• 대한기계학회논문집A
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• 제30권12호
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• pp.1534-1542
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• 2006

In this paper, the concept of accelerated life test, which is a popular research field nowadays, is applied to the shot peened material. To predict the efficient and exact room temperature fatigue characteristics from the high temperature fatigue data, the adequate accelerated model is investigated. Ono type rotary bending fatigue tester and high temperature chamber were used for the experiment. Room temperature fatigue lives were predicted by applying accelerated models and doing reliability evaluation. Room temperature fatigue tests were accomplished to check the effectiveness of predicted data and the adequate accelerated life test models were presented by considering errors. Experimental result using Arrhenius model, fatigue limit obtain almost 5.45% of error, inverse power law has about 1.36% of error, so we found that inverse power law is applied well to temperature-life relative of shot peened material.

• 대한기계학회논문집A
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• 제27권11호
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• pp.1873-1880
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• 2003

The sliding wear characteristics of the crane sheave were investigated using a pin on disk rig tester. The experiment was conducted using a high carbon steel wire that was upper material, also carbon steel castings that was disk material. There are various operating conditions in this work. At the room temperature, we carried out the wear test under a grease lubrication and dry condition. The results of wear test showed that an annealed-casted have lower, also the wear curves are linearly increased with increasing of sliding distance. For the specific wear rate of annealed-casted, the wear resistance was increased with decreasing diameter of wire. The wear of a wire and a disk have a different mechanism, the one is the abrasive wear due to fatigue wear under lubrication, another is the adhesion wear under dry condition.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제30회 추계학술대회
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• pp.94-100
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• 1999

The friction and wear behavior of MoS$_2$Coatings were investigated using a pin and disk type tester. The experiment was conducted using silicon nitride as pin material and MoS$_2$-on-bearing steel as disk material under different operating conditions that include linear sliding speeds in the range of 22~66mm/sec, normal loads varying from 9.8~29.4N, corresponding to maximum contact pressure of 1.78~2.830GPa and atmospheric conditions of high vacuum, medium vacuum, ambient air. The results showed that low friction coefficient of the coating has been identified when running in high vacuum and that friction coefficient and wear volume increased with increasing normal load. Also at high load conditions, the friction coefficient and wear volume increased with increasing sliding velocity.

• 한국소음진동공학회논문집
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• 제19권3호
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• pp.274-281
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• 2009

The carbon fiber epoxy composite material and aluminum have many advantages over other materials because of their high specific stiffness and good fatigue characteristics. Basically, the propeller shaft of automobile requires bending frequency of higher than 2,700 Nm and high natural frequency of higher than 9,200 rpm occurred by fast revolution. For this reason, natural frequency and torsion torque characteristics of hybrid shaft was studied in variation of its outer-diameter and thickness. Vibration and torque characteristics of hybrid shaft were compared by torsion tester, natural frequency experiments and FE analysis. Designed hybrid shaft satisfied its vibration and torque characteristics when its outer-diameter was 60 mm and thickness was 5 mm. Therefore, hybrid material enables to manufacture one piece structure hybrid propeller shaft rather than current two piece structure.

• 한국레이저가공학회지
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• 제2권2호
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• pp.27-33
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• 1999

Electron beam was applied on the low carbon steel in order to fabricate Metal/Metal GBM(Graded Boundary Material). Ni sheet was placed on the steel substrate. The electron beam was irradiated on the surface and produced a homogeous alloyed layer. Sequential repetition of electron beam treatments for 4 times resulted in 8mm thick graded layer. To determine each layers property, optical microscopy, XRD, microhardness tester and EDS were used. The residual stress was measured by the low angle x-ray diffraction method. The graded boundary layer was stepwise profile, but Ni content incresed up to 80 wt% and Fe content decreased 20 wt% near surface. Each layers microstructure and hardness varied by different Fe/Ni composition. The compressive residual stress was induced by martensite transformation in the 1st and End layers and the shrinkage cracks were formed in graded layer by rapid cooling.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2003년도 학술대회지
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• pp.50-55
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• 2003

Tribological testing of DLC films was conducted using a rotating type ball on a disk friction tester in a dry chamber. This study made use of four kinds of mating balls that were made with stainless steel but subjected to diverse annealing conditions in order to achieve different levels of hardness. In all load conditions using martensite mating balls, the test results demonstrated that the friction coefficient was lower when the mating materials were harder. The high friction coefficient found in soft martensite balls appeared to be caused by the larger contact areas. The wear track on the mating balls indicated that a certain amount of material transfer occurs from the DLC film to the mating ball during the high friction process. Raman Spectra analysis showed that the transferred materials were a kind of graphite and that the contact surface of the DLC film seemed to undergo a phase transition from carbon to graphite during the high friction process.

• 한국전기전자재료학회논문지
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• 제18권5호
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• pp.450-456
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• 2005

In this paper, the effect of adhesion properties of semiconductive-insulating interface layer of silicone rubber on electrical properties was investigated. The modifications produced on the silicone surface by oxygen plasma were accessed using ATR-FTIR, contact angle and Surface Roughness Tester. Adhesion was obtained from T-peel tests of semiconductive layer haying different treatment durations. In addition, ac breakdown test was carried out for elucidating the change of electrical property with duration of plasma treatment. From the results, the treatment in the oxygen plasma produced a noticeable increase in surface energy, which can be mainly ascribed to the creation of O-H and C=O. It is observed that adhesion performance was determined by surface energy and roughness level of silicone surface. It is found that at dielectric strength was increased with improving the adhesion between the semiconductive and insulating interface.

• 대한기계학회논문집A
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• 제31권6호
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• pp.644-650
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• 2007

Mechanical property evaluation of micrometer-sized structures is necessary to help design reliable microelectromechanical systems(MEMS) devices. Most material properties are known to exhibit dependence on specimen size and such properties of microscale structures are not well characterized. This paper describes techniques developed for tensile testing of thin film used in MEMS. Epi-polycrystalline silicon is currently the most widely used material, and its tensile strength has been measured as 1.52GPa. We have developed a tensile testing machine for testing microscale specimen using electro-magnetic actuator. The field magnet and the moving coil taken from an audio-speaker were utilized as the components of the actuator. Structure of specimen was designed and manufactured for easy handling and alignment. In addition to the static tensile tests, it is described that new techniques and procedures can be adopted for high cycle fatigue test of a thin film.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.509-512
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• 2004

This research is targeting that estimate the effect on cement concrete pavement with type of chloride deicers. In order to this study objective, when chloride deicers were spread on road surface, thermal characteristics test was conducted. Also, skid resistance test according to types and concentration of chloride deicier, road surface conditions were investigated. As a test results, thermal characteristics with kind of chloride deicier could know that sodium chloride(NaCl) is exothermic reactive material, calcium chloride$(CaCl_2)$ is endothermic reactive material. And, in case of mixed salt of the calcium and sodium chloride, it could know that can change to the exothermic or endothermic reaction according to dosage ratios. Skid value by British Pendulum Tester(BPT) has shown that it is seldom difference between the types($CaCl_2$, NaCl, mixed salt) and solution concentrations(0.5, 0.8, 1.0, 4.0, $10\%$) of chloride deicier comparing with tap water except mixed salt($10\%$ solution concentration).

• 한국지반신소재학회논문집
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• 제5권4호
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• pp.43-47
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• 2006

다짐조건을 달리하여 3가지 종류 지오그리드의 내시공성을 측정하였다. 이 실험은 ENV ISO 10722-1에 근거하여 실행되었다. 채움재와 관계없이 다짐횟수가 증가할수록 지오그리드의 인장강도는 감소하였으며, 지오그리드 종류에 따라 감소되는 경향이 다르게 나타남을 알 수 있었다. Woven 및 warp-knitted type 지오그리드의 경우 접합형 지오그리드에 비해 더 큰 감소경향을 나타내었다.