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SLM 공정으로 제조된 AlSi10Mg 합금의 마모, 인장 및 고주기 피로 특성에 미치는 후열처리의 영향
박태현(T.-H. Park),백민석(M.-S. Baek),Yongho Sohn,이기안(K.-A. Lee) 한국소성가공학회 2020 한국소성가공학회 학술대회 논문집 Vol.2020 No.6
본 연구에서는 selective laser melting (SLM) 공정으로 제조된 AlSi10Mg 합금의 미세조직과 마모, 인장 및 고주기 피로 특성에 대해 조사하였다. 이와 함께 여러 기계적 특성에 미치는 석출 경화 열처리 효과도 알아보고자 하였다. 석출 경화 열처리로는 Al-Si 합금에 주로 사용되는 T6 열처리 그리고 direct aging (DA) 열처리를 수행하였다. 초기 미세조직 관찰결과, as-built 소재는 molten pool 내부에 cellular structure가 형성되어 있었으며 cellular structure boundary에 eutectic Si 들이 존재하는 것으로 나타났다. T6 열처리 이후 molten pool 및 cellular structure는 모두 사라졌고 Si 상들은 조대한 크기로 (μm 수준) 관찰되었다. 상온 인장 시험 결과 DA 소재는 as-built 소재보다 항복 및 인장 강도가 향상되었지만, T6 소재는 오히려 감소하였다. 고주기 피로 시험에서 피로한 (fatigue limit)은 DA 소재가 가장 높게 나타났고 모든 피로 응력 조건에서 우수한 피로특성을 보였다. 이에 반해 T6 소재는 상대적으로 낮은 피로 특성을 나타냈지만, 상온 마모 시험 결과에서 T6 소재가 asbuilt와DA 소재보다 우수한 특성을 나타냈다. 상기 결과들과 함께 파단면 해석을 기반으로 SLM 공정으로 제조된 AlSi10Mg 합금의 석출 경화 열처리에 따른 마모, 인장 및 피로 변형 기구를 규명하고자 하였다.
남조류와 녹조류에서의 수소생산을 위한 배양 조건의 최적화
윤종현(J. H. Yoon),공경택(K. T. Kong),심상준(S. J. Sim),김미선(M.S. Kim),박태현(T. H. Park) 한국수소및신에너지학회 2002 한국수소 및 신에너지학회논문집 Vol.13 No.4
Blue-green algae and green algae have the unique characteristic of using CO₂ in the air as a carbon source and solar energy as an energy source and producing H₂ with water used as the primary electron donor. The cells take up CO₂ first to produce cellular substances, which are subsequently used for H₂ production. Since the optimal operating conditions for the CO₂ uptake and H₂ production are different, a two-stage system can be effectively employed to separate these two phases. For the efficient production of H₂ in the second stage, in this study, the culture condition of blue-green algae was optimized for the effective CO₂ uptake and cell growth in the first stage, and high cell density culture was carried out using repeated injections of CO₂. In green algae, the amount and patterns of organic compounds have a connection with growth stage or dark fermentation time. The hydrogen production was greatly influenced by dark fermentation time.
키높이 인솔두께에 따른 족부의 생체역학적 특성변화에 대한 연구
박태현,정태곤,한동욱,이성재,Park, T.H.,Jung, T.G.,Han, D.W.,Lee, Sung-Jae 대한의용생체공학회 2013 의공학회지 Vol.34 No.2
Recently, functional insoles of wedge-type it is for the young to raise their height inserted between insole and heel cause foot pain and disease. Additionally, these have a problem with stability and excessively load-bearing during gait like high-heel shoes. In this study, we compared the changes in biomechanical characteristics of foot with different insole thickness then we will utilize for the development of the insole with the purpose of relieving the pain and disease. Subjects(male, n = 6) measured COP(center of pressure) and PCP(peak contact pressure) on the treadmill(140cm/s) using F-scan system and different insole thickness(0~50 mm) between sole and plantar surface during gait. Also, we computed changes of stresses at the foot using finite element model with various insole thickness during toe-off phase. COP moved anterior and medial direction and, PCP was increased at medial forefoot surface, $1^{st}$ and $2^{nd}$ metatarsophalangeal, ($9%{\uparrow}$) with thicker insoles and it was show sensitive increment as the insole thickness was increased from 40 mm to 50 mm. Change of the stress at the soft-tissue of plantar surface, $1^{st}$ metatarsal head represents rapid growth($36%{\uparrow}$). Also, lateral moments were increased over the 100% near the $1^{st}$ metatarsal as the insole thickness was increased from 0 mm to 30 mm. And it is show sensitive increment as the insole thickness changed 10 mm to 20 mm. As a result, it was expected that use of excessively thick insoles might cause unwanted foot pain at the forefoot region. Therefore, insole thickness under 30 mm was selected.
박태현(T. H. Park),문중수(J. S. Moon),이인혜(I. H. Lee),심우승(W. S. Sim),신현수(H. S. Shin) 대한조선학회 2011 대한조선학회 학술대회자료집 Vol.2011 No.6
Considering the wave impact load is required in the structural assessment of FPSOs. The importance of the wave impact load on offshore structures in the deep water has increased after the casualty by the wave impact was reported in FPSO installed in the North Sea. The wave impact load on offshore structures can be divided into the green water impact load and the wave slamming impact load. It is known that these wave impact loads show the strong nonlinear characteristics. On the other hand, the classification rule is not sufficiently specified enough to assess the wave impact load. Therefore, more accurate evaluation method of the nonlinear wave impact load is necessary for the safe design of offshore structures. In this paper, the estimation procedures of the green water impact load and the wave slamming impact load are proposed for considering the wave impact load in the design step of offshore structures. These estimation procedures were verified by comparing with the design impact loads of the previous FPSO projects.