• 제목/요약/키워드: Core welding

검색결과 105건 처리시간 0.019초

알루미늄 압출재의 구조적 거동 특성 및 최적설계에 관한 연구 (A Study on the Optimum Design and Structural Behaviors of Aluminium Extrusions)

  • 서승일;손건호
    • 대한조선학회논문집
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    • 제35권1호
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    • pp.88-97
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    • 1998
  • 파형 심재를 가지는 샌드위치 평판은 종 횡방향으로 충분한 강도를 가지며, 부재를 연결하기 위한 용접라인이 감소되고, 종 부재를 보강하기 위한 횡부재가 필요하지 않는다. 이러한 특성을 활용한 대형 알루미늄 압출재는 철도 차량과 초고속선의 중량 및 생산비용 절감을 위하여 사용될 수 있다. 그러나, 대형 알루미늄 압출판의 적절한 설계를 위해서는 압출재의 구조적인 거동에 대한 이해가 선행되어야 한다. 본 논문에서는 먼저, 구조적인 거동을 이해하기 위한 상세 유한요소 해석을 수행하였고 둘째로, 설계에 적용하기 위한 간략화된 이론식을 제안하였다. 제안된 간략식은 상세 유한요소 해석에 의한 결과와 비교해 볼 때 높은 정확도를 보이고 있음을 알 수 있었고, 제안된 간략식은 초기 설계 단계에서의 반복적인 해석에서 유용하게 사용될 수 있을 것이다.

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직접식 에너지 용착 공정을 활용한 축 보수 방법 및 활용 사례 연구 (A Study on the Method and Application of Shaft Repair using Directed Energy Deposition Process)

  • 이윤선;이민규;성지현;홍명표;손용;안석;정외철;이호진
    • 한국기계가공학회지
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    • 제20권9호
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    • pp.1-10
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    • 2021
  • Recently, the repair and recycling of damaged mechanical parts via metal additive manufacturing processes have been industrial points of interest. This is because the repair and recycling of damaged mechanical parts can reduce energy and resource consumption. The directed energy deposition(DED) process has various advantages such as the possibility of selective deposition, large building space, and a small heat-affected zone. Hence, it is a suitable process for repairing damaged mechanical parts. The shaft is a core component of various mechanical systems. Although there is a high demand for the repair of the shaft, it is difficult to repair with traditional welding processes because of the thermal deformation problem. The objective of this study is to propose a repair procedure for a damaged shaft using the DED process and discuss its applications. Three types of cases, including a small shaft with a damaged surface, a medium-size shaft with a worn bearing joint, and a large shaft with serious damage, were repaired using the proposed procedure. The microstructure and hardness were examined to discuss the characteristics of the repaired component. The efficiency of the repair of the damaged shaft is also discussed.

Cu-Si계 삽입금속을 사용한 페라이트계 스테인리스강의 아크 브레이징에서 인장성질에 미치는 입열량의 영향 (Effect of the Heat Input on the Tensile Properties in Arc Brazing of Ferritic Stainless Steel using Cu-Si Insert Alloy)

  • 김명복;김상주;이봉근;원신건;윤병현;우인수;강정윤
    • 대한금속재료학회지
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    • 제48권4호
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    • pp.289-296
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    • 2010
  • The effects of heat input and different microstructureswere investigated on the tensile-shear properties of an arc-brazed joint of theferritic stainless steel 429EM using a Cu-Si insert alloy. The brazing speed was fixed at 800 mm/min whilethe brazing current varied from 80 to 120A. For abrazing current lower than 100A, fracturing occurred at the joint root in the direction perpendicular to the tensile load. As the brazing current increased to 120A, fracturing occurred at the base metal or the joint root. The joint and the base metal had very similar yield and tensile load values. However, the amount of elongation was decreased considerably compared to when the base metal was used. The fracturing began at the triple point of the root part and was classified into three types. The difference in the tensile-shear properties was closely related to the three fracture types.

원전 1차 계통수 모사환경에서 Type 304 스테인리스강의 응력부식균열개시 민감도 (Susceptibility of Stress Corrosion Crack Initiation of Type 304 SS in Simulated Primary Water Environment of PWR)

  • 조성환;김성우;이종연
    • 한국압력기기공학회 논문집
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    • 제20권1호
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    • pp.25-31
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    • 2024
  • The core shroud of rector vessel internals (RVI) of OPR1000 and ARP1400 is made of Type 304 stainless steel (SS) by bending and welding process that may induce high deformation and residual stress in manufacturing. This work aims to evaluate the susceptibility of stress corrosion crack (SCC) initiation of bent parts of RVI in high temperature primary water environment. For SCC initiation test, tensile specimens were fabricated from the 90 degree bent plate of Type 304 SS (DT specimen), that is an archived part of a Korean APR1400. After the SCC initiation test, the specimen surface was thoroughly examined by optical and scanning electron microscopy, and compared to the specimen fabricated from the as-received plate of Type 304 SS (AR specimen). The surface observation revealed that SCC initiated on the AR specimen surface in typical intergranular (IG) mode, while SCC on the DT specimen occurred in transgrannular mode as well as IG mode. It was also found that the size and number of SCC on the DT specimen were larger than that on the AR specimen. This was attributable to a strain-hardening during the bending process. To compare the susceptibility of SCC initiation, total crack density (TCD) was calculated from the total crack length divided by the measured area of AR and DT specimens. TCD of DT specimen was 4.6 times higher than AR specimen in average, indicating that higher possibility of degradation of bent parts of RVI for a long-term operation.

설비공학 분야의 최근 연구 동향 : 2016년 학회지 논문에 대한 종합적 고찰 (Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2016)

  • 이대영;김사량;김현정;김동선;박준석;임병찬
    • 설비공학논문집
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    • 제29권6호
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    • pp.327-340
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    • 2017
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2016. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of flow, heat and mass transfer, the reduction of pollutant exhaust gas, cooling and heating, the renewable energy system and the flow around buildings. CFD schemes were used more for all research areas. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results of the long-term performance variation of the plate-type enthalpy exchange element made of paper, design optimization of an extruded-type cooling structure for reducing the weight of LED street lights, and hot plate welding of thermoplastic elastomer packing. In the area of pool boiling and condensing, the heat transfer characteristics of a finned-tube heat exchanger in a PCM (phase change material) thermal energy storage system, influence of flow boiling heat transfer on fouling phenomenon in nanofluids, and PCM at the simultaneous charging and discharging condition were studied. In the area of industrial heat exchangers, one-dimensional flow network model and porous-media model, and R245fa in a plate-shell heat exchanger were studied. (3) Various studies were published in the categories of refrigeration cycle, alternative refrigeration/energy system, system control. In the refrigeration cycle category, subjects include mobile cold storage heat exchanger, compressor reliability, indirect refrigeration system with $CO_2$ as secondary fluid, heat pump for fuel-cell vehicle, heat recovery from hybrid drier and heat exchangers with two-port and flat tubes. In the alternative refrigeration/energy system category, subjects include membrane module for dehumidification refrigeration, desiccant-assisted low-temperature drying, regenerative evaporative cooler and ejector-assisted multi-stage evaporation. In the system control category, subjects include multi-refrigeration system control, emergency cooling of data center and variable-speed compressor control. (4) In building mechanical system research fields, fifteenth studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, renewable energies, etc. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which could be help for improving the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the analyses of indoor thermal environments controlled by portable cooler, the effects of outdoor wind pressure in airflow at high-rise buildings, window air tightness related to the filling piece shapes, stack effect in core type's office building and the development of a movable drawer-type light shelf with adjustable depth of the reflector. The subjects of building energy were worked on the energy consumption analysis in office building, the prediction of exit air temperature of horizontal geothermal heat exchanger, LS-SVM based modeling of hot water supply load for district heating system, the energy saving effect of ERV system using night purge control method and the effect of strengthened insulation level to the building heating and cooling load.