• Progress in Superconductivity and Cryogenics
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• v.13 no.2
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• pp.17-20
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• 2011

Superconducting magnetic energy storage (SMES) has attracted a great deal of interest from the viewpoint of energy saving. The magnet of conduction-cooled high temperature superconducting (HTS) SMES is cooled down by a cryocooler. One of the most important problems to be assured the protection of magnet and cryocooler is breakdown at cryogenic temperature. In this study, we investigated insulation materials such as Kapton, Aluminum Nitride(AIN), Alumina($Al_2O_3$), glass fiber reinforced plastics(GFRP) and vacuum in cryogenic temperature. Also, we analyzed statistically the Weibull distribution of breakdown voltage.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.5
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• pp.1055-1062
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• 1988

The characteristics of tool wear and the machinability in cutting of GFRP have been studied. The wear behavior of carbide insert tools(P20, M10, K10) and Cermet in TiC grade was studied by turning of changing the cutting condition. Machinability could be estimated as the following empirical formula, CT$^{n}$ =W The main results obtained are as follows: (1) Dependence of rate of tool wear on cutting speed; with increases of cutting speed, the rate of tool wear initially increases gradually(1st range), then it increases proportionally to cutting speed(2nd range), and finally the rate is constant(3rd range). (2) When the contact length has a main, effect on tool wear, the cutting speed does nit affect the tool wear. On the contrary, the cutting speed has a main effect on tool wear, the contact length does not affect the tool wear. (3) The order of machinability is K10, M10, P20 and Cermet in TiC grade.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.7
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• pp.1222-1230
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• 2022

The rotor blade is an important component of a tidal stream turbine and is affected by a large thrust force and load due to the high density of seawater. Therefore, the performance must be secured through the geometrical and structural design of the blade and the blade structural safety to which the composite material is applied. In this study, a 1 MW class large turbine blade was designed using the blade element momentum (BEM) theory. GFRP is a fiber-reinforced plastic used for turbine blade materials. A sandwich structure was applied with CFRP to lay-up the blade cross-section. In addition, to evaluate structural safety according to flow variations, static load analysis within the linear elasticity range was performed using the fluid-structure interactive (FSI) method. Structural safety was evaluated by analyzing tip deflection, strain, and failure index of the blade due to bending moment. As a result, Model-B was able to reduce blade tip deflection and weight. In addition, safety could be secured by indicating that the failure index, inverse reserve factor (IRF), was 1 or less in all load ranges excluding 3.0*Vr of Model-A. In the future, structural safety will be evaluated by applying various failure theories and redesigning the laminated pattern as well as the change of blade material.

• Journal of the Korean Wood Science and Technology
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• v.45 no.1
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• pp.53-61
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• 2017

In this study, specimens were produced with a column member and a wooden gusset only by inserting an wooden gusset which is a substitute for steel plate into the center of a slit-processed column member. The moment resistance performance of the specimens was compared with that of control specimens that used a steel plate. The measured maximum moments of the specimens produced with GFRP-reinforced wooden laminated gussets and pins were lower by 24% on average compared to the steel plate-inserted specimens, but they showed good toughness. The fracture shape suggests that it was fractured along the annual rings between the pin and the end of the column member. The rigid specimen that integrated a laminated wood and a wooden laminated gusset with adhesive showed 2.8 times greater initial rigidity and 40% greater maximum moment on average compared to the control specimen. The rigid specimens mainly fractured on a glulam around glue line.

• Composites Research
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• v.32 no.5
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• pp.279-283
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• 2019

A flight training simulator of a fully spherical configuration is being developed to precisely and quickly control six degrees of freedom (Dof) motions especially with unlimited rotations. The full-scale simulator should be designed with a lightweight material to reduce inertial effects for fast and stable feedback controls while no structural failure is ensured during operations. In this study, a sandwich composite consisting of glass fiber reinforced plastics and a foam core is used to obtain high specific strengths and specific stiffnesses. T-type stainless steel frames are inserted to minimize the deformation of the sphere curvature. Finite element analysis is carried out to evaluate structural safety of the simulator composed of the sandwich sphere and steel frames. The analysis considers the weights of the equipment and trainee and it is assumed to be 200 kg. Gravity acceleration is also considered. The stresses and displacement acting on the simulator are calculated and the safety is assessed under two different situations.