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Al 5083 합금 용접부의 기계적 물성에 미치는 Mg의 영향
김동윤 ( Dongyoon Kim ),김동철 ( Dongcheol Kim ),강문진 ( Munjin Kang ),김영민 ( Young-min Kim ) 대한금속ㆍ재료학회 2017 대한금속·재료학회지 Vol.55 No.10
A new aluminum welding wire with 0.8 wt% higher in Mg content was developed and compared with commercial welding wire of the 5000 series. The weldability of the Al5083 base material was evaluated using high current metal inert gas (MIG) welding, using the developed Al5183 and commercial Al5183 welding wire. For the wire with 5.1 wt% Mg content, the hardness of the weld metal decreased with increasing heat input to the center of the weld under low and high heat input conditions. For the wire with 5.9 wt% Mg content, the hardness of the weld metal did not decrease under low and high heat input conditions. The wire with 5.1 wt% Mg content exhibited a tensile strength of about 300 MPa under the low/medium heat input conditions. The tensile strength decreased to 284 MPa under high heat input conditions. However, the welding wire with 5.9 wt% Mg content exhibited a tensile strength of 300 MPa regardless of the heat input condition. Dendritic microstructures were observed in the center of the welds in both wires, with Mg contents of 5.1 wt% and 5.9 wt%, and the second dendrite arm spacing (SDAS) increased with increasing heat input. (Received May 8, 2017; Accepted July 10, 2017)
스마트팩토리 설비를 위한 예지 보전 시스템 구축에 대한 연구
김진희(JinHee Kim),김동철(DongCheol Kim),제승현(SeungHyun Je),이종승(JongSeung Lee),김도희(DoHui Kim),지승한(SeungHan Ji) 한국정보기술학회 2022 Proceedings of KIIT Conference Vol.2022 No.12
현대 사회의 제조업 트렌드(trend)가 빠르게 변화함에 따라, 제품의 수명주기 감소 및 소비자들의 니즈(needs)가 다양화되면서 개인 맞춤형 생산이 요구되고, 경제 구조가 제조업에서 정보기술(IT)를 포함한 서비스업 중심으로 전향되면서, 전통 제조업은 큰 타격을 받아 제조업의 혁신이 요구되고 있으며 현재 진행형이다. 따라서, 본 연구에서는 스마트팩토리가 4차 산업의 핵심 개념으로 등장함과 동시에, 제조업에서 전 세계적으로 관심이 높아지고 있음에 착안하였으며, 스마트팩토리 설비를 위한 중요 기술의 하나인 ‘예지 보전’(PdM, Predictive Maintenance) 기술에 대하여 깊게 연구를 진행할 필요성이 있다고 판단하여, 스마트센서를 사용한 실험 데이터 취득 후 이를 분석한 결과에 대한 그래프 해석을 연구 방법으로 선정하여, 예지 보전시스템 구축 가능성에 대하여 연구를 진행하였다. As the manufacturing trend in modern society rapidly changes, personalized production is required as the life cycle of products and consumer needs are diversified, and the economic structure has shifted from manufacturing to service industries, including information technology, and manufacturing innovation is required. Therefore, this study focused on the growing interest in the manufacturing industry as well as the core concept of the 4th industry. It was judged that it was necessary to conduct a deep study on PdM (Preditive Maintenance) technology for smart factory facilities.
플럭스 코어드 와이어별 권취 위치 및 대기노출시간이 용착금속의 확산성 수소량에 미치는 영향
김동윤(Dong Yoon Kim),황인성(In Sung Hwang),김영민(Young-Min Kim),김동철(Dongcheol Kim),강문진(Munjin Kang) 대한용접·접합학회 2020 대한용접·접합학회지 Vol.38 No.5
In this study, the diffusible hydrogen contents of each weld using three flux cored wires with different hoop types were measured. The hoop shape of the flux cored wire used in the experiment is one seamless type and two fold types. In general, the flux cored wire is manufactured in a spool type. When the spool type wire is exposed to air, the diffusible hydrogen content may vary depending on each winding position. Therefore, diffusion hydrogen contents according to the winding position of each flux core wire were compared. Second, diffusible hydrogen contents of spool-type flux cored wire were measured according to the change in time exposed to air. The test specimen was prepared in accordance with AWS A4.3 specification, and diffusible hydrogen contents were measured using the gas chromatogram method. The welding conditions were fixed at current 260 A, voltage 28.0 V, welding speed 45 cm/min, shielding gas 100% CO₂, and gas flow rate 25 ℓ/min. As a result, diffusible hydrogen contents tend to decrease as the wire located inside than the outside. The seamless-type flux-cored wire showed the least change diffusible hydrogen contents in the weld according to winding positions. Diffusible hydrogen contents of the weld using the fold-type flux-cored wire are higher than that of the seamless-type flux-cored wire weld. Diffusible hydrogen contents in the weld was different depending on hoop joint shapes of the fold-type flux-cored wire.
강민정,김철희,김준기,김동철,김종훈,Kang, Minjung,Kim, Cheolhee,Kim, Junki,Kim, Dongcheol,Kim, Jonghoon 대한용접접합학회 2014 대한용접·접합학회지 Vol.32 No.4
The use of light-weight Al alloys in the automotive industry is increasing to meet requirements for fuel efficiency and emission reduction. Joining Al alloy to the conventional steel sheet is also very important issue with the increased use of Al alloy, and several joining processes have been introduced to enhance joining strength between dissimilar metals. This paper deals with a galvanic corrosion in the dissimilar metal joining. Salt spray tests up to 2000 hours were conducted on a self-piercing rivet, spot welded, adhesive bonded and weld-bonded joints, and cross-sections and tensile shear strength according the salt spray duration were analyzed at every 500-hour. Self-piercing rivet joint had relative low initial strength but the joint strength did not change regardless of the salt spray duration. The strength of other joints (spot welded, adhesive bonded and weld-bonded joints) decreased with the increase of salt spray duration and the corrosion behaviour of each joint was discussed.
김현수(Hyunsoo Kim),문성민(Sungmin Moon),길용덕(Yongduck Kil),김동철(Dongcheol Kim) 대한설비공학회 2016 대한설비공학회 학술발표대회논문집 Vol.2016 No.6
Recently, large scale government building and their energy consumption are rapidly increasing, the energy efficiency of such government building is becoming a very important issue. This paper provide sustainable design case of mechanical equipment in Kyeong-Buk provincial government building. A heat source in this building apply the geothermal heat-pump cooling and heating system. And high-efficiency equipment. The plumbing system in this building apply the rainwater utilizing system. In the field of sustainable architecture, the rainwater reuse in building is a significant category for the saving of water resource.
이인로(Inro Lee),김동철(Dongcheol Kim) 한국증권학회 2016 한국증권학회지 Vol.45 No.5
본 연구는 국내 주식시장에서 부도위험과 주식수익률의 관계를 분석하였다. 외국의 대다수 연구가 부도위험과 주식수익률 간의 음(-)의 관계를 나타내는 부도위험 이례현상을 보고하는 것과 달리 국내연구에서는 일치된 결론을 제시하지 못하고 있다. 이에 본 연구는 기존연구보다 다양한 부도예측모형을 이용하여 국내 기존연구에서 상이한 연구결과를 제시하는 원인을 분석하였다. 분석을 시행한 결과, 국내 주식시장에서 부도위험과 주식수익률의 관계는 표본에 따라 다른 것으로 나타났다. 인터넷버블이 발생한 1999년부터 2000년 중에는 규모가 작고 부도위험이 높은 기업이 매우 큰 수익률을 나타냈다. 이 기간이 표본에 포함될 경우 부도예측모형에 따라 부도위험과 주식수익률 간의 양(+)의 관계가 나타났다. 하지만 인터넷버블 기간을 제외한 2001년부터 2014년 중에는 어떠한 부도예측모형을 이용하더라도 부도위험과 주식수익률은 매우 유의한 음(-)의 관계를 갖는 것으로 나타났다. 인터넷버블기간의 샘플 포함여부 이외에도 표본에 관리종목을 포함하는지 여부도 부도위험과 주식수익률 간의 관계에 영향을 미친것으로 나타났다. 또한 본 논문은 2001년부터 2014년까지 국내 주식시장에서 나타나는 부도위험 이례현상은 수익성요인으로 설명됨을 보여주고 있다. 수익성요인을 통제할 경우 부도위험과 주식수익률 간의 유의한 음(-)의 관계는 발견되지 않았다. There has been no consensus in the finance literature in Korea on whether the financial distress risk puzzle, which is a negative relation between financial distress and subsequent stock returns in the cross-section, is prominent in the Korean stock markets. By using various bankruptcy prediction models and a longer time-series of stock return data, we examine which cause(s) drives the conflicting results on the financial distress risk puzzle. We find that one of the main causes is the inclusion or not of a specific sample period such as 1999~2000, which is the period of the internet bubble. When this period is excluded, we find that the financial distress puzzle is prominent. However, when this period is included, the puzzle is no longer observed, since during this period, small-sized firms with high financial distress earn high return. We also find that the financial distress puzzle is related with future profitability and the puzzle is well explained by a four-factor model including the Fama-French three-factor plus the profitability factor.
초음파 금속 용접에서 다층 배터리 셀 용접 공정에 적용되는 혼과 앤빌의 정렬 조건에 따른 용접성 평가
신승민(Seungmin Shin),김동철(Dongcheol Kim) 대한용접·접합학회 2021 대한용접·접합학회지 Vol.39 No.5
A battery cell has a foil-to-tab structure that is connected with multi-layer foils and a tab, and it is important to secure the weld quality to improve the battery performance. Ultrasonic metal welding (UMW) is widely applied as a technology suitable for battery cell welding because it provides a relative low heat input to welds owing to solid-state welding. In this study, 40 layers of 8 ㎛ Cu foil and one layer of nickel-plated 0.2 ㎜ Cu strip applied to a multilayered battery cell were used to evaluate the weldability of the materials for the UMW process. An experiment was conducted under four alignment conditions of a horn and an anvil to investigate the effect of the alignment on the weldability. The weld quality was classified based on the weld strength, discoloration, and failure mode of the test specimen to obtain a suitable welding range. The effect of the alignment condition on the deformation and weld shape was investigated by observing the cross-section of welds made under the four alignment conditions.