• Title/Summary/Keyword: Rotational temperature

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A Study on the Joining of Different Al Alloys by Centrifugal Casting (원심주조를 이용한 2종 알루미늄의 접합에 대한 연구)

  • Jang, Young-Soo;Lee, Moon-Hyoung;Moon, Jun-Young;Hong, Chun-Pyo
    • Journal of Korea Foundry Society
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    • v.27 no.6
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    • pp.237-242
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    • 2007
  • To improve the quality of the product and the cost efficiency, the joining of A356 alloy to an Al-18wt%Si alloys has been performed by centrifugal casting. The influence of the mold preheating temperature, the pouring temperature and the rotational velocity of the mold on the microstructures of the shell in the centrifugal casting was investigated using the experimental and simulation methods. In the present study, the cellular automaton (CA) technique and the finite volume method (FVM) were adopted to simulate the evolution of the macro structures and to calculate the temperature profiles, respectively. The evolution of the microstructures was also simulated using a modified cellular automaton (MCA) model. The optimal rotational speed of the mold for obtaining the sound shape of the shell was estimated experimentally to be over 1200 rpm. For the uniform microstructure, the outer shell needs to be cast with higher preheated mold temperature and lower pouring temperature, and the melt was poured at lower temperature in the inner shell. In order to obtain the sound shape of the joining, the different materials were poured simultaneously.

Design and Performance Evaluation of a Spindle System for Centerless Grinding Machine (무심연삭기 주축계의 설계 및 성능평가)

  • Park Chun Hong;Hwang Joo Ho;Cho Soon Joo;Cho Chang Rae
    • Journal of the Korean Society for Precision Engineering
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    • v.22 no.11 s.176
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    • pp.142-150
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    • 2005
  • Design and performance evaluation of a spindle system which was composed of a grinding spindle and a regulating spindle for the centerless grinding of ferrule were performed in this paper. Layout and details of spindle system were designed and hydrostatic bearings for spindles were also designed. Prototype of spindle system was developed and its availabilities to machine the ferrule were discussed using the experimental results on the spindle stiffness of each spindle, loop stiffness, rotational accuracy and thermal characteristics. Loop stiffness of the spindle system was $130\;N/{\mu}m$, which was enough to machine the ferrule. Rotational accuracies of each spindle were about $0.2{\mu}m$ at the primary speed of 2,300 rpm(grinding spindle) and 300 rpm(regulating spindle). Temperature rises at the same speed were about $4.4\~4.7^{\circ}C$ in the case of grinding spindle and $1.8^{\circ}C$ in the case of regulating spindle, which agreed well with the designed value. From these results, it was estimated that the prototype of spindle system had enough performances for the centerless grinding machine to machine the ferrule.

Mesospheric Temperatures over Apache Point Observatory (32°N, 105°W) Derived from Sloan Digital Sky Survey Spectra

  • Kim, Gawon;Kim, Yong Ha;Lee, Young Sun
    • Journal of Astronomy and Space Sciences
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    • v.34 no.2
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    • pp.119-125
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    • 2017
  • We retrieved rotational temperatures from emission lines of the OH airglow (8-3) band in the sky spectra of the Sloan digital sky survey (SDSS) for the period 2000-2014, as part of the astronomical observation project conducted at the Apache Point observatory ($32^{\circ}N$, $105^{\circ}W$). The SDSS temperatures show a typical seasonal variation of mesospheric temperature: low in summer and high in winter. We find that the temperatures respond to solar activity by as much as $1.2K{\pm}0.8K$ per 100 solar flux units, which is consistent with other studies in mid-latitude regions. After the seasonal variation and solar response were subtracted, the SDSS temperature is fairly constant over the 15 year period, unlike cooling trends suggested by some studies. This temperature analysis using SDSS spectra is a unique contribution to the global monitoring of climate change because the SDSS project was established for astronomical purposes and is independent from climate studies. The SDSS temperatures are also compared with mesospheric temperatures measured by the microwave limb sounder (MLS) instrument on board the Aura satellite and the differences are discussed.

Numerical Study of Turbine Blade Surface Gas Temperature with Various RPM and Blade Edge Shape (터빈 블레이드 회전수 변화와 터빈 블레이드 엣지 형상 변화에 따른 표면 가스온도 분포 해석)

  • Lee, In-Chul;Byun, Yong-Woo;Koo, Ja-Ye;Lee, Sang-Do;Kim, Kui-Soon;Moon, In-Sang;Lee, Soo-Young
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.05a
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    • pp.49-52
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    • 2008
  • The numerical analysis for gas temperature of turbine blade surface has been performed to investigate development of temperature with various blade edge shape. Two different types of the turbine which one is "Sharp" edge and the other is "Round" edge was modeled. Computations have been carried out several turbine rotational speeds in the range from 0 to 10,000 rpm for the each types of turbine edge shape. As a result, the more rotational speed of turbine increased, the more turbine blade's temperature decreased. It is also found that the surface temperature of turbine blades for sharp type edge were lower than the round type edge.

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Buckling of restrained steel columns due to fire conditions

  • Hozjan, Tomaz;Planinc, Igor;Saje, Miran;Srpcic, Stanislav
    • Steel and Composite Structures
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    • v.8 no.2
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    • pp.159-178
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    • 2008
  • An analytical procedure is presented for the determination of the buckling load and the buckling temperature of a straight, slender, geometrically perfect, axially loaded, translationally and rotationally restrained steel column exposed to fire. The exact kinematical equations of the column are considered, but the shear strain is neglected. The linearized stability theory is employed in the buckling analysis. Behaviour of steel at the elevated temperature is assumed in accordance with the European standard EC 3. Theoretical findings are applied in the parametric analysis of restrained columns. It is found that the buckling length factor decreases with temperature and depends both on the material model and stiffnesses of rotational and translational restraints. This is in disagreement with the buckling length for intermediate storeys of braced frames proposed by EC 3, where it is assumed to be temperature independent. The present analysis indicates that this is a reasonable approximation only for rather stiff rotational springs.

Designing of Rotational Raman Lidar system measuring Atmospheric Temperature (대기 온도 측정용 회전 라만 라이다 시스템의 설계)

  • ;;;Serguei Bobronikov
    • Proceedings of the Optical Society of Korea Conference
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    • 2000.08a
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    • pp.208-209
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    • 2000
  • 라이다 방법을 이용한 대기의 온도 측정은 크게 1) DIAL 방법을 이용하는 방법 2) 공기분자의 밀도를 측정하는 진동 라만 산란을 이용하는 방법 3)공기분자의 회전 라만 산란을 이용하는 방법 4) Rayleigh 산란의 선폭을 이용하는 방법 등으로 나누어진다. 이 중에서 대류권의 온도 측정에 적용가능한 방법은 3 번째의 방법으로 질소나 산소의 회전 라만 산란(RRS:Rotational Raman Scattering)이 가장 흔히 사용되는 기술이다. 질소와 산소의 회전 라만 신호를 이용한 온도 측정 기술은 Cohen$^1$ 등에 의하여 처음 시도되었으며, 그 후 많은 사람들에 의하여 검증되었다.$^2$ (중략)

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Numerical Analysis on Heat Transfer and Fluid Flow Characteristics of Traction Motor for Electric Car (전동차용 견인전동기의 열유동 특성에 관한 전산해석)

  • 남성원;김영남;채준희
    • Proceedings of the KSR Conference
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    • 1998.11a
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    • pp.137-143
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    • 1998
  • Numerical simulation is conducted to clarify the heat transfer and fluid flow characteristics of traction motor for electric car SIMPLE algorithm based on finite volume method is used to make linear algebra equation. The governing equations are solved by TDMA(TriDiagonal Matrix Algorithm) with line-by-line method and block correction. From the results of simulation, the characteristics of cooling pattern is strongly affected by the size of hole in stator core. In the case of high rotational speed of rotor, temperature difference along the axial direction is more decreased than that of low rotational speed.

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A Study on the Thermal Behaviro of Machine Tool Spindle System (공작기계 주축계 열적거동에 관한 연구)

  • 김종관
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.8 no.1
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    • pp.28-34
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    • 1999
  • According to the development of tool material and the improvement of machinability of cutting material like aluminium alloy, the higher spindle speed is needed. However, the higher speed causes the heat generation of bearings, the deformation of spindle unit parts, and the rotational accuracy of spindle to be worse. Therefore, it is essential to analyze and control the heat generation and the thermal behavior of spindle unit in order to have higher speed and better rotational accuracy. This paper shows the analogy between the analyzation of heat generation and thermal behavior of high speed spindle system by finite element method and the test results of actual temperature rise through running test, and shows the necessity of cooling the spindle and inner ring side of bearings for the thermal balance of high speed spindle system.

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Characteristics of Friction Torques and Lubrication in High Speed Angular Contact Ball Bearings (고속 앵귤러 콘택트 볼베어링의 마찰 토크 및 윤활 특성)

  • 반종억;김경웅
    • Tribology and Lubricants
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    • v.13 no.4
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    • pp.47-52
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    • 1997
  • Friction torques, electrical contact resistances and bearing temperatures were measured on high speed angular contact ball beatings for the spindle of machine tools. The test bearings ran with oil-air lubrication at the thrust loads from 320 N to 1920 N and at the rotational speed of up to 12000 rpm. Electrical contact resistances between balls and races were measured to evaluate the formation of the lubricant film in the contact area. The test results with sufficient lubrication showed that the variations of friction torques were sensitive to the thrust loads and the rotational speeds, and that the friction torques were higher than those with insufficient lubrication. With insufficient lubrication and high thrust loads, the collapse of the lubricant film was detected even at a high rotational speed. It was concluded that these high speed beatings to run in condition of fluid lubrication should require monitoring not only the temperature increase of the bearing but also the lubricant film formation in contact areas resulting from the change in the applied load and the lubricant amount.

Study on Temperature Characteristics of Friction Stir Welding Process by Numerical Analysis (수치해석을 활용한 마찰교반용접 공정의 온도 특성 분석 연구)

  • Kim, Moosun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.12
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    • pp.513-518
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    • 2019
  • Friction Stir Welding is a welding technique for metal materials that utilizes the heat generated by friction between the material to be welded and the welding tool that rotates at high speed. In this study, a numerical analysis method was used to analyze the change in the internal temperature of the welded material during friction stir welding. As the welding target material, AZ31 magnesium alloy was applied and the welding phenomenon was considered a flow characteristic, in which a melting-pool was formed. FLUENT was used as the numerical tool to perform the flow analysis. For flow analysis of the welding process, the welding material was assumed to be a high viscosity Newtonian fluid, and the boundary condition of the welding tool and the material was considered to be the condition that friction and slippage occur simultaneously. Analyses were carried out for various rotational speeds and the translational moving speed of the welding tool as variables. The analysis results showed that the higher the rotational speed of the welding tool and the slower the welding tool movement speed, the higher the maximum temperature in the material increases. Moreover, the difference in the rotational speed of the welding tool has a greater effect on the temperature change.