• Title, Summary, Keyword: Flexual strength

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Flexual strength of resins for provisional fixed prostheses (임시 고정성 보철물 제작용 레진의 굽힘강도)

  • Choi, Myoung-Ah;Ahn, Seung-Geun;Cho, Kuk-Hyeon
    • Journal of Dental Rehabilitation and Applied Science
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    • v.16 no.3
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    • pp.221-227
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    • 2000
  • Provisional fixed partial dentures(FPDs) are an important part of many prosthodontic treatment procedures. These provisional fixed prostheses must fulfill biologic, mechanical, and esthetic requirements to be considered successful. Consideration of all these factors and requirements are important because provisional resin restorations may be worn over a long period to assess the results of periodontal and endodontics therapies, and also during the restorative phase of implant reconstructive procedures. This in vitro study examined flexual strength of four resins commonly used for fixed provisional prostheses. The effects of polymerization conditions were also evaluated. The four resins tested were : Caulk Temporary bridge resin(L.D. Caulk Co. Dentsply International Millford), Jet(Lang Dental Mfg. Co. Chicago. ILL. U.S.A), Alike (Coe Laboratories. Inc. Chicago. ILL. U.S.A) and Tokuso Curefast (Coe Laboratories. Inc. Chicago. ILL. U.S.A) The test specimens were 65mm long, 14mm wide, and 3.5mm thickness. 10 specimens of four resins were cured for 15 minutes at atmospheric pressure and 10 specimens of four resins were cured at an additional pressure of approximately 20 psi. A total of 80 specimens were prepared. The flexual strength was determined by three-point bending test. Data were analysed with the Paired samples T-test and Tukey student-range test Within the limitations imposed in this study, the following conclusions can be drawn : 1. Under the condition of bench curing, Caulk Temporary bridge resin showed the highest flexual strength. In decreasing order, the flexual strength of the other materials was as follows : Jet, Tokuso Curefast, Alike, and Caulk Temporary bridge resin demonstrated significantly higher strength than other resins. 2. Under the condition of pressure curing, Jet showed the highest flexual strength. In decreasing order, the flexual strength of the other materials was as follows : Caulk Temporary bridge resin, Tokuso Curefast, and Alike. There were all statistically significant differences among four resins 3. There was a statistically significant difference between bench- and pressure-cured specimens in all four materials.

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Effect of Water Environment on the Mechanical Properties of Unidirectional CFRP (일방향 탄소섬유강화 복합재료의 기계적 성질에 미치는 수 환경의 영향)

  • 손선영;김재동;고성위
    • Journal of Ocean Engineering and Technology
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    • v.11 no.4
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    • pp.23-30
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    • 1997
  • The purpose of this paper is to investigate the water environmental effect on the mechanical properties of carbon fiber/epoxy composites. Moisture concentration absorbed in CFRP under various water environment was calculated and degradation of mechanical properties for each wet composite laminates is investigated by performing the flexual and tensile test. The results show that moisture absorption is accelerated in higher temperature environment and under the same temperature sea water environment prompts more absorption than fresh water. As increasing the water temperature and moisture concentration tensile and flexual strength decreased as much as 25%-40% compared with dry condition.

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Hysteretic Behavior of RC Beam-Column Joint for High Strength Structures using Belite Cement (베라이트 시멘트를 이용한 고강도 철근콘크리트 보-기둥 접합부의 이력특성)

  • 배흥한;이상원;윤정배;김기수;이세웅
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.582-588
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    • 1998
  • The experimental study for the interior beam-column joint for high strength conccrete using Belite cement is presented. Test parameters are compressive strength, flexual strength ratio and joint shear stresslevel. The results from cyclic loading tests show different behaviors from the various parameters. Also, The different behaviors on beam-column joint can be achived by the different concrete strength.

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An Experimental Study on the Physical Properties of Porous Concrete (투수 콘크리트의 물리적 특성에 관한 실험적 연구)

  • 채창우;정문영;이형우
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.166-171
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    • 1999
  • Porous concrete contains about 20% voids after compaction so that it has high permeability which secures underground water resources. It is introduced in domestic since 1980' but has problems such as lack of optimized mixture, low strength and durability, efflorescence and other defects, etc. In this study, several mixture were designed based upon site works, and test specimens for compressive strength, tensile strength, flexual strength and permeability, were prepared in a laboratory. After 28days of curing, every performance was tested to find optimum mixture. The mixture was proposed as 380kg/㎥ of unit cement weight, 32% of W/C 10∼13mm of aggregate.

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Using Recycled Aggregates in Sustainable Resource Circulation System Concrete for Environment Preservation (녹색자연환경 보존을 위한 지속가능한 자원순환시스템 콘크리트)

  • Lee, Young-Joo;Jang, Jung-Kwun;Kim, Yoon-Il;Lim, Chil-Soon
    • Proceedings of the Korean Institute of Building Construction Conference
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    • pp.57-61
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    • 2010
  • In this study, many concrete specimens were tested to investigate the variations of strength characteristics of high-strength concrete due to amount of recycled coarse aggregates, and to investigate the effect of steel-fiber reinforcement on concrete using recycled coarse aggregates. Test results showed that all of the variations of compressive, tensile and flexural strength appeared in linear reduction according to icrease the amount of recycled coarse aggregates, and steel-fiber reinforcement of 0.75% volumn of concrete recovered completely spliting tensile strength and flexual strength and recovered greatly compressive strength of concrete using recycled coarse aggregates of 100% displacement. And test results showed that the shear strength falled rapidly at 30% of replacement ratio so far as 34% of strength reduction ratio, but after that it falled a little within 3% up to the replacement ratio 100%, and steel-fiber reinforcement of 0.75% of concrete volumn recovered completely the deteriorated shear strength, moreover improved the shear strength above 50% rather than that of concrete using natural coarse aggregates.

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A Study on the Waterproof Properties of Cement Mortar with the Addition Rate of the Inorganic Admixture and Zinc Stearate (무기질 혼화재 및 금속비누의 혼입률 변화에 따른 시멘트 모르터의 방수 특성에 관한 연구)

  • Choi, Hoon;Jiang, Yi-Long;Han, Min-Cheol;Ryu, Hyun-Ki;Han, Cheon-Goo
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.139-144
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    • 1998
  • This study is intended to devolop the self waterproof agents for high performance concrete by analyzing the properties of fresh and hardened mortar with various addition ratios of the inorganic admixture and zinc stearate. As the results of the test, the flow and air content increase with the addition of expansive additives. When the replacement rate of silica fume increases, the flow decreases for the increased viscidity. And the flow and sir content decrease with the addition of zinc stearate. At hardened state, the compressive strength, tensile strength and flexual strength decrease with the addition of expansive additives and zinc stearate. With the increase of silica fume's replacement, they show a little decrease at early age and then increase gradually. Also, absorption and permeability show a steep decrease when zinc stearate is added, and a slack decrease with the replacement of silica fume.

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Thermal, Mechanical Properties of LAS with the Addition of Mullite ($Li_2O-Al_2O_3-SiO_2$계 소지의 Mullite 첨가에 의한 열적, 기계적 특성에 관한 연구)

  • 최도문;유재근;이응상
    • Journal of the Korean Ceramic Society
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    • v.30 no.5
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    • pp.381-388
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    • 1993
  • Due to the anisotropy of thermal expansion, LAS system which has low thermal expansion property is hard to obtain a dense sintered body. Therefore, the thermal expansion coefficient and the mechanical strength were decreased. In this study, mullite, which has good mechanical properties in high temperature and comparatively low thmeral expansion coefficient, was taken as a additive in LAS system. And then, sintering, thermal, and mechanical properties were investigated. The results are follows; When mullite is added in eucryptite composition (Li2O.Al2O3.2SiO2) of LAS system, the creation of liquid phase results in the densification of sintered body and the specimen sintered at 136$0^{\circ}C$ for 2 hours shows optimum sintering condition. With the addition of mullite in eucryptite composition, mechanical strength is increased by the control of grain growth. Especially, flexual strength of EM0 specimen was about double value than the basic composition. Thermal expansion coefficients of EM0 and EM15 specimens sintered at 136$0^{\circ}C$ were -8.23$\times$10-6/$^{\circ}C$ and -4.90$\times$10-6/$^{\circ}C$ in the temperature range of RT.~80$0^{\circ}C$. As the mullite content are increased, negative thermal expansion ratios are decreased.

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Influence of CuO Dopants on the Sintering Ability and Phase Stability of Yttria-Stabilized Tetragonal Zirconia Polycrystals (Y-TZP의 燒結性 및 相 安定性에 대한 CuO添加의 影響)

  • Pee, Jae-Hwan;Kim, Yun-Hae;Motozo Hayakawa
    • Journal of Ocean Engineering and Technology
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    • v.13 no.2
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    • pp.35-40
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    • 1999
  • Effects of CuO addition on the sintering ability and the phase stability of Y-TZP. (Yttria doped Tetragonal Zirconia Polycrystals) were studied. The CuO dopants were found to be quite effective in reducing the sintering temperature to obtain full density and refining the grain size. The maximum allowable concentration of the dopants was limited to 0.3%mol% for CuO to maintain fully tetragonal phase. With the addition of these dopants, the flexual strength decreased by 20% in comparison with the undoped specimen but the fracture toughness increased by 15%.

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Manufacture of Black Color Zirconia Ceramics Used by Eco-Friendly Materials (친환경 재료를 사용한 흑색 지르코니아 세라믹스 제조)

  • Joo, In-Don;Lee, Byung-Ha
    • Korean Journal of Materials Research
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    • v.21 no.12
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    • pp.685-689
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    • 2011
  • The goal of this investigation was to produce a zirconia-family black ceramics that has enhanced functionality and reliability. Color zirconia ceramics have been produced by adding pigments. Pigments cause structural defects within zirconia and result in a drop in physical properties. Using environmentally friendly rice husk, we produced a black zirconia that is free of structural defects. In optimal firing conditions for black zirconia the calcining temperatures of the molding product are changed from $400^{\circ}C$ to $1200^{\circ}C$, and the firing temperatures are changed from $1400^{\circ}C$ to $1600^{\circ}C$. Color of testing the specimens was analyzed using Ultraviolet (UV) spectroscopy. Scanning Electron Microscope (SEM), EDAX (EDX), and Fourier transform infrared spectroscopy (FT-IR) analyses were carried out in order to examine impregnation properties and crystal phases. Universial Test Machine (UTM) was used to measure the flexual strength as well as the compressive strength. From experimental results, it was found that in optimal firing conditions the sample was calcined from $1000^{\circ}C$ to $1500^{\circ}C$. Commission internationalde I'Edairage (CIE) values of manufactured black zirconia color were $L^*$ = 29.73, $a^*$ = 0.23, $b^*$ = -2.68. The bending strength was 918 MPa and the compressive strength was 2676 MPa. These strength values are similar to typical strength values of zirconia, which confirms that carbon impregnation did not influence physical properties.

The Effect of Axial Force on the Behavior and Average Crack Spacing of Reinforced Concrete Flexural Member (축력이 철근콘크리트 휨부재의 거동과 평균 균열간격에 미치는 영향)

  • 양은익;김진근;이성태;임전사랑
    • Magazine of the Korea Concrete Institute
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    • v.9 no.4
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    • pp.207-214
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    • 1997
  • This study was performed to verify the effect of axial force due to restraint on the mechanical behavior and the average crack spacing of the reinforced concrett. ilexural menlbers. For. this purpose, the flexural sttvngt.h and rigidity werc experimentally investigated undcl. axially rcstmined and unr.est.rainrd conditions. Furthermore , the average crack spacing was also checkcd for the axilly restrained contlit.ion. Thc test results showd that the flexual strength and rigidity of t,he restrained beam were higher. than those of the unrestrained beam. The major. factors affecting on the average crack spacing were steeel stress, axial force, cicumference of reinforcing bar and effective tension arm of concrete. However. the concrete compressive strength was minor effect. Including thesc factors, a prediction equation for the average crack spacing of the restrained member was proposed.