• Title, Summary, Keyword: Thermal expansion

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A study on Thermal expansion of Inlay waxes (Inlay wax의 열팽창에 관한 연구)

  • Nam, Sang-Yong;Kwak, Dong-Ju;Cha, Sung-Soo
    • The Journal of Korean Academy of Dental Technology
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    • v.30 no.2
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    • pp.17-22
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    • 2008
  • The purpose of this study was to observe the thermal expansion of the inlay waxes at temperature. Inlay pattern wax shows not only a high coefficient of expansion but also a tendency to warp or distort when allowed to stand unrestrained. The thermal expansion of inlay waxes was tested according to the treatment conditions for 10 minutes at $40^{\circ}C$ The thermal expansion of inlay waxes at various temperatures was measured with an electro dial gauge. The results were as fellows: 1. It is shown that the rate of thermal expansion of wax A is 0.2%, wax B is 0.29%, wax C is 0.38%, and wax D is 0.22% at $40^{\circ}C$ 2. It is shown that the coefficient of thermal expansion of wax A is $106{\times}10^{-6}/^{\circ}C$, wax B is $152{\times}10^{-6}/^{\circ}C$, wax C is $199{\times}10^{-6}/^{\circ}C$, and wax D is $116{\times}10^{-6}/^{\circ}C$ at $40^{\circ}C$ 3. The thermal expansion of the inlay waxes at $40^{\circ}C$ was shown to increase in the order of wax C, B, D, A.

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Analysis of Thermal Expansion of Latex-Modified Concrete (라텍스개질 콘크리트의 열팽창 특성 분석)

  • Choi, Seong-Yong;Lee, Joo-Hyung;Lim, Hong-Beom;Yun, Kyong-Ku
    • Journal of Industrial Technology
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    • v.23 no.A
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    • pp.157-163
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    • 2003
  • The properties of mechanics and durability of LMC have been performed actively. However, little studies on analysis and properties of thermal expansion has been on the temperature variation. Especially, the low of bonding strength and tensile cracking are caused by difference of thermal expansion between LMC and the substrate concrete. Therefore, this study focused on effect of thermal expansion behavior and properties of LMC according to temperature variation. To identify the property of thermal expansion of LMC, tests of modulus of thermal expansion were carried out at 28 days after casting specimen, subjected to temperature variation between $10^{\circ}C$ and $60^{\circ}C$. The results of this study showed the modulus of elastic of LMC was similar to that of ordinary portland concrete(OPC). It means that stresses caused by difference of modulus of elastic did not occur on interface between LMC and existing concrete. The modulus of thermal expansion of LMC had a little smaller than that of OPC. The modulus of thermal expansion of polymer modified concrete is generally larger than OPC, but the result of this test is disagree with the fact, which may be due to the humidity evaporation difference and aggregate properties.

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Thermal Shock Resistance and Thermal Expansion Behavior of $Al_2TiO_5$ Ceramics

  • Kim, Ik-Jin
    • Proceedings of the Korea Association of Crystal Growth Conference
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    • pp.179-193
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    • 2000
  • Aluminium titanate (Al₂TiO5) with an excellent thermal shock resistant and a low the expansion coefficient was obtained by solid solution with MgO, SiO₂, and ZrO₂ in the Al₂TiO5 lattice or in the grain boundary solution through electrofusion in an arc furnace. However, these materials have low mechanical strength due to the presence of microcracks developed by a large difference in thermal expansion coefficients along crystallographic axes. Pure Al₂TiO5 tends to decompose into α-Al₂O₃ and TiO₂-rutile in the temperature range of 750-1300℃ that rendered it apparently useless for industrial applications. Several thermal shock tests were performed: Long therm thermal annealing test at 1100℃ for 100h; and water quenching from 950 to room temperature (RT). Cyclic thermal expansion coefficients up to 1500℃ before and after decomposition tests was also measured using a dilatometer, changes in the microstructure, thermal expansion coefficients, Young's modulus and strengths were determined. The role of microcracks in relation to thermal shock resistance and thermal expansion coefficient is discussed.

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Measurements of Thermal Expansion Coefficients in GRP Pipe (GRP 복합관의 열팽창계수 측정)

  • Oh, Jin-Oh;Yoon, Sung-Ho
    • Composites Research
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    • v.25 no.1
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    • pp.26-30
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    • 2012
  • This study was focused on the measurement of thermal expansion coefficients for GRP pipe through strain gage circuits. First of all, thermal expansion coefficients of aluminum beam were measured to examine the validity of the suggested method by using various types of strain gage circuits. Thermal expansion coefficients of GRP pipes along axial and hoop directions were measured to investigate the effect of the location of strain gages, number of repeated measurements, and strain gage types with different thermal expansion coefficients on the thermal strains and the repeatability of measured results. According to the results, thermal expansion coefficients of GRP pipes along hoop direction were lower than those along axial direction due to the constraint effect of reinforced glass fibers on thermal strains along hoop direction. As measurements were repeated, thermal expansion coefficients of GRP pipes were slightly increased, but the degree of increase became smaller. Finally, the same thermal expansion coefficients were obtained irrespective of different types of strain gages with different thermal expansion coefficients if thermal strains of strain gages were compensated by using reference compensation specimen.

Coefficient of Thermal Expansion Measurement of Concrete using Electrical Resistance Strain Gauge (전기저항식 변형률 게이지를 이용한 콘크리트의 열팽창계수 측정법)

  • Nam, Jeong-Hee;An, Deok-Soon;Kim, Yeon-Bok
    • International Journal of Highway Engineering
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    • v.15 no.6
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    • pp.25-32
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    • 2013
  • PURPOSES : The purpose of this study is to provide the method of how to measure the coefficient of thermal expansion of concrete using temperature compensation principle of electrical resistance strain gauge. METHODS : The gauge factor compensation method and thermal output(temperature-induced apparent strain) correction method of self-temperature compensation gauge were investigated. From the literature review, coefficient of thermal expansion measurement method based on the thermal output differential comparison between reference material(invar) and unknown material(concrete) was suggested. RESULTS : Thermal output is caused by two reasons; first the electrical resistivity of the grid conductor is changed by temperature variation and the second contribution is due to the differential thermal expansion between gauge and the test material. Invar was selected as a reference material and it's coefficient of thermal expansion was measured as $2.12{\times}10^{-6}m/m/^{\circ}C$. by KS M ISO 11359-2. The reliability of the suggested measurement method was evaluated by the thermal output measurement of invar and mild steel. Finally coefficient of thermal expansion of concrete material for pavement was successfully measured as $15.45{\times}10^{-6}m/m/^{\circ}C$. CONCLUSIONS : The coefficient of thermal expansion measurement method using thermal output differential between invar and unknown concrete material was evaluated by theoretical and experimental aspects. Based on the test results, the proposed method is considered to be reasonable to apply for coefficient of thermal expansion measurement.

Effect of cold working on the thermal expansion and mechanical properties of Fe-29%-Ni-17%Co low thermal expansion alloy (Fe-29%Ni-17%Co 저열팽창성 합금의 기계적 및 열팽창 특성에 미치는 냉간 가공의 영향)

  • Lee, Kee-Ahn;Kim, Song-Yi;NamKung, Jung;Kim, Mun-Chul
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.355-356
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    • 2009
  • The change of thermal expansion and mechanical behaviors by cold working has been investigated in Fe-29%Ni-17%Co low thermal expansion Kovar alloy. Fe-29%Ni-17%Co alloy was cold rolled gradually and prepared to plates having reduction ratio of 0%, 20%, 40%, 60%, and 80%. Annealing effect on the properties was also studied. Thermal expansion was measured from $25^{\circ}C$ to $600^{\circ}C$ with a heating rate of $5^{\circ}C$/min by using vacuum differential dilatometer. It was found that thermal expansion coefficient ($\alpha_{30{\sim}400}$) slightly decreased (reduction ration of 20%) and then remarkably increased (above reduction ration of 40%) with increasing reduction ratio of cold rolling. Thermal expansion coefficient ($\alpha_{30{\sim}400}$) was sharply decreased after annealing heat-treatment. Yield and tensile strengths were continuously increased and elongation was decreased by cold roiling. Microstructural observation and X-ray diffraction analysis results showed that the $\alpha$ phase significantly increased as the reduction ratio increased. The slight decrease of thermal expansion coefficient bellow reduction ration of 20% could be explained by the destroying short-range ordering and the decreasing of grain size. The significant increase of thermal expansion coefficient with cold rolling mainly attributed to the appearance of $\alpha$ phase. The correlation between the microstructural cause and invar phenomena for the low thermal expansion behavior was also discussed.

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Thermal Properties of Graphene

  • Yoon, Du-Hee;Lee, Jae-Ung;Son, Young-Woo;Cheong, Hyeon-Sik
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.14-14
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    • 2011
  • Graphene is known to possess excellent thermal properties, including high thermal conductivity, that make it a prime candidate material for heat management in ultra large scale integrated circuits. For device applications, the key parameters are the thermal expansion coefficient and the thermal conductivity. There has been no reliable experimental determination on the thermal expansion coefficient of graphene whereas the estimates of the thermal conductivity vary widely. In this work, we estimate the thermal expansion coefficient of graphene on silicon dioxide by measuring the temperature dependence of the Raman spectrum. The shift of the Raman peaks due to heating or cooling results from both the intrinsic temperature dependence of the Raman spectrum of graphene and the strain on the graphene film due to the thermal expansion mismatch with silicon dioxide. By carefully comparing the experimental data against theoretical calculations, it is possible to determine the thermal expansion coefficient. The thermal conductivity is measured by estimating the thermal profile of a graphene film suspended over a circular hole of the substrate.

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Effects of Co Addition in High Strength and Low Thermal Expansion Invar Alloy (고강도 저열팽창 인바합금에 있어서 CO 첨가의 영향)

  • Kim, Bong-Seo;Jo, Yeong-Am;Yoo, Kyung-Jae;Kwon, Hae-Woong;Lee, Hui-Ung;Kim, Byung-Geol
    • Proceedings of the KIEE Conference
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    • pp.1901-1903
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    • 1999
  • To investigate invar alloy as a core material for increased capacity over-head transmission line which have high strength and low thermal expansion coefficient, hardness and thermal expansion coefficient of Fe-Ni-Co alloy have been studied. It is necessary that invar alloy have low thermal expansion coefficient and high strength for increased capacity over-head transmission line. In this paper. we tried to find out the effect of Ni and Co which has ferromagnetic properties and high saturation magnetization. It was found that Ni decrease thermal expansion coefficient and hardness, Co decrease thermal expansion coefficient but increase hardness in Fe-xNi-Co system. In Fe-(29-x)Ni-Co system, the material has no low thermal expansion properties substituting Co instead of Ni in concentration range of $1\sim7$%Co.

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Thermal Expansion Behavior of Cordierite-SiC Whisker Ceramic Composites (코디어라이트-SiC위스커 복합재료의 열팽창 특성)

  • ;Weisskopf
    • Journal of the Korean Ceramic Society
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    • v.24 no.5
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    • pp.411-416
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    • 1987
  • Thermal expansions and thermal expansion coefficients of cordierite ceramics reinforced by SiC whiskers up to 40 vol. % were investigated. The composite specimens were hot pressed at 1523K for 30 min under 28.5 MPa pressing pressure in Ar atmosphere. Thermal expansions of the hot pressed composites were measured using a differential dilatometer up to 1262 K in air. Thermal expansions and thermal expansion coefficient of the composites increased with SiC whisker content. Thermal expansion behaviors of the composites were well explained by modelling parallel slabs randomly distributed on the whisker plane as the microstructural element of the composites.

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Grain Boundary Microcracking in ZrTiO4-Al2TiO5 Ceramics Induced by Thermal Expansion Anisotropy

  • Kim, Ik-Jin;Kim, Hyung-Chul;Lee, Kee-Sung;Han, In-Sub
    • Journal of the Korean Ceramic Society
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    • v.40 no.2
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    • pp.109-112
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    • 2003
  • The grain-boundary microcracking materials in the system $Al_2$TiO$_{5}$ -ZrTiO$_4$(ZAT) is influenced by the thermal expansion anisotropy. The range of ZAT compositions investigated had showed very low thermal expansions of 0.3~1.3$\times$10$^{-6}$ K loin compared to 8.29$\times$10$^{6}$ K of pure ZrTiO$_4$and 0.68$\times$10$^{6}$ K of polycrystalline $Al_2$TiO$_{5}$ , respectively, compared with the theoretical thermal expansion coefficient for a single crystal of $Al_2$TiO$_{5}$ , 9.70$\times$10$^{6}$ K. The low thermal expansion and microcraking temperature are apparently due to a combination of thermal contraction and expansion caused by the large thermal expansion anisotropy of the crystal a ies of the $Al_2$TiO$_{5}$ phase.