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열처리로 제조된 물결모양 와이어 철망 층 구조의 압축강도
최정호(J. H. Choi),이정환(J. H. Lee),Krishna Shankar,Murat Tahtali,Andrew Neely 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.5
The objective in this paper presents an attempt to understand and characterize the behavior of corrugated wire mesh laminates (CWML) under transverse compression loading. Specimens of the CWML are made of stainless steel type 316 woven metal and crossed points in the mesh are bonded with eutectic at low temperature. Experimental testing is conducted on several samples of single layer, two layer, and four layer wire mesh laminates under transverse compression The load deflection behaviors of the single and multi layer laminates observed in the tests are analyzed. Therefore, it does provide significant insight into aspects that influence the deformation behavior of CWML.
최정호(J. H. Choi),이동복(D. B. Lee) 한국표면공학회 2007 한국표면공학회지 Vol.40 No.1
The pure CrN powders oxidized to Cr₂O₃ noticeably above 850℃ in air. When these powders were sintered into bulk samples at 1500℃ under 40 atm of N₂ pressure, the CrN phase partly changed into the Cr₂N phase, owing to the partial loss of nitrogen from CrN. When the bulk sample was heated at 1000-1200 ℃ for 100 hr under vacuum, the CrN phase also progressively changed into Cr ₂N. At the same time, a relatively thin Cr₂O₃ layer formed on the bulk sample due to the reaction of chromium with residual oxygen in vacuum.
이중나선구조를 응용한 개방형 트러스 구조의 최신 단위셀에 대한 강성 및 강도에 대한 연구
최정호(J. H. Choi),권영도(Y.D. Kwon),이정환(J. H. Lee) 한국소성가공학회 2013 한국소성가공학회 학술대회 논문집 Vol.2013 No.10
The objective of this paper is to find an effective stiffness and effective strength for a new unit-cell model which is designed by double helical structure coming from DNA (deoxyribonucleic acid) geometry. The unit-cell model in here is a laminated pinwheel truss defined like fourfold truss. Relative density for the double pinwheel truss is derived at first. It is expected that the relative density is proportional to a ratio with a thickness of truss and a length as a square exponent when the outer volume in the pinwheel truss is a regular hexagon. The ideal solution for both effective modulus and effective strength is based on an open-cell structure reported by Gibson and Ashby and exponent of relative density in there is defined as an unknown number, n. Applied software is ABAQUS and designed pinwheel truss models are six totally; three for a pinwheel truss and three for a laminated pinwheel truss. Applied material is stainless steel 304 which is a common material. Applied boundary condition is a uniaxial compression. Thus, it can expect the exponent of the relative density related to effective stiffness is about 1 which infers stiffness for the double pinwheel truss is similar to honeycomb unit-cell model. The exponent of the relative density related to effective strength is closed until 1. In addition, as a thickness of truss is to be bigger, the effective stiffness or strength for the double pinwheel unit-cell truss is to be lower than a single pinwheel unit-cell truss. In conclusion, effective stiffness or effective strength is proportional to a thickness of truss and is reciprocal proportion to a laminated number of a pinwheel unit-cell truss.
가스터빈 엔진부품용 NiCoCrAlY-(Ta, Re, Ir) 코팅의 고온산화특성
최정호(J. H. Choi),이동복(D. B. Lee) 한국표면공학회 2006 한국표면공학회지 Vol.39 No.3
The high velocity oxy-fuel sprayed coatings of 38Ni-23Co-20Cr-11Al-3Y-5Ta, 25Ni-34Co-20Cr-11Al-3Y-2Re and 32Ni-34.5Co-22Cr-11Al-0.5Ir (in wt%) were oxidized at 1000 and 1100oC in air in order to find the alloying effect of Ta, Re and Ir on the oxidation properties of the NiCoCrAlY-base coatings. The primary phase of the coatings was Ni₃Al. The oxides formed on the coatings consisted primarily of α-Al₂O₃, together with some CoCr₂O₄, CoAl₂O₄, and Al?Y₃O12. Tantalum oxidized to Ta₂O? and Ta₂O2.2. However, no oxides of Re and Ir were detected by XRD owing to their thermodynamic inertness and/or their small amount.
崔正鎬,張圭寬,田璟秀,鄭鎭澈 圓光大學校大學院 1993 論文集 Vol.11 No.-
A total of 27 quardrats of 10m×10m, 4 trantrect, mountaineering road was in vestigated in Mt. Mireuk. The results are as follows; 1. The forest communities of this area were classified into eight community Ⅰ, Quercus serrata community Ⅱ. Quercus serrata-Rhododendron schlippenbachii community Ⅲ, Quercus serrata-Pinus densiflora community Ⅳ, Pinus densiflora communiyty Ⅴ, Quercus acutissima-Quercus dentata community Ⅵ, Styrax japonica community Ⅶ, Robinia Pseudo-acacia forest Ⅷ, Acer saccharium forest, Ⅸ. Pinus rigida forest. 2. The importance value of major species indicated Pinus densiflora 38.77, Quercus serrata 27.72, Pinus rigida 25.40. 3. Planting tress in cultural assets preservation is in demanded to replanting for natural vegetation gradually. 4. The flora of vascular plants distributed in Mt. Mireuk area was 35 famillies, 54 genera, 106 species.