• 제목, 요약, 키워드: fiber model

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강섬유보강 콘크리트의 휨인장강도 특성을 고려한 휨강성 평가 (Evaluation of Flexural Stiffness Considering Flexural Tensile Strength of Steel Fiber Reinforced Concrete)

  • 홍건호;정승원
    • 대한건축학회논문집:구조계
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    • v.35 no.8
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    • pp.131-138
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    • 2019
  • Since concrete has a low tensile strength compared to the compressive strength, reinforced concrete flexural members represent easy crack occurance under a small load. In order to overcome this problem, steel fiber reinforced concrete has been developed to compensate the tensile strength and brittleness of members. However, in the design formula of the domestic building code, it is not specified in the design formula reflecting the material characteristics. Therefore, the field application of the steel fiber reinforced concrete have had many restrictions. In this study, a flexural tensile strength model of steel fiber reinforced concrete is proposed by collecting and analyzing the material properties of material test results conducted by various researchers, and verified by the test results of cracking and stiffness evaluation of flexural members based on the proposed model. As a result of this study, the flexural tensile strength model of steel fiber reinforced concrete which can reflect the mixing ratio and aspect ratio of the steel fiber was proposed and the validity of the proposed material model equation was evaluated from the load-deflection relationship in the flexural test of the slab member.

스텝 인덱스 멀티모드 광섬유의 투광 조도분포 모델링 (Modeling of Transmitting Light Irradiance Distribution of Step-index Multimode Optical Fiber)

  • 신우철;홍준희
    • 한국광학회지
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    • v.17 no.2
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    • pp.136-142
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    • 2006
  • 광강도 변조방식 광섬유 센서의 변위응답해석에 필요한 투광 조도분포를 수학적으로 모델링 하였다. 유도된 조도분포 모델은 스텝인덱스 멀티모드 광섬유를 대상으로 하며 실험적 검증을 통해 타당성을 확인하였다. 검증된 조도분포 모델을 적용하여 얻은 광섬유 센서의 변위응답 해석결과를 변위측정 결과와 비교하여 거의 일치함을 확인하였다. 또한 기존의 가우시안 조도분포 모델을 적용한 해석결과와 비교했을 때 제안한 조도분포 모델이 보다 정확한 결과를 나타냄을 보이고 있다.

Relations between rheological and mechanical properties of fiber reinforced mortar

  • Cao, Mingli;Li, Li;Xu, Ling
    • Computers and Concrete
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    • v.20 no.4
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    • pp.449-459
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    • 2017
  • Fresh and hardened behaviors of a new hybrid fiber (steel fiber, polyvinyl alcohol fiber and calcium carbonate whisker) reinforced cementitious composites (HyFRCC) with admixtures (fly ash, silica fume and water reducer) have been studied. Within the limitations of the equipment and testing program, it is illustrated that the rheological properties of the new HyFRCC conform to the modified Bingham model. The relations between flow spread and yield stress as well as flow rate and plastic viscosity both conform well with negative exponent correlation, justifying that slump flow and flow rate test can be applied to replace the other two as simple rheology measurement and control method in jobsite. In addition, for the new HyFRCC with fly ash and water reducer, the mathematical model between the rheological and mechanical properties conform well with the quadratic function, and these quadratic function curves are always concave upward. Based on mathematical analysis, an optimal range of rheology/ flowability can be identified to achieve ideal mechanical properties. In addition, this optimization method can be extended to PVA fiber reinforced cement-based composites.

FPF(Fibrillated Polypropylene Fiber)보강 성토재료의 강도 특성에 관한 연구 (Characteristics of Soils Reinforced by FPF(Fibrillated Polypropylene Fiber))

  • 김낙경;박종식
    • 한국지반공학회:학술대회논문집
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    • pp.433-440
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    • 2001
  • This study was to analyze characteristics of soils reinforced by FPF(Fibrillated Polypropylene Fiber). Laboratory test, model test and field tests were performed on soils reinforced by fibers, to evaluate the shear strength characteristics. For the silty sand, clayey sand and silty clay, the influence of fiber shape, fiber length and fiber content were evaluated from compaction test, direct shear test, uniaxial test, california bearing ratio(CBR) test. Fibrillated type fiber, 5cm long with a content of 0.5% shows 5∼30% increase of friction angle and 7∼55 percent increase of CBR value.

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Analysis of Temperature Dependence of Thermally Induced Transient Effect in Interferometric Fiber-optic Gyroscopes

  • Choi, Woo-Seok
    • Journal of the Optical Society of Korea
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    • v.15 no.3
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    • pp.237-243
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    • 2011
  • Thermal characteristics, such as diffusivity and temperature induced change in the fiber mode index of rotation sensing fiber coil are critical factors which determine the time varying, thermo-optically induced bias drift of interferometric fiber-optic gyroscopes (IFOGs). In this study, temperature dependence of the transient effect is analyzed in terms of the thermal characteristics of the fiber coil at three different temperatures. By applying an analytic model to the measured bias in the experiments, comprehensive thermal factors of the fiber coil could be extracted effectively. The validity of the model was confirmed by the fact that the extracted values are reasonable results in comparison with well known properties of the materials of the fiber coil. Temperature induced changes in the critical factors were confirmed to be essential in compensating the transient effect over a wide temperature range.

Kinetic Model for Oxidation of Carbon Fiber/Glass Matrix Composites

  • Park, Chan;Park, Hee-Lack
    • The Korean Journal of Ceramics
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    • v.4 no.3
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    • pp.254-259
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    • 1998
  • A kinetic model predicting the oxidation of carbon fiber reinforced glass matrix composites has been described. The weight loss of composites during oxidation implied that a gasification of carbon fiber takes place and the transport of reactants $(O_2)$ or product (CO or $CO_3$) in the glass matrix was partially the rate controlling step. The kinetic model in this study was based on the work of Sohn and Szekely which may be regarded as a generalization of numerous models in the gas-solid reaction system. A comparison of this model with experimental data is also presented.

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Characterization of Surface Quality in Orthogonal Cutting of Glass Fiber Reinforced Plastics

  • Choi Gi Heung
    • International Journal of Safety
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    • v.3 no.1
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    • pp.1-5
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    • 2004
  • This study discusses frequency analysis based on autoregressive (AR) time series model, and the characterization of surface quality in orthogonal cutting of a fiber-matrix composite materials. A sparsely distributed idealized composite material, namely a glass reinforced polyester (GFRP) was used as workpiece. Analysis method employs a force sensor and the signals from the sensor are processed using AR time series model. The experimental correlations between the fiber pull-out and AR model coefficients are then established.

Compression failure and fiber-kinking modeling of laminated composites

  • Ataabadi, A. Kabiri;Ziaei-Rad, S.;Hosseini-Toudeshky, H.
    • Steel and Composite Structures
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    • v.12 no.1
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    • pp.53-72
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    • 2012
  • In this study, the physically-based failure models for matrix and fibers in compression and tension loading are introduced. For the 3D stress based fiber kinking model a modification is proposed for calculation of the fiber misalignment angle. All of these models are implemented into the finite element code by using the advantage of damage variable and the numerical results are discussed. To investigate the matrix failure model, purely in-plane transverse compression experiments are carried out on the specimens made by Glass/Epoxy to obtain the fracture surface angle and then a comparison is made with the calculated numerical results. Furthermore, shear failure of $({\pm}45)_s$ model is investigated and the obtained numerical results are discussed and compared with available experimental results. Some experiments are also carried out on the woven laminated composites to investigate the fracture pattern in the matrix failure mode and shown that the presented matrix failure model can be used for the woven composites. Finally, the obtained numerical results for stress based fiber kinking model and improved ones (strain based model) are discussed and compared with each other and with the available results. The results show that these models can predict the kink band angle approximately.

Contact interface fiber section element: shallow foundation modeling

  • Limkatanyu, Suchart;Kwon, Minho;Prachasaree, Woraphot;Chaiviriyawong, Passagorn
    • Geomechanics and Engineering
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    • v.4 no.3
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    • pp.173-190
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    • 2012
  • With recent growing interests in the Performance-Based Seismic Design and Assessment Methodology, more realistic modeling of a structural system is deemed essential in analyzing, designing, and evaluating both newly constructed and existing buildings under seismic events. Consequently, a shallow foundation element becomes an essential constituent in the implementation of this seismic design and assessment methodology. In this paper, a contact interface fiber section element is presented for use in modeling soil-shallow foundation systems. The assumption of a rigid footing on a Winkler-based soil rests simply on the Euler-Bernoulli's hypothesis on sectional kinematics. Fiber section discretization is employed to represent the contact interface sectional response. The hyperbolic function provides an adequate means of representing the stress-deformation behavior of each soil fiber. The element is simple but efficient in representing salient features of the soil-shallow foundation system (sliding, settling, and rocking). Two experimental results from centrifuge-scale and full-scale cyclic loading tests on shallow foundations are used to illustrate the model characteristics and verify the accuracy of the model. Based on this comprehensive model validation, it is observed that the model performs quite satisfactorily. It resembles reasonably well the experimental results in terms of moment, shear, settlement, and rotation demands. The hysteretic behavior of moment-rotation responses and the rotation-settlement feature are also captured well by the model.

섬유 집속체 연신 동역학의 실험적 확인 (Experimental Verification of the Fiber Bundle Drawing Dynamics)

  • 김종성;허유
    • 한국섬유공학회지
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    • v.47 no.5
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    • pp.314-321
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    • 2010
  • Short staple fibers are processed in forms of bundle, and the thickness variation of the fiber bundles plays an important role in determining the bundle quality. Since the staples in a bundle generally have a length distribution, the processed bundle thickness is affected by the fiber length distribution, which is strongly dependent on the flow dynamics during the drawing process of bundles. This study examined the effectiveness of a dynamic model for describing the roller drawing process, while considering the power form of the beard diagram for the fiber length distribution of the bundle. Two factors, the drawing ratio and fiber length distribution, were considered, and the draft ratio was set in two levels: a low drawing ratio level and a high drawing ratio level. Slivers with different beard diagrams were treated under the roller drawing operation and the output sliver thickness was measured. In addition, the output thickness was simulated based on the theoretical model. The simulation results were compared with the experimental results. The theoretical model describing the bundle flow matched the real roller drawing operation quite well, which was confirmed by the agreement of the simulation and experiments results. A low drawing ratio of the output bundle is advantageous from a quality point of view. In addition, the bundle with a fiber length distribution resulted in better linear density regularity of the output bundle than the bundle with a uniform fiber length. However, the irregularity difference due to the fiber length distribution disappeared at drawing ratios above a critical value, between 20 and 30.