• Title/Summary/Keyword: In-situ Fracture

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Mechanical Properties of Carbon-Fiber Reinforced Polymer-Impregnated Cement Composites

  • Park, Seung-Bum;Yoon, Eui-Sik
    • KCI Concrete Journal
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    • v.11 no.3
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    • pp.65-77
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    • 1999
  • A portland cement was reinforced by incorporating carbon fiber(CF), silica powder, and impregnating the pores with styrene monomers which were polymerized in situ. The effects of type, length, and volume loading of CF, mixing conditions, curing time and, curing conditions on mechanical behavior as well as freeze-thaw resistance and longer term stability of the carbon-fiber reinforced cement composites (CFRC) were investigated. The composite Paste exhibited a decrease in flow values linearly as the CF volume loadings increased. Tensile, compressive, and flexural strengths all generally increased as the CF loadings in the composite increased. Compressive strength decreased at CF loadings above approx. 3% in CFRC having no impregnated polymers due to the increase in porosity caused by the fibers. However, the polymer impregnation of CFRC improved all the strength values as compared with CFRC having no Polymer impregnation. Tensile stress-strain curves showed that polymer impregnation decreased the fracture energy of CFRC. Polymer impregnation clearly showed improvements in freeze-thaw resistance and drying shrinkage when compared with CFRC having no impregnated polymers.

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In-situ Rock Stress Measurement at the Water Tunnel Sites in the OO Oil Storage Facility with Hydraulic Fracturing Method (수압파쇄법을 이용한 OO 원유비축시설 내 수벽 터널에서의 초기응력 측정)

  • Bae, Seong-Ho;Kim, Jae-Min;Kim, Jang-Soon;Lee, Young-Ho
    • Tunnel and Underground Space
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    • v.18 no.1
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    • pp.80-89
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    • 2008
  • The influence of in-situ rock stress on the stability of an underground rock structure increases as the construction depth become deeper and the scale of a rock structure become larger. In general, hydraulic fracturing stress measurement has been performed in the surface boreholes of the target area at the design stage of an underground structure. However, for some areas where the high horizontal stresses were observed or where the overstressed conditions caused by topographical and geological factors are expected, it is desirable to conduct additional in-situ stress measurement in the underground construction site to obtain more detailed stress information for ensuring the stability of a rock structure and the propriety of current design. The study area was a construction site for the additional underground oil storage facility located in the south-east part of OO city, Jeollanam-do. Previous detailed site investigation prior to the design of underground structures revealed that the excessive horizontal stress field with the horizontal stress ratio(K) greater than 3.0 was observed in the construction area. In this study, a total of 13 hydraulic fracturing stress measurements was conducted in two boreholes drill from the two water tunnel sites in the study area. The investigation zone was from 180 m to 300 m in depth from the surface and all of the fracture tracing works were carried out by acoustic televiewer scanning. For some testing intervals at more than 200 m ind depth from surface, the high horizontal stress components the horizontal stress ratio(K) greater than 2.50 were observed. And the overall investigation results showed a good agreement with the previously performed test.

How to Improve the Ductility of Nanostructured Materials

  • Eckert J.;Duhamel C.;Das J.;Scudino S.;Zhang Z. F.;Kim, K. B.
    • Journal of Powder Materials
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    • v.13 no.5 s.58
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    • pp.340-350
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    • 2006
  • Nanostructured materials exhibit attractive mechanical properties that are often superior to the performance of their coarse-grained counterparts. However, one major drawback is their low ductility, which limits their potential applications. In this paper, different strategies to obtain both high strength and enhanced ductility in nanostructured materials are reported for Ti-base and Zr-base alloys. The first approach consists of designing an in-situ composite microstructure containing ductile bcc or hop dendrites that are homogeneously dispersed in a nanostructured matrix. The second approach is related to refining the eutectic structure of a Ti-Fe-Sn alloy. For all these materials, the microstructure, mechanical properties, deformation and fracture mechanisms will be discussed.

Phase Transformation and Mechanical Properties of Reaction Sintered Mullite-Zirconia (Yttria) Composite (반응소결된 물라이트-지르코니아(이트리아) 복합체의 상변태와 기계적 성질에 관한 연구)

  • 오경영;장성도
    • Journal of the Korean Ceramic Society
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    • v.28 no.7
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    • pp.549-555
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    • 1991
  • Mullite-zirconia (0∼4 mol% yttria) composites were obtained by In-situ sintering of zircon and alumina mixture, and their mechanical properties were studied in conjuction with microstructure observation. Martensitic transformation temperature (Ms) of zirconia dispersed in the mullite matrix decreased with Y2O3 contents and was about 600$^{\circ}C$ for ZrO2 containing 4 mol% Y2O3. On cooling of this composites, tetragonal to monoclinic phase transformation induced microcracks at the grain boundary of mullite matrix. The microcracks seemed to absorb the fracture energy in stress field during mechanical tests. Therefore, toughening mechanisms of this composite were considered to nucleation and extension of microcrack, and crack deflection mechanism due to the difference of thermal expansion coefficient between matrix and dispersed phase.

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Tensile Failure Characterization of Composites for Railway Vehicle (철도차량 복합소재의 인장파괴 특성분석)

  • Kim, Jeong-Guk;Kwon, Sung-Tae;Kim, Jung-Seok;Yoon, Hyuk-Jin
    • Proceedings of the KSR Conference
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    • 2010.06a
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    • pp.1231-1235
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    • 2010
  • The tensile failure behavior of polymer matrix composite materials was investigated with the aid of a nondestructive evaluation (NDE) technique. The materials, E-glass fiber reinforced epoxy matrix composites, which are applicable to carbody materials in railway vehicles to reduce weight, were used for this investigation. In order to explain stress-strain behavior of polymer matrix composite sample, the infrared thermography technique was employed. A high-speed infrared (IR) camera was used for in-situ monitoring of progressive damages of polymer matrix composite samples during tensile testing. In this investigation, the IR thermography technique was used to facilitate a better understanding of damage evolution, fracture mechanism, and failure mode of polymer matrix composite materials during monotonic loadings.

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Microstructure and Mechanical Properties of P/M Processed 2XXX Al-${SiC}_{p}$ Composites (분말야금방법으로 제조된 2XXX Al-${SiC}_{p}$ 복합재료의 미세조직과 기계적 성질)

  • 심기삼
    • Journal of Powder Materials
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    • v.4 no.1
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    • pp.26-41
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    • 1997
  • The powder metallurgy (P/M) processed 2009 and 2124 Al composites reinforced with SiC particulates were studied by focusing on the effect of consolidation temperature on the microstructural and mechanical Properties. The mechanical properties such as tensile properties and microhardness of the second phases were analysed in relation to the microstructures observed by a SEM and an optical microscope. The in situ fracture process study using SEM showed that the grain refinement and the removal of manganese-containing particles often observed in the 2124 Al-${SiC}_{p}$ composites were important for the improvement of the mechanical properties. This study offers an optimum consolidation temperature for the control of the manganese-containing particles in the 2124 Al-${SiC}_{p}$ composites that yields mechanical properties higher than those of the 2009 Al-${SiC}_{p}$ composites.

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Material Properties of Polymer-Impregnated Concrete and Nonlinear Fracture Analysis of Flexural Members (폴리머 침투콘크리트의 재료특성과 휨부재의 비선형 파괴해석)

  • 변근주;이상민;최홍식;노병철
    • Magazine of the Korea Concrete Institute
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    • v.6 no.2
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    • pp.97-107
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    • 1994
  • The objective of this study is to develop polymer-impregnated concrete(PIC), which is a newly developed composite material made by impregnating polymer impregnanls into hardened normal concrete, and to develop analytical techniques for its proper applications. Crystalline methyl methacrylate(MMA) is chosen as a monomer of polymer impregnants. The corrlpositions of polymer impregnants and producing processes are developed by analyzing the effects of penetration, polymerization, thermal safety, and strengthening characteristics. On t he basis of experimental results of this study, various strength characteristics and stress strain constitutive relations are formulated in terms of the compressive strength of normal concrete and the polymer loadings, which can be applied for analysis and design of PIC members. In order to provide a model for fracture analysis of flexural members, fracture toughness, fracture energy, critical crack width, and tension softening relations near crack tip are also formulated in terms of member depth, initial notch depth, and the flexural strength of normal concrete. The structural analysis procedure and the finite element computer program developed in the study are applicable to evaluate elastic behavior, ultimate strength, and tension softening behavior of MMA type PIC structural members subject to various loading conditions. The accuracy and effectiveness of the developed computer program is examined by comparing the anal ytical results with the experimental results. Therefore, it is concluded that the developed structural analysis procedure and the finite element computer program are applicable to analysis and design of in-situ and precast PIC structural members.

Tensile test of multi-walled carbon nanotube with different growth methods (성장방법이 서로 다른 탄소나노튜브의 인장시험)

  • Jang, Hoon-Sik;Lee, Yun-Hee;Baek, Un-Bong;Park, Jong-Seo;Nahm, Seung-Hoon
    • Proceedings of the KSME Conference
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    • 2007.05a
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    • pp.200-203
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    • 2007
  • Carbon nanotubes (CNTs) have attracted an increasing attention due to their superior mechanical properties and potential application in industries. The strength of CNT has been predicted or calculated through several simulation techniques but actual experiments on stress-strain behavior are rare due to its dimensional limit, nanoscale positioning/manipulation, and instrumental resolution. We have attempted to observe straining responses of a multi-walled carbon nanotube (MWNT) with different growth methods by performing an in-situ tensile testing in a scanning electron microscope. Linear deformation and fracture behaviors of MWNT were successfully observed and its force-displacement curve was also measured from the bending stiffness and displacement of the force sensor and manipulator. We also obtained different tensile load of carbon nanotube with different growth methods.

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A Case Study on the Slope Reinforcement by Improved Steel Pipe Nailing (개량 강관네일링 공법을 이용한 사면 보강사례 연구)

  • Choi, Dong-Nam;Lim, Heui-Dae;Song, Young-Su;Lee, Kyu-Hwan
    • Journal of the Korean Society of Safety
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    • v.22 no.1 s.79
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    • pp.54-60
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    • 2007
  • This paper describes typical design and construction practice for in-situ ground reinforcement technique using improved steel pipe pressure grouting. A case history is presented to illustrate the benefit gained by application of the technique. This technique was applied to cut slopes developed in the construction of auxiliary spillway of 00 dam. Applicable conditions, method of survey, slope stability analysis and construction are given in this parer. As for the construction method, a procedure is given and the main points are the control of construction work. As a result of the pull-out test, it is shown that seel pipe nailing is particularly useful for stabilizing rock slope.

Korea Stress Map 2020 using Hydraulic Fracturing and Overcoring Data (수압파쇄와 오버코어링 자료를 활용한 한국응력지도 2020)

  • Kim, Hanna;Synn, Joong-Ho;Park, Chan;Song, Won Kyong;Park, Eui Seob;Jung, Yong-Bok;Cheon, Dae-Sung;Bae, Seongho;Choi, Sung-Oong;Chang, Chandong;Min, Ki-Bok
    • Tunnel and Underground Space
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    • v.31 no.3
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    • pp.145-166
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    • 2021
  • Korea Stress Map database is built by integrating actual data of 1,400 in-situ stress measurements using hydraulic fracturing and overcoring method in South Korea. Korea Stress Map 2020 is presented based on the guideline proposed by World Stress Map Project. As detailed data, stress ratio and maximum horizontal stress direction distribution for each region are also presented. The dominant maximum horizontal stress direction in the Korean Peninsula is from northeast to southeast, and the magnitude of the in-situ stress is relatively distributed. There is some stress heterogeneity caused by local characteristics such as topographical and geological properties. We investigated case studies in which the in-situ stress was affected by mountainous topography, difference in rock quality of fracture zone, presence of mine or underground cavities, and geological structure of fault zone.