• 한국산학기술학회논문지
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• 제15권8호
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• pp.5400-5405
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• 2014

수상태양광을 개발하기 위해서는 무엇보다 가볍고 높은 인장을 갖는 재료를 적용하여 부력에 부담을 줄여주고 부식 저항이 높은 재료특성이 요구된다. 따라서 수상태양광발전 구조물에 적합한 강도, 내구성, 제작 및 용접성을 개선시킨 새로운 고강도 강재의 수상태양광 적용가능성 연구가 필요하다. 본 논문에서는 수상태양광에 적합한 강재선정을 위해 일반강재(SS400)와 고강도강재(POSH 690)의 기계적 하중시험과 강재의 부식시험을 수행하였다. 고강도 신소재강에 대한 시험결과 기존 일반 강재에 비해 기계적 성능이 우수한 것으로 검증되었고, 이 강재를 실제 현장에 제작하여 비교한 결과 기존 강재에 비해 중량이 30~40% 정도 중량감소 효과를 확인하였다.

• International Journal of Korean Welding Society
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• 제5권1호
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• pp.53-59
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• 2005

Auto industry has employed resistance spot welding(RSW) to join steel sheets for structural rigidity of automobile body. Driven by the need to reduce weight and fuel consumption, car companies have been evaluating aluminum intensive vehicles(AIVs) as a way to reduce vehicle weight without downsizing. During the transition from all steel-construction vehicle body to aluminum intensive body, joining aluminum to steel sheets emerges as a serious contender in automobile body. This paper deals with application of transition material to RSW aluminum to steel. Placing transition material insert between the aluminum/steel interface was found very effective to overcome physical incompatibility between aluminum and steel. Use of transition insert allows for two separate weld nuggets to be formed in their respective aluminum/aluminum and steel/steel interfaces. This RSW processes was monitored with the aid of dynamic resistance sampling. Typical patterns in sampled dynamic resistance curves indicated formation of sound nugget. The growth of two separate nuggets was examined by micro-cross section test.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제33회 춘계학술대회 개최
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• pp.319-326
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• 2001

The sliding wear characteristics of carbon steel castings were Investigated using a ball on disk type tester. The experiment was conducted using high carbon steel wire rods as ball material and carbon steel castings as disk material and different operating conditions, at room temperature under a lubrication and dry conditions. The results showed that the carbon steel castings appeared average wear volume Is lowed after annealing under a lubrication conditions and wear curve linear Increased. The specific wear rate of carbon steel castings Increased with wire diameter lubrication and dry also Increased 125 times In Ory. The sliding wear mechanism were Investigated due to fatigue wear lubrications and abrasive wear dries also wire Included fatigue and abrasive wear by plastic flow.

• Journal of Welding and Joining
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• 제18권2호
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• pp.239-239
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• 2000

Automobile manufacturers have employed resistance spot welding(RSW) to join steel sheets for structural rigidity o automobile body. Driven by the need to reduce weight and fuel consumption, car companies have been evaluating aluminum intensive vehicles(AIVs) as a way to reduce vehicle weight without downsizing. During the transition from all steel-construction vehicle body to aluminum intensive body, joining aluminum to steel sheets emerges as a serious contender in automobile body. This paper deals with application of transition material to RSW aluminum to steel. Placing transition material insert between the aluminum/steel interface was found very effective to overcome incompatibility between aluminum and steel. Use of transition insert allows for two separate weld muggets to be formed in their respective aluminum/ aluminum and steel/ steel interfaces. This RSW process was monitored with the aid of dynamic resistance sampling. Typical patterns in sampled dynamic resistance curves indicated formation of sound nugget. (Received February 28, 2000)

• Journal of Welding and Joining
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• 제18권2호
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• pp.112-118
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• 2000

Automobile manufacturers have employed resistance spot welding(RSW) to join steel sheets for structural rigidity of automobile body. Driven by the need to reduce weight and fuel consumption, car companies have been evaluating aluminum intensive vehicles(AIVs) as a way to reduce vehicle weight without downsizing. During the transition from all steel-construction vehicle body to aluminum intensive body, joining aluminum to steel sheets emerges as a serious contender in automobile body. This paper deals with application of transition material to RSW aluminum to steel. Placing transition material insert between the aluminum/steel interface was found very effective to overcome incompatibility between aluminum and steel. Use of transition insert allows for two separate weld nuggets to be formal in their respective aluminum/aluminum and steel/steel interfaces. This RSW process was monitored with the aid of dynamic resistance sampling. Typical patterns in sampled dynamic resistance curves indicated formation of sound nugget.

• Nuclear Engineering and Technology
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• 제45권4호
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• pp.553-564
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• 2013

This study evaluates the local damage of a turbine in an auxiliary building of a nuclear power plant due to an external impact by using the LS-DYNA finite element program. The wall of the auxiliary building is SC structure and the material of the SC wall plate is high manganese steel, which has superior ductility and energy absorbance compared to the ordinary steel used for other SC wall plates. The effects of the material of the wall, collision speed, and angle on the magnitude of the local damage were evaluated by local collision analysis. The analysis revealed that the SC wall made of manganese steel had significantly less damage than the SC wall made of ordinary steel. In conclusion, an SC wall made of manganese steel can have higher effective resistance than an SC wall made of ordinary steel against the local collision of an airplane engine or against a turbine impact.

• 무역학회지
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• 제47권2호
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• pp.133-154
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• 2022

The Baltic Capesize Index (BCI), which is used as an indicator for marine transportation of steel raw materials, is one of the key economic indexes for managing the risk of loss due to rapid market fluctuations when steel companies establish business strategies and procuring plans for raw materials. Still, the conditions of supply and demand of steel raw materials has been extremely affected by volatility shocks from drastic events like the financial crisis such as the Lehman Brothers incident and changes in the external environment such as COVID-19. And, especially since the 2008 financial crisis, endeavors to predict the market conditions of the steel raw material is becoming more and more arduous for the deepening uncertainty and increased volatility of BCI, which has been used as a leading indicator of the real economy. This study investigates the correlation between the steel raw material market and the marine transportation market by estimating the spillover effect of information between markets. The vector error correction model (VECM) was used to analyze information transfer based on the correlation between the BCI and crude steel production, capesize fleet supply, raw material price, and cargo volume.

• 한국레이저가공학회지
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• 제2권1호
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• pp.22-29
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• 1999

This work was carried out as a fundamental experiment to fabricate a Graded-Boundary Ni/Steel material using a laser beam. A Ni sheet was placed on a steel substrate, and then a series of high power $CO_2$ laser beams were irradiated on the surface in order to produce a homogeneous alloyed layer. The processing parameters were : 4 ㎾ laser power, 2m/min traverse speeds, -2mm defocuing, 17 l/min sheiding gas flow rates. The sequential repetition of the laser surface alloying treatment up to 4 times, resulted in about 5mm thick of fair compositional gradient systems. In order to determine the microstructure, phase and compositional profiles in this material, optical microscopy, XRD and EDS were used. The compositions varied from 66% to 0% for Ni and 34% to 100% for Fe in this material The microstructures were typical morphologies of rapid solidification and solid-state cooling. Since compressive stress was formed in the heat affected region due to martensitic transformation, while relative tensile stress was developed in the alloyed region, cracks were formed between the alloyed region and the substrate region.

• Corrosion Science and Technology
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• 제9권5호
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• pp.209-215
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• 2010

To elucidate the effect of aging time on resistance to localized corrosion of hyper duplex stainless steel, a double-loop electrochemical potentiokinetic reactivation test a potentiodynamic anodic polarization test, a scanning electron microscope-energy dispersive spectroscope analysis, and a thermodynamic calculation were conducted. With an increase in aging time, sigma phases are precipitated much more than chi phases due to the meta-stable chi phase acting as a transition phase. As aging time at $850^{\circ}C$ increases, the corrosion resistance decreases owing to an increase in Cr, Mo and W depleted areas adjacent to the intermetallic phases such as sigma phases and chi phases.

• 선박안전
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• 통권24호
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• pp.4-20
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• 2008

Stainless steel 304 or stainless steel 630 types using propeller shaft of a small ship or a FRP fishing boat generally restrain localization corrosion and abrasion damage occurrence to shaft bearing or grand packing contact. In general, the residual stress which remains after welding or heat treatment in material can cause the stress concentration or localization corrosion. In case of small ship, stainless steel such as STS304 has long been used for propeller shaft. Meanwhile, crew of small ship tend to reuse damaged propeller shaft after repair by welding and performing heat treatment to save cost. However, it was found that reused propeller shaft by repair often caused troubles in ship's operation. In this study, the basic guideline for maintenance and treatment of propeller shaft are investigated. From the results of investigation, remarkable deterioration of the material properties and corrosion resistance on the welded work part was observed.