• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.77-81
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• 2006

An attempt has been made to measure existing steel stress using magnetoelasticity. A device has been developed and used for the measurement of magnetism in response to the deformation of a steel bar. The proposed technique can be used for the assessment of existing reinforced concrete structures by the measurements of steel stress embedded inside concrete. A traditional technique requires to break the existing steel bar to measure existing strain. However, the proposed technique is developed to measure the stress without damaging the steel bar. A successful application of magnetoelasticity depends on the establishment of relationship between elastic and magnetic response due to loading. To investigate the correlation between the two, steel bars are loaded in tension under uniaxial loading while the magnetic reading is recorded. Based on the test results, equations are suggested to predict stress for steel bars with different diameters.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.549-554
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• 2000

In this study, using linear and nonlinear deformation theories and by closed-form analysis and finite difference energy methods, respectively, various buckling load factors are obtained for stiffened laminated composite cylindrical panels with rectangular type longitudinal stiffeners and various longitudinal length to radius ratios, which are made from Carbon/Epoxy USN150 prepreg and are simply-supported on four edges under uniaxial compression, and then for them, buckling behavior design analyses are carried out by the nonlinear search optimizer, ADS

• Journal of Mechanical Science and Technology
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• 제14권5호
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• pp.477-482
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• 2000

This study discusses a non-contact optical technique (electronic speckle pattern interferometry) that is well suited for thermal deformation measurement without any surface preparation and compensating process. Fiber reinforced plastics ($[0]_{16},\;[0/90]_{8S}$) were analyzed by ESPI to determine their thermal expansion coefficients. The thermal expansion coefficient of the transverse direction of a uniaxial composite is evaluated as $48.78{\times}10^{-6}(1/^{\circ}C)$. Also, the thermal expansion coefficient of the cross-ply laminate $[0/90]_{8S}$ is numerically estimated as $3.23{\times}10^{-6}(1/^{\circ}C)$ that is compared with that measured by ESPI.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.402-406
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• 2000

Strain energy function of the isoprene rubber was accurately determined by the experiments of uniaxial tension, planar tension, biaxial tension and volumetric compression. Deformation behavior of alternatively laminated structure of elastomer and reinforced aluminium layers, was analysed by Finite Element method. As a result, Ogden strain energy function obtained from the experiments describes the hyperelastic characteristics of the rubber very well. The compressibility of the rubber reduces axial stiffness of the structure. The axial stiffness of alternatively laminated structure being larger than shear stiffness. Which enables the structure to be shear-deformed easily.

• Fibers and Polymers
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• 제7권2호
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• pp.123-128
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• 2006

The present study aims at characterizing and modeling the anisotropic creep behavior of coated textile membrane, a class of flexible textile composites that are used for moderate span enclosures (roofs and air-halls). The objective is to develop a creep model for predicting the lifetime of coated textile membrane. Uniaxial creep tests were conducted on three off-axis coupon specimens to obtain the directional creep compliance. A potential with three parameters is shown to be adequate for modeling the anisotropic creep behavior of coated textile membrane. Furthermore, a possibility of predicting the creep deformation of coated textile membrane in a multi-axial stress state is discussed using the three-parameter potential.

• Steel and Composite Structures
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• 제7권5호
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• pp.355-376
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• 2007

The purpose of this study is to predict and investigate the time-dependent creep behavior of composite materials. For this, firstly the evaluation method for the modulus of elasticity of whole fiber and matrix is presented from the limited information on fiber volume fraction using the singular value decomposition method. Then, the effects of fiber volume fraction on modulus of elasticity of GFRP are verified. Also, as a creep model, the nonlinear curve fitting method based on the Marquardt algorithm is proposed. Using the existing Findley's power creep model and the proposed creep model, the effect of fiber volume fraction on the nonlinear creep behavior of composite materials is verified. Then, for the time-dependent analysis of a composite material subjected to uniaxial tension and simple shear loadings, a user-provided subroutine UMAT is developed to run within ABAQUS. Finally, the creep behavior of center loaded beam structure is investigated using the Hermitian beam elements with shear deformation effect and with time-dependent elastic and shear moduli.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.132-137
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• 2004

In this work, effects of hyper-elastic rubber material properties on the indentation load-deflection curve and subindenter deformation are first examined via [mite element (FE) analyses. An optimal data acquisition spot is selected, which features maximum strain energy density and negligible frictional effect. We then contrive two normalized functions. which map an indentation load vs. deflection curve into a strain energy density vs. first invariant curve. From the strain energy density vs. first invariant curve, we can extract the rubber material properties. This new spherical indentation approach produces the rubber material properties in a manner more effective than the common uniaxial tensile/compression tests. The indentation approach successfully measures the rubber material properties and the corresponding nominal stress.strain curve with an average error less than 3%.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 제2회 박판성형심포지엄 논문집 박판성형기술의 현재와 미래
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• pp.156-163
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• 1998

During an actual forming operation, a material may undergo considrably large changes in strain path, and these changes can significantly alter the forming limits. So, in this study, modified forming limit curves(FLCs) in complex strain path are determined with specially designed jig to give test specimens with desired prestrains in uniaxial or biaxial deformation mode. In another part of present study, theoretical prediction of FLCs is attempted with MK's theory and Hosford's yield criterion to give forming limit curves in positive minor strain region and with Hill's local necking theory in negative minor strain region. Comparison of these theoretical results with experimental ones will be mentioned for both linear and complex strain path.

• 대한기계학회논문집A
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• 제28권11호
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• pp.1752-1759
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• 2004

Reinforced braid layer (RBL) in automobile power steering hose plays an important role in power steering system. When the working oil is applied to the power steering hose, RBL suppresses rubber hose deformation from internal pressure and heat expansion. RBL is woven textile composites having a double-row structure of nylon cords twisted with the specific helix angle. In this paper, effective material properties of RBL are estimated using a detailed 3-D finite element model considering its complicated geometry. Numerical experiments based on a superposition method are carried out to simulate uniaxial tensile loading condition.

• Advances in concrete construction
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• 제5권1호
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• pp.75-86
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• 2017

An experimental work was carried out to study the effect of hybrid fiber on the tension stiffening and cracking characteristics of geopolymer concrete (GPC). A total of 24 concentrically reinforced concrete specimens were cast and tested under uniaxial tension. The grade of concrete considered was M40. The variables mainly consist of the volume fraction of crimped steel fibers (0.5 and 1.0%) and basalt fibers (0.1, 0.2 and 0.3%). The load deformation response was recorded using LVDT's. At all the stages of loading after the first cracking, crack width and crack spacing were measured. The addition of fibers in hybrid form significantly improved the tension stiffening effect. In this study, the combination of 0.5% steel fiber and 0.2% basalt fiber gave a better comparison than the other combinations.