• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.3
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• pp.129-138
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• 2002

The purpose of this study is to propose the nonlinear analysis method which combines the nonlinear incremental method with the layered method to solve the problems due to the geometric and the material nonlinearities. As numerical analysis models, the reinforced concrete simple beam and the steel arch frame are used to verify the algorithm of the proposed nonlinear method. The results are gotten from the computation procedures. According to the results of this study, the fracture pattern of the beam according to the ratio of tensile steel and the strength of the concrete and the steel can be estimated by the proposed method. Therefore, the load-deflection curve of structure can be, exactly, depicted by the proposed method. Also, the rupture load, the site and the depth of crack of the beam can analytically be checked by the proposed method. In this respect, the proposed method contributes for the solving the stability problem of the actual structure.

• Journal of Power System Engineering
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• v.20 no.5
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• pp.5-13
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• 2016

This study is on wear damage of the material for a molding machine that be used at finally cutting of metal beam made in roll forming process of vehicle bump beam process line. SKD11 steel was used with the material for cutting mold jig. In the cutting mold jig, Ti diffusion heat treatment after vacuum heat treatment was carried out for upgrade of surface hardness and anti-wear. Also, the heat treatments by various methods were performed to compare the wear damage degree against above the existing heat treatment. Wear loss and friction coefficient were obtained from wear test. And, micro Vickers hardness values were compared with damaged parts or not of cutting mold jig. Micro Vickers hardness value appeared higher at the undamaged part by Ti diffusion heat treatment. The micro Vickers hardness well followed a two-parameter Weibull probability distribution.

• Corrosion Science and Technology
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• v.14 no.5
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• pp.226-231
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• 2015

In spite of highly advanced paint coating techniques, corrosion damage of marine metal and alloys increase more and more due to inherent micro-cracks and porosities in coatings formed during the coating process. Furthermore, flowing seawater conditions promote the breakdown of the protective oxide of the materials introducing more oxygen into marine environments, leading to the acceleration of corrosion. Various corrosion protection methods are available to prevent steel from marine corrosion. Cathodic protection is one of the useful corrosion protection methods by which the potential of the corroded metal is intentionally lowered to an immune state having the advantage of providing additional protection barriers to steel exposed to aqueous corrosion or soil corrosion, in addition to the coating. In the present investigation, the effect of flow velocity was examined for the determination of the optimum corrosion protection current density in cathodic protection as well as the corrosion rate of the steel. It is demonstrated from the result that the material corrosion under dynamic flowing conditions seems more prone to corrosion than under static conditions.

• Journal of Korea Foundry Society
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• v.30 no.5
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• pp.179-186
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• 2010

To elucidate the effects of alloying elements on the characteristics of microstructure and high temperature oxidation of cast austenitic stainless steel, a thermodynamic calculation, a cyclic oxidation test, a X-ray diffraction, a scanning electron microscopy-back scattered electron, a electron probe microanalysis were conducted. The thermodynamic calculation for the effect of vanadium (V) addition on the formation of various precipitates leads to a decrease of chromium (Cr)-rich $M_{23}C_6$ carbides due to the formation of M (C, N) carbo-nitrides containing V and / or niobium (Nb). The V added alloy increased the resistance to high temperature oxidation due to a decrease of Cr-depleted zone deteriorating the oxidation resistance and due to the V-enriched oxide layer formed in inner oxide layer blocking the outward transport of cations.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.4
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• pp.333-342
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• 2004

Tensile and low cycle fatigue (LCF) tests on prior cold worked 316L stainless steel were carried out at various temperatures from room temperature to 650$^{\circ}C$. At all test temperatures, cold worked material showed the tendency of higher strength and lower ductility compared with those of solution treated material. The embrittlement of material occurred in the temperature region from 300$^{\circ}C$ to 600$^{\circ}C$ due to dynamic strain aging. Following initial cyclic hardening for a few cycles, cycling softening was observed to dominate until failure occurred during LCF deformation, and the cyclic softening behavior strongly depended on temperature and strain amplitude. Non-Masing behavior was observed at all test temperatures and hysteresis energy curve method was employed to describe the stress-strain hysteresis loops at half$.$life. The prediction shows a good agreement with the experimental results.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.10a
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• pp.289-294
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• 2002

Unlike Tubular Steel Tower, This Composite Material Tower is a low-technology Component, whose design is easy to optimize, and which therefore during the design process-lends itself easily as an object for possible cost reduction at very little effort. This may come in useful as the cost of a tower usually significant part of the total cost of a structure. This paper is written by the Composite Materials Tower which loaded Complex loading in Off and On shore. This Composite Material Tower is made by the Method of Filament Winding, and the Component of Composite Material is used by the Roving RS220PE-535. When it loaded Complex trading, there is a results which is bigger than steel tower deflection. We controlled this 1a18e deflection by stiffeners which has thickness 20mm. At last, Off and On Shore Tower which used Composite Materials is compared with Off and On Shore Tower which used Steel.

• Korean Journal of Materials Research
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• v.16 no.12
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• pp.766-770
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• 2006

The frictional behavior of oxide films on top of the plasma nitrocarburized compound layers was investigated in terms of post-oxidation treatment temperatures. The post-oxidation treatment at both temperatures($400^{\circ}C,\;500^{\circ}C$) produced magnetite($Fe_3O_4$) films which led to a significant enhancement in corrosion resistance. However, this process did not result in any improvement in frictional behavior of the nitrocarburized surface. The wear mechanisms were governed predominantly by the abrasive action of the slider on the surface irrespective of the counterface material(SiC and Bearing steel). When the specimen was sliding against a SiC counterface, the oxide films were destroyed during the early stage of the sliding process and the wear debris of the oxide film at the sliding track had a great influence on the friction coefficient. On the other hand, when sliding against a bearing steel counterface, the slider was mainly worn out due to the much higher hardness of the surface hardened layer. The fluctuation of the friction coefficient of $400^{\circ}C$-oxidized/ nitrocarburized specimen is much severer than that of $500^{\circ}C$ specimen, due to the less amount of wear debris.

• Transactions of Materials Processing
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• v.28 no.5
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• pp.266-274
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• 2019

Metal sealing is used to connecting the parts between valves and fuel pipes for a FCEV which utilizes hydrogen gas of 700 bar. Instead of general carbon steel, stainless steel is the primary material used to manufacture fuel pipes due to hydrogen embrittlement. The shape of deformation between metals is an important factor on the air-tightness of the metal to metal contact. Since the stainless steel pipe is hardened using the plastic forming during the tip shaping stage, this work hardening could have an effect on the deformed shape and characteristics of contact surfaces in fastening of pipes. In this paper, the deformation history of the pipe model was considered in order to analyze the hydrogen-tightness on the metal sealing part. The contact distance and the forward displacement for fastening were compared using experimental results and the simulation results. The simulation of the effect of material change on the fitting body demonstrated that the hardness or the strength of the formed tip of the pipe was designed to a proper valued level since the characteristics of the contact surface was exhibited better when the strength of the pipe was lower than that of the fitting body.

• Structural Monitoring and Maintenance
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• v.10 no.2
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• pp.117-132
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• 2023

The most prevalent and oldest type of structure is unreinforced masonry (URM) structures; URM walls are still a widely used construction material in India and many other developing countries due to their simplicity, ease of construction, economic sustainability, and ability to be built with locally available materials. URM walls are significantly weak while carrying lateral loads. The poor performance of URM walls during earthquakes has necessitated investigating an effective method for strengthening a newly built masonry building or retrofitting an old structure. Wire mesh, being cost-effective and easily available, satisfies the requirements to strengthen new and old URM buildings. The use of wire mesh to strengthen and retrofit the URM structure is simple to use, quick to construct, and inexpensive, especially in developing nations where heavy machinery and highly qualified labour are lacking. The current paper reviews the effectiveness of steel wire mesh as a reinforcing material for enhancing masonry strength. The finding gave encouraging results for the field application of wire mesh.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.263-264
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• 2008