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마찰접합 된 STK400 Tube의 미세조직과 기계적 특성 평가
김경우,송국현,Kim, Gyeong-Woo,Song, Kuk-Hyun 한국재료학회 2019 한국재료학회지 Vol.29 No.1
We evaluate the properties of friction welded STK400 steel tube in terms of the relationship between microstructures and mechanical properties. Friction welding is conducted at a rotation speed of 1,600 rpm and upset time of 3-7 sec for different thicknesses of STK 400 tubes. To analyse the grain boundary characteristic distributions(GBCDs) in the welded zone, electron backscattering diffraction(EBSD) method is introduced. The results show that a decrease in welding time (3 sec.) creates a notable increase grain refinement so that the average grain size decreases from $15.1{\mu}m$ in the base material to $4.5{\mu}m$ in the welded zone. These refined grains achieve significantly enhanced microhardness and a slightly higher yield and higher tensile strengths than those of the base material. In particular, all the tensile tested specimens experience a fracture aspect at the base material zone but not at the welded zone, which means a soundly welded state for all conditions.
경량기포콘크리트 대체 패널공법 적용에 따른 바닥충격음 및 단열성능 평가에 관한 연구
최경석(Choi Gyeong-Seok),최현중(Choi Hyoun-Joung),김경우(Kim Kyoung-Woo),강재식(Kang Jae-Sik),양관섭(Yang Kwan-Seop) 한국건축친환경설비학회 2007 한국건축친환경설비학회 학술발표대회 논문집 Vol.- No.-
Ondol is a traditional Korean heating system with a long history. The ondol heating system is a default in ordinary houses and high-rise apartments alike. A new system capable of freely changing the interior space is being developed as exemplified by the prevalence of the dry process due to the popularity of high-rise buildings, and SI housing. However, as ondol uses cement and water, it is heavy and needs curing time, which is a shortcoming. This study examined a new ondol system that answers the call of the times by improving the existing concept of ondol. The floor impact sound isolation and thermal performance of the panel-type structure using Styrofoam granules, cement and plaster was examined.