• Composites Research
• /
• 제16권4호
• /
• pp.10-21
• /
• 2003

본 논문에서는 특성길이 결정을 위해 시편에 가해지는 하중과 내부 응력분포의 관계가 거의 선형적으로 변한다는 특성을 이용하여. 실험을 수행하지 않고 복합재 체결부 파손해석을 위한 특성길이를 결정할 수 있는 방법을 제안하였다. 제안된 방법을 사용할 경우 특성길이 결정을 위한 실험 없이도 실험값을 사용한 결과와 동일한 압축특성길이를 얻을수 있음을 보였다. 압축특성길이 결정에서와 마찬가지로 실험 없이 인장특성길이를 결정하기 위해, 기존의 방법에서와 달리, 인장특성길이의 정의를 위해 사용하는 적층판의 강도값을, 원공이 없는 적층판의 값이 아닌 원공을 가진 적층판의 값을 사용하였다. 유한요소해석은 MSC/NASTRAN을 이용하였고, 체결재와 복합재의 접촉부는 접촉면 요소를 사용하여 모델링하였다. 제안된 방법으로 해석한 복합재 체결부의 파손하중은 Graphite/Epoxy 복합재료 체겯부의 실험 견과와 매우 잘 일치함을 확인하였다

• Transactions on Electrical and Electronic Materials
• /
• 제7권6호
• /
• pp.283-292
• /
• 2006

So that high-strength and electrical properties apply by excellent high voltage insulator electricity material, ATH content and platinum-based flame retardant that influence in flame retardant and tracking characteristic among composite of silicone rubber studied mechanical strength and influence getting to electrical properties. Composition of ${\alpha}$, ${\omega}-vinyl$ poly (dimethyl-methylphenyl) siloxane(VPMPS) of a polymer quantity made doing mole of D4, $D3^{Me,Ph}$ and VMS by 1000:15:0.2 mole ratio and uses basic catalyst tetramethylammonium silanolate(TMAS) and do opening equilibrium polymerization to be used to main polymer for high voltage insulation insulator. Control ATH content and content of platinum-based flame retardant and made high voltage insulation silicone rubber. Measured mechanical strength of making silicone rubber using UTM, and tracking characteristic according to standard of IEC 60587, flame retardant test studied effect that flame retardant characteristic gets in tracking characteristic, measuring according to UL94V method of test.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1995년도 봄 학술발표회 논문집
• /
• pp.154-159
• /
• 1995

Cold weather concrete presents the many characteristic variation of quality, according to the mixing and cooling point, the cooling time and the quantity of air besides the compressive strength of concrete. Thus, in this study to verify the character of cold-weather concrete we make the concrete specimens at laboratory and cool them at cooling-melting machine and then test the 7days compressive strength of them, with the variation of compressive strength of concrete, cooling point, cooling time, cooling weather and air quantity. At the results, the compressive strength of concrete decrease in the case of early cooling point, long cooling time, low cooling temperature and the low design compressive strength

• Journal of the Korean Wood Science and Technology
• /
• 제26권2호
• /
• pp.16-23
• /
• 1998

This paper examines the effects of specimen length and grade on the strength and stiffness properties of structural timber of radiata pine. The tensile strength and modulus of elasticity of 1,902 machine-graded boards with 3.15- and 1.62-m clear span lengths, were determined using a horizontal tension test machine. The mean failure and characteristic stress values for tensile strength show an extremely high dependency on test specimen length. The mean and characteristic values of both modulus of elasticity and tensile strength show significant dependency on machine stress grades.

• 동력기계공학회지
• /
• 제4권1호
• /
• pp.74-80
• /
• 2000

This present study was investigated effect of Ni contents on the high temperature strength characteristic in 9Cr ferritic heat-resistant steel added 1.7%W in place of Mo in order to restraint laves phase formation. Precipitation amount of carbide, number of particle per unit area and particle size of carbide were decreased with increase of Ni content. In the steels, carbides of $M_{23}C_6$ type was mainly precipitated, but laves phases could not precipitated. Tensile and yield strength, creep strength and creep rupture time was decreased, but elongation were increased due to decreasing of particle number per unite area and carbide amount precipitated with increase of Ni content.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
• /
• pp.445-448
• /
• 2004

Recently, bridge deck overlay with latex modified concrete is widely applied in domestic. the capacity of bridge deck overlay depends on bond state on the surface. factors that have an effect on bond state are clean condition on the surface, absence of surface microcracking, absence of laitance, overlay curing. In this study, it is researched that characteristic of bond strength according to moisture condition on the surface and the removal method of concrete. As a result, it shows high bond strength in dry condition when w/c is $31\%$ and in moisture condition when w/c is $38\%$ respectively. characteristic of bond strength according to the removal method of concrete shows high bond strength when using water-jets rather than jackhammers.

• Elastomers and Composites
• /
• 제52권4호
• /
• pp.295-302
• /
• 2017

Polyurethane dispersion (PUD) polymers were synthesized by using polyether and polyester polyol. The effect of ionomeric centers, r(NCO / OH) values, chain extender process, and chain extender types on the adhesion properties was investigated. In the case of polyether-based PUD, the ionic center, r value, chain extension process and chain extender types were not adjusted even after adjustment. In the case of polyester-based PUD, when the ionic center content was more than 2.5%, the state of adhesive strength was $2.0kgf/cm^2$ or more. On the other hand, the initial adhesive strength was excellent at about $1kgf/cm^2$ when the ionic center content was over 3.5%. When the r value was 1.3 or more, it was found that the initial bonding strength and the state of bonding strength were excellent at about $1kgf/cm^2$ and $2.1kgf/cm^2$ or higher, respectively. An IR spectrum analysis of the synthesized PUD confirmed that PUD was composed of urethane based on the N-H characteristic peak at $3340cm^{-1}$ and the urethane characteristic peak at $1730cm^{-1}$. Moreover, the characteristic peaks of the isocyanate ($2260cm^{-1}$) used in the preparation of the prepolymer were not observed. As a result, the residual -NCO was not observed, and urethane was completely synthesized.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
• /
• pp.159-162
• /
• 2001

A combined finite element and experimental study based on the characteristic length method is performed to investigate the strength and behavior of the pin joint in composite control rod. The failure is estimated by the Yamada-Sun and Tsai-Wu criteria on the characteristic curve. The gap elements are used to simulate the contact between the pin and the composite fitting with hole. The accuracy and applicability of the method are validated by the joint tests. All the specimens were failed in the bearing mode in the test and finite element analysis, and good agreement was found between the predicted and test results on the joint strength of composite control rod.

• 한국구조물진단유지관리공학회 논문집
• /
• 제5권1호
• /
• pp.188-194
• /
• 2001

A reinforced concrete structure is complex structure that works as one body with bonding role of steel bar and concrete. The bonding action between steel bar and concrete makes possible the compound structure. The transmission of mutual strength of the steel bar with concrete in structure is determined by the bonding characteristic of steel bar and concrete surface. But the efficiency of bonding characteristic of steel bar is Questionable by the corrosion cause by the delay construction term, the wrong management, etc. So this study investigate bonding characteristic of reinforced concrete using pull-out test method which steel bar removed rust and the principal variables of this study are concrete compression strength and the degree of corrosion. The result showed that bonding strength tend to increase when removed rust of steel bar whereas it tend to decrease when not removed rust.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2003년도 봄 학술발표회 논문집
• /
• pp.103-110
• /
• 2003

This study is as for shale that attract recently geotechnical engineer more and more. like sedimentary rocks and metamorpic rocks, shales have many problem with anisotropy for stength and deformation and they have many problems with quick weathering progress and differential weathering of alternate bedding. In foreign countries, many renowned schalors, like Jaeger(1960),McLamore,Gray(1967),Donath(1972),Nova(1980),Hoek&Brown(1980),Ranamurthy(1985), have already studied for a variety of characteristic and announced high level results of their studies. In domestic also, there are many scholars who have announced high level research papers for shale. this study is a part of these stream. and this study not only analyzed strength anisotropy characteristic along with direction of testing(two-direction) by using point-load test(log-log method) but also compared uniaxial strength between the maximum saturated and dried condition. In this study, we also conducted slaking test. these results of slaking test show weathering characteristic of shales. also, we made the most of field data that obtained during slope stability project and we noticed that RQD measured in the field is much differ from drilled core RQD. In order to come close two different value or access to reality, we suggest new RQD method that artificially reduce RQD by separating core with light hand force.