용융법으로 제조된 치료의 경우 박리된 구조를 관찰할 수 없었으나 용액법에 의해 제조된 경우 박리된 구조를 관찰할 수 있었다. 이는 OMTS 층 내ㆍ외부의 경화 속도차이 때문인 것으로 생각된다. 박리된 에폭시 나노복합체의 OMTS 첨가량에 따른 기계적 물성을 동적기계적 분석기 (DMA)를 이용해 측정한 결과 OMTS의 첨가량이 증가할수록 모둘러스는 증가하였으나 유리전이온도는 큰 차이가 없었다. OMTS 첨가량에 따른 열적 성질을 열중량분석기(TGA)와 한계산소지수 (LOI)를 이용해 측정한 결과 OMTS양이 증가할수록 OMTS 판의 차단효과로 인해 열분해 시작 온도와 LOI 값이 증가하였다.

• 한국정밀공학회지
• /
• 제17권10호
• /
• pp.83-88
• /
• 2000

multi-beam optical drive is a method to improve the data transfer rate for the optical disc systems by parallel recording and reading on neighboring multi-tracks. In this paper, the beam rotating actuator, which is necessary for the multi-bean optical disc drive to from beam spots on multi-tracks simultaneously, has been developed. The Voice Coil Motor is used as a drive mechanism for high resolution and small size of the actuator. And rotating guide based on link structure is designed for frictionless and axisless rotation of rotating part including dove prism and for rotating in axis of geometric center of dove prism. The characteristics of the actuator are experimented by laser vibrometer, Polytec OFV1102 and a dynamic analyzer, HP35670A. It shows that the actuator has good linearity, rotating range $\pm0.34^\circ$, minimum rotating angle $0.0066^\circ$and natural frequency 113.9Hz. Therefore the actuator can be applied in a multi-beam optical disc system.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2007년도 추계학술대회 논문집
• /
• pp.852-858
• /
• 2007

The durability of carbon/epoxy composites under salt water environment was investigated through salt water spray tester. Salt water environment was obtained through salt spray and salt immersion. 5% NaCl solution was used for salt water as natural salt water. Mechanical test was performed to obtain tensile properties, flexural properties, and shear properties of carbon/epoxy composite over 12 months under salt water environment. Dynamic mechanical analyzer was used to investigate thermal analysis properties such storage modulus, loss modulus, and tan ${\delta}$. Also FT/IR test was conducted to investigate a change in chemical structure. According to the results, mechanical properties were found to be slowly degraded as a function of exposure times. Regarding to thermal analysis properties, storage modulus was insensitive to exposure times, but loss modulus was shown to be slightly decreased. Although the shape and location of peak in FT/IR were not much changed, the intensity of peak in FT/IR was affected on exposure times. We also found that salt water immersion was more severe to the durability of carbon/epoxy composite rather than salt water spray.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
• /
• pp.190-193
• /
• 2004

Two different diene monomers [dicyclopentadiene (DCPD) and 5-ethylidene-2-norbomene (ENB)] as self­healing agent for polymeric composites were microencapsuled by in-situ polymerization of urea and formaldehyde. The healing agents were investigated by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Exothermic reaction and glass transition temperature from DSC and storage modulus (G') and tan $\delta$ from DMA curves were analyzed for the samples cured for 5 min and 24 h in the presence of different amounts of catalyst. Micorcapsules were successfully formed for both diene monomers. Microcapsules containing the healing agent were manufactured and its thermal properties were characterized by thermo gravimetric analysis (TGA). Optical microscope (OM) and particle size analyzer (PSA) were employed to observe morphology and size distribution of microcapsules, respectively. Comparison of the two self-healing agents and their microcapsules with the two was made in this study.

• Advanced Composite Materials
• /
• 제17권1호
• /
• pp.89-99
• /
• 2008

Using a Dynamic Mechanical Analyzer (DMA), mechanical properties like modulus and phase transition temperature of polyester composites of banana fibers (treated and untreated) are measured simultaneously. The shifting of phase transition temperature is observed in some treatments. The performance of the composite depends to a large extent on the adhesion between polymer matrix and the reinforcement. This is often achieved by surface modification of the matrix or the filler. Banana fiber was modified chemically to achieve improved interfacial interaction between the fiber and the polyester matrix. Various silanes and alkalies were used to modify the fiber surface. Chemical modification was found to have a profound effect on the fiber/matrix interaction, which is evident from the values of phase transition temperatures. Of the various chemical treatments, simple alkali treatment with 1% NaOH was found to be the most effective.

• 폴리머
• /
• 제26권3호
• /
• pp.335-343
• /
• 2002

블렌드 (PET/PETG 70/30 블렌드) 수지는 폴리에틸렌테레프탈레이트 (PET)와 폴리에틸렌테레프탈레이트 글리콜 (PETG)을 무게 비 70/30으로 혼합하여, 이축 압출기를 사용하여 제조하였다. 미연신 필름은 이 블렌드와 순수 PETG 수지를 압축성형기로 각각 용융 압축시켜 제조하였고 연신 필름은 미연신 필름을 모세관 레오메타를 사용하여 연신시켜 제조하였다. 제조된 블렌드 연신 필름과 PETG 연신 필름의 결정성, 수축율, 열적, 동역학적 및 기계적 특성을 X-선 회절분석기, 오븐기, DSC, 및 인장시험기를 사용하여 조사하였다. 블렌드와 PETG필름의 결정화도와 밀도는 연신비와 연신 속도의 증가와 더불어 증가하였으나 반면 연신 온도 증가와 더불어 감소하였다 또한 블렌드 필름의 결정화도와 밀도는 PETG 필름보다 높게 나타났다. 두 필름의 인장강도와 인장탄성률은 연신비 및 연신 속도 증가와 더불어 증가하였고 연신온도 증가에 따라 감소하였다. 또한 블렌드 필름의 인장강도와 인장탄성률이 PETG 필름 보다 높게 나타났다. 두 필름의 수축율은 연신비와 연신 속도가 증가할수록 감소하였고 미연신 블렌드 필름의 수축율이 순수 PET 필름보다 600% 증가함을 보였다.