• Title, Summary, Keyword: Coefficient of thermal expansion

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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.

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 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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The Effect of Grain Size and Film Thickness on the Thermal Expansion Coefficient of Copper and Silver Thin Films (구리와 은 박막의 열팽창계수에 미치는 결정립 크기와 박막 두께의 영향)

  • Hwang, Seulgi;Kim, Youngman
    • Korean Journal of Metals and Materials
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    • v.48 no.12
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    • pp.1064-1069
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    • 2010
  • Thin films have been used in a large variety of technological applications such as solar cells, optical memories, photolithographic masks, protective coatings, and electronic contacts. If thin films experience frequent temperature changes, thermal stresses are generated due to the difference in the coefficient of thermal expansion between the film and substrate. Thermal stresses may lead to damage or deformation in thin film used in electronic devices and micro-machined structures. Thus, knowledge of the thermomechanical properties of thin films, such as the coefficient of thermal expansion, is an important issue in determining the stability and reliability of the thin film devices. In this study, thermal cycling of Cu and Ag thin films with various microstructures was employed to assess the coefficient of thermal expansion of the films. The result revealed that the coefficient of thermal expansion (CTE) of the Cu and Ag thin films increased with an increasing grain size. However, the effect of film thickness on the CTE did not show a remarkable difference.

Effect of Heat-treatment in Low Thermal Expansion Coefficient Fe-Ni-Co alloy for Core Material of Increased Capacity Transmission Line (증용량 송전선 강심용 저열팽창 Fe-Ni-Co 합금에 있어서 용체화처리 영향)

  • 김봉서;유경재;김병걸;이희웅
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.950-952
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    • 2000
  • Considering the effective distribution coefficient of Ni in Fe-Ni-Co invar alloy containing a little amount of carbon, we investigated on the thermal expansion coefficient(${\alpha}$). Fe-Ni-Co invar alloy had a large thermal expansion coefficient in as-casted compared with solution treated. The thermal expansion coefficient of Fe-Ni-Co alloy increased with the carbon content in both state of as-casted and solution treated. The effective distribution coefficient(Ke$\^$Ni/) of Ni was smaller than unity in alloy of not containing carbon, but is way larger than unity in alloy of containing carbon. It was considered that the homogeneity of Ni in primary austenite affected thermal expansion coefficient.

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Effects of Mo, V addition on Linear Thermal Expansion Coefficient and Hardness of Low Thermal Expansion Cast Steel (주강계 저열팽창 주조합금의 열팽창 계수와 경도에 미치는 Mo, V 첨가의 영향)

  • Kim, Young-Han;Yoon, Eui-Park;Moon, Byoung-Moon;Hong, Young-Myung
    • Journal of Korea Foundry Society
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    • v.18 no.5
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    • pp.467-473
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    • 1998
  • For enhancing the mechanical properties of LTE (low thermal expansion) cast steel, systematic researches have been carried out. The effects of alloying elements such as vanadium, molybdenum and carbon on the hardness and linear thermal expansion coefficient were investigated. In the range of $0.5{\sim}2.3\;wt%$ carbon, addition of 1.73 wt% carbon caused hardness increase due to the formation of eutectic carbide having high hardness but over the range of 1.73 wt% carbon, hardness was decreased. Thermal expansion coefficient increases with carbon contents. In the LTE cast steel containing 0.6 wt% carbon, hardness increased up to 1.96 wt% vanadium addition. But over the range of 1.96 wt% vanadium hardness was decreased by coarse eutectic carbide. Thermal expansion coefficient of LTE cast steel containing 0.6 wt%carbon moderately increased with increasing vanadium contents. There was no significant variation of hardness and thermal expansion coefficient according to molybdenum content in LTE cast steel.

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Effect of Carbide Forming Elements on Hardness and Linear Thermal Expansion Coefficient of Low Thermal Expansive Cast Irons (저 열팽창 주철의 경도향상 및 선팽창계수에 미치는 탄화물 형성원소의 영향)

  • Moon, Byung-Moon;Hong, Chun-Pyo
    • Journal of Korea Foundry Society
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    • v.17 no.1
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    • pp.36-50
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    • 1997
  • Invar-type austenitic cast irons are being used as low thermal expansive materials because of its good low thermal expansion characteristics and castability despite its low hardness. The effects of alloying elements such as Cr, Ti, V, and Mo on hardness and linear thermal expansion coefficient of the invar-type austenitic cast irons were investigated. A combined use of V and Mo addition was found to be the most effective for the improvement of hardness without causing an increase in the thermal expansion coefficient. With a combined addition of 4.6wt%V and 3.8wt%Mo, the hardness increased up to 180HB and the thermal expansion coefficient was kept at a relatively low value of $4.6{\times}10^{-6}/^{\circ}C$ in the temperature range from room to $250^{\circ}C$.

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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
    • Journal of Technologic Dentistry
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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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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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Synthesis of Nano-Sized Cu Powder by PVA Solution Method and Thermal Characteristics of Sintered Cu Powder Compacts (PVA 용액법을 통한 나노 Cu 분말합성 및 소결체의 열적 특성)

  • Oh, Bok-Hyun;Ma, Chung-Il;Lee, Sang-Jin
    • Korean Journal of Materials Research
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    • v.30 no.2
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    • pp.93-98
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    • 2020
  • Effective control of the heat generated from electronics and semiconductor devices requires a high thermal conductivity and a low thermal expansion coefficient appropriate for devices or modules. A method of reducing the thermal expansion coefficient of Cu has been suggested wherein a ceramic filler having a low thermal expansion coefficient is applied to Cu, which has high thermal conductivity. In this study, using pressureless sintering rather than costly pressure sintering, a polymer solution synthesis method was used to make nano-sized Cu powder for application to Cu matrix with an AlN filler. Due to the low sinterability, the sintered Cu prepared from commercial Cu powder included large pores inside the sintered bodies. A sintered Cu body with Zn, as a liquid phase sintering agent, was prepared by the polymer solution synthesis method for exclusion of pores, which affect thermal conductivity and thermal expansion. The pressureless sintered Cu bodies including Zn showed higher thermal conductivity (180 W/m·K) and lower thermal expansion coefficient (15.8×10-6/℃) than did the monolithic synthesized Cu sintered body.