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고온 가열시 W/B 변화에 따른 고강도 콘크리트의 잔존강도특성
김상식 ( Kim Sang-shik ),송용원 ( Song Yong-won ),한창평 ( Hann Chang-pyung ),이성연 ( Lee Seong-yeun ),한민철 ( Han Min-cheol ),김성수 ( Kim Seoung-soo ) 한국구조물진단유지관리공학회 2007 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.11 No.2
This study investigates the fundamental properties and residual strength of the high strength concrete subjected to the elevated temperature corresponding to various W/B. The results are summarized as following. All measurement of the fresh concrete are satisfied with the target values. For the properties of the hardened concrete, the compressive strengths of the W/B 20, 25, and 35% are 89, 86, and 71 MPa. The residual compressive strength corresponding to the elevated temperature is slightly increased at 200℃, but suddenly decreased about 54~60% over 600℃. The stress-strain is similar to the standard condition at 200℃, but it is extremely increased over 400℃.
고온 가열시 골재 종류 변화에 따른 고강도 콘크리트의 강도 특성
김상식(Kim Sang-Shik),장기현(Jang Ki-Hyun),이보형(Lee Bo-Hyeong),한창평(Hann Chang-Pyung),한민철(Han Min-Cheol),김성수(Kim Seoung-Soo) 대한건축학회 2007 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.27 No.1
Results of this experiment tests showed that all specimens, as for the properties of fresh concrete, had favorable fluidity, satisfying 600±100㎜ of slump flow. Air content was varied with aggregate types which indicated 3.0±0.5% in the specimens using granite and lime stone as a coarse aggregate, but basalt used specimens increased the value more than 80%, compared with others. This is due to the multi porous properties of the basalt. The compressive strength of all specimens was indicated at around 80㎫ at 28 elapse days, but this strength values of the specimens gradually decreased at fire circumstance. It is demonstrated that the residual compressive strength of high strength structure, which was once exposed to the fire and cooled down, is deteriorated. This is highly affected by higher temperature, so that the careful attention should be considered whether the structures could be recycled again.
김성수 ( Kim Seong-soo ),김상식 ( Kim Sang-shik ),이우진 ( Lee Woo-jin ) 한국구조물진단유지관리공학회 2003 한국구조물진단유지관리공학회 논문집 Vol.7 No.2
This paper presents the results of an experimental research project on 7 Super Deck Plates with continuous or simple beam types. The test parameters included the distance of truss, depth of deck plate and the type of beam. The test results are as follows ; When thickness of deck plate was increased, maximum strength was improved When the distance of truss bar was reduced from 20cm to 15cm, the mean value of maximum load was increased to 1.21 times. Continuous beam shown superior to simple beam, such as 5.03 times high strength, low deflection at yield point.
ARB가공된 인탈산동의 어닐링에 따른 미세조직 및 기계적 특성 변화
이성희,김춘수,김상식,한승전,임차용,Lee, Seong-Hee,Kim, Chun-Su,Kim, Sang-Shik,Han, Seung-Zeon,Lim, Cha-Yong 한국재료학회 2007 한국재료학회지 Vol.17 No.7
A deoxidized low-phosphorous copper processed by eight cycles of accumulative roll-bonding (ARB) was annealed at various temperatures ranging from 100 to $400^{\circ}C$. The annealed copper was characterized by transmission electron microscopy (TEM) and tensile & hardness test. TEM observation revealed that the ultrafine grains developed by the ARB still remained up to $350^{\circ}C$, however above $400^{\circ}C$ they were replaced by equiaxed and coarse grains due to an occurrence of the static recrystallization. The hardness of the copper decreased slightly with the annealing temperature up to $350^{\circ}C$, however they dropped largely above $400^{\circ}C$. Annealing characteristics of the copper were compared with those of an oxygen free copper processed by ARB and subsequently annealed.
기계적합금화법을 이용한 고온 고강도 Al-Nb-Zr 합금 제조 및 특성 평가
권대환,안인섭,김상식,이광민,박민우,Kwon, Dae-Hwan,Ahn, In-Shup,Kim, Sang-Shik,Lee, Kwang-Min,Park, Min-Woo 한국재료학회 2000 한국재료학회지 Vol.10 No.7
최근에 고온용 항공기 구조 재료로 Ti, Zr, V, Nb 및 Ta 등의 천이금속을 첨가한 Al 합금계 제조와 특성에 관한 연구가 되어져 왔다. 본 연구에서는 Al-Nb합금에 Zr을 첨가하여 상형성거동을 연구하였다. Al-1.3at.%(Nb+Zr) 합금에서 Nb와 Zr의 원자비를 1:3, 1:1 및 3:1로 하여 기계적합금화하였다. 기계적합금화하는 동안 Al-Nb-Zr의 형태변화와 미세구조를 SEM, XRD 및 TEM으로 관찰하였다. X-선 회절 시험에 의하여 $Nb_2Al$ 과 $Al_3Zr_4$가 생성됨을 확인하였다. $500^{\circ}C$에서 1시간동안의 진공열처리에 의하여 $Al_3Zr$, $Al_3Zr_4$ 등의 금속간화합물을 형성하였다. 30시간동안 기계적 합금화한 분말을 열처리하여 TEM으로 관찰한 결과 100nm 이하의 금속간화합물 입자들을 관찰하였다. Recently there have been many investigations on the synthesis and properties of transition metal trialuminides based on Ti, Zr, V, Nb and Ta for use aircraft structure materials in an elevated environment. The effect of Zr additions on the formation behaviour of Al-Nb alloy was investigated. Al-1.3at.%(Nb+Zr) alloys with different Nb to Zr atomic 1:3, 1:1 and 3:1 were prepared by mechanical alloying(MA). The morphological changes and microstructural evolution of Al-Nb-Zr powders during MA were investigated by SEM, XRD and TEM. The intermetallic compound phase of $Nb_2Al\; and\; Al_3Zr_4$ was identified by X-ray diffraction. The intemetallic compound of $Al_3Zr,\; Al_3Nb$ and $Al_3Zr_4$ were formed by heat treatment for 1 hour at $500^{\circ}C$. The size of intermetallic compounds observed by TEM were approximately below 100nm, when they were heat treated after mechanically alloying for 30 hours.
선형회귀분석법을 통한 주조용 A356 합금의 인장특성에 미치는 미세조직적 인자의 영향
홍성진 ( Seong Jin Hong ),김상식 ( Sang Shik Kim ),이재현 ( Je Hyun Lee ),권용남 ( Yong Nam Kwon ),이영선 ( Young Seon Lee ),이정환 ( Jung Hwan Lee ) 대한금속재료학회 ( 구 대한금속학회 ) 2006 대한금속·재료학회지 Vol.44 No.8
The effects of microstructural variables, including DAS (dendrite arm spacing), the size of primary a phase, the size of eutectic Si particle and the thickness of eutectic structure, on tensile behavior of A356 cast aluminum alloy were quantitatively identified using linear regression analysis method. For systematic microstructural control in A356 alloy, directional solidification method was used with different solidification rates of 5, 25, 50 and 100 ㎛/s, respectively. The linear regression analysis suggests that both DAS and the size of primary a phase dominantly affect tensile strength of A356 cast aluminum alloy, while tensile ductility is most strongly dependent on the thickness of eutectic structure. The change in tensile behavior with varying microstructural variables in A356 alloy is discussed based on fracto graphic and micrographic observations.