• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.1
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• pp.53-58
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• 2003

Carbon fiber sheet has been used to rehabilitate many types of reinforced concrete members with its superior characteristics such as their lightweight, high strength, corrosion resistance, and easy execution. But the failure behavior of reinforced concrete members show a high variation by the bond characteristics between carbon fiber sheet and concrete surface. In this study, a bond stress-slip model, which accounts for changes in bonding behavior between concrete and carbon fiber sheet with some link elements, is proposed. The link elements are used to represent the concrete-carbon fiber sheet interface. To investigate the efficiency of this method, the analytical solutions for the behavior of reinforced concrete beam strengthened with carbon fiber sheet are compared with experimental ones. Results from the proposed model comparatively well agree with the experimental results.

• Journal of Welding and Joining
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• v.30 no.4
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• pp.24-30
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• 2012

Laser welding by fiber laser accompanied by a lot of spatter and humping bead. This is because the deep and narrow keyhole usually form due to high beam quality. So the weld bead is formed defects, because the plasma jet with a high vapor pressure make the molten pool on keyhole wall scattered. For such a reason, unstable behavior of keyhole is difficult to monitor laser welding by using the laser induced plasma. Mostly, fiber laser welding of thick plates most be influenced by this effect. Therefore, fiber laser welding has been difficult to apply the sole. Thus, laser welding monitoring based on plasma measurements have much difficulty in measurements and analysis of signal. In this study, influence of the plasma emission signal according to welding speed and laser power in fiber laser welding analysed by using RMS and FFT analysis. We can verify that RMS value of the plasma emission signal changes with welding parameters in fiber laser welding, and aspect ratio greater than 1, the peak of FFT frequency had been moved in accordance with welding parameter.

• Computers and Concrete
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• v.28 no.5
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• pp.451-463
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• 2021

Inorganic basalt fiber (BF) is a novel sort of commercial concrete fiber which is made with basalt rocks. Previous studies have not sufficiently handled the behavior of self-compacted concrete, at elevated temperature, containing basalt fiber. Present endeavor covers experimental work to examine the characteristics of this material at high temperature considering different fiber content and applied temperature. Different tests were carried out to measure the mechanical properties such as compressive strength (fc), modulus of elasticity (E), Poisson's ratio, splitting tensile strength (fsplit), flexural strength (fflex), and slant shear strength (fslant) of HSC and hybrid concrete. Gene expression programming (GEP) was employed to propose new constitutive relationships depending on experimental data. It was noticed from the testing records that there is no remarkable effect of BF on the Poisson's ratio and modulus of elasticity of self-compacted concrete. The flexural strength of basalt fiber self-compacted concrete was not sensitive to temperature in comparison to other mechanical properties of concrete. Fiber volume fraction of 0.25% was found to be the optimum to some extend according to degradation of strength. The proposed GEP models were in good matching with the experimental results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.8
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• pp.2123-2138
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• 1994

A study on the dynamic mechanical properties of the high strength carbon fiber epoxy composite beam was carried out. The macromechanical model was used for the theoretical analysis of the symmetric laminated composite beam. The anisotropic plate theory and Bernoulli-Euler beam theory were used to predict the effective flexural elastic modulus and the specific damping capacity of laminated composite beam. The free flexural vibration and torsional vibration tests were carried out to determine the specific damping capacities of the unidirectional laminated composite beam. The vibration tests were performed in a vacuum chamber with laser vibrometer system and electromagnetic hammer to obtain accurate experimental data. From the computational and experimental results, it was found that the theoretical values with the macromechanical analysis and the experimental data of symmetric laminated composite beam were in good agreement.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.8 no.4
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• pp.139-144
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• 1983

In this paper, the ploarization and Faraday rotation properties of the single mode optical fiber have been investigated for magnto-optic current transformer application. On the analysis, the optical fiber is modeled as a linear retarder and the intrinsic birefreingence of the optical fiber is approximately found to be 2.57'/m from the measurement, and the bend-induced birefringence is proportional to the inverse square of bending radius. The polarization rotation sensitivity is foung to be F/H=1.4x$10^-5$rad/[A/m] from the analysis of Faraday rotation of single mode optical fiber.

• Structural Engineering and Mechanics
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• v.37 no.5
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• pp.529-542
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• 2011

Three dimensional solutions for free vibrations analysis of functionally graded fiber reinforced cylindrical panel are presented, using differential quadrature method (DQM). The orthotropic panel is simply supported at the edges and is assumed to have an arbitrary variation of reinforcement volume fraction in the radial direction. Suitable displacement functions that identically satisfy the simply supported boundary condition are used to reduce the equilibrium equations to a set of coupled ordinary differential equations with variable coefficients, which can be solved by differential quadrature method to obtain natural frequencies. The main contribution of this work is presenting useful results for continuous grading of fiber reinforcement in the thickness direction of a cylindrical panel and comparison with similar discrete laminate composite ones. Results indicate that significant improvement is found in natural frequency of a functionally graded fiber reinforced composite panel due to the reduction in spatial mismatch of material properties.

• Journal of Sensor Science and Technology
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• v.15 no.1
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• pp.28-33
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• 2006

Optical-fiber sensors have been developed to determine the concentrations of glucose and lactic acid in blood samples. Fluorescence dye [tris(2,2'-biphenyridine)-ruthenium(II)-chloride (RuBPY)] was entrapped by using a silicon to the unclad tip of a glass optic fiber. Enzymes like glucose oxidase (GOD) and lactate oxidase (LOD) have been immobilized by acrylamide resin adhesive, adsorption with zeolite or covalent bonding with aminopropyl-triethoxysilan. The fiber-optic glucose/lactate sensor was then used to analyze the concentrations of glucose and lactate in blood samples. The results were compared with the results of HPLC analysis and their difference was in error by less then 5 %.

• Journal of the Korean Society of Industry Convergence
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• v.11 no.4
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• pp.195-199
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• 2008

The carbon fiber has low x-ray absorption property and high stiffness. This is the reason why many CT(Computed Tomography) manufacturer use carbon fiber in couch tabletop for CT scanner. In this paper, we design and make the couch tabletop made of carbon fiber composite, and verify the validity in CT scanner. In designing the couch tabletop, to determine the aluminum equivalent thickness of couch tabletop, we evaluate X-ray the transmissivity of aluminum and carbon plate in 80-120kVp X-ray energy range. And we perform structural analysis and mechanical design using determined thickness of carbon sheet. In conclusion, it was evaluated that manufactured couch tabletop satisfies X-ray transmissivity and mechanical requirements in CT scanner.

• Steel and Composite Structures
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• v.10 no.4
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• pp.349-360
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• 2010

Three dimensional free vibrations analysis of functionally graded fiber reinforced cylindrical shell is presented, using differential quadrature method (DQM). The cylindrical shell is assumed to have continuous grading of fiber volume fraction in the radial direction. Suitable displacement functions are used to reduce the equilibrium equations to a set of coupled ordinary differential equations with variable coefficients, which can be solved by differential quadrature method to obtain natural frequencies. The main contribution of this work is presenting useful results for continuous grading of fiber reinforcement in the thickness direction of a cylindrical shell and comparison with similar discrete laminate composite ones. Results indicate that significant improvement is found in natural frequency of a functionally graded fiber reinforced cylinder due to the reduction in spatial mismatch of material properties and natural frequency.

• Korean Journal of Optics and Photonics
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• v.18 no.3
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• pp.196-201
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• 2007

A theoretical study of Brillouin optical time domain analysis (BOTDA) using two pulse lasers is performed. Even though a point detection is made for a pump pulse period, the dynamic range of BOTDA using two pulse lasers is approximately 5 dB more than that of a pulse and a CW laser when the fiber length is 140 km and the Stokes power is 1 mW.