• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 A
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• pp.339-341
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• 2002

The remaining life of ACSR exposed to the atmosphere for a long period may rely on deterioration caused by environmental indices such as atmospheric corrosion, galvanic corrosion, crevice corrosion and fatigue corrosion. One of reduction of useful life in overhead transmission lines built on the ridge of mountain is often caused by forest fires. This paper deals with investigation of strength deterioration performance of ACSR due to fires through several testing and analyzing data for both tension load and material analysis. Test samples are ACSR $480[mm^2]$ conductors, which are artificially fired to regular durations. As a result, it can be verified that tension load of ACSR are reduced by increasing fro duration. Hence, it is obvious that ACSR due to forest fires may lead to mechanical deterioration.

• 한국자동차공학회논문집
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• 제11권5호
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• pp.140-146
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• 2003

Metal matrix composites had generated a lot of interest in recent time because of their high specific strength and stiffness in specific properties. It was also highlighted as the material of frontier industry because strength, heat-resistance, corrosion-resistance and wear-resistance were superiored. In this study, the strength properties of $Al_{18}B_{4}O_{33}$/AC4CH composites were represented mixing the binder of $SiO_2$. It was also fabricated by squeeze casting. $Al_{18}B_{4}O_{33}$/AC4CH was fabricated at the melt temperature of $760^{\circ}C$, the perform temperature of $700^{\circ}C$ and mold temperature of $200^{\circ}C$ under the pressure of 83.4MPa. Consequently, fatigue life was observed roughly in the order of AC4CH> nobiner> $SiO_2$, independently on crack propagation direction and stress ratio.

• 한국세라믹학회지
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• 제41권1호
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• pp.69-75
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• 2004

인공치아용 3Y-TZP와 (Y,Nb)-TZP/$Al_2O_3$ 복합체를 유사 구강분위기인 인공타액 하에서 500-3000N의 하중 조건으로 $10^6$ 횟수까지 헤르찌안 반복하중 피로특성을 조사하였다. 500N의 하중에서 $5{\times}10^5$까지 반복피로 실험결과, 강도 저하 및 균열 현상은 관찰되지 않았다. 피로특성은 SY-TZP가 (T,Nb)-TZP/$Al_2O_3$ 복합체보다 상전이에 의한 응역회복 때문에 우수하였다. 하중값이 증가함에 따라 링 균열에서 방사상 균열로 전이되었을 때 급격한 강도 저하 현상이 발생하였다. 강도 저하 현상은 유사 구강 분위기하에서 반복 하중 접촉 시 발생한 균열을 통해 침투한 인공타액의 화학적 침식으로 더욱 가속화 되었다.

• 한국자동차공학회논문집
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• 제11권6호
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• pp.101-107
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• 2003

Since stainless steel sheets have good mechanical properties, weldability, appearance and corrosion resistance, they are commonly used as one of the structural materials of the railroad cars or the commercial vehicles which are manufactured by the spat welding. Among the many kinds of spot welded lap joints, it can be found that multi-lap joints are employed in their body structure. But, fatigue strength of these joints is lower than that of base metal due to high stress concentration at the nugget edge of spot weld and is considerably influenced by welding conditions as well as the mechanical and geometrical factors. Thus, it is necessary to establish a reasonable and systematic design criterion for the long life design of the spot-welded body structures. In this paper, the stress distribution and deformation around the spot-welded multi-lap joints subjected to tensile shear load was numerically analyzed. Also, the $\Delta$P-Nf curve was obtained by fatigue tests. Using these results, $\Delta$P-Nf curves were rearranged in to the ${\Delta}{\sigma}$-Nf relation with the maximum stress at nugget edge of spot weld.

• Corrosion Science and Technology
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• 제11권5호
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• pp.184-190
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• 2012

Cu alloy is widely used for marine applications due to its excellent ductility and high resistance for corrosion as wells as cavitation. However, long term exposure of the material to marine environments may result in damages caused by cavitation and corrosion. Water cavitation peening has been introduced in order to improve resistance of Cu alloy to corrosion and cavitation. The technology induces compressive residual stress onto the surface, and thus enhances the fatigue strength and life. In this study, the characteristics of the material were investigated by using water cavitaiton peening technique, and results showed that 2 minutes of water cavitation peening indicated the considerable improvement in hardness. On the other hand, over 10 minutes of water cavitation peening accelerated damages to the surface. In the case of ALBC3, water cavitation peening in the range of 2 to 10 minutes has shown the excellent durability and corrosion resistance while minimizing surface damages.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 춘계학술대회 논문집
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• pp.155-160
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• 2002

Metal matrix composites had generated a lot of interest in recent times because of significant in specific properties. It was also highlighted as the materials of frontier industry because strength, heat-resistant, corrosion-resistant, wear-resistant were superiored. In this study the strength properties of $Al_{18}B_4O_{33}/AC4CH$ were represented mixing the binder of $Al_2O_3$ and $TiO_2$. It was also fabricated by squeeze casting. $Al_{18}B_4O_{33}/AC4CH$ was fabricated at the melt temperature of $760^{\circ}C$ the perform temperature of $700^{\circ}C$ and mold temperature of $200^{\circ}C$ under the pressure of 83.4MPa and observed SEM. Fatigue crack growth rate tests on compact tension specimen(half-size) of thickness 12.5mm were conducted by using sinusoidal waveform. Compact tension specimens(half-size) were used and fatigue crack growth rate da/dN and stress intensity factor range ${\Delta}K$ were analyzed concerning to the R value of 0.1 and 0.05. In order to find out the value of ${\Delta}K$, load amplitude constant method was applied by the standard fatigue testing method describes in ASTM E647-95a. As the results of this study, Fatigue crack growth rate increased with in creasing the load ratio, Consequently, At equivalent stress intensity factors, the fatigue crack growth rates in MMC were faster than those of AC4CH alloy. then the fatigue life and the fatigue crack growth rate was investigated using scanning election microscopy(SEM)

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2006년 추계학술발표대회 개요집
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• pp.277-279
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• 2006

Due to the numerous environmental factors, cracks and corrosion are frequently occured especially in old steel bridge, which deteriorate the structural integrity; thus bring about the problems of structural safety of the steel bridge. Therefore, repair and reinforcement are required for the damaged structure. the replacement repair welding method is spotlighted for its brilliant features, i.e. it can be achieved without incurring traffic dislocation. the method cuts the damaged parts and replaces them with new steel plate by welding under live loads. However, the mechanical behavior of the welded joints under cyclic loads due to the traffic which passes along bridge is not clarified. In this paper, the fatigue strength of the replacement repair welded joints was investigated in order to improve reliability in the repair welded joints of old steel bridge.

• 한국생산제조학회지
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• 제9권3호
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• pp.76-82
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• 2000

It is well known that during the oxygen cutting process residual thermal stresses are produced in weldment. The local non-uniform heating and subsequent cooling which takes place during any welding process causes complex thermal strains and stresses to finally lead to residual stresses exceed to the yield stress. High tensile stresses combined with applied structural load in the region near the welded joint can given rise to distortion brittle fracture change of the fatigue strength and stress corrosion cracking. The appropriate treatment of the welded component which reduces the peak of he welding residual stresses is believed to lower risk of the fracture during the service of the structure. In this study the impact loading in oxygen cutting frame was applied to reduce the residual stress. After applying the impact loading redistribution of resid-ual stress was measured by cutting method and the effect of fatigue was tested.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1269-1270
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• 2006

Mg-Zn-RE alloys had a novel lond period stacking ordered (LPO) structure. Their rapidly solidified powder metallurgy (RS P/M) alloys exhibited a combination of high strength and god ductility (tensile yield strength above 550 MPa and elongation above 5%). The LPO Mg-Zn-RE RS P/M alloys had high elevated temperature strength (tensile yield strength above 380 MPa at 473 K) and exhibited a high-strain-rate superplasticity at higher temperatures. In Japan, a national project for developing high strength LPO Mg-Zn-RE RS P/M alloys has started at 2003 for 5 years, which is founded by the Ministry of Economy, Trade and Industry (METI) of Japan. In the national project, project targets in materials performances have been achieved. The developed LPO Mg-Zn-RE RS P/M alloys exhibited higher tensile yield strength, fatigue strength and corrosion resistance than high strength aluminum alloys of extra-super-duralumin (7075-T6).

• Corrosion Science and Technology
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• 제23권1호
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• pp.72-81
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• 2024

The Ti-6Al-4V alloy is widely used as an implant material due to its higher fatigue strength and strengthto-weight ratio compared to pure titanium, excellent corrosion resistance, and bone-like properties that promote osseointegration. For rapid osseointegration, the adhesion between the titanium surface and cellular biomolecules is crucial because adhesion, morphology, function, and proliferation are influenced by surface characteristics. Polymeric peptides and similar coating technologies have limited effectiveness, prompting a demand for alternative materials. There is growing interest in 2D nanomaterials, such as MoS₂, for good corrosion resistance and antibacterial, and bioactive properties. However, to coat MoS₂ thin films onto titanium, typically a low-temperature hydrothermal synthesis method is required, resulting in the synthesis of films with a toxic 1T@2H crystalline structure. In this study, through high-temperature annealing, we transformed them into a non-toxic 2H structure. The implant coating technique proposed in this study has good corrosion resistance and biocompatibility, and antibacterial properties.