• Title/Summary/Keyword: Thermal Expansion Model

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Study of 2-Dimensional Model for the Thermal Expansion of Composite Materials (열팽창 계수의 2차원 해석 모델에 관한 연구)

  • Jeon, Hyeong-Jin;Yu, Sang-Won
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2005.11a
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    • pp.95-98
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    • 2005
  • This paper proposes the solutions predicting the coefficient of the thermal expansion changes of composites which include the fiber-like shaped ($a_1$ > ($a_2$ = ($a_3$) and the disk-like shaped (al = a2> a3) inclusions like two dimensional geometries, which has one aspect ratios, ${\alpha}$ = ($a_1$ /($a_3$). The analysis follows the procedure developed for elastic moduli by using the generalized approach of Eshelby’s equivalent tensor. The influences of the aspect ratios, on the effective coefficient of thermal expansion of composites containing aligned isotropic inclusions are examined. This model should be limited to analyze the composites with unidirectionally aligned inclusions and with complete binding to each other of both matrix and inclusions having homogeneous properties. The coefficient of thermal expansion of composites (${\theta}_{11}$,${\theta}_{22}$and ${\theta}_{33}$) are investigated. From material data of the composites with glass fiber in epoxy resin, the thermal expansions along the aspect ratio were obtained and similar to the Chow model. The longitudinal coefficients of thermal expansion ${\theta}_{11}$decrease, as the aspect ratios increase. However, the transverse coefficients of thermal expansion ${\theta}_{22}$increase or decrease, as the aspect ratios increase. And both of them decrease, as the concentration increases.

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A Study on the Development of 25.8kV 25kA Gas Circuit Breaker Using Thermal-Expansion Principle(II) (25.8kV 25kA 열팽창분사식 가스차단기 개발에 관한 연구(II) - 팽창실 용적이 차단성능에 미치는 영향 -)

  • Song, K.D.;Park, K.Y.;Shin, Y.J.;Kim, K.S.;Kim, J.G.
    • Proceedings of the KIEE Conference
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    • 1996.07a
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    • pp.80-82
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    • 1996
  • This paper deals with the effects of the volume of thermal expansion chamber on the interrupting performance in thermal expansion type 25.8kV 25kA gas circuit breaker. Model interrupters with 5 type thermal expansion chamber were designed and manufactured. Short-circuit tests were carried out for those model interrupters with 25kA breaking current. Pressure rise in the expansion chamber were measured and compared with the calculated one which was obtained from a self-developed program in our team. The analysis on the interrupting performance of each model interrupter has been done on the base of the short-circuit test results.

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Mixing Rules of Young's Modulus, Thermal Expansion Coefficient and Thermal Conductivity of Solid Material with Particulate Inclusion

  • Hirata, Yoshihiro;Shimonosono, Taro
    • Journal of the Korean Ceramic Society
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    • v.53 no.1
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    • pp.43-49
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    • 2016
  • This analyzed a Young's modulus (E), a thermal expansion coefficient (TEC, ${\beta}$) and a thermal conductivity (${\kappa}$) of the material with simple cubic particulate inclusion using two model structures: a parallel structure and a series structure of laminated layers. The derived ${\beta}$ equations were applied to calculate the ${\beta}$ value of the W-MgO system. The accuracy was higher for the series model structure than for the parallel model structure. Young's moduli ($E_c$) of sintered porous alumina compacts were theoretically related to the development of neck growth of grain boundary between sintered two particles and expressed as a function of porosity. The series structure model with cubic pores explained well the increased tendency of $E_c$ with neck growth rather than the parallel structure model. The thermal conductivity of the three phase system of alumina-mullite-pore was calculated by a theoretical equation developed in this research group, and compared with the experimental results. The pores in the sintered composite were treated as one phase. The measured thermal conductivity of the composite with 0.5-25% porosity (open and closed pores) was in accordance with the theoretical prediction based on the parallel structure model.

A Study on the Thermal Behavior of Bearing Surroundings using State-Space in Machine Tool Spindle System (공작기계 스핀들시스템에서 상태공간을 이용한 베어링 주변의 열거동에 대한 연구)

  • 신동수;정성종
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1995.10a
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    • pp.1045-1049
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    • 1995
  • This paper proposes the state-space model of the thermal behavior of the spindle system to establish dynamic mathematical model of thermal characteristics in machine tool spindle system. the model is derived form physical law of heat transfer and thermoelasticity and represents the thermal behavior induced by uneven thermal expansions whitin a bearing. The model, which is sucessfully validated for two typical configurations of high speed spindle assembles, provides a tool for understanding the basis mechanics of induced thermal expansion as a function of initial preload, spindle speed and housing cooling conditions.

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Thermal volume change of saturated clays: A fully coupled thermo-hydro-mechanical finite element implementation

  • Wang, Hao;Qi, Xiaohui
    • Geomechanics and Engineering
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    • v.23 no.6
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    • pp.561-573
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    • 2020
  • The creep and consolidation behaviors of clays subjected to thermal cycles are of fundamental importance in the application of energy geostructures. This study aims to numerically investigate the physical mechanisms for the temperature-triggered volume change of saturated clays. A recently developed thermodynamic framework is used to derive the thermo-mechanical constitutive model for clays. Based on the model, a fully coupled thermo-hydro-mechanical (THM) finite element (FE) code is developed. Comparison with experimental observations shows that the proposed FE code can well reproduce the irreversible thermal contraction of normally consolidated and lightly overconsolidated clays, as well as the thermal expansion of heavily overconsolidated clays under drained heating. Simulations reveal that excess pore pressure may accumulate in clay samples under triaxial drained conditions due to low permeability and high heating rate, resulting in thermally induced primary consolidation. Results show that four major mechanisms contribute to the thermal volume change of clays: (i) the principle of thermal expansion, (ii) the decrease of effective stress due to the accumulation of excess pore pressure, (iii) the thermal creep, and (iv) the thermally induced primary consolidation. The former two mechanisms mainly contribute to the thermal expansion of heavily overconsolidated clays, whereas the latter two contribute to the noticeable thermal contraction of normally consolidated and lightly overconsolidated clays. Consideration of the four physical mechanisms is important for the settlement prediction of energy geostructures, especially in soft soils.

Structural Analysis of Thermal Expansion of Aluminum Alloy Gearbox Case of High Speed Train (고속전철용 알루미늄합금 감속기 케이스의 열변형에 대한 구조해석)

  • 최진욱;민일홍;김완두;박순원;임영식
    • Proceedings of the KSR Conference
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    • 1999.11a
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    • pp.181-188
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    • 1999
  • For weight reduction of the gearbox of power bogie of high speed train, aluminum alloy is recommended for the material of the gerabox case. In this paper, three models(Steel G/B Case-Steel BRG. Case[model-S], Aluminum G/B Case-Aluminum BRG. Case[model-A], Aluminum G/B Case-Steel BRG. Case[model-AS]) were compared to each other in the view of thermal expansion. The evaluation of the internal load, thermal expansion deformation and lug analysis were executed. It results that the 'model-A' is excessively deformed and fail in the bolt hole of bearing case. Material change of the bearing case to steel(model-AS) is effective to restrain the deformation of the inner radios of the bearing case and to prevent the failure of that.

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Reliability Estimation of Ball Grid Array 63Sn-37Pb Solder Joint (Ball Grid Array 63Sn-37Pb Solder joint 의 건전성 평가)

  • 명노훈;이억섭;김동혁
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2004.10a
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    • pp.630-633
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    • 2004
  • Generally, component and FR-4 board are connected by solder joint. Because material properties of components and FR-4 board are different, component and FR-4 board show different coefficients of thermal expansion (CTE) and thus strains in component and board are different when they are heated. That is, the differences in CTE of component and FR-4 board cause the dissimilarity in shear strain and BGA solder joint s failure. The first order Taylor series expansion of the limit state function incorporating with thermal fatigue models is used in order to estimate the failure probability of solder joints under heated condition. A model based on plastic-strain rate such as the Coffin-Manson Fatigue Model is utilized in this study. The effects of random variables such as frequency, maximum temperature, and temperature variations on the failure probability of the BGA solder joint are systematically investigated by using a failure probability model with the first order reliability method(FORM).

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Pressure Rise in the Thermal Expansion Chamber With Arc (유부하시의 열팽창분사식 소호부내의 상승압력)

  • Park, K.Y.;Song, K.D.;Shin, Y.J.;Chang, K.C.;Kim, K.S.;Kim, J.K.
    • Proceedings of the KIEE Conference
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    • 1995.07c
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    • pp.1344-1346
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    • 1995
  • The interrupting capability of gas circuit breakers(GCB) are critically dependent on the pressure rise of the puffer cylinder or the thermal expansion chamber at current zero. Therefore it's very useful for the designers to know the pressure rise there at the design stage. Much effort has been done to predict the pressure rise in the puffer cylinder or the thermal expansion chamber in no-load condition. Thus, we now calculate it with reasonable accuracy with the simple programs coded by ourselves or with the commercial CFD packages. However, it has been still difficult problem to calculate it under the existence of arc. In this paper, we propose a method which can be used to predict the pressure rise in the thermal expansion chamber of thermal expansion type GCB. The method has been applied to the 25.8kV 25kA thermal expansion type model GCB and the calculated results have been compared with those from experiment.

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Effects of tensile softening on the cracking resistance of FRP reinforced concrete under thermal loads

  • Panedpojaman, Pattamad;Pothisiri, Thanyawat
    • Structural Engineering and Mechanics
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    • v.36 no.4
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    • pp.447-461
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    • 2010
  • Fiber reinforced polymer (FRP) bars have been widely used as reinforcement for concrete structures. However, under elevated temperatures, the difference between the transverse coefficients of thermal expansion of FRP rebars and concrete may cause the splitting cracks of the concrete cover. As a result, the bonding of FRP-reinforced concrete may not sustain its function to transfer load between the FRP rebar and the surrounding concrete. The current study investigates the cracking resistance of FRP reinforced concrete against the thermal expansion based on a mechanical model that accounts for the tensile softening behavior of concrete. To evaluate the efficacy of the proposed model, the critical temperature increments at which the splitting failure of the concrete cover occurs and the internal crack radii estimated are compared with the results obtained from the previous studies. Simplified equations for estimating the critical temperature increments and the minimum concrete cover required to prevent concrete splitting failure for a designated temperature increment are also derived for design purpose.

A Study on the Development of 25.8kV 25kA Gas Circuit Breaker Using Thermal-Expansion Principle (I) (25.8kV 25kA 열팽창분사식 가스차단기 개발에 관한 연구 (I))

  • Song, K.D.;Park, K.Y.;Shin, Y.J.;Chang, K.C.;Kim, K.S.;Kim, J.G.
    • Proceedings of the KIEE Conference
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    • 1995.07a
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    • pp.160-164
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    • 1995
  • In order to develop a medium voltage class gas circuit breaker by our own technology, we designed and manufactured the model interrupters using the hybrid arc extinguishing principle which adopts the thermal expansion principle in the large current region and the arc rotation principle by permanent magnet in the small current region. As the results of the first year research out of three years' research period, the main design parameters such as the volume of thermal expansion chamber, the distance between fixed contact and nozzle, the length of nozzle throat, the nozzle expansion angle and the magnitude of permanent magnet etc. have been determined. 4 types of model interrupters have been designed and manufactured considering the main design parameters. The 25kA short-circuit test and capacitive current breaking test have been performed for the model interrupters and the test results analyzed to improve the model interupters.

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