• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.17-18
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• 2014

최근 자동차 성능 및 연비향상을 위해서 엔진의 고출력화 및 소형화 경향이 뚜렷해지고 있으며, 이로 인해 엔진내부의 부품이 받는 환경은 더욱 가혹해 지고 있다. 즉, 자동차 엔진 구동부품은 금속간의 접촉가능성이 매우 높은 경계윤활조건에 놓이게 되며, 또한 배기가스 규제로 인한 첨가제를 최소화 하려는 경향에 따라 경계윤활 환경에서 더욱 심한 마모문제에 직면할 것으로 예상되어 내구성 및 내마모성이 높은 코팅기술에 대한 요구가 더욱 증가하고 있다. 본 연구에서는 Zr기지의 비정질 형성능을 갖는 합금계를 이용하여 아르곤 및 질소분위기에서 스퍼터링 함으로써 고경도의 ZrN상과 엔진오일과 반응하여 저마찰 트라이보 필름을 형성시킬 수 있는 금소계 원소가 Tissue phase로 존재하는 질화물 나노박막합성기술을 개발한 후 자동차 구동부품인 벨브트레인계 및 피스톤링/라이너 부품에 적용하여 마찰특성을 평가하였다.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.1
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• pp.133-138
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• 2007

The balance shaft housing in the recent engines tends to have the high cycle fatigue crack caused by increased engine power. In this paper, a CAE procedure is introduced to predict the durability of the balance shaft housing. The procedure is performed through two analysis steps. In the first step, the multibody dynamic simulation is used to obtain more accurate loading boundary conditions applied to the finite element model for the following step. Next, the finite element analysis is performed to predict the durability of the balance shaft housing through the calculation of the safety factor. Through this CAE procedure, the revised balance shaft housing was developed to improve the durability. And the durability of the housing was confirmed experimentally.

• Proceedings of the KIPE Conference
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• 2016.11a
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• pp.25-26
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• 2016

본 논문에서는 전기자동차용 충전기를 위한 전해커패시터가 없는 단일단 인터리브드 토템폴 소프트스위칭 AC-DC 컨버터를 제안한다. 제안하는 단일단 충전기는 토템폴 구조에 인터리빙 회로를 적용하여 소자의 수를 최소화하였으며 넓은 전압 및 부하영역에서 스위치의 ZVS 턴 온 및 다이오드의 ZCS 턴 오프를 성취하여 고효율을 달성할 수 있다. 또한 CCM 동작으로 인해 입력필터가 작고 스위치의 도통손실을 감소시킬 수 있으며 전해커패시터를 제거하고 필름커패시터를 사용하여 높은 전력밀도와 내구성을 만족한다. 제안하는 전기자동차용 충전기의 동작원리를 제시하고 시작품을 통해 본 논문의 타당성을 검증하였다.

• Journal of the Korean Geotechnical Society
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• v.23 no.12
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• pp.25-32
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• 2007

This study is to evaluate the effect of chemical attack on durability and deterioration of lining concrete in tunnel. Surface examination, nondestructive inspection, uniaxial compressive strength test, carbonation test, chloride diffusion test, micro-structural analysis were performed to analyze the deterioration of lining concrete in tunnel constructed 70 years ago. From surface examination results, the tunnel had been repaired and reinforced in several times. It has many cracks, water-leakage, efflorescence and exploitation. Compressive strengths obtained from nondestructive inspection and uniaxial compressive strength test have measured $17.5{\sim}34.7MPa$, and $12.8{\sim}40.3MPa$, respectively. Carbonation depth specimen cored from concrete lining has ranged from 3mm to 27mm. From chloride diffusion test, most specimens have low permeability. And the XRD analysis was able to detect ettringite and thaumasite, which were confirmed by SEM and EDS results to be the causes for the deterioration of lining concrete.

• Journal of Korean Tunnelling and Underground Space Association
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• v.3 no.1
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• pp.11-19
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• 2001

The purpose of this study is to improve the problems in Umbrella Arch Method, such as the oxidation, the difficulties in installation and cutting of the steel pipe. The applicability of the high strength FRP (Fiber-Reinforced-Plastic) materials composed of glass fiber as a substitute of steel pipe was investigated in this study. The results of this study show that FRP material is better than steel pipe in work performance and the durability of material except for its price. From the numerical analysis with various types of FRP, it was evaluated that the equiangular curve type is more efficient than the flat type developed abroad, and the supporting effect of FRP-grout mixture is similar to that of steel-grout mixture in results of bending strength test.

• Journal of the Korean GEO-environmental Society
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• v.11 no.1
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• pp.53-59
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• 2010

In seawater deposition condition, the corrosion and chemical attack of grouts are similar to those of concrete structure. Used in domestic MSG (Micro Silica Grouting) mixtured large amounts of silicate materials containing as cement powder is $8,000cm^2/g$ of the specific surface area or more due to the high hydration activity and high-strength, high durability, and features, $C_3A$ content of less than 5% to meet the standards chemical attack of seawater was evaluated as a cement material. Therefore, in this paper, with excellent seawater attack resistant MSG in combination with rapid hardening mineral was used, those of seawater characteristics were evaluated experimentally. Typically, sodium-silicate minerals or rapid hardening cements are used in domestic. About the homogel specimens with combination of MSG and rapid hardening agents for compressive strength, weight and length change characteristics were evaluated experimentally, and so we could present the excellent seawater resistant grouts combination.

• Journal of the Korean Geotechnical Society
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• v.16 no.1
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• pp.227-234
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• 2000

Soilcrete has been a traditional material for pavement and soft ground improvement techniques. However, since the durability is not excellent and the quality is not consistent, it has not been used for various purposes up to date. However, with the increase of naturally oriented needs for light traffic roads such as pedestrian roads of garden, golf courses and sidewalks, the cases of the high strength soilcrete paving have been increased lately. This study aims at making a reference table of mix design in accordance with the required design specifications fur the high strength soilcrete admixtured with the pozzolanic cement by using a statistical experimental method. The treated soil is the clay which is widely found in Korea. As the results of this study, we could derive an effective reference mix design table for the clay treated with the pozzolanic cement stabilizer in accordance with the compressive strength of $50~150kg/cm^2$ soilcrete.

• Magazine of the Korea Concrete Institute
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• v.11 no.1
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• pp.141-148
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• 1999

Recently, high performance concrete developed has a good quality at fresh and hardened state, but high binder contents results in spending much money on manufacturing and many cracks by drying and autogenous shrinkage, Therefore, in this paper, not only prevention of cracks caused by drying and autogenous shrinkage, but improvement of quality and accomplishment of economy by applying F.A(fly ash), S.F(silica fume) and CSA(calcium sulfa aluminate) expansive additives as an inorganic admixtures in W/B 35% are discussed. According to the experimental results, when 5% of CSA expansive additives and 15:5(F.A:S.F)are replaced at unit cement content, high performance concrete with both good fluidity at fresh state and high compressive strength, compensation of drying and autogenous shrinkage at hardened state are accomplished.

• Journal of the Korea Institute of Building Construction
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• v.20 no.1
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• pp.27-34
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• 2020

In the industry, due to the carbon dioxide gas produced during cement production is increasing, research on recycling by-products has been actively conducted. In the industrial by-products, the high calcium fly ash(HCFA) produced by the blast-furnace in the circulating fluidized bed combustion method has a high ratio of CaO and CaSO4. In view of this, the purpose of this is to use high calcium fly ash(HCFA) as a stimulant in blast furnace slag powder and use it as a cement substitute. As a result, it is judged that the substitution ratio of HCFA should be 15% or less. In addition, although durability and strength are relatively lower than of OPC, it is considered that it can be utilized as an environmentally building material.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.6
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• pp.182-188
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• 2018

Recently, various researches on the utilization of carbon nanotube(CNT) with superior electrical conductivity and large surface areas into concrete have been actively conducted. Thus, mechanical and thermal properties of cement-flyash composites were evaluated concerning the CNT replacements. Based on the low binder-to-water ratio, the cement composites were produced with 0.2 % and 0.5 % of CNT solids. The compressive strengths with various ages, isothermal calorimetry measurement, SEM analysis, thermal conductivity of cement composites and thermal gravimetry analysis were implemented. As the amount of CNT addition was increased, the thermal conductivity of cement composites were also increased. Also, there was no significant mechanical property differences between mixtures with and without CNTs.