• Journal of Welding and Joining
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• v.21 no.3
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• pp.68-77
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• 2003

It is important to understand the characteristics of material strength and fracture under the dynamic loading like as earthquakes to assure the integrity of welded structures. The characteristics of dynamic strength and fracture in structural steels and their welded joints should be evaluated based on the effects of the strain rate and the service temperature. It is difficult to predict or measure temperature rise history with the corresponding stress-strain behavior. In particular, material behaviors beyond the uniform elongation can not be precisely evaluated, though the behavior at large strain region after the maximum loading point is much important for the evaluation of fracture. In this paper, the coupling phenomena of temperature and stress-strain fields under the dynamic loading was simulated by using the finite element method. The modified rate-temperature parameter was defined by accounting for the effect of temperature rise under the dynamic deformation, and it was applied to the fully-coupled analysis between heat conduction and thermal elastic-plastic behavior. Temperature rise and stress-strain behavior including complicated phenomena were studies after the maximum loading point in structural steels and their undermatched joints and compared with the measured values.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.922-924
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• 2014

This paper is concerned with the analysis of natural vibration characteristics of an accelerometer used in power plant. The malfunction of the accelerometer in high-temperature environment may produce erroneous sensor signal and the erroneous signal may cause unpredicted accidents in power plants. Hence, the accelerometer which endures high temperature needs to be developed. In this study, the natural vibration characteristics of the accelerometer were investigated prior to the development of the high-temperature accelerometer. The main mechanical part of the accelerometer is a spiral spring. In this study, the dynamic characteristics of the spiral spring were investigated first by using a commercial finite element code. Numerical results show that the thickness of the spiral spring affects the dynamic characteristics. Numerical investigation on the effect of temperature on the performance of the accelerometer will follow.

• Smart Structures and Systems
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• v.25 no.5
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• pp.593-604
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• 2020

Temperature may have more significant influences on structural responses than operational loads or structural damage. Therefore, a comprehensive understanding of temperature distributions has great significance for proper design and maintenance of bridges. In this study, the temperature distribution of the steel box girder is systematically investigated based on the structural health monitoring system (SHMS) of the Sutong Cable-stayed Bridge. Specifically, the characteristics of the temperature and temperature difference between different measurement points are studied based on field temperature measurements. Accordingly, the probability density distributions of the temperature and temperature difference are calculated statistically, which are further described by the general formulas. The results indicate that: (1) the temperature and temperature difference exhibit distinct seasonal characteristics and strong periodicity, and the temperature and temperature difference among different measurement points are strongly correlated, respectively; (2) the probability density of the temperature difference distribution presents strong non-Gaussian characteristics; (3) the probability density function of temperature can be described by the weighted sum of four Normal distributions. Meanwhile, the temperature difference can be described by the weighted sum of Weibull distribution and Normal distribution.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.12
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• pp.70-77
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• 1996

Fatigue tests were carried out at high temperature on a Cr-Mo-V steel in order to assess the fatigue life of components used in power plants. The characteristics of high temperature fatigue were divided in terms of cycle-dependent fatigue and time-dependent fatigue, each crack propagation rate was examined with respect to fatigue J-integral range, .DELTA. J$_{f}$and creep J-integral range, .DELTA. J$_{c}$. The fatigue life was evaluated by analysis of J-integral value at the crack tip with a dimensional finite element method. The results obtained from the present study are summarized as follows : The propagation characteristics of high temperature fatigue cracks are determined by .DELTA. J$_{f}$for the PP(tensile plasticity-compressive plasticity deformation) and PC(tensile plasticity - compressive creep deformation) stress waveform types, and by .DELTA. J$_{c}$for the CP(tensile creep- compressive plasticity deformation) stress waveform type. The crack propagation law of high temperature fatigue is obtained by analysis of J-integral value at the crack tip using the finite element method and applied to examine crack propagation behavior. The fatigue life is evaluated using the results of analysis by the finite element method. The predicted life and the actual life are close, within a factor of 2.f 2.f 2.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.1
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• pp.46-55
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• 2004

Thermal characteristics of the various cooling methods in electronic equipment are studied numerically. A common chip cooling system is modeled as a parallel channel with protruding heat sources. A two-dimensional model has been developed for the numerical analysis of compressible. viscous. laminar flow. and conjugate heat transfer between parallel plates with uniform block heat sources. The finite volume method is used to solve this problem. The assembly consists of two channels formed by two covers and one printed circuit board that is assumed to have three uniform heat source blocks. Various cooling methods are considered to find out the efficient cooling method in a given geometry and heat sources. The velocity and the temperature fields. the local temperature distribution along the surface of blocks. and the maximum temperature in each block are obtained. The results are compared to examine the thermal characteristics of the different cooling methods both quantitatively and qualitatively.

• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.499-503
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• 1987

The electrical characteristics of Epoxy Robin vary with temperature. In this study, the variation of the electric characteristics of Epoxy Resin with various hardening temperature was studied. Epoxy Resin used as samples are Epotohto YD-128 of Diglycidyl Ether of Bisphenol A (DGEBA) series and hardener, Goodmide G-240. It's mixing rate is 3 to 1. Hardening temperature was varied from 25[$^{\circ}C$] to 50[$^{\circ}C$] by 5[$^{\circ}C$]. During the hardening progress, illumination, resistivity and the internal temperature of material which were dependet on the variety of hardening temperature were measured. The electrical properties of hardened samples were examined by means of X-ray diffraction, tan $\delta$ test, TG-DTA analysis and treeing test. On this basis, optimal hardening temperature in insulation characteristics was examined.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.1021-1026
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• 2000

The thermal characteristics of high-speed air spindle system with built-in motor are studied. Experiment and finite element method analysis obtain temperature rise and temperature distribution of housing. For the analysis three-dimensional model is built and temperature rise and distribution in thermal steady state are computed for each rotational frequency. Generally. It is said that the heat generation of air bearing is negligible. But it is certain that the heat generation of air bearing can not be negligible especially in high-speed conditions Frequency response test for air spindle system is executed. In case that the heat generation of air spindle system is high, natural frequency of the system becomes lower when it reaches thermal steady-state and it means that the stiffness of air hearing becomes smaller due to the change of bearing clearance. It is shown that the temperature rise of all spindle system causes thermal expansion md induces the variation of hearing clearance. In consequence the st illness of air bearing becomes smaller.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.1
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• pp.86-91
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• 2006

Magnesium alloys have been widely used for many structural components of automobiles and aircraft because of high specific strength and good castability in spite of hexgonal closed-packed crystal structure of pure magnesium. In this paper, FE analysis was executed about the formability of AZ3l magnesium alloy on press forging process. For this, the variation of sheet temperature, distribution of punch force and the effect of heat transfer and friction between punch and sheet on the forming characteristics during press forging of AZ31 has been analyzed by finite element analysis. In order to obtain temperature dependence of material characteristics, uniaxial tension tests at elevated temperature were done under temperature of $100^{\circ}C\~ 500^{\circ}C$.

• Journal of Institute of Convergence Technology
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• v.1 no.1
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• pp.5-8
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• 2011

Thermal analysis of a cooling module using Peltier elements are performed using a commercial software, CFD-ACE+. A standard k-e two-equation turbulent model is applied in order to represent the turbulent shear stress. Computed values are compared with the theoretical values for the validation. The effect of mass flow rates and transferred heat amounts on the temperature distributions inside the cooling system is analyzed. It was found that the increase in the mass flow rates causes the exit temperature rise. The increase in the absorbed heat amount diminished the overall temperature on the fin surfaces. In the present analysis, the material characteristics of the Peltier element itself are not considered. In the future, the effect of the turbulence models and material characteristics will be studied in detail.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.2150_2151
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• 2009

Solar, as an ideal renewable energy, has inexhaustible, clean and safe characteristics. However, solar energy is an extreme intermittent and inconstant energy source. In order to improve the photovoltaic system efficiency and utilize the solar energy more fully, and the DC current vary with module temperature, it is necessary to study the characteristics of photovoltaic I-V according to the external factors. This paper presents the analysis of characteristics of photovoltaic I-V according to the module temperature. The results show that it seems that when the module temperature increases, the DC current increases. But actually, because when the irradiation increases, the DC current increases, the result of the relationship between DC current and the module temperature of solar cell will be effects by the increasing irradiation.