• 한국염색가공학회지
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• 제27권3호
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• pp.165-174
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• 2015

To develop automobile parts, the unsaturated polyester based matrix resin(PR)/reinforcement(randomly oriented chopped E-glass fiber, GF) composites were prepared using sheet molding compound(SMC) compression molding. The effects of GF length(0.5, 1.0 1.5 and 2.0inch)/content (15, 20, 25, 30wt%) and number of ply(3, 4 and 5) on the specific gravity and mechanical properties of PR/GF composites were investigated in this study. The optimum length of GF was found to be about 1.0inch for achieving improved mechanical properties(tensile strength and initial modulus). The tensile strength and initial modulus of composites increased with increasing GF content up to 30wt%, which is favorable content range for SMC. The specific gravity, tensile strength/initial modulus, compressive strength/modulus, flexural strength/modulus and shear strength increased with increasing the number of ply up to 5, which is the maximum number of ply range for SMC. The effectiveness of ply number increased in the flexural strength > shear strength > compressive strength > tensile strength.

• 동력기계공학회지
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• 제12권3호
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• pp.55-59
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• 2008

In this paper, we have investigated on collection efficiency of fine particle of glass fiber-filter bag according to the surface treatment. The solution consisted of polytetrafluoroethylene(teflon), graphite powder, silicon resin and water was used as a basic surface treatment agent. Tensile strength of glass filter-bag increased with up to 3hrs and then decreased with surface treatment time. Tensile strength and initial modulus of the glass fiber-filter bag treated by iodine after basic surface treatment for 3hrs were lower than those of basic surface treatment for 3hrs, however collection efficiency and fracture strain were higher than those of basic surface treatment for 3hrs. Glass fiber-filter bag with lower initial modulus and more strain will be extend the durable period and the one treated by iodine after basic surface treatment 3or 3hrs is expected high collection efficiency of fine particle. This method makes it possible to manufacture glass fiber-filter bag of the optimum condition.

• 한국의류산업학회지
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• 제9권3호
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• pp.347-350
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• 2007

To analyse basic properties for making packing batt according to doubling condition, packing batt yarn, of $300^D$, $900^D$, $3600^D$ made from DTY yarn $150^D$/48 were produced from KTDI. The results are as follows: The birefringence of the sample yarn increased with increasing the annealing temperature and denier. The initial modulus of the sample yarn decreased with increasing the annealing temperature and denier. The higher than annealing temperature of $160^{\circ}C$, initial modulus of the sample are equilibrated. The strain recovery ratio of samples decreased with increasing the annealing temperature and denier. The lower than annealing temperature of $140^{\circ}C$, strain recovery ratio of the sample are decreased Where the $900^D$, $3600^D$ yarns are at $100^{\circ}C$ the specific bending rigidity value obtained is 0.65kgf/d but the twisted yarn (3,600) obtained 0.006 ($gfcm^2/tex^2$). However, where the heat temperature is $160^{\circ}C$, specific bending rigidity value obtained 0.003($gfcm^2/tex^2$).

• 한국산업융합학회 논문집
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• 제5권4호
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• pp.361-366
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• 2002

The change of mechanical properties of drawn PP filaments which was treated by isothermally annealed after elevated heating. Measurements were carried out with UTM for mechanical properties. Isothermally heat treatment were carried out $100^{\circ}C$, $120^{\circ}C$, $140^{\circ}C$ for 10min., 30min., 60min, in silicon oil bath. And isothermally heat treatment after elevated heating from $20^{\circ}C$ were carried out $100^{\circ}C$, $120^{\circ}C$, $140^{\circ}C$ for 10min., 30min., 60min., with heating rate of $1^{\circ}C/min$., $5^{\circ}C/min$., $10^{\circ}C/min$. From the results of this study, it found the following facts. Initial modulus and tensile strength were increased with increasing of annealed temperature and time. Also initial modulus of tensile strength of samples which were isothermally annealed after elevated heating from $20^{\circ}C$ were higher than those of isothermally annealed samples.

• Advances in concrete construction
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• 제9권2호
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• pp.161-171
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• 2020

In this paper, an experimental study was conducted on the compressive behavior of steel tube confined concrete (STCC) and concrete-filled steel tube (CFST) columns with active and passive confinement. To create active confinement in the STCC and CFST specimens, an innovative method was used in this study, in which by applying pressure on the fresh concrete, the steel tube was laterally pretensioned and the concrete core was compressed simultaneously. Of the benefits of this technique are improving the composite column behavior, without the use of additives and without the need for vibration, and achieving high prestressing levels. To achieve lower and higher prestressing levels, short and long term pressures were applied to the specimens, respectively. Nineteen STCC and CFST specimens in three groups of passive, short-term active, and long-term active confinement were subjected to axial compression, and their mechanical properties including the compressive strength, modulus of elasticity and axial strain were evaluated. The results showed that the proposed method of prestressing the STCC columns led to a significant increase in the compressive strength (about 60%), initial modulus of elasticity (about 130%) as well as a significant reduction in the axial strain (about 45%). In the CFST columns, the prestressing led to a considerable increase in the compressive strength, a small effect on the initial and secant modulus of elasticity and an increase in the axial strain (about 55%). Moreover, increased prestressing levels negligibly affected the compressive strength of STCCs and CFSTs but slightly increased the elastic modulus of STCCs and significantly decreased that of CFSTs.

• 한국지반공학회지:지반
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• 제2권1호
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• pp.55-66
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• 1986

유효구속추력, 초기전단응력, 응력비 및 반복회수등의 영향을 고려하면서 비배수조건하에 있는 연약점토시료의 동력학적 전단탄성계수 및 감쇠비의 변화특성을 파악하기 위하여 일련의 삼축롱륜시험을 수행하였다. 그 결과, 초기전단응력 및 구속압력이 동력학적 토성치에 미치는 영향은 크지 않았지만, 축방향 변형의 증가에 따라 전단탄성계수는 감소하고 감쇠하는 증가하는 영향을 나타낸다. 또한, 전단탄성 계수는 Marcuson et al(3)과 Kokusho et al.(4)에 의해 제안된 경험식으로 얻어진 범위내에 분포되었고, 감쇠비는 Kokusho et al.(4)과 Ishihara et al.(9)에 의해 얻어진 범위에 분포됨을 보이고 있다.

• 한국세라믹학회지
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• 제21권1호
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• pp.51-59
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• 1984

In this paper mechanical properties of reaction-bonded silicon nitride are studied with the variation of initial nitrogen partial pressure. At 1, 25$0^{\circ}C$ the amount of nitridation and the nucleation of nitride increase linearly with the nitrogen partial pressure increase. After the nitridation is completed the density of nitride and modulus of rupture at room temperature are increased with the amount of nitridation. When the partial pressure of nitrogen is 0.5 atm the specimen show the optimum properties that is the highest density of nitride and modulus of rupture. Also the microstructure of $\alpha$-matte is deveoped very well at that pressure of nitrogen which contributes to the strength development of specimen. It is shown that with proper control of initial partial pressure of nitrogen high strength silicon nitride body can be manufactured for dynamic applications.

• 한국진공학회지
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• 제10권4호
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• pp.387-395
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• 2001

증착 조건에 따라 나타나는 폴리머상, 경질, 흑연상의 다이아몬드상 카본(DLC) 박막에서 두께 감소에 따른 탄성률의 변화거동을 구조적인 관점에서 살펴보았다. 실험에 사용된 박막은 r.f.-PACVD 장비를 이용하여 증착하였으며, 반응 가스로는 벤젠과 메탄을 사용하였다. 기판을 식각 과정을 통해 완전히 제거시켜 주기 때문에 다른 방법들과는 달리 기판의 영향 없이 박막만의 탄성률을 정확히 측정할 수 있는 free overhang 방법을 이용하여 DLC 박막의 biaxial elastic modulus를 측정하였다. 또한 Raman 분석을 이용하여 박막의 구조를 조사하였다. 박막이 폴리머상 혹은 흑연상인 경우 두께가 감소함에 따라 탄성률이 감소하는 것을 확인하였고, Ramanm spectrum의 G-peak 위치를 분석한 결과 그 원인은 폴리머상인 경우 증착 초기에 낮은 물성을 가지는 폴리머상의 박막이 형성되기 때문이며, 흑연상인 경우 증착 초기에 낮은 물성을 가지는 흑연상의 박막이 증착되기 때문이다. 반면에 경질의 박막에서는 두께에 상관없이 일정한 탄성률을 가지고 있었으며, 두께에 따른 박막의 구조적인 변화도 관찰되지 않았다.

• 한국지반공학회지:지반
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• 제13권6호
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• pp.95-106
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• 1997

공내재하시험은 고무 튜브를 보링공에 넣어 압축을 가함으로써 압력과 변형관계 곡선을 얻을 수 있는데 지반교란이 해석 결과에 큰 영향을 미친다. 공내재하시험의 지배방정식은 공동확장이론과 쌍곡선 형태의 흙모델을 기본으로 이론적으로 유도할 수 있으며 이렇게 유도된 식과 곡선 보정기법을 적용시키면 지반교란이 없는 상태의 응력-변형 곡선을 얻을 수 있다. 이러한 해석 방법은 재하단계에 적용할 수 있으며 국내의 화강풍화토의 공내재하시험 결과에 적용하여 초기전 단계수를 구하였다. 이렇게 구한 초기전단계수값을 표준관입시험 결과와 비교 분석하여 초기전 단계수값과 표준관입시험의 상관관계를 구하였다.

• 한국수소및신에너지학회논문집
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• 제20권6호
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• pp.471-478
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• 2009

The specific some types of compressors are appropriate for a use in hydrogen gas station. Metal diaphragm type of hydrogen compressor is one of them, which can satisfy the critical requirements of maintaining gas purity and producing high pressure over 850 bar. The objective of this study is to investigate an characteristics of compression through two-way Fluid-Structure-Interaction (FSI) analysis as bulk modulus and initial volume of oil independently varies. Deflection of diaphragm, oil density, gas and oil pressure were analyzed during a certain period of compression process. According to the analysis results, bulk modulus and initial volume remarkably affected deflection of diaphragm, oil density, gas and oil pressure. The highest gas pressure were attained with the highest bulk modulus of $7e^9\;N/m^2$ and the lowest initial oil volume of 80 cc.