• Progress in Superconductivity and Cryogenics
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• 제6권1호
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• pp.22-27
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• 2004

It is important to mechanical properties of dielectric paper and cable to optimum electrical insulation design of HTS cable, because the cable has experience of mechanical stress, such as tensile stress, bending stress. Also, it is operated at cryogenic temperature. From the results, it was observed that the tensile strength of PPLP in liquid nitrogen was high more than that of air, but tensile strain decrease sharply. According as tensile strength increases, the breakdown stress of PPLP in liquid nitrogen is decreased. Because PPLP was deteriorated by microcrack and tensile strain. According as bending radius multiple is decrease, the ac and impulse breakdown stress of mini-model cable is sharply decreased.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 한국추진공학회 2006년도 제26회 춘계학술대회논문집
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• pp.31-35
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• 2006

Degradation characteristics of filament-winded composites due to accelerated environmental aging have been evaluated under high temperature, water immersion and thermal impact conditions. Two kinds of laminated composites coated by an urethane resin have been used: carbon-fiber reinforced epoxy(T700/Epon-826, CFRP) and glass-fiber reinforced phenolic (E-glass/phenolic, GFRP). For tensile strength of $0^{\circ}$ composites, CFRP did high reduction by 25% under the influence of high temperature and water while CFRP showed little degradation. However for water-immersed $90^{\circ}$ composites both CFRP and GFRP showed high reduction in tensile strength. Bending strength and modulus of $90^{\circ}$ composites were largely reduced in water-immersion as well as high temperature environment. Urethane coating on the composite surface improved the bending properties by 20%, however hardly showed such improvement for water-immersed $90^{\circ}$ composites.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2010년도 춘계학술대회 논문집
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• pp.34-34
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• 2010

This paper describes effect of the bending deformation of high voltage composite bushing with winding tension. The composite bushing can be formed, by adding silicone rubber sheds to a tube of composite materials. The FRP tube is internal insulating part of a composite bushing and is designed to ensure the mechanical characteristics. Generally the properties of FRP tube can be influenced by the winding angle, wall thickness and winding tension. As winding tension is increased glass contents was increased in the range of 70.4~76.6%. In the bending test, winding tension is increased residual deflection was decreased in the range of 14.0~12.2 mm.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1647-1650
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• 2003

The Objective of this work was to design Surface Antenna Structure (SAS) and investigate fatigue behavior of SAS that was asymmetric sandwich structure. This term, SAS, indicates that structural surface becomes antenna. Constituent materials were selected considering electrical properties, dielectric constant and tangent loss as well as mechanical properties. For the antenna performance, SSFIP elements inserted into structural layers were designed for satellite communication at a resonant frequency of 12.5 GHz and final demonstration article was 16${\times}$8 array antenna. From electrical measurements, it was shown that antenna performances were in good agreement with design requirements. In cyclic 4-point bending, flexure behavior was investigated by static and fatigue test. Fatigue lift curve of SAS was obtained. The fatigue load was determined experimentally at a 0.75(1.875kN) load level. SAS concept is the first serious attempt at integration for both antenna and composite engineers and promises innovative future communication technology.

• Steel and Composite Structures
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• 제16권4호
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• pp.339-356
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• 2014

This paper presents a study of the nonlinear cylindrical bending of an exponential functionally graded plate (simply called E-FG) with variable thickness. The plate is subjected to uniform pressure loading and his geometric nonlinearity is introduced in the strain-displacement equations based on Von-Karman assumptions. The material properties of functionally graded plates, except the Poisson's ratio, are assumed to vary continuously through the thickness of the plate in accordance with the exponential law distribution; and the solution is obtained using Hamilton's principle for constant plate thickness. In order to analyze functionally graded plate with variable thickness, a numerical solution using finite difference method is used, where parabolic variation of the plate thickness is studied. The results for E-FG plates are given in dimensionless graphical forms; and the effects of material and geometric properties on displacements and normal stresses through the thickness are determined.

• Progress in Superconductivity and Cryogenics
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• 제4권1호
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• pp.45-59
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• 2002

Evaluation of the mechanical properties of Bi-2223/Ag HTS tapes was carried out by the tension and bending tests. Most of the Bi-2223/Ag tapes retained critical current up to 10 kgf/mm$_2$ axial tension stress, and 0.2% tension strain at room temperature. Applied tension strain exceeding 0.3% in superconducting tapes at 77 K leaded to rapid degradation of the critical current. It was observed that the more filaments, the better axial tension property at 77 K, self-field The influence of bending strain on critical current degradation was revealed to be less sensitive for Bi-2223/Ag HTS tapes with a more number of filaments and higher silver ratio.

• Steel and Composite Structures
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• 제34권6호
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• pp.795-802
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• 2020

The subject of the paper is a circular plate with symmetrically thickness-wise varying mechanical properties. The plate is simply supported and carries a concentrated force located in its centre. The axisymmetric bending problem of the plate with consideration of the shear effect is analytically and numerically studied. A nonlinear function of deformation of the straight line normal to the plate neutral surface is assumed. Two differential equations of equilibrium based on the principle of stationary potential energy are obtained. The system of equations is analytically solved and the maximum deflections and shear coefficients for example plates are derived. Moreover, the maximum deflections of the plates are calculated numerically (FEM), for comparison with the analytical results.

• Proceedings of the Korean Society For Composite Materials Conference
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• 한국복합재료학회 2003년도 춘계학술발표대회 논문집
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• pp.108-111
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• 2003

The Objective of this work was to design Surface Antenna Structure (SAS) and investigate fatigue behavior of SAS that was asymmetric sandwich structure. This term, SAS, indicates that structural surface becomes antenna. Constituent materials were selected considering electrical properties, dielectric constant and tangent loss as well as mechanical properties. For the antenna performance, SSFIP elements inserted into structural layers were designed for satellite communication at a resonant frequency of 12.5 GHz and final demonstration article was $16\;{\times}\;8$ array antenna. From electrical measurements, it was shown that antenna performances were in good agreement with design requirements. In cyclic 4-point bending, flexure behavior was investigated by static and fatigue test. Fatigue life curve of SAS was obtained. The fatigue load was determined experimentally at a 0.75(1.875kN) load level. SAS concept is the first serious attempt at integration for both antenna and composite engineers and promises innovative future communication technology.

• Journal of the Korean Ceramic Society
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• 제34권6호
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• pp.577-582
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• 1997

The mechanical properties of Al2O3-ZrO2 composites fabricated by RBAO(reaction bonded aluminium oxide) process were investigated. As the amount of ZrO2 increased the sinstered density of Al2O3-ZrO2 composites decreased slightly, but wear resistance was enhanced. Bending strength of Al2O3-ZrO2 composites increased in proportion to the amount of al in case of a fixed ZrO2 content. When the amount of Al was fixed bending strength reached its maximum value at 25 wt% ZrO2. The fracture toughness(K1c) increased with increasing content of ZrO2, but decreased with increasing Al amount. On the other hand, the fracture mode of Al2O3-ZrO2 composites was the mixed mode of inter-and transgranular fracture.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 한국농공학회 2000년도 학술발표회 발표논문집
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• pp.284-289
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• 2000

This study is performed to evaluate an the crack properties and repair-reinforcement of concrete introduced crack. Materials used are portland cement, coarse aggregate, fine aggregate, unsaturated polyester resin and fly ash. Specimen is used beam of 76${\times}$76${\times}$412mm for measurement of pulse velocity, dynamic modulus of elasticity and bending strength and is introduced crack artificially. The following conclusions are drawn; Pulse velocity, dynamic modulus of elasticity and bending strength of concrete introduced crack is shown the lower 1.24∼11.91%, 3.42∼17.21% and 38.17∼61.0% than that of the control concrete, respectively. Pulse velocity, dynamic modulus of elasticity and bending strength of concrete repaired and reinforced crack is shown the higher 0.5∼2.60%, 1.57∼3.07% and 28.17∼47.25% than that of the concrete introduced crack and the lower than that of the control concrete, respectively.