• International Journal of Highway Engineering
• /
• v.11 no.3
• /
• pp.23-32
• /
• 2009

In this paper an experimental program was launched to determine the mechanical and durability properties of spall repair materials (RCC: 3 items, PCC: 2 items, PC: 3 items). Test items were mechanical property tests such as setting times, strengths, modulus of elasticity, plastic shrinkage, and durability tests such as dynamic modulus ratio, bond property with freeze-thaw, water absorption, chemical resistance, ultraviolet exposure. Modulus of the PC products exhibits ductile while the modulus is in the order of RCC > PCC > PC. At early ages the PC products experience higher plastic shrinkage than others, henceforth stable at 28 days. Other test results such as dynamic modulus ratio, absorption, and chemical resistance show that the PCs are superior to the PCCs and the RCCs. Except for PC-2, all patch materials had bond strength more than 1.3MPa after freeze-thaw cycles of 200~300 while the PCs and the PCCs seem to be better than the RCCs. With 500 hours of ultraviolet exposure, all patch materials showed to have no crack or deterioration at the surface.

• Composites Research
• /
• v.28 no.4
• /
• pp.226-231
• /
• 2015

Various characteristics(thermal expansion, microstructure, etc.) and mechanical properties of CNT-aluminum nano composites manufactured by volume production system were evaluated. Also, formability and durability were evaluated for potential applications in automotive parts, via compared with high-elasticity material (A390) and the current commercial product. As a result, this composite has excellent mechanical properties and formability, therefore, to verity its potential for application as light and high strength materials in automobile part.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.39 no.3
• /
• pp.319-325
• /
• 2015

High-strength steel has replaced mild steel as the material of choice for truck decks or frames, owing to the growing demand for lightweight vehicles. Although studies on the weld fatigue characteristics of mild steel are available, studies on high-strength steels have been seldom conducted. In this study, firstly, we surveyed a chosen number of approaches and selected the Radaj method, which uses the notch factor approach, as the one suitable for evaluating the fatigue life of commercial vehicles. Secondly, we obtained the S-N curves of HARDOX and ATOS60 steel welds, and the F-N curves of the T-weld and overlapped-weld structures. Thirdly, we acquired a general S-N curve of welded structures made of high-strength steel from the F-N curve, using the notch factor approach. Fourthly, we extracted the weld fatigue characteristics of high-strength steel and incorporated the results in the database of a commercial fatigue program. Finally, we compared the results of the fatigue test and the CAE prediction of the example case, which demonstrated sufficiently good agreement.

• Korean Chemical Engineering Research
• /
• v.61 no.1
• /
• pp.26-31
• /
• 2023

For durability improvement of polymer electrolyte membrane fuel cell (PEMFC) polymer membrane, accelerated durability evaluation methods that can evaluate durability in a short time have been researched and developed. However, the lifespan of fuel cells for large commercial vehicles such as trucks and buses is more than three times that of passenger cars, and the chemical accelerated stress test (AST) time is also longer, reaching 1,500 hours or more. Therefore, in this study, as a method to evaluate the chemical durability of a membrane within a short time, it was examined whether the durability could be predicted by the pristine membrane characteristics. Hydrogen crossover current density (HCCD) and short resistance (SR) were estimated as initial characteristics, and AST time was predicted through the Fenton experiment, which was possible as an out-of-cell experiment for 3 hours. As the HCCD and fluoride ion emission concentration increased, the AST time tended to be linearly shortened, but there was a deviation (R² ≒0.65). When the SR decreased, the AST time showed a linear increase, and the accuracy was high (R² =0.93), so the AST time could be predicted with the initial SR of the membrane.

• Proceedings of the Korean Fiber Society Conference
• /
• 2003.04a
• /
• pp.432-433
• /
• 2003

미생물의 침해로부터 인체와 섬유제품을 보호하기 위하여 사용되는 항균 가공제로는 아민 또는 제4급 암모늄계, biguanide계, 알코올계, 페놀계, 알데하이드계 등의 유기계, 금속 이온 무기계, 산화물 및 광 촉매계, 유기 무기계, 천연 화합물 둥이 사용되고 있다[1-2]. 이러한 항미생물 가공제는 우수한 살균력, 섬유제품의 고유한 성질을 변화시키지 않는 특성, 탁월한 세탁 내구성, 인체에 대한 무독성 등의 조건을 가져야 한다[2-3]. (중략)

• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.05a
• /
• pp.991-996
• /
• 2001

The long-term durability characteristics of high-early-strength concrete were assessed. The effect of long-term durability characteristics of high-early-strength concrete were investigated. In experiment, two different types of fiber were adopted for improvement of durability. High-early-strength fiber reinforced concretes using regulated-set cements are compared with high-early-strength concrete without fiber. The durability performance of the laboratory-cured high-early-strength concrete specimens was determined by conducting an accelerated chloride permeability, abrasion resistance, freeze-thaw, surface deicer salt scaling and wet-dry repetition test. The results indicated that incorporation of fibers enhance durability performance.

• Proceedings of the Korean Society of Dyers and Finishers Conference
• /
• 2003.04a
• /
• pp.123-127
• /
• 2003

최근의 항균가공법을 대별하면 후가공법과 원사 개량법이 알려져 있으며 제품의 특성에 따라 선택되고 있다. 원사개량법은 항균 내구성을 확보할 수 있으나 합섬 원사 제조업체만 개발 가능한 방법으로 원사 구입의 어려움과 구입 단가가 높으며 섬유자체의 물성 및 염색성 등의 문제점이 있다. 한편 일반적인 가공법인 후가공법은 일반 제조업체에서 선호하는 가공법이나 항균효과의 내구성이 부족하며 사용수지 및 가공 환경상의 문제로 유리포르말린 및 중금속함량, 염색견뢰도 저하 등의 문제점을 가지고 있다. (중략)

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2015.07a
• /
• pp.213-215
• /
• 2015

플로팅 건축용 콘크리트 구조물은 부식환경에 노출되어 매립된 철근의 부식에 따른 구조물의 내구성능에 문제가 발생하게 된다. 철근 부식에 의한 내구성이 저하되는 문제의 여러 효과적인 해결방법 중 하나로 철근 코팅 기법이 있으며, 철근의 용융아연도금시 표면에 용융아연층이 형성되어 철근을 보호하는 장점이 있으나 콘크리트와의 부착 성능에 대한 연구는 미비한 실정이다. 따라서, 본 연구에서는 플로팅 건축용 콘크리트 구조물의 철근 겹이음에 따른 거동 특성연구를 수행하였다.

• Proceedings of the Korean Institute of Resources Recycling Conference
• /
• 2005.10a
• /
• pp.341-345
• /
• 2005

• Proceedings of the Korea Concrete Institute Conference
• /
• 2000.04a
• /
• pp.142-147
• /
• 2000

Durability characteristics of controlled low strength material(flowable fill) with high volume fly ash content was examined. The mix proportions used for flowable fill are selected to obtain low-strength material in the 10 to 15kgf/㎥ range. The optimized flowable fill was consisted of 60kgf/㎥ cement content, 280kgf/㎥ fly ash content, 1400kgf/㎥sand content, and 320kgf/㎥water content. Subsequently, durability tests including permeability warm water immersion, repeated wetting & drying, freezing & thawing for high volume fly ash-flowable fill are conducted The test results indicated that flowable fill has has acceptable durability characteristics.