• 한국정밀공학회지
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• 제29권6호
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• pp.632-639
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• 2012

A fully coupled thermo-mechanical model is adopted to study the temperature distribution and the material deformation in friction stir welding(FSW) process. Rotational speed is most important parameters in this research. Three dimension results under different process parameters were presented. Result indicate that the maximum temperature is lower than the melting point of the welding material. The higher temperature gradient occurs in the leading side of the workpiece. The maximum temperature can be increased with increasing the tool angular velocity, rpm in the current numerical modeling. In this research ABAQUS Ver.6.7 is to analyze a fully coupled thermo-mechanical model. ALE(Arbitrary Lagrangian-Eulerian) finite element formulation is used for the large deformation in FSW process and using the Mass scaling for the analysis time efficiency.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2003년도 학술대회지
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• pp.324-328
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• 2003

Water-lubricated frictional characteristics of stainless steel ball bearing is not well known compared to oil-lubricated frictional characteristics. Furthermore study on friction at high temperature is rare because bearing maintenance strategy for water-lubricated or chemicals-lubricated bearings of equipment is mostly based on change of failed bearings and parts. Ball bearings and ball screw are installed on the power transmission for a developing integral reactor and these are lubricated with high temperature and high pressure chemically-controlled pure water. Bearings and power transmitting mechanical elements for an atomic reactor needs high reliability. and high performance during estimated lifetime, and it should be verified. In this paper, experimental research results of frictional characteristics of water-lubricated ball bearing as a preliminary investigation.

• 한국결정성장학회지
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• 제10권6호
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• pp.381-388
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• 2000

Czochralski 결정 성장 시스템에서 baroclinic 불안정성에 의해 발생하는 유동과 온도 변동에 대해 실험적으로 고찰하였다. 실리콘과 유사한 프란틀 수를 갖는 Wood's metal을 작동유체로 사용하고, 일체형 자석 프로브를 제작하여 멜트의 회전 유속을 측정하였다. 측정 결과 회전 유속은 멜트 바닥에 비해 자유 표면에서 빠르고 특히 결정 근처에서 유속이 증가하는 것을 확인하였다. 또한 도가니 회전 속도를 증가시키면서 속도와 온도 변동을 관찰한 결과 Ro<1.01, Ta>$9.63{\times}10^8$인 영역에서 baroclinic 불안정성이 나타나고, 이 영역에서 유동과 온도가 동일한 주파수를 가지고 변동하였다.

• International Journal of Concrete Structures and Materials
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• 제6권2호
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• pp.111-121
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• 2012

The research presented in this paper analytically examines the fire performance of flat plate buildings. The modeling parameters for the mechanical and thermal properties of materials are calibrated from relevant test data to minimize the uncertainties involved in analysis. The calibrated models are then adopted to perform a nonlinear finite element simulation on a flat plate building subjected to fire. The analysis examines the characteristics of slab deflection, in-plane deformation, membrane force, bending moment redistribution, and slab rotational deformation near the supporting columns. The numerical simulation enables the understanding of structural performance of flat plate under elevated temperature and, more importantly, identifies the high risk of punching failure at slab-column connections that may trigger large-scale failure in flat plate structures.

• 한국안전학회지
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• 제20권2호
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• pp.11-17
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• 2005

Rotational motion in the atmosphere around a fire may have a profound influence on the fire plume. This process underlies the occurrence of fire whirls. Fire whirls are rare but highly destructive phenomenon which were observed in a large forest, urban and building fires. The present study aims to investigate of the effect of rotation Strength on the fire whirl characteristics expeimentally. Experiments are performed for various sizes of fire source with different rotation strength. From the experimental observations, it is noted that the mean centerline temperature is gradually increased and mean radial temperature is decreased as increases rotation strength. The characteristic mean flame height of fire based on the visible observation is increased as increases of dimensionless swirl parameter, $\Omega/\alpha$, represented by swirl induced motion to buoyancy driven motion.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.841-845
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• 1995

In this study, a motor-integrated high-speed spindle system with .psi. 65mm*25,000rpm is developed by introducing the oil-jet lubrication method,ceramic angular contact ball bearing, a built-in motor and so on. And oil-jet lubrication experiments for evaluating the system performance are performed under various operation conditions. Especially, in order to establish the oil-jet lubrication conditions related to the development of a high-speed spindle system, the effects of oil supply rate and rotational spindle speed are investigated on the temperature rise, temperature distribution,motor current and so on.

• Structural Engineering and Mechanics
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• 제40권3호
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• pp.347-371
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• 2011

This paper focuses on post-buckling analysis of Timoshenko beams with various boundary conditions subjected to a non-uniform thermal loading by using the total Lagrangian Timoshenko beam element approximation. Six types of support conditions for the beams are considered. The considered highly non-linear problem is solved by using incremental displacement-based finite element method in conjunction with Newton-Raphson iteration method. As far as the authors know, there is no study on the post-buckling analysis of Timoshenko beams under uniform and non-uniform thermal loading considering full geometric non-linearity investigated by using finite element method. The convergence studies are made and the obtained results are compared with the published results. In the study, the relationships between deflections, end rotational angles, end constraint forces, thermal buckling configuration, stress distributions through the thickness of the beams and temperature rising are illustrated in detail in post-buckling case.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제21회 추계학술대회 논문집
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• pp.257-260
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• 2003

스마트 무인기용 터보제트 엔진의 동적 성능모사 프로그램을 개발하였다. 천이 성능 프로그램에는 일정공기유량(Constant Mass Plow) 방법을 적용되었으며 잉여토크의 적분에는 오일러 적분법을 이용하였다. 천이성능해석은 가스발생기의 아이들로부터 최대 회전수까지 증가하는 것을 수행하였다. 엔진의 동적거동을 살펴보기 연료유량을 step과 ramp 증가로 주었다. 연료가 step으로 증가되었을 때 터빈 입구온도에서 오버슈트가 발생하였으며 연료유량을 0.6sec 이상으로 증가시켰을 때 오버슈트가 제거됨을 확인할 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제34권12호
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• pp.3800-3804
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• 2013

In this study, molecular dynamics simulations of SPC/E (extended simple point charge) model have been carried out in the canonical NVT ensemble over the range of temperatures 300 to 550 K with and without Ewald summation. The quaternion method was used for the rotational motion of the rigid water molecule. Radial distribution functions $g_{OO}(r)$, $g_{OH}(r)$, and $g_{HH}(r)$ and self-diffusion coefficients D for SPC/E water were determined at 300-550 K and compared to experimental data. The temperature dependence on the structural and diffusion properties of SPC/E water was discussed.

• Preventive Nutrition and Food Science
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• 제22권1호
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• pp.62-66
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• 2017

This study was conducted to determine the rheological properties of gochujang and chogochujang at different temperatures (25, 35, and $45^{\circ}C$). Rheological properties of the samples were determined using a rotational rheometer at a shear range of 1 to $40s^{-1}$. Gochujang and chogochujang were found to be non-Newtonian fluids according to the Herschel-Bulkley model. Yield stress and consistency coefficient of gochujang at different temperatures were higher than those of chogochujang, whereas the opposite was observed for flow behavior index. Moreover, all rheological properties of gochujang and chogochujang decreased with increasing temperature. The consistency coefficient was related to temperature using an Arrhenius-type relationship. Gochujang (14.48 kJ/mol) had slightly higher activation energy than chogochujang (14.03 kJ/mol).