• 한국정밀공학회지
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• 제19권9호
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• pp.59-65
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• 2002

Grinding temperature between a grinding wheel and a workpiece surface, rising rapidly during a machining operation, has bad effects on a surface integrity such as the burning, the residual stress and the crack. In this study, the temperature distribution was obtained briefly by the finite element method and the grinding temperature of a workpiece varying with the grinding condition was measured experimentally. For obtaining the grinding temperature, a thermocouple method was applied. Three thermocouples were inserted in a surface of each workpiece. Changed grinding conditions were the depth of cuts, the feedrate, the dry and wet grinding, the up and down grinding and the number of pieces.

• KSTLE International Journal
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• 제1권1호
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• pp.63-68
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• 2000

Angular contact ball bearings are mainly used in the spindle, which requires high speed and stiffness. The heat generation is studied by experiments and simulations using a pair of angular contact ball bearings. The temperature variation of inner and outer races and the temperature increment distribution are measured by using thermocouples for the rotational speed, preload, viscosity of lubricant. The measured values from experiments are used to estimate the heat conduction rate. The method of oil-air lubrication is used for the experiment. The amount of conduction heat transfer to the test spindle and the convection heat transfer coefficients long the spindle are computed by using inverse method with temperature increment distribution. Total heat generation rate is estimated with the heat partition rate which is calculated from temperatures of inner and outer races. In addition, the empirical factor of oil-air lubrication method for Palmgren's heat generation model is suggested. The empirical friction coefficients, which are obtained from the experiments, depend on the preload condition, and can give us more accurate estimation of the heat generation in ball bearings.

• 한국정밀공학회지
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• 제18권2호
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• pp.96-101
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• 2001

This paper shows the temperature characteristics of a high speed angular contact ball gearing which is 7004C type with ISO P2 tolerance class. A built-in motor type high speed spindle which adopts an oil-air lubrication system was used to measure the temperature rise up to 60,000rpm. The gearing temperature was measured using thermocouples that were attached to the outside surfaces of the outer rings. The result showed that the continuous test method which was suggested in this paper is more effective than on and off method and the lubrication oil supply rate should be reduced in high speed rolling bearings as long as the seizure does not occur. And the result were confirmed that the bearings packed with ceramic balls are superior to those with steel balls in temperature characteristics.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1998년도 가을 학술발표회 논문집
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• pp.159-166
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• 1998

To study temperature effect of P.C. box girder bridge, field measurement was performed for six months, along with thermal analysis for the newly constructed viaduct of Gangbyun Highway in Seoul. Thermocouples were installed inside and surface of the flange and web of the box and temperature of box section md ambient temperature was measured. Measured environmental data are incorporated in finite element thermal analysis and computed temperature of the section was compared with measured one. Temperature gradient from thermal analysis was compared with Korean Highway Specification(1996)and the New Zealand Ministry of Works and Development code(1976). Thermal stress distribution across the box section was also compared.

• 소성∙가공
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• 제12권4호
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• pp.370-375
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• 2003

Determination of the interface heat transfer coefficient was investigated in non-isothermal bulk forming of glass-coated Ti-6Al-4V. FE analysis and experiments were conducted. Equipment consisting of AISI Hl3 die was instrumented with thermocouples located at sub-surface of the bottom die. Die temperature changes were investigated in related to the process variables such as reduction, lubricant and initial die temperature. The calibration approach based on heat conduction and FE analysis using an inverse algorithm were used to evaluate the interface heat transfer between graphite-lubricated die and glass-coated workpiece. The coefficients determined were affected mainly by the contact pressure. The validation of the coefficients was made by the comparison between experimental data and FE analysis results.

• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 1998년도 추계학술발표회 논문 초록집
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• pp.53-60
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• 1998

In this study, smoke filling behaviors in a large space were investigated. For experimental study, thermocouples were used to measure the temperature of the hot gases layer and also to determine the smoke layer depth. Height markers were also hung from the roof so that observers could visibly assess the smoke layer depth. Ethanol was used as fuel. The smoke filling times were predicted with zone model and field model and numerical results were compared with experimental data. Good results were obtained.

• 한국분말재료학회지
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• 제11권5호
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• pp.363-368
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• 2004

In the present study, the focus is on the analysis of the effect of the mold dimensions on the temperature distribution of a die during plasma activated sintering. The temperature distribution of a cylindrical mold with various dimensions was measured using K-type thermocouples. The temperature homogeneity of the die was studied based on the direction and dimensions of the die. A temperature gradient existed in the radial direction of the die during the plasma activated sintering. Also, the magnitude of the temperature gradient was increased with increasing sintering temperature. In the longitudinal direction, however, there was no temperature gradient. The temperature gradient of the die in the radial direction strongly depended on a ratio of die volume to punch area.

• International Journal of Air-Conditioning and Refrigeration
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• 제13권1호
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• pp.11-21
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• 2005

The present paper investigates the heat transfer characteristics in a cylinder packed with porous medium of solid spheres for various parameters such as mass flow rate, sphere diameter, length of the porous medium, and gas temperatures. Pressures and temperatures at the inlet and outlet regions were measured by using static pressure gages and R-type thermocouples. The modified relationship based on the Ergun equation is suggested for the estimation of pressure drops. In addition, the useful empirical correlation for thermal efficiency is obtained in the current study. Thermal efficiency is expressed in terms of non-dimensional time, sphere diameter, porosity, and pressure drops. It is also found that the pressure drop through the cylinder becomes larger as the gas temperature does higher at the inlet region, whereas it substantially decreases when the inlet flow rate decreases.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제20회 춘계학술대회 논문집
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• pp.164-167
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• 2003

열충격은 재료가 갑작스런 온도나 압력변화 혹은 급냉 조건하에 있을때 발생하는 물리적 현상이다. 본 논문에서는 레이저 조사를 이용하여 열충격 강도와 열충격 파괴인성을 평가하였다. 시험편의 온도 분포는 타입 K와 C 열전대를 이용하여 측정하였다. 조사된 표면은 SEM을 이용하여 관찰하였다. 파괴에 필요한 임계 레이저 파워가 재료의 열충격 강도와 열충격 파괴인성을 결정짓는 주요한 요소라고 할 수 있다.

• 한국안전학회지
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• 제16권3호
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• pp.12-18
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• 2001

The objective of the present work is to examine the effect of inclined angle of channel with multi heat source on thermal stability of electronic equipment. The heat sources are mounted on both sides of channel walls by two kinds of configuration such as the zig-zag md symmetric on. Conductive heat transfer was estimated by using of thermocouples and heat flux sensor. Thus, convective heat transfer and mean Nusselt number could be obtained. With increased inclined angle, the convective heat transfer coefficient was decreased. When inclined angle was smaller than 30 degree, The average Nusselt number of Big-zag configuration was larger than that of symmetric. Furthermore, when protruding ration was 0.082, the temperature was strongly affected by inclined angle. whereas, when protruding ration was 0.25, the temperature was strongly affected by heat source configuration.