• Progress in Superconductivity and Cryogenics
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• v.19 no.2
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• pp.53-57
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• 2017

In superconducting power devices including power cables in which high temperature superconducting (HTS) tapes are utilized, a reliable electrical insulation should be achieved for its maximum performance. For an efficient design of HTS superconducting devices, a comparative evaluation of the mechanical and thermal propperties for various insulation materials at cryogenic temperatures is required. Especially, in the process of the property evaluation of the sheet-shaped insulation materials, anisotropy according to the machining direction should be considered because the mechanical and thermal properties are significantly influenced by the sample orientation. In this study, the cryogenic thermal and mechanical properties of various insulation material sheets such as PPLP, Cryoflex, Teflon, and Kapton were determined considering sample orientation. All samples tested at cryogenic temperature showed significantly higher tensile strength as compared with that of room temperature. The ultimate tensile strength at both temperature conditions significantly depended upon the sample orientation. The thermal properties of the insulation materials exhibited a slight difference among samples depending on the orientation: for the PPLP and Cryoflex, the CD orientation showed larger thermal contraction up to 77 K as compared to the MD one. MD samples in PPLP and Cryoflex showed a lower CTE and thermal contraction which made it more promising as an insulation material due to its comparable CTE with HTS CC tapes.

• Journal of Mechanical Science and Technology
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• v.19 no.2
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• pp.496-504
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• 2005

The thermal and mechanical properties of an electro-slag cast steel of a similar chemical composition with an AISI-6F2 steel are investigated and compared with a forged AISI-6F2 steel. AISI-6F2 is a hot-working tool steel. Electro-slag casting (ESC) is a method of producing ingots in a water-cooled metal mold by the heat generated in an electrically conductive slag when current passes through a consumable electrode. The ESC method provides the possibility of producing material for the high quality hot-working tools and ingots directly into a desirable shape. In the present study, the thermal and mechanical properties of yield strength, tensile strength, hardness, impact toughness, wear resistance, thermal fatigue resistance, and thermal shock resistance for electro-slag cast and forged steel are experimentally measured for both annealed and quenched and tempered heat treatment conditions. It has been found that the electro-slag cast steel has comparable thermal and mechanical properties to the forged steel.

• Korean Journal of Human Ecology
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• v.24 no.2
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• pp.285-295
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• 2015

To identify optimized thermal properties of mold brassiere cup for improved thermal comfort during summer, we compared the thermal resistance and the water vapor permeability of Polyurethane (PU) foam, 3D spacer fabric and the two combined materials of the PU foam and the 3D spacer fabric. Four experimental mold brassieres were made of the materials for wearing test. Six women in their twenties evaluated the wearing sensation in the hot and humid environment. The changes in microclimate temperature and humidity while wearing test brassiere cups were measured. Results indicate that thermal resistance increased as more PU foam were combined, while the water vapor permeability was higher as the content of the 3D spacer fabric increased at thickness of 18mm and over. However, in the wear test, the PU foam brassiere was the most preferred in all ambient conditions due to its soft, flexible and smooth texture, despite its high thermal resistance and low water vapor permeability. This indicates that the textures of mold foams are more dominant properties than thermal properties for mold foams in determining the wear comfort of mold brassieres.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09b
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• pp.45-52
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• 2010

Thermal properties of geomaterial are overlooked with other geomechanical properties. The transient line-source (TLS) method is one of the most used testing methods for measuring the thermal conductivity (K) and thermal diffusivity ($\alpha$) of materials. But more recently, Transient Plane-Source method was developed to measure these. It has several advantage of comparing with TSL method, but there has not been documented application in geomaterial. A Resistance Temperature Detector is used to construct sensor. For durability of Probe, Adopt a new technique that two probes are bonded in exact matching. For standard materials, such as glycerin, and ice the measured K and a values of these materials were generally within 2-5% from the standard values in the literature. This document present to evaluate the thermal properties of geomaterials and its application was tested for varying degree of saturation using the Transient Plane Source method. The result of this study suggests that it is an comparatively accurate method for simultaneously measuring thermal conductivity and thermal diffusivity and can identify the feasibility to geomaterial.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.11
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• pp.1651-1656
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• 2017

This paper deals with the thermal and mechanical properties of ceramic coating material for bus bars. A ceramic coated samples were prepared for the mechanical properties test. There are two types of samples. One is a square shape and the other is a busbar shape. Each sample was deteriorated for 30 days to compare the thermal and mechanical properties with the non-degraded samples. Two thermal properties tests are TGA and flammability tests, and four mechanical properties tests are drop impact test, cross cut, tensile test, and bend test. The ceramic coating material was never damaged by impact and did not separate from aluminum in the cross cut test. In the tensile test, the breakage of the insulating material did not occur until aluminum fractured, and the breakage of the insulating material did not occur until the maximum load in the bending test. The decomposition temperature (melting point) of the ceramic coating material was higher than that of other epoxy insulators. This ceramic coating material is nonflammable and it has excellent fire stability.

• Polymer(Korea)
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• v.39 no.2
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• pp.200-209
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• 2015

In this study, the influence of dilauroyl peroxide on mechanical and thermal properties of different polypropylene (PP) matrices was investigated. Polypropylene matrices, different molecular weight isotactic PP containing 0.01, 0.02, 0.04, 0.06, 0.08, and 0.1 wt% of dilauroyl peroxide (DLP) were prepared by using a single-screw extruder. The effect of the visbreaking agent (DLP) on mechanical, physical, thermal and morphological properties of different molecular weight PP had been studied. Mechanical properties (tensile strength at break point, at yield and elongation at break point), melt flow index (MFI), scanning electron microscope (SEM) and differential scanning calorimetric (DSC) analyses of these matrices were examined. Melting ($T_m$) and crystallization ($T_c$) temperatures, crystallinity ratio (%) and enthalpies were determined. The microstructure of isotactic polypropylene matrix was investigated by scanning electron microscopy (SEM). From SEM analysis, it was observed that the surface disorder increased by the increasing amount of DLP. As a result of DSC analyses, the crystallinity ratio of the PP matrices has varied between 1.64-7.27%. Mechanical properties of the matrices have been improved. Particularly, the mechanical tests of PP have given interesting results when compounded with 0.06-0.08 wt% dilauroyl peroxide (DLP). Mechanical properties and thermal decomposition processes were all changed by increasing the amount of DLP in the matrix structure.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.946-951
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• 1998

In order to calculate the thermal stresses of massive concrete structures in non-steady state conditions the thermal properties of the materials have to be well known. Structural materials such as concrete, rock and soil are heterogeneous, damp and porous so that measurements of their thermal properties by conventional methods would result in large errors. In this study, thermal conductivity was measured by the device, QTM-D3 which is usually used in Japan. Variables are chosen as age, water content, temperature, aggregate content, S/A ratio and type of cementitious materials. Finally a model for thermal conductivity was proposed.

• Journal of The Korean Astronomical Society
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• v.37 no.5
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• pp.583-587
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• 2004

With the aim to investigate the statistical properties and the connection between thermal and non-thermal properties of the ICM in galaxy clusters, we have developed a statistical magneto-turbulent model which describes, at the same time, the evolution of the thermal and non-thermal emission from galaxy clusters. In particular, starting from the cosmological evolution of clusters, we follow cluster. mergers, calculate the spectrum of the magnetosonic waves generated in the ICM during these mergers, the evolution of relativistic electrons and the resulting synchrotron and Inverse Compton spectra. We show that the broad band (radio and hard x-ray) non-thermal spectral properties of galaxy clusters can be well accounted for by our model for viable values of the parameters (here we adopt a EdS cosmology).

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.58-62
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• 2000

The fabrication process and analysis of thermal properties of 50~76vo1% SiCp/Al metal matrix composites(MMCs) for heatsink materials in electronic packaging were investigated. The 50~76vo1% SiCp/Al MMCs fabricated by pressure infiltration casting process showed that thermal conductivities were 85~170W/mK and coefficient of thermal expansion(CTE) were ranged 10~6ppm1k. Specially, the thermal conductivity and CTE of 71vo1%SiCp/Al MMCs were ranged 115~156W/mK and 6~7ppm/K. respectively, which showed a improved thermal properties than the conventional electronic packaging materials such as ceramics and metals.

• Steel and Composite Structures
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• v.11 no.4
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• pp.341-358
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• 2011

This paper presents the effects of thermal environment and temperature-dependence of the material properties on axisymmetric bending of functionally graded (FG) circular and annular plates. The material properties are assumed to be temperature-dependent and graded in the thickness direction. In order to accurately evaluate the effect of thermal environment, the initial thermal stresses are obtained by solving the thermoelastic equilibrium equations. Governing equations and the related boundary conditions, which include the effects of initial thermal stresses, are derived using the virtual work principle based on the elasticity theory. The differential quadrature method (DQM) as an efficient and robust numerical tool is used to obtain the initial thermal stresses and response of the plate. Comparison studies with some available results for FG plates are performed. The influences of temperature rise, temperature-dependence of material properties, material graded index and different geometrical parameters are carried out.