• 제목/요약/키워드: flexural fracture behavior

검색결과 157건 처리시간 0.02초

국산 지르코니아 분말 소결체 품질의 글로벌 제품과의 비교 연구 (Comparative Study on the Quality of Sintered Zirconia Block Fabricated by Using Domestic Powder and Global-Brand Powder)

  • 김용인;이승미;변재원
    • 한국신뢰성학회지:신뢰성응용연구
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    • 제15권3호
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    • pp.216-221
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    • 2015
  • Sintering behavior of 3%yttria-stabilized zirconia was comparatively studied using a spray-dried powder produced by a domestic and global company. Quality of the sintered block was analysed in terms of relative density, shrinkage rate, grain growth, hardness, and fracture toughness. Relative density, shrinkage rate, and hardness value of the finally sintered block was similar between domestic and global zirconia powder, respectively. But, flexural strength of the domestic powder specimen was about 70% of the sintered block produced by using a global powder. The poor sintering quality of the domestic powder was discussed in relation with compressibility of the spray-dried granule-type powder and the amount of monoclinic phase in the as-received powder.

입체트러스형 전단연결재를 갖는 합성판의 피로거동 (Fatigue Behavior of Composite Beams with Pyramidal Shear Connector)

  • 이경동;한재익
    • 한국구조물진단유지관리공학회 논문집
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    • 제6권2호
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    • pp.211-216
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    • 2002
  • A steel plate-concrete composite slab with pyramidal shear connectors, named TSC composite slab, is expected to have sufficient bending strength and flexural rigidity for loads during and after construction. Fatigue problems play an important role in designing composite slab as bridge decks under traffic conditions. In this paper, a series of fatigue tests was carried out on TSC beam specimens under various loading conditions, in order to evaluate the fatigue strength of TSC composite slabs. The results are as follows : (1) the fatigue failure of TSC composite beams results from the tensile fracture of bottom steel plate and shear connector, and (2) fatigue strength of the steel plate for two million cycles can be estimated to be $1144kgf/cm^2$ from the S-N curves.

SiC Fiber 강화 다공질 반응 소결 탄화규소 Composite의 제조 및 기계적 특성 (Fabrication of SiC Fiber Reinforced Porous Reaction Bonded SiC Composite and Its Mechanical Properties)

  • 한재호;박상환
    • 한국세라믹학회지
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    • 제43권8호
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    • pp.509-514
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    • 2006
  • In this study, chopped Hi-Nicalon SiC fiber Reinforced Porous Reaction Bonded SiC (RBSC) composites and it fabrication process were developed by using Si melt infiltration process. The porosity and average pore size in fabricated chopped SiC fiber reinforced porous RBSC composites were in the range of $30{\sim}40%$ and $40-90{\mu}m$, which mainly determined by the SiC powder size used as starting material and amount of residual Si in porous composites. The maximum flexural strength of chopped SiC fiber reinforced porous RBSC composite was as high as 80 MPa. The delayed fracture behavior was observed in chopped SiC fiber reinforced porous RBSC composites upon 3-point bending strength test.

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

  • Park, Seung-Bum;Yoon, Eui-Sik
    • KCI Concrete Journal
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    • 제11권3호
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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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다이아몬드 마이크로블레이드의 내구성과 절삭성능에 미치는 흑연과 MoS2의 첨가효과 (The Effect of Graphite and MoS2 on Endurance and Cutting Performance of Diamond Micro Blades)

  • 문종철;김송희
    • 한국표면공학회지
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    • 제41권6호
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    • pp.335-340
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    • 2008
  • Cutting performance and wear behavior were studied with the diamond micro-blade of Cu/Sn bond materials containing various amount of lubricant materials such as graphite and $MoS_2$. Measurement of instantaneous electric power consumption for cutting glass workpiece at the constant velocity was conducted and proposed as a method to assess cutting efficiency. The energy consumption of micro-blade for glass cutting decreased with the content of graphite and $MoS_2$ while wear amount of blade in volume increased with the amount of lubricant addition during the dicing test. It is because that hardness, flexural strength, and fracture toughness ($K_{IC}$) reduced with the amount of lubricant addition. Blades with $MoS_2$ additive showed higher mechanical properties than those with graphite additives when the same amount of the lubricant additive in wt.% was added. Due to the lower density of graphite than $MoS_2$, higher volume fraction of graphite could result in stronger effect on lowering electric power consumption by reducing the friction between blade and work piece however increasing wear rate due to the reduction in strength and fracture toughness. Adhesive wearing mode of micro blade could be remarkably improved by the addition of graphite as well as $MoS_2$.

합성섬유를 사용한 변형경화형 시멘트 복합체의 휨 및 인장성능 (Flexural and Tensile Performance of Strain-Hardening Cement Composite with Synthetic Fibers)

  • 김선우;이민정;장용헌;장광수;송선화;윤현도
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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    • pp.925-928
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    • 2008
  • 최근 내진부재 및 기존 구조물의 내진보강요소의 손상제어(Damage tolerance)성능을 충족할 수 있는 변형경화형 시멘트 복합체(Strain-hardening cement composites, SHCC)의 개발 및 활용 연구가 진행 중이며, 하이브리드화에 따른 경제성 및 성능향상 가능성도 보고되고 있다. 그러나 이러한 우수한 성능을 갖는 SHCC 재료가 실구조물의 보수/보강재 및 내진보강부재에 적용되기 위해서는 우수한 인장성능 발현뿐만 아니라, 보강섬유의 단가를 고려한 경제적 효과(Economical efficiency) 및 시공성 (Workability)이 요구된다. 따라서 본 연구에서는 SHCC를 내진부재 및 보강재료로써 적용하기 위한 연구의 일환으로 합성섬유를 하이브리드하여 혼입시 휨 및 인장강도, 변형능력 등 거동특성을 분석함으로써 각 보강섬유의 인장강도 탄성계수 등 기계적 특성과 혼입율에 따른 재료성능과의 상관관계를 비교 분석하여 평가하고자 한다. 또한 물시멘트비를 변수로 하여 시멘트 복합체의 강도특성과 보강섬유의 부착특성 및 균열제어성능을 규명하고자 한다. 이러한 결과를 근거로 향후 SHCC 재료의 실구조물 적용시 요구성능 및 경제성을 고려한 재료배합에 관한 기초자료를 제시하고자 한다.

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하이브리드 탄소섬유 적층구조에 따른 복합재료의 기계적 특성 연구 (Study on the Mechanical Properties of Hybridized Carbon Fiber Composite According to Stacking Structure)

  • 구선웅;오우진;원종성;이하람;윤주영;이승구
    • 한국염색가공학회지
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    • 제30권4호
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    • pp.313-320
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    • 2018
  • As carbon fiber reinforced composites(CFRP) are widely used in aerospace, automobile, marine, and sports goods applications, they have been studied extensively by various researchers. However, CFRP have been pointed out because of machining problems such as delamination and burr phenomenons. Especially, hole machining process, drilling, has non-smooth features on inlet and outlet surfaces of drilled hole. This kind of machining problem can be controlled to some extent by using high modulus pitch-CF, which has considerable effects on fracture behavior of composite compared with only PAN CF composite. Therefore, PAN and pitch hybridized CF composites were prepared having high strength and modulus. The results demonstrate that the hybrid CFRP specimens with pitch CF offer the good potential to enhance modulus as well as strength properties. Dynamic mechanical, flexural, and impact properties were measured and analyzed. Morphological surface of the composites were also observed by IFS-28, canon after hole machining.

강섬유 혼입 폴리머 시멘트 고강도 콘크리트 보의 전단거동 (Shear Behavior of Polymer Cement High Strength Concrete Beams Mixed with Steel Fiber)

  • 곽계환;박종건;곽경헌
    • 한국농공학회지
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    • 제44권1호
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    • pp.93-102
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    • 2002
  • Steel fiber and polymer are used widely for reinforcement material of RC structures because of its excellences of the durability, serviceability as well as mechanical properties. The purpose of this study is to investigate the shear behavior of polymer cement high strength concrete beams mixed with steel fiber. The compressive strength of concrete was based on the 100$\times$200 mm cylinder specimens. The compressive strength of concrete are 320$kgf/cm^2$, 436 $kgf/cm^2$ and 520 $kgf/cm^2$ in the 28 days. The static test was carried out to measure the ultimate load, the initial load of flexural and diagonal cracking, crack patterns and fracture modes. Also, load-strain and load-deflection examined. During the test cracks were sketched against the load values according to the growth of crack. result are as follows; (1) The failure modes of the specimens are increased in rigidity and durability with mixing steel fiber and polymer. (2) The load of initial crack was similar a theory of shear-crack strength. (3) The deflection and strain at failure load of Polymer-steel fiber high strength concrete beams were increased, improving the brittleness of the high strength concrete.

강봉댐퍼로 보강한 기존 저층 철근콘크리트 필로티 건물의 내진성능 (Seismic Performance of an Existing Low-Rise Reinforced Concrete Piloti Building Retrofitted by Steel Rod Damper)

  • 백은림;오상훈;이상호
    • 한국지진공학회논문집
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    • 제18권5호
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    • pp.241-251
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    • 2014
  • In this study, shaking table test was carried out to evaluate the seismic behavior and performance of low-rise reinforced concrete (RC) piloti structures with and without retrofit. The specimens were designed considering the characteristics of existing building with pilotis such as natural period, distribution factor of strength and stiffness between columns and core wall on the first soft story. The test for the non-retrofit specimen showed that damage was concentrated on the stiffer member on the same floor as the core wall failed by shear fracture whereas columns experienced slight flexural cracks. Considering the failure mode of the non-retrofit specimen, the retrofit method using steel rod damper was presented for improving the seismic performance of piloti structures. The results of the test for retrofit specimen revealed that the retrofit method was effective for controlling the damage as the main RC structural members were not destroyed and most of input energy was dissipated by hysteretic behavior of the damper.

보강된 노후 구조물 파괴거동 예측을 위한 수치해석기법 개발 (Numerical Analysis of Fracture Behavior in Aged RC Structures)

  • 신승교;고태호;김문겸;임윤묵
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
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    • pp.1031-1036
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    • 2000
  • In this study, a numerical simulation that can effectively predict the strengthening effect of repaired aged RC structures is developed using the axial deformation link elements. In repaired structures, concrete and interface are modeled as quasi-brittle materials. An elastic-perfectly plastic constitutive relationship is introduced for reinforcing bars. Also, a linear-elastic relationship for repair materials such as FRP or CFS. Structural deterioration in terms of corrosion of steel rebar is considered. The interfacial property between steel and concrete which is reduced by corrosion of steel rebar is obtained by comparing numerical results with experimental results of pull out tests. Obtained values are used in repaired reinforced concrete structures under flexural loading conditions. To investigate strengthening effect of the structures repaired with carbon fiber sheet(CFS), repaired and unrepaired RC structures are analyzed numerically. From analysis, rip-off, debonding and rupture failure mechanisms of interface between substrate and CFS can be determined. Finally, strengthening effect according to the variation of interfacial material properties is investigated, and it is shown that interfacial material properties have influence on the mechanical behavior of repaired structure systems Therefore, the developed numerical method using axial deformation link elements can use for determining the strengthening effects and failure mechanism of repaired aged RC structure.