• Title/Summary/Keyword: 와도 강도

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Bond Strength and Tensile Strength of Polymer-Modified Mortar Using Styrene and Butyl Acrylate (St/BA를 혼입한 폴리머 시멘트 모르타르의 부착강도 및 인장강도 특성)

  • You, Kipyo;Hyung, Wongil
    • Polymer(Korea)
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    • v.38 no.6
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    • pp.820-826
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    • 2014
  • The objective of this study is to find the relationship between the tensile strength of the polymer film and the bond strength and tensile strength of the polymer-modified mortar using styrene (St) and butyl acrylate (BA), and porosity. In the test results, the bond strength and tensile strength of the polymer-modified mortar increased with increases in the tensile strength of polymer film and the fine pore volume.

Anatomical and Physical Properties of Pitch Pine (Pinus rigida Miller) - The Characteristics of Stem, Branch, Root and Topwood - (리기다소나무(Pinus rigida Miller)의 목재해부학적(木材解剖學的) 및 물리학적성질(物理學的性質)에 관(關)한 연구(硏究) - 간(幹), 지(枝), 근(根), 초두목(梢頭木)의 특성(特性)을 중심(中心)으로 -)

  • Lee, Phil Woo
    • Journal of Korean Society of Forest Science
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    • v.16 no.1
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    • pp.33-62
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    • 1972
  • Pitch pine (Pinus rigida Miller) in Korea has become one of the major silvicultural species for many years since it was introduced from the United States of America in 1907. To attain the more rational wood utilization basical researches on wood properties are primarily needed, since large scale of timber production from Pitch Pine trees has now been accomplishing in the forested areast hroughout the country. Under the circumustances, this experiment was carried out to study the wood anatomical, physical and mechanical properties of Pitch Pine grown in the country. Materials used in this study had been prepared by cutting the selected pitch pine trees from the Seoul National University Forests located in Suwon. To obtain and compare the anatomical and physical properties of the different parts of tree such as stem, branch, top and rootwood, this study had been divided into two categories (anatomical and physical). For the anatomical study macroscopical and microscopical features such as annual ring, intercellular cannal, ray, tracheid, ray trachid, ray parenchyma cell and pit etc. were observed and measured by the different parts (stem, branch, root and topwood) of tree. For the physical and mechanical properties the moisture content of geen wood, wood specific gravity, shrinkage, compression parallel to the grain, tension parallel and perpendicular to the grain, radial and tangential shear, bending, cleavage and hardness wree tested. According to the results this study may be concluded as follows: 1. The most important comparable features in general properties of wood among the different parts of tree were distinctness and width of annual ring, transition from spring to summerwood, wood color, odor and grain etc. In microscopical features the sizes of structural elements of wood were comparable features among the parts of tree. Among their features, length, width and thickness of tracheids, resin ducts and ray structures were most important. 2. In microscopical features among the different parts of tree stem and topwood were shown simillar reults in tissues. However in rootwood compared with other parts on the tangential surface distinctly larger ray structures were observed and measured. The maximum size of unseriate ray was attained to 27 cell ($550{\mu}$) height in length and 35 microns in width. Fusiform rays were formed occasionally the connected ray which contain one or several horizontal cannals. Branchwood was shown the same features like stemwood but the measured values were very low in comparing with other parts of tree. 3. Trachid length measured among the different parts of tree were shown largest in stem and shortest in branchwood. In comparing the tracheid length among the parts the differences were not shown only between stem and rootwood, but shown between all other parts of tree. Trachid diameters were shown widest in rootwood and narrowest in branchwood, and the differences among the different parts were not realized. Wall thickness were shown largest value in rootwood and smallest in branchwood, and the differences were shown between root and top or branchwood, and between stem and branch or top wood, but not shown between other parts of tree. 4. Moisture contents of green wood were shown highest in topwood and lowest in heartwood of stem. The differences among the different parts were recognized between top or heartwood and other parts of tree, but not between root and branchwood or root and sapwood. 5. Wood specific gravities were shown highest in stem and next order root and branchwood, but lowest in topwood. The differences were shown clearly between stemwood and other parts of tree, but not root and branchwood. However the significant difference is realized as most lowest value in topwood. 6. In compression strength parallel to the grain compared among the different parts of tree at the 14 percent of moisture content, highest strength was appeared in stem, next order branch and rootwood, but lowest in topwood. 7. In bending strength compared among the different parts of tree at the 14 percent of moisture content clearly highest strength was shown in branchwood, next order stem and root, but lowest in topwood. Though the branchwood has lower specific gravity than stemwood it was shown clearly high bending strength.

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Seasonal Change of Phytoplankton Community and Water Quality in Yeongsan River Watershed (영산강 수계의 수질과 식물플랑크톤의 계절적 변화)

  • Son, Misun;Park, Jong-Hwan;Lim, Chaehong;Kim, Sekyung;Lim, Byung-Jin
    • Korean Journal of Environmental Biology
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    • v.31 no.2
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    • pp.105-112
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    • 2013
  • Environmental parameters and phytoplankton community structure were investigated at four sites of Yeongsan River between April 2010 and December 2011. The standing crops of the phytoplankton ranged from $275cells{\cdot}mL^{-1}$ to $58,600cells{\cdot}mL^{-1}$ with an average of $5,850cells{\cdot}mL^{-1}$. The dominant species were Cyclotella sp., Stephanodiscus sp., Aulacoseira granulata, Scenedesmus quadricauda, Pediastrum biwae, Coelastrum sp., Aphnizomenon sp., and Oscillatoria sp.. The most dominant species was Stephanodiscus sp.. The concentration of chlorophyll-a ranged from $2.3mg{\cdot}m^{-3}$ to $164.2mg{\cdot}m^{-3}$. The phytoplankton community structure of the survey area was influenced by temperature and rainfall.

Experimental Studies on the Properties of Mortars by Foaming Agent (기포제(起泡劑)를 사용(使用)한 모르터의 제성질(諸性質)에 관(關)한 실험적(實驗的) 연구(硏究))

  • Ahn, Young Durg;Kang, Sin Up
    • Korean Journal of Agricultural Science
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    • v.12 no.2
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    • pp.292-308
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    • 1985
  • This study was performed to obtain the basic data which can be applied to the use of foamed mortars using foaming agent of prefoamed type. The data was based on the properties of foamed mortars depending upon various mixing ratios of cement to fine aggregates, flow values and foam-cement ratio to compare those of cement mortar. The results obtained were summarized as follow; 1. At the mixing ratio of 1:0 and the foam-cement ratio of 6.00%, the increasing rate of water-cement ratio was 25% by flow $200{\pm}5mm$, 28% by flow $240{\pm}5mm$ and 32% by flow $280{\pm}5mm$. But it decreased as the mixing ratio gets poorer. The result showed that water amount increased because of the high viscosity caused by the increase of foam-cement ratio. The decrease of water-cement ratio was the greatest when the foam-cement ratio was 1.50%. 2. Absolute aridity bulk density of foamed mortars decreased with the increase of foam-cement ratio and the decrease of flow values. 3. Generally, compressive, tensile and bending strenghs of foamed mortars decreased with the decrease of flow values and the increase of foam-cement ratio. 4. The compressive strength was in proportion to tensile strength. It was estimated that the compressive strength was 8.8 times of tensile strength. The compressive strength was in proportion to bending strength. It was estimated that the compressive strength was 4.0 times of bending strength. The bending strength was in proportion to tensile strength. It was estimated that the bending strength was 2.1 times of tensile strength. 5. At the mixing ratio of 1:1 the lowest absorption rates were showed by foamed mortars, respectively. It was significantly higher at the early stage of immersed water.

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The Propagation Behaviour of the Fatigue Crack in the Compact Tension Specimens of the Welded Structural Steels (On according to the difference of the welding direction, the input heat level, the strength of weld material and so on) (용접(鎔接)이음한 구조강(構造鋼)의 소인장시험편(小引張試驗片)에서의 피로구열진전거동(疲勞龜裂進展擧動) (용접방향(鎔接方向), 입열량(入熱量), 용접재료(鎔接材料)의 강도(强度) 등이 다를 때))

  • Chang, Dong Il;Chung, Yeong Wha
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.4 no.2
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    • pp.133-142
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    • 1984
  • With the weld-joined compact tension specimens compared with each other, that is, transverse and lengthwise about the crack propagation direction, high and low in the input heat level, same as and lower than the base metal in the strength of weld material, the fatigue test were performed. With these data, the log-log curves between the fatigue crack propagation rate ${\frac{da}{dN}}$ and the transition range of the stress intensity factor ${\Delta}K$ ahead the crack tip were drawed. These curves were compared and estimated among each compared specimens, among each zones, that is, the base metal, the heat-affected metal and the weld-mixed metal, and between this study and the past studies. Basically, Little difference in the slope of the $da/dN-{\Delta}K$ relation was showed in all the welded directions, all the input heat levels and all the zones. But, First, to comparison with in the past studies about the base metals, it was showed that da/dN started in the much later rate, increased faster and stoped in the little faster rate. Second, it was showed that, near the time the crack's going from the heat-affected zone to the weld-mixed metal da/dN decreased a little for a while. Third, in the lengthwise weld compared with the transverse weld, in the high input heat weld compared with the low input heat weld in the case used the weld material of the same strength as the base metal, in the opposite case in the case used the one of the lower strength than the base metal, in the case used the weld material of the same strength as compared with the lower strength than the base metal beside the high input heat and the lengthwise weld, it was showed that the crack occured earlier in lower ${\Delta}K$ and later da/dN, the curves went with the same slope. Forth, in the lengthwise weld compared with the transverse weld in the low input heat weld, in the low input heat weld compared with the high input heat weld, it was showed that da/dN went with the lower level.

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The Intensity Scale of Multiple Scattering of X-rays in Non-Crystalline Solids (비정질 고체에 대한 X선의 다중 산란 강도)

  • 박성수;장윤식;류봉기;박희찬
    • Journal of the Korean Ceramic Society
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    • v.34 no.1
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    • pp.109-113
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    • 1997
  • When the intensity of X-rays scattered from amorphous materials (very weakly absorbing materials) is measured using standard diffractometric technique, the intensity caused by multiple scattering is obtained in the measured X-ray intensity. Computer programs have been developed to estimate the intensity of the mul-tiple scattering obtained in vitreous SiO2 and B2O3 with various X-rays. Using the above computer program, the intensity ratios of multiple scattering to single scattering in vitreous SiO2 were 0.10~0.16% at CuK$\alpha$, 0.98~5.87% at MoK$\alpha$, and 1.88~17.86% at AgK$\alpha$ in the range of 2$\theta$=0~180$^{\circ}$. Therefore, pri-or to the structural analysis of vitreous SiO2 and B2O3 performed experimentally using X-ray diffractometric technique, the intensity data measured in MoK$\alpha$ and AgK$\alpha$ radiations must be corrected for multiple scattering effect.

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Ultimate Behavior of Plate Girders with High Strength Steel in Combined Bending and Shear (휨과 전단을 받는 고강도강 플레이트거더의 극한거동)

  • Kim, Jong-Min;Hwang, Min-Oh;Kang, Young-Jong
    • 한국방재학회:학술대회논문집
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    • 2010.02a
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    • pp.84.1-84.1
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    • 2010
  • 국내에서는 플레이트거더의 휨 강도 및 전단 강도를 허용응력설계법에 기반한 도로교설계기준(2005)에 근거하여 규정하고 있으며, 국외의 경우 하중저항계수설계법에 근간을 둔 AISC(2005) 등의 규정을 통해 산정하고 있다. 최근에는 인장강도 800MPa 급의 강재가 생산되고 있으나 국내 설계기준에서는 아직까지 상기 인장강도를 갖는 고강도강에 대한 설계기준은 마련되지 않고 있다. 본 연구에서는 휨과 전단이 동시에 작용하는 고강도강 적용 플레이트거더의 극한거동 해석을 통해 국내기준의 적용성을 판단하고, 국외기준인 AISC(2005)와 비교하여 나타내어 허용응력설계법에 근거한 국내기준의 강도산정법의 한계점에 대해 고찰하였다.

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Comparison of bracket bond strength in various directions of force (교정용 브라켓에 가해지는 힘의 방향에 따른 결합강도의 비교)

  • Lee, Hyun-Jung;Lee, Hyung-Soon;Jeon, Young-Mi;Kim, Jong-Ghee
    • The korean journal of orthodontics
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    • v.33 no.5 s.100
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    • pp.359-370
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    • 2003
  • The purpose of this study was to evaluate the bond strength of orthodontic brackets bonded to metal bar with chemically cured adhesive (Ortho-one, Bisco Co, USA) in various types and directions of force application. Three types of metal bracket with different bracket base configurations; Micro-Loc base(Tomy Co, Japan), Chessboard base(Daesung Co, Korea), Non-etched Foil-Mesh base(Dentaurum, Germany); were used in this study. Peel, shear, tensile bond strengths were measured by universal testing machine and compared each other. The peel force directions applied were $0^{\circ},\;15^{\circ},\;30^{\circ},\;45^{\circ},\;60^{\circ},\;75^{\circ},\;90^{\circ}$ And then, in consideration of the different surface area of the bracket bases, the bond strength Per unit area were calculated and compared. The results obtained were summarized as follows: 1. The bond strengths according to the types and the directions of the forces were greatest at the shear forces in all three bracket base configuration groups(p<0.01). 2. As the peel force direction grew higher in degree, peel bond strength decreased. The Patterns of peel bond strength change according to force direction was similar in all three bracket base configurations. The minimum bond strength was 60 degree-peel bond strengths in all three bracket base configurations. 3. In Micro-Loc base group, minimum peel bond strength$(_{60}PBS)$ was in $29\%$ level of shear bond strength and $52\%$ level of tensile bond strength. In Chessboard base group, $_{60}PBS$ was in $34\%$ level of shear bond strength and $61\%$ level of tensile bond strength. In Non-etched Foil-Mesh base group, $_{60}PBS$ was in $34\%$ level of shear bond strength and $55\%$ level of tensile bond strength. 4. The bond strengths per unit area were lowest in Non-etched Foil-Mesh base group and highest in Chessboard base group(p<0.05). However, there were no differences in shear bond strength, tensile bond strength, $75^{\circ}\;and\;90^{\circ}$ per unit area between Micro-Loc and Chessboard base groups.

A Study on the Evaluation of Material Degradation for High Temperature Sturctural Components by Using Grain Boundary Etching method (입계육식법에 의한 고온부재의 경년 열화도 평가에 관한 연구)

  • Yu, Hyo-Seon;Jeong, Se-Hui
    • Korean Journal of Materials Research
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    • v.6 no.3
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    • pp.253-263
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    • 1996
  • 고온.고압하에서 장시간 사용되는 고온부재용 구조물은 경년열화현상을 나타낸다 그러므로 구조물의 안정성 측면에서 재질열화의 정도를 정량적으로 평가하는 것이 중요하다. 그러나 실기 구조물에서 채취할 시험편의 크기와 수는 제한이 되기 때문에 새로운 비파괴적인 평가법이 요구되고 있다. 따라서 본 연구에서는 화력발전설비에 이용되는 탄소강과 페라이트강에 대한 열화도의 평가를 위해 입계부식법의 적용 가능성을 조사한다. 시험결과, 재질열화의 정도는 사용시간보다 사용온도에 더 큰 영향을 받았으며, Larson-Miller인자와 열화도([$\Delta$DBTT]SP)사이의 관계는 선형적이었으나, 강종에 따라 다른 기울기를 보였다. 반면, 연성-취성천이온도 ([$\Delta$DBTT]SP)와 격자절단비(Ni/No)와 관계는 강종에 무관하게 선형적인 비례관계를 나타내었다. 또한, [$\Delta$DBTT]SP와 Ni/No 의 관계로부터 입계부식법은 페라이트계 강뿐만아니라 탄소강에 대해서도 유용한 재질열화 평가 방법임을 알 수 있었다.

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The characteristic of photoluminescence ZnO thin film deposited by ALE (ALE법으로 증착된 ZnO 박막의 photoluminescence 특성)

  • 신경철;임종민;김현우;이종무
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2003.11a
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    • pp.164-164
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    • 2003
  • UV 발광소자 재료로서 유망한 ZnO film을 ALE법으로 증착하고 photoluminescence특성을 조사하였다. Zn소스로서 DEZn(Diethylzinc)를, 산소 소스로서 DI water를 사용하였고 $N_2$ gas로서 챔버내에 주입된 소스물질을 purge하였다. ALE 공정온도 범위인 17$0^{\circ}C$와 CVD 반응온도 범위인 40$0^{\circ}C$로 ZnO 박막을 증착하고 이 시편을 산소 분위기에서 600-100$0^{\circ}C$의 온도로 1시간 동안 열처리하였다. 그리고 He-Cd laser를 사용하여 photoluminescence를 측정하였다. 17$0^{\circ}C$와 40$0^{\circ}C$ 에서 증착된 시편 모두 as-grown 상태에서는 거의 발광특성을 나타내지 못하였으나 후열처리를 거치면서 발광특성을 나타내었고 열처리 온도가 높을수록 발광강도가 증가하였다. 40$0^{\circ}C$에서의 증착된 시편의 경우는CVD반응이 발생하여 Zn-Zn결합이 많이 생성되어 열처리 온도가 증가하여도 발광강도가 약하였고 가시광 영역의 발광 또한 크게 증가하였으며 17$0^{\circ}C$에서 증착된 시편의 경우는 열처리 온도가 증가할수록 UV영역의 발광강도만이 크게 증가하였으며 가시광 영역의 발광은 거의 증가하지 않았다.

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