• Title, Summary, Keyword: thermal processes

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A study for multi thermal cycle effect on mechanical property change in carbon epoxy composite (탄소섬유 복합재료의 열사이클에 의한 물성치 변화에 관한 연구)

  • 최순권;박세만;박명균
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.43-48
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    • 2000
  • Composite materials have been increasingly used in automotive and aircraft industries, naturally leading to active researches on the materials. The carbon-epoxy composite is selected to study its thermal characteristics. During multiple thermal cycles composed of repeated cooling and heating variations of elastic constants are investigated to understand thermal effects on the carbon-epoxy composite. In this investigation longitudinal resonance method and flexural resonance method was used to characterize. The values of $E_1$ show small amount of increases depending on number of cycles of the thermal fatigue processes whereas values of $G_13$ do not indicate noticeable changes. Also, in cases of $E_2$ and $G_23$ their values decrease to a certain extend in initial stages after applications of thermal fatigue processes. However, the number of cycles of the applied thermal fatigue processes does not seem to affect their values.

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Finite Element Analysis of Thermal Deformations for Microaccelerometer Sensors using SOI Wafers (SOI웨이퍼의 마이크로가속도계 센서에 대한 열변형 유한요소해석)

  • 김옥삼;구본권;김일수;김인권;박우철
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.11 no.4
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    • pp.12-18
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    • 2002
  • Silicon on insulator(SOI) wafer is used in a variety of microsensor applications in which thermal deformations and other mechanical effects may dominate device Performance. One of major Problems associated with the manufacturing Processes of the microaccelerometer based on the tunneling current concept is thermal deformations and thermal stresses. This paper deals with finite element analysis(FEA) of residual thermal deformations causing popping up, which are induced in micrormaching processes of a microaccelerometer. The reason for this Popping up phenomenon in manufacturing processes of microaccelerometer may be the bending of the whole wafer or it may come from the way the underetching occurs. We want to seek after the real cause of this popping up phenomenon and diminish this by changing manufacturing processes of mic개accelerometer. In microaccelerometer manufacturing process, this paper intend to find thermal deformation change of the temperature distribution by tunnel gap and additional beams. The thermal behaviors analysis intend to use ANSYS V5.5.3.

STUDY PROCESSES OF INTUMESCENCE IN FIRE-PROTECTING COATINGS

  • Efremov, V.L.;Paltseva, N.G.;Leiman, Z.A.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.657-658
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    • 2005
  • Flame retard of polymers was studied for prevention from burning by various additives stimulated the char formation during heating and thermal degradation of polymer materials. Forming char have high porosity, low thermal conductivity and act as thermal shield for heat transmission from the flame to the polymer and. oxygen towards the polymer. The results showed that various additives may regulate the processes of intumecsence. The efficient fire protective intumescent char was result of processes of melting, gas evolution, cross-linking, carbonization etc.

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The effects of repetitive firing processes on the optical, thermal, and phase formation changes of zirconia

  • Ozdogan, Alper;Ozdemir, Hatice
    • The Journal of Advanced Prosthodontics
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    • v.12 no.1
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    • pp.9-14
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    • 2020
  • PURPOSE. The aim of this study was to investigate the effect of different numbers of heat treatments applied to superstructure porcelain on optical, thermal, and phase formation properties of zirconia. MATERIALS AND METHODS. Forty zirconia specimens were prepared in the form of rectangular prism. Specimens were divided into four groups (n = 10) according to the number of firing at heating values of porcelain. Color differences and translucency parameter were measured, and X-ray diffraction (XRD) analysis and differential scanning calorimetry (DSC) were performed. Data were analyzed with analysis of variance (ANOVA). RESULTS. There were no statistically significant differences in ∆E, TP, L, a, and b value changes of the zirconia specimens as a result of repetitive firing processes (P>.05). CONCLUSION. Although additional firing processes up to 4 increase peak density in thermal analysis, additional firing processes up to 4 times can be applied safely as they do not result in a change in color and phase character of zircon frameworks.

Effect of Conductive Additives on $FeS_2$ Cathode ($FeS_2$ 양극에 미치는 전도성 첨가제의 영향)

  • Choi, Yu-Song;Cheong, Hae-Won;Kim, Ki-Youl;Cho, Sung-Baek
    • Journal of the Korea Institute of Military Science and Technology
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    • v.15 no.2
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    • pp.224-230
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    • 2012
  • Thermal batteries have excellent mechanical robustness, reliability, and long shelf life. Due to these characteristics as well as their unique activation mechanism, thermal batteries are widely adopted as military power sources. Li(Si)/$FeS_2$ thermal batteries, which are used mostly in these days, use LiCl-KCl and LiBr-LiCl-LiF as molten salt electrolyte. However, it is known that Li(Si)/$FeS_2$ thermal batteries have high internal resistance. Especially, $FeS_2$ cathode accounts for the greater part of internal resistance in unit cell. Many efforts have been put into to decrease the internal resistance of thermal batteries, which result in the development of new electrode material and new electrode manufacturing processes. But the applications of these new materials and processes are in some cases very expensive and need complicated additional processes. In this study, internal resistance study was conducted by adding carbon black and carbon nano-tube, which has high electron conductivity, into the $FeS_2$ cathode. As a results, it was found that the decrease of internal resistance of $FeS_2$ cathode by the addition of carbon black and carbon nano-tube.

Heat Transfer Analysis of Freezing Processes Including Thermal Resistance of Mold(I) - One - dimensional Analysis of Saturated Liquid - (용기를 고려한 응고과정의 열전달 해석(I) - 포화액의 일차원 해석 -)

  • Yoo, Jai Suk
    • The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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    • v.17 no.4
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    • pp.377-381
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    • 1988
  • Effects of thermal resistance of mold during freezing processes have been investigated. Saturated liquid is chosen to present one-dimensional quasi-steady solution and this solution is compared with numerical solutions. Front tracking finite element method has been applied for the numerical solutions. Results show that mold should be considered as well as phase change material except the cases when the very thin mold with relatively high thermal conductivity is used.

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Investigation of Molecular Coupling Effects on Photothermal Properties of Polar Solutions by Thermal Lens

  • 하정현;임종태;최중길;김용록
    • Bulletin of the Korean Chemical Society
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    • v.17 no.8
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    • pp.682-685
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    • 1996
  • Photothermal properties depend on the characteristics of energy transfer processes in solution. In this study, a time-resolved single beam thermal lens experiment in various solvents is employed to investigate the energy coupling effects which govern the energy transfer processes. Interestingly, it is observed that the behaviour of the photothermal propagation in solution depends on the property of solution and the concentration of solute in a single beam thermal lens configuration. These characteristics lead us to consider the solute-solvent coupling effects as well as the solvent-solvent interactions.

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Analysis of Thermal Behavior and Temperature Estimation by using an Observer in Drilling Processes (드릴링 공정의 열거동 해석과 관측기를 이용한 온도 추정법)

  • Kim, Tae-Hoon;Chung, Sung-Chong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.9
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    • pp.1499-1507
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    • 2003
  • Physical importance of cutting temperatures has long been recognized. Cutting temperatures have strongly influenced both the tool life and the metallurgical state of machined surfaces. Temperatures in drilling processes are particularly important, because chips remain in contact with the tool for a relatively long time in a hole. Tool temperatures tend to be higher in drilling processes than in other in machining processes. This paper concerns with modeling of thermal behaviors in drilling processes as well as estimation of the cutting temperature distribution based on remote temperature measurements. One- and two-dimensional estimation problems are proposed to analyze drilling temperatures. The proposed thermal models are compared with solutions of finite element methods. Observer algorithms are developed to solve inverse heat conduction problems. In order to apply the estimation of cutting temperatures, approximation methods are proposed by using the solution of the finite element method. In two-dimensional analysis, a moving heat source according to feedrate of the drilling process is regarded as a fixed heat source with respect to the drilling location. Simulation results confirm the application of the proposed methods.

Characterization of Artificial Graphite Electrodes

  • Park, Sei-Min;Han, Sang-Moo;Oh, Seh-Min
    • Carbon letters
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    • v.1 no.2
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    • pp.76-81
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    • 2000
  • Physical properties of artificial graphite electrodes were evaluated along three different directions; circumferential (X), radial (Y), and axial (Z) directions. Four kinds of commercial electrode products were used in this study for the evaluation; pole (AP) and nipple (AN) of manufacturer A, pole (BP) and nipple (BN) of manufacturer B. The mechanical, electrical, and thermal properties in X and Y directions were very similar to each other. In Z direction, however, the mechanical properties, including flexural strength and compressive strength, were higher, and electric resistance and thermal expansion were much lower than those in the other directions. The microstructures observed by optical microscope and scanning electron microscope revealed that the differences in properties by the measuring direction were caused by the preferential alignment of needle cokes along the Z direction. When comparing the properties of the electrode samples in the same direction, the mechanical properties mainly depended on the bulk density or porosity of the samples as well as preferential alignment of needle cokes.

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