• Journal of Wind Energy
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• v.10 no.4
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• pp.20-27
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• 2019

High-speed shaft coupling in a wind power system transmits power and absorbs variations in length and spindle dislocation between the gearbox and generator. Furthermore, the coupling has an insulation function that prevents electrical corrosion caused by the flow of the generator's current into the gearbox and prevents overload resulting from sudden power failure from being transferred to the gearbox. Its design, functions, and part verification are described in the IEC61400 and GL Guidelines, which specify that the part must have a durability life of 20 years or longer under distance variation and axial misalignment between the gearbox and the generator. This study presents the design of a high-speed coupling through composite stiffness calculation, structural analysis, and comparative analysis of test and theory to identify the characteristics of high-speed coupling for a large-capacity 6 MW wind power generator. A prototype was fabricated by optimizing the manufacturing process for each part based on the design, and the reliability of the fabricated prototype was verified by evaluating the performance of the target quantitative evaluation items.

• Steel and Composite Structures
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• v.44 no.4
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• pp.519-529
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• 2022

Sandwich structures with the superior mechanical properties such as high stiffness and strength-to-weight ratio, good thermal insulation, and high energy absorption capacity are used today in aerospace, automotive, marine, and civil engineering industries. These structures are composed of moderately stiff, thin face sheets that withstand the majority of transverse and in-plane loads, separated by a thick, lightweight core that resists shear forces. In this research, the finite element technique is used to simulate a sandwich panel with a truss core under axial compressive stress using ABAQUS software. A review of past experimental studies shows that the bondline between the core and face sheets plays a vital role in the critical failure load. Therefore, this modeling analyzes the damage initiation modes and debonding between face sheet and core by cohesive surface contact with traction-separation model. According to the results obtained from the modeling, it can be observed that the adhesive stiffness has a significant influence on the critical failure load of the specimens. To achieve the full strength of the structure as a continuum, a lower limit is obtained for the adhesive stiffness. By providing this limit stiffness between the core and the panel face sheets, sudden failure of the structure can be prevented.

• Applied Chemistry for Engineering
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• v.22 no.5
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• pp.501-507
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• 2011

To develop environmental-friendly insulating composite materials, natural cellulose and porous ceramic balls were used as core materials and activated Hwangtoh was used as a binder. Various specimens were prepared with different water/binder ratios and core material/binder ratios. The physical properties of these specimens were then investigated through compressive strengths, flexural strengths, absorption test, hot water resistance test, pore analysis, thermal conductivity, and observation of micro-structures using scanning electron microscope. Results showed that the maximum compressive strength varied appreciably with the water/binder ratios and core material/binder ratios, but the flexural strength increased with the core material/binder ratios regardless of water/binder ratios. The compressive strength and the flexural strength measured after the hot water resistance test decreased remarkably compared to those measured before test. The pore analysis measured after the hot water resistance test showed that total pore volume, porosity and average pore diameter decreased, while bulk density increased by the acceleration of hydration reaction of binder in the hot water. The thermal conductivity decreased gradually with an increase of core material/binder ratios. It can be evaluated that the composite insulation materials having good insulating properties and mechanical strengths can be used in the field.

• Journal of the Korea Institute of Building Construction
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• v.18 no.2
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• pp.117-123
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• 2018

The increase in energy efficiency has became a significantly important issue for building construction and maintenance. The energy efficiency is known to be achieved by using a material with lower thermal conductivity, and the best method is to increase the internal porosity of the material. Typical ways to increase internal porosity within cementitious composite are to use foaming agents or to use reactive powder such as aluminum. However, in this work, hydrogen peroxide was chosen as an alternative material to make lightweight cement mortar. The volume expansion of fresh cement mortar and unit weight, compressive strength and thermal conductivity of 28 day old cement mortar were measured. According to the experimental results, the incorporation of hydrogen peroxide increased internal porosity, and thereby reducing the compressive strength and thermal conductivities of cement mortar. It was found that hydrogen peroxide can be successfully used to produce lightweight mortar for thermal insulation purposes of buildings.

• Fashion & Textile Research Journal
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• v.20 no.5
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• pp.600-607
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• 2018

Polypropylene fibers, while having many advantages such as light weight, sweat fast drying, water-repellent, drainage, thermal insulation, anti-static property has a drawback in dyeing. In recent years, the development of dyeable polypropylene fibers has expanded its value in the textile market. The purpose of this study is to fabricate composite spun yarns using polypropylene, acrylic, rayon and wool and to analyze tensile properties, uniformity characteristics, bending properties, hairiness, and surface shape according to the degree of fineness and blended ratio. The specimens consisted of 100% polypropylene spun yarn pp30, pp40 and ppa(pp/acrylic), ppr(pp/rayon), ppw(pp/wool), 5 altogether sed in this study. The results of the study are as follows. The breaking strength of polypropylene spun yarn blended with rayon and acrylic was higher than that of 100% polypropylene spun yarn. The polypropylene spun yarn is higher the fineness been shown to decrease the breaking strength and elongation. The bending properties of polypropylene spun yarns were in the order of ppa>ppr>pp40>pp30>ppw. The unevenness of ppw, ppr, and ppa was higher than pp40 and pp30. With the exception of ppw with crimp properties, pp30 and pp40 were found to have a hairiness index greater than ppr, ppa. In the microscopic photographs of polypropylene spun yarn, pp30, which had the highest hairiness index, was found to have a thick yarn and a large number of hairs, and ppw had hairs of 3 mm or more protruding elongated outwardly.

• Korean Journal of Bronchoesophagology
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• v.12 no.2
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• pp.19-25
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• 2006

There have been numerous modalities to recover blink function of orbicularis oculi muscle in patients with facial paralysis. However, there is still no optimal method for reanimation of eyelid. In this study, we tried to recover blink function of paralyzed rabbit's eyelid with the ion polymer metal composite (IPMC) which is one of the electroactive polymers that is spotlighted as artificial muscle. We manufactured IPMC by plating the platinum over perfluorosulphonic acid polymer ($Nafion^{(R)}$). IPMC was coated by Norland optical adhesive for the purpose of insulation and keeping it from dry. IPMC modifications by roughening the surface of Nafion, repetitive plating (maximum 4 times) with platinum, and lengthening the width of IPMC were done. The facial paralysis was induced in the rabbit by sectioning of facial nerve at the main trunk. After minimum period of 4 weeks, IPMC was inserted in the paralyzed rabbit's eyelid. By modification, the force generated by IPMC was enhanced. Restoration of blink function in paralyzed rabbit was achieved on electrical stimulation of the IPMC by 5 voltage direct current. IPMC can be promising option for facial reanimation, but further studies are needed to enhance the efficiency of IPMC.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.1
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• pp.39-46
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• 2008

The end plates of fuel cell assemblies are used to fasten the inner stacks, reduce the contact pressure, and provide a seal between Membrane-Electrode Assemblies (MEAs). They therefore require sufficient mechanical strength to withstand the tightening pressure, light weight to obtain high energy densities, and stable chemical/electrochemical properties, as well as provide electrical insulation. The design criteria for end plates can be divided into three parts: the material, connecting method, and shape. In the past, end plates were made from metals such as aluminum, titanium, and stainless steel alloys, but due to corrosion problems, thermal losses, and their excessive weight, alternative materials such as plastics have been considered. Composite materials consisting of combinations of two or more materials have also been proposed for end plates to enhance their mechanical strength. Tie-rods have been traditionally used to connect end plates, but since the number of connecting parts has increased, resulting in assembly difficulties, new types of connectors have been contemplated. Ideas such as adding reinforcement or flat plates, or using bands or boxes to replace tie-rods have been proposed. Typical end plates are rectangular or cylindrical solid plates. To minimize the weight and provide a uniform pressure distribution, new concepts such as ribbed-, bomb-, or bow-shaped plates have been considered. Even though end plates were not an issue in fuel cell system designs in the past, they now provide a great challenge for designers. Changes in the materials, connecting methods, and shapes of an end plate allow us to achieve lighter, stronger end plates, resulting in more efficient fuel cell systems.

• Journal of the Korean Society of Safety
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• v.28 no.4
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• pp.48-52
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• 2013

This study was carried out, using toxicity test apparatus, to analyze toxic gases of heat insulation material and adhesives of composite panels used for the architectural surface material when a fire occurs. The findings of this study show that CO, $CO_2$, HCOH, $CH_2CHCN$ and $NO_x$ were detected from styrofoam, reinforced styrofoam, polyurethane foam and glass fiber, but in the case of the polyurethane foam, HCl and HCN were detected as well. All the architectural adhesives released CO, $CO_2$ and $NO_x$, but HCHO was only detected from the adhesives for styrofoam, wood, tile, windows and doors; $CH_2CHCN$ was only from those for wood and stone; $C_6H_5OH$ was only from those for wood. The toxicity index was also measured for architectural surface material and adhesives. Polyurethane foam showed the highest index, 11.7, and glass fiber was followed as 6.8. Reinforced styrofoam showed 5.7 and styrofoam revealed the least 4.9. In the case of architectural adhesives, the highest ranking was those for stone 7.4, windows and doors 6.1, wood 5.3, tile 3.8, and styrofoam 3.7 were followed, respectively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.4
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• pp.347-355
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• 2014

Thermal problems that are directly related to the lifetime of an electronic device are becoming increasingly important owing to the miniaturization of electronic devices. To solve thermal problems, it is essential to study thermal stability through thermal diffusion and insulation. A honeycomb sandwich plate has anisotropic thermal conductivity. To analyze the thermal deformation and temperature distribution of a system that employs a honeycomb sandwich plate, the thermal and elastic properties need to be determined. In this study, the thermal and elastic properties of a honeycomb sandwich plate, such as thermal conductivity, coefficient of thermal expansion, elastic modulus, Poisson's ratio, and shear modulus, are predicted. The properties of a honeycomb sandwich plate vary according to the hexagon size, thickness, and material properties.

• Journal of the Korean institute of surface engineering
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• v.31 no.1
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• pp.12-23
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• 1998

The Thermal Barrier Coating(TBC) has been used to improve the heat barrier and tribological properties of the aircraft engine and the automobile engine in high temperature. Especially, the high temperature tribological propertied of the cylinder haed and the piston crown of diesel engine was emphasized. Therefore, the purpose of this work was to evaluate the microstructure, tribological propeer in high tempearmal shock resistance and bonding strength of five layer functionally gradient TBC for the applications. The five layerwere composed with 100% ceramic insulating later, 75(ceramic):25 (metal) layer, 50:50 layer, 25:75 layer and 100% metal bonding layer to redude the thermal stress. the YSL and MSL poweders were the insulation ceramics powers. The NiCrAly, Inconel625 and SUS powders were the bonding and mixingg powders for plasma spray process. According to the result of high temperature wear test, the wera resistance of YSZ/NiCrAlY siytem was most out standing at 600 and $800^{\circ}C$. At $400^{\circ}C$, the wear resistance of YSZ/Inconel system was better than others. Wear volume at other temperature because of the low temperature degration of zirconia. The thermal shock mechanism of 5 later is the vertical crack gegration in insulating layer. this means that the initial cracks were generated in the top layer, and then developed into the composite layers during thermal shock test. Finally, these cracks werereached to the interface of coating and substrate and also, these vertioal cracks join with the horizontal cracks of the each layers. The bonding strength of YSZ/NiCrAlY and YSZ/Inconel 5 layer system is better than other 5layer systems. The theramal shock resistance of thermal barrier coating s with 5 layer system is better than that of 3 layers and 2 layers.