• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.3
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• pp.166-175
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• 2002

Tank track rubbers, which undergo dynamic stresses and strains under various road conditions, leads to a result of considerable internal temperature rise due to the heat generation. Since rubber materials are not fully elastic, a part of the mechanical energy is converted into heat because of the hysteresis loss. Heat generation without adequate heat dissipation leads to heat build-up, i.e. internal temperature rise which, if excessive, exerts a bad influence upon the performance and the life of the tank track rubbers. The purpose of this paper is to predict temperature distributions of the rubber components off tank track subjected to complex dynamic loads under various read conditions. In steady state analysis temperature fields are displayed in contour shapes, and in unsteady analysis the temperature variations of some important nodes are represented graphically with respect to the running time of the tank.

• Applied Science and Convergence Technology
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• v.25 no.4
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• pp.77-80
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• 2016

The $PbSc_{1/2}Nb_{1/2}O_3$ ceramics at a relatively low temperature of $1300^{\circ}C$ was successful synthesized. Solid state reaction of two-step process is not necessary. The dielectric constant, dielectric loss and admittance of ceramic samples were determined. The pyroelectric characteristics are in good agreement with the dielectric properties. Ferroelectric properties of well-formed the $PbSc_{1/2}Nb_{1/2}O_3$ ceramics are in agreement with broad distribution of relaxation phenomenon. Relatively strong frequency dependent of dielectric constant is observed at about $110^{\circ}C$. The distinct thermal hysteresis was observed in the measurement of the dielectric constant and dielectric loss. The critical exponents of during cooling and heating measurements in the $PbSc_{1/2}Nb_{1/2}O_3$ ceramics were 1.14 and 1.59 at 1 kHz, respectively.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.12
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• pp.2065-2071
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• 2007

This paper suggests the harmonic effects on HTS(High Temperature Superconducting) power cable. HTS cable is regarded as not only one of the important countermeasure to supply high density power demand area, but also one of countermeasures greenhouse technology. However, with the development of digital society, the distribution line power is much contaminated with harmonics generated by various power electronic equipments. This paper describes how the HTS cable responds to the harmonic and increases AC losses caused by hysteresis phenomenon. EMTDC based harmonic simulation results are compared with AC loss measured values.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.699-703
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• 2018

Flux-switching permanent magnet machines (FSPMM) have doubly-salient and simple structures making it cost effective and suitable for mass production. In addition, it is possible to increase the rotor rotating speed and concentrate the flux of the permanent magnet on the air-gap. Due to these merits, the FSPMM can be applied to the various industry applications. To improve the performance, various design variables need to be studied in terms of design techniques. In this paper, we especially concentrate on the distribution of iron losses using a two-dimensional finite-element method (2D FEM). As a result, we can get an information for high efficiency FSPMM design.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.262-264
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• 1999

The AC losses of BSCCO-2223 multifilamentary superconducting tapes were measured using magnetization method and compared with the results of theoretically calculated values. In general, AC losses in multifilamentary superconducting tapes could be quantitatively explained by the simple sum of the Hysteresis and Coupling Loss. As a result of experiment, We found that AC losses of multifilamentary superconducting tape increase rapidly in large magnetic field region.

• Electrical & Electronic Materials
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• v.8 no.6
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• pp.787-794
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• 1995

To improvement the magnetic and frequency properties of YIG(Yttrium-Iron Garnet) in microwave region, it is investigated that the effect of $Al^{3+}$ ions on magnetic and frequency characteristics of YIG, using samples of basic YIG composition( $Y_{3}$F $e_{5}$ $O_{l2}$) added with A1$_{2}$ $O_{3}$ from 0 to 2.5 [mol%]. The measurment is conducted mainly for the structural properties and magnetical properties. The structural properties is measured using SEM(Scanning Electro Microscope), EDX(Energy-dispersive X-ray spectrometer) and XRD(X-ray diffraction equipment). The magnetical properties is measured with B-H curve tracer and impedance analyzer. As a result, it is confin-ned that the effect of eddy current loss is minimized while maintaining high saturation flux density of YIG, when YIG is added with 0.5 [mol%] of A1$_{2}$ $O_{3}$.>.>.

• Computers and Concrete
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• v.2 no.5
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• pp.367-380
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• 2005

Recent earthquakes have shown that many of existing buildings in Iran sustain heavy damage due to defective seismic details. To assess vulnerability of one common type of buildings, which consists of low rise framed concrete structures, three defective and three standard columns have been tested under reversed cyclic load. The substandard specimens suffered in average 37% loss of strength and 45% loss of energy dissipation capacity relative to standard specimens, and this was mainly due to less lateral and longitudinal reinforcement and insufficient sectional dimensions. A relationship has been developed to introduce variation of plastic length under increasing displacement amplitude. At ultimate state, the length of plastic hinge is almost equal to full depth of section. Using calibrated hysteresis models, the response of different specimens under two earthquakes has been analyzed. The analysis indicated that the ratio between displacement demand and capacity of standard specimens is about unity and that of deficient ones is about 1.7.

• Elastomers and Composites
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• v.56 no.4
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• pp.209-216
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• 2021

In this study, we observed the mechanical properties, thermal stability, and low temperature sealing performance of fluorosilicone elastic composites. When the blend ratio of Phenyl vinyl methyl silicone (PVMQ) was increased, the tensile strength, modulus at 100%, and compression set were decreased. The thermal stability of fluorosilicone elastic composites showed a similar tendency. These were caused by poorer green strength of PVMQ than Fluorosilicone rubber (FVMQ). The change in the tensile strength and elongation at -40℃ showed a decreasing tendency with increasing PVMQ blend ratio. By increasing the PVMQ blend ratio, low-temperature performance was improved. The Dynamic mechanical analysis (DMA) results showed that T_g was decreased and low-temperature performance was improved with increasing PVMQ blend ratio. However tanδ was decreased becaused of the poor green strength and elasticity of PVMQ. From a hysteresis loss at -40℃, the hysteresis loss value was increased and fluorosilicone elastic composites showed the decreasing tendency of elasticity with increasing PVMQ blend ratio. From the TR test, TR10 was decreased with increasing PVMQ blend ratio. FS-4 (45% PVMQ blended composites) showed a TR10 of -68.0℃ that was 5℃ lower than that of FS-1 (100% FVMQ). The gas leakage temperature was decreased with increasing PVMQ blend ratio. The gas leakage temperature of FS-4 was -69.2℃ that was 5℃ lower than that of FS-1. Caused by the polymer chain started to transfer from a glassy state to a rubbery state and had a mobility of chain under T_g, the gas leakage temperature showed a lower value than T_g. The sealing performance at low temperature was dominated by T_g that directly affected the mobility of the polymer chain.

• Tribology and Lubricants
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• v.36 no.6
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• pp.332-341
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• 2020

High-speed turbomachinery implements gas foil bearings (GFBs) due to their distinctive advantages, such as high efficiency, lesser part count, and lower weight. This paper provides the test results of the static structural stiffnesses and loss factors of bump-type foil thrust bearings with increasing preload and bearing deflection. The focus of the current work is to experimentally quantify variability in structural stiffnesses and loss factors among the four test thrust bearings with identical design values and material of the bump and top foil geometries using the same (open-source) fabrication method. A simple test setup, using a rigidly mounted non-rotating shaft and thrust disk, measures the bearing bump deflections with increasing static loads on the test bearing. The inner and outer diameters of the test bearings are 41 mm and 81 mm, respectively. The loss factor, best-representing energy dissipation in the test bearings, is estimated from the area inside the local hysteresis loop of the load versus the bearing deflection curve. The measurements show that structural stiffnesses and loss factors of the test bearings significantly rely on applied preloads and bearing deflections. Local structural stiffnesses of the test bearings increase with applied preloads but decrease with bearing deflections. Changes of loss factors are less sensitive to applied preloads and bearing deflections compared to those of structural stiffnesses. Up to 35% variability in static load structural stiffnesses is found between bearings, while up to 30% variability in loss factors is found between bearings.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.5
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• pp.377-383
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• 2016

The effect of long-term aging degradation on magnetic properties of ferritic 11Cr low-carbon steel was investigated. Coercivity and hysteresis loss measured from the hysteresis loops decreased with long-term aging time and showed that the relation was well fitted by a second order exponential function. Vickers hardness also decreased with aging time and resulted in mechanical softening. In addition, the microstructural evolution was observed by the scanning electron microscopy, backscattered electron image and X-ray diffraction. The $Cr_{23}C_6$ precipitates along grain boundary grew fast and Laves ($Fe_2W$) phase on martensitic lath boundaries in interior grains was developed. The solid solution atoms depleted in matrix and lath subgrains recovered owing to precipitate coarsening with long-term aging degradation. There was a close relation with softening of magnetic and mechanical properties.