• Title/Summary/Keyword: thermo-mechanical

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Thermomechanical effects on the bending of antisymmetric cross-ply composite plates using a four variable sinusoidal theory

  • Chattibi, F.;Benrahou, Kouider Halim;Benachour, Abdelkader;Nedri, K.;Tounsi, Abdelouahed
    • Steel and Composite Structures
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    • v.19 no.1
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    • pp.93-110
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    • 2015
  • The thermomechanical bending response of anti-symmetric cross-ply composite plates is investigated by the use of the simple four variable sinusoidal plate theory. The theory accounts for sinusoidal distribution of transverse shear stress, and satisfies the free transverse shear stress conditions on the top and bottom surfaces of the plate without using shear correction factor. By dividing the transverse displacement into bending and shear parts, the number of unknowns and governing equations for the present theory is reduced, significantly facilitating engineering analysis. The validity of the present theory is demonstrated by comparison with solutions available in the literature. Numerical results are presented to demonstrate the behavior of the system. The influences of aspect ratio, side-to-thickness ratio, thermal expansion coefficients ratio and stacking sequence on the thermally induced response are studied. The present study is relevant to aerospace, chemical process and nuclear engineering structures which may be subjected to intense thermal loads.

Reliability Assesment Test on the Regular Maintenance of HTS Cable System (초전도케이블시스템 유지.보수에 따른 신뢰성 평가 시험)

  • Sohn, Song-Ho;Yang, Hyung-Suk;Lim, Ji-Hyun;Choi, Ha-Ok;Kim, Dong-Lak;Ryoo, Hee-Suk;Hwang, Si-Dole
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.06a
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    • pp.361-361
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    • 2009
  • KEPCO High Temperature Superconducting (HTS) cable system rated with $3\Phi$, 22.9kV, 1250A was laid in 2006, and the long term test is in progress. The HTS cable system with the cooling system has been operated below cryogenic temperature. That environment exposes the system to the thermo-mechanical stress due to the significant temperature difference, and the cooling system has moving parts for the forced circulation of the coolant. Therefore the HTS cable system experiences thermal fatigue and moving part such as liquid nitrogen pump need a regular replacement every 5000 hours Building the assessment criterion, the maintenance procedure was established and regular preventive maintenance was done; improvement of the termination structure and the replacement of the bearing of liquid nitrogen pump. Following the proper process, the reliability assessment test including He leakage detection and the stability of flow rate was performed. This paper describes the process and result of the first regular maintenance of KEPCO HTS cable system

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A Study on the Visualization and Characteristics of Mixed Convection between Inclined Parallel Plates Filled with High Viscous Fluid (경사진 평행평판 내 고 점성유체의 혼합대류 열전달 특성 및 가시화에 관한 연구)

  • Piao, Ri-Long;Bae, Dae-Seok
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.18 no.9
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    • pp.698-706
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    • 2006
  • Experiment and numerical calculation have been peformed to investigate mixed convection heat transfer between inclined parallel plates. Particle image velocimetry (PIV) with thermo-sensitive liquid crystal (TLC) tracers is used for visualizing and analysis. This method allows simultaneous measurement of velocity and temperature fields at a given instant of time. Quantitative data of the temperature and velocity are obtained by applying the color-image processing to a visualized image, and neural network is applied to the color-to-temperature calibration. The governing equations are discretized using the finite volume method. The results are presented for the Reynolds number ranges from 0.004 to 0.062, the angle of inclination, ${\Theta}$, from 0 to 45 degree and Prandtl number of the high viscosity fluid is 909. The results show velocity, temperature and mean Nusselt numbers distributions. It is found that the periodic flow of mixed convection between inclined parallel plates is shown at $0^{\circ}{\leq}{\Theta}<30^{\circ}$, Re<0.062, and the flow pattern can be classified into three patterns which depend on Reynolds number and the angle of inclination. The minimum Nusselt numbers occur at Re=0.05 regardless of the angle of inclination.

Study on the prevention of spragging in a tilting pad journal bearing using the variation of preload (예압 변경을 통한 틸팅패드 저널베어링의 Spragging 방지에 관한 연구)

  • Yang, Seong-Heon;Park, Chul-Hyun;Ha, Hyun-Cheon;Kim, Chae-Sil
    • Proceedings of the KSME Conference
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    • 2001.06c
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    • pp.281-286
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    • 2001
  • Tilting pad journal bearings have been widely used in a high speed rotating machinery, such as steam turbines and gas turbines, owing to their inherent stability characteristics. However, some peculiar fatigue failure in the babbitt metal due to spragging has been continuously occurred at the leading edge of the upper pads. The spragging is defined as the pad vibration initiated on the upper unloaded pads in a tilting pad journal bearing. This paper describes both several kinds of bearing failure related with spragging and the theoretical investigation on the prevention of the spragging phenomenon using the variation of preload. Results show that positive preload(m>0.5) assures all pads remain statically loaded under all operating conditions. For the change of design parameter to prevent spragging, thermo-hydrodynamic lubrication and rotor dynamic analysis were performed to verify temperature limitation on bearing and vibration problems on rotor bearing system.

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Numerical Study for The Critical-Flow-Characteristics of The Pressure Regulator and Considerations as a Pipe Network Element (I);Influence of the Inlet-Outlet Pressure Ratio (정압기 임계유동특성 및 배관망해석 요소로서의 고려에 관한 수치해석적 연구 (I);입출구 압력비 변화 영향)

  • Shin, C.H.;Ha, J.M.;Lee, C.G.;Her, J.Y.;Im, J.H.;Joo, W.G.
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.1448-1453
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    • 2004
  • The major parameters governing the fluid dynamical and thermo-dynamical behavior in the large pipeline network system are friction loss and the pipeline length. But in local pipeline networks and relatively short distance pipeline system, secondary loss and the considerations of the moving states of the fluid machine are also important. One of the major element in local pressure control system is pressure regulator. It causes the variations of the physical properties in that pipeline system. Especially, as there is not enough information to obtain reliable physical property values such as density, temperature etc. at the downstream of the pressure regulator, It is hard to calculate accurate solution in the pipeline network analysis. In this study, some numerical approaches to investigate the critical-flow-characteristics of the pressure regulator have been done and the detail examinations and considerations of the pressure regulator as a pipeline network elements according to the variations of the inlet-outlet pressure ratio have been carried. Finally the flow-flied distributions, relations and critical-flow-characteristics have been studied. in detail and the 1D analytic method to analyze critical pipe flow have been investigated

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Numerical Study for The Critical-Flow-Characteristics of The Pressure Regulator and Considerations as a Pipe Network Element (II);Influence of the Cross-Sectional-Area and Opening Ratio (정압기 임계유동특성 및 배관망해석 요소로서의 고려에 관한 수치해석적 연구(II);단면적 및 개도 변화)

  • Shin, C.H.;Ha, J.M.;Lee, C.G.;Her, J.Y.;Im, J.H.;Joo, W.G.
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.1454-1459
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    • 2004
  • The major parameters governing the fluid dynamical and thermo-dynamical behavior in the large pipeline network system are friction loss and the pipeline length. But in local pipeline networks and relatively short distance pipeline system, secondary loss and the considerations of the moving states of the fluid machine are also important. One of the major element in local pressure control system is pressure regulator. It causes the variations of the physical properties in that pipeline system. When it is under working, the accurate analysis of the flow properties is so difficult. In this study, some numerical approaches to investigate the critical-flow-characteristics of the pressure regulator have been done according to the variations of the opening ratio or cross-sectional area and the detail examinations and considerations of the pressure regulator as a pipeline network elements have been carried. Finally the flow-flied distributions and critical-flow-characteristics have been presented in detail and the critical flow phenomena and the relation to the opening ratio or cross-sectional-area ratio have been studied.

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Influence of Pad-Pivot Friction on the Performance of Tilting-Pad proceeding Bearing (패드와 피봇 사이의 마찰이 틸팅패드 저널베어링에 미치는 영향)

  • Kim, Sung-Gi;Kim, Kyung-Woong;Ha, Hyun-Cheon
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.1016-1021
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    • 2004
  • The need for developing a mathematical model for pad-pivot friction in tilting pad proceeding bearings has been well-recognized, since previous experimental work about the performances of the bearings hypothesized that the friction in the bearings is closely related to their performances. Especially, the sliding friction between pad and pivot in the ball and socket type of the bearings can influence the performance of the bearing. We propose a mathematical model for pad-pivot friction in the ball and socket type, which considers the geometrics of the pad and pivot of the bearings, by assuming the sliding friction in the ball and socket bearing as Coulomb friction. By utilizing the proposed model for pad-pivot friction, we show the analysis of Reynolds equation and energy equation, which explain the thermo-hydrodynamic characteristics of tilting pad proceeding bearings, by taking into account the turbulence and inlet pressure building as well. The results of the study show that the performance of titling-pad proceeding bearings can be greatly influenced by the pad-pivot friction. In particular, we have shown that the analysis of the pad-pivot friction is useful to explain the static proceeding loci and the dynamic characteristics of the ball and socket type of the bearings. Furthermore, for a given operating condition, we can obtain various equilibrium states which satisfy the static equilibrium conditions, by considering the pad-pivot friction.

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Design Effect of Different Components and Economic Evaluation of an Adsorption Chiller on the System Performance

  • Bidyut B. Saha;Shigeru Koyama;K.C. Amanul Alam;Lee, Jong-Boong
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2002.04a
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    • pp.17-22
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    • 2002
  • A conventional silica gel/water adsorption chiller has been analyzed numerically. A novel non-dimensional mathematical model has been presented to analyze the design effect of different components of an adsorption chiller. The design parameters of this system are characterized by the number of transfer unit, NTU, of different components and the inert material alpha number, ${\alpha}$of different components of the systems. Results show that condenser NTU$\sub$a/ has the most influential effect on the system performance, which is fellowed by absorber NTU$\sub$e/. It is also seen that coefficient of performance (COP) and non-dimensional specific cooling capacity increases with the increase of NTU$\sub$a/ and NTU$\sub$e/, but decreases with the increase of inert material alpha number. A thermo-economic data of the adsorption chiller and some other heat pump systems those are in practical operation are also presented.

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NUMERICAL APPROACH TO MICROSTRUCTURAL CHARACTERIZATIONS FOR DENSE AND POROUS THERMAL BARRIER COATINGS

  • Kim, Seok-Chan;Go, Jae-Gwi;Jung, Yeon-Gil;Paik, Un-Gyu
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.15 no.3
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    • pp.223-231
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    • 2011
  • During spray coating, especially in an air plasma spray (APS), pores, cracks, and splat boundaries are developed and those factors exert influence on thermomechanical properties such as elastic modulus, thermal conductivity, and coefficient of thermal expansion. Moreover, the thermo mechanical properties are crucial elements to determine the thermoelastic characteristics, for instance, temperature distribution, displacements, and stresses. Two types of thermal barrier coating (TBC) model, the dense and porous microstructures, are taken into account for the analysis of microstructural characterizations. $TriplexPro^{TM}$-200 system was applied to prepare TBC samples, and the METECO 204 C-NS powder is adopted for the relatively porous microstructure and METECO 204 NS powder for the dense microstructure in the top coat of TBCs. Governing partial differential equations were derived based on the thermoelastic theory and approximate estimates for the thermoelastic characteristics were obtained using a finite volume method for the governing equations.

Thermal Characteristic Analysis of a High-Precision Centerless Grinding Machine for Machining Ferrules (페룰 가공용 초정밀 무심 연삭기의 열 특성 해석)

  • Kim S.I.;Cho J.W.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2005.06a
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    • pp.90-95
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    • 2005
  • To perform the finish outside-diameter grinding process of ferrules which are widely used as fiber optic connectors, a high-precision centerless grinding machine is necessary. In this study, the thermal characteristics of the high-precision centerless grinding machine such as the temperature distribution, temperature rise and thermal deformation, are estimated based on the virtual prototype of the grinding machine and the heat generation rates of heat sources related to the machine operation conditions. The reliability of the predicted results is demonstrated by the temperature characteristics measured from the physical prototype. Especially, the predicted and measured results show the fact that the high-precision centerless grinding machine consisted of the hydrostatic GW and RW spindle systems, hydrostatic RW feeding mechanism, RW swivel mechanism, on-machine GW and RW dressers, and concrete-filled steel bed, has very stable thermal characteristics.

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