• 한국주조공학회지
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• 제17권1호
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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 $250^{\circ}C$.

• 한국주조공학회지
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• 제18권5호
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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.

• 한국세라믹학회지
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• 제42권5호
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• pp.346-351
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• 2005

The linear thermal expansions of $UO_2$ and $(U_{1-y}Ce_y)O_2$ pellet were measured from room temperature to $1400^{\circ}C$ as a function of Ce contents (0, 7.63, 14.84, and $21.68 mol\%$) by using the TMA(Thermo-Mechanical Analysis) method. From the measured data, the linear thermal expansion rate, the coefficient of linear thermal expansion and density variation with temperature were calculated, and the best-fitted temperature-dependent equations were recommended. It was shown that the rate and coefficient of $(U_{1-y}Ce_y)O_2$ thermal expansion increased and the density decreased with increasing Ce contents.

• Structural Engineering and Mechanics
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• 제60권2호
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• pp.313-335
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• 2016

In this article, a four-variable refined plate theory is presented for buckling analysis of functionally graded plates subjected to uniform, linear and non-linear temperature rises across the thickness direction. The theory accounts for parabolic distribution of the transverse shear strains, and satisfies the zero traction boundary conditions on the surfaces of the plate without using shear correction factor. Young's modulus and Poisson ratio of the FGM plates are assumed to remain constant throughout the entire plate. However, the coefficient of thermal expansion of the FGM plate varies according to a power law form through the thickness coordinate. Equilibrium and stability equations are derived based on the present theory. The influences of many plate parameters on buckling temperature difference such ratio of thermal expansion, aspect ratio, side-to-thickness ratio and gradient index will be investigated.

• 방사성폐기물학회지
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• 제16권3호
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• pp.339-346
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• 2018

고준위폐기물을 처분하기 위한 심층처분시스템의 구성 요소로는 처분용기, 완충재, 뒷채움 및 근계 암반이 있다. 이 중 완충재는 심층 처분시스템에 있어 필수적인 요소이다. 처분용기에서 발생하는 고온의 열량은 완충재로 전파되기에 완충재의 열적 특성은 처분시스템의 안정성 평가에 상당히 중요하다고 할 수 있다. 특히, 고온의 열량은 완충재의 열적 팽창을 야기하여 근계 암반에 열응력을 야기할 수 있기에 완충재의 열팽창 특성 규명은 반드시 필요하다고 할 수 있다. 따라서 본 연구에서는 국내 경주산 압축 벤토나이트 완충재(KJ-II)에 대한 열팽창 거동 특성을 실내 실험을 통해 분석하고 선형 열팽창계수에 대한 추정 모델을 제시하고자 하였다. 압축 벤토나이트 완충재의 선형 열팽창계수는 딜라토미터 장비를 이용하여 승온속도, 건조밀도, 온도 범위에 따라 측정되었으며 선형 열팽창계수 값은 대략 $4.0{\sim}6.0{\times}10^{-6}/^{\circ}C$ 로 측정되었다. 또한 실험 데이터를 토대로 비선형 회귀분석 방법을 이용하여 건조밀도에 따른 경주 압축 벤토나이트 완충재의 선형 열팽창계수를 추정할 수 있는 모델을 제시하였다.

• Archives of Metallurgy and Materials
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• 제67권3호
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• pp.909-912
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• 2022

The thermal expansion of a ZrO₂-20 mol% Gd₂O₃ pellet has been systematically investigated using a thermo-mechanical analyzer in the temperature range of 293-1773 K. Variations in the thermal expansion coefficient and density upon temperature change were calculated using the thermal expansion data. The average linear thermal expansion coefficient of the ZrO₂-20 mol% Gd₂O₃ pellet was found to be 9.522 × 10^-6 K^-1 in the range of 298-1073 K. This value is smaller than that of ZrO₂ and larger than that of Gd₂O₃. Further, with an increase in temperature to 1773 K, the density of ZrO₂-20 mol% Gd₂O₃ pellet was found to decrease to 94.98 % of the initial density at 293 K.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 C
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• pp.1346-1348
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• 2001

Generally, Invar alloy shows very low thermal expansion characteristics, lower than $2{\times}10^{-6}$/K approximately. To apply Fe-Ni-Co-C Invar alloy as a core material for large ampacity transmission line we studied the effects of magnetic properties on coefficient of thermal expansion. The coefficient of thermal expansion(CTE) suddenly decreases with addition of a little carbon(0.08%), increases with the increasing carbon and has a constant value at the composition over than 1.0%C. The trend of Curie temperature change with carbon is similar with that of CTE. Therefore, the CTE has a linear relationship with Curie temperature. However, the CTE linearly decreases with the ratio of saturation magnetization and Curie temperature(${\sigma}_s/T_c$).

• 폴리머
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• 제31권3호
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• pp.206-214
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• 2007

3차원적 타원체 형태 ($a_1>a_2>a_3$)를 사용하여, 2가지의 종횡비 (1차 종횡비 $\rho_{\alpha}$와 2차 종횡비 $\rho_{\beta}$)를 갖는 배열된 3차원 형태의 충전제를 포함하는 복합체의 열팽창 변화를 이론적으로 예측하는 모델을 연구하였다. Eshelby의 등가 텐서를 이용하여 배열된 타원형 충전제를 기지재의 이론에 의해 열팽창 계수를 예측할 수 있었다. 종단방향 열팽창 계수 ${\alpha}_{11}$는 두 가지 종횡비 모두 증가하면, 감소하여 충전제의 열팽창에 접근한다. 수직방향 열팽창 계수 ${\alpha}_{33}$는 충전제 함유량에 따라 초기에는 증가하여 최대값을 갖는 경향을 보인다. 1차 종횡비 $\rho_{\alpha}$가 증가하면, 횡단방향 열팽창 계수는 감소하나, 2차 종횡비 $\rho_{\beta}$가 증가하면, 같이 증가한다. 또한, 수직방향 열팽창 계수 ${\alpha}_{33}$는 $\rho_{\alpha}$가 증가하면 증가하나, $\rho_{\beta}$가 증가하면, ${\alpha}_{33}$는 반대로 감소한다.

• 대한치과보철학회지
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• 제35권1호
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• pp.144-164
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• 1997

The purpose of this study were to investigate the chemical composition, mean particle size, linear thermal expansion coefficient and metal-bonding strength of the regular opaque powder and core powder. In this study, 4 types of ceramic powders, namely Duceram Jacket Opaque powder, Duceram Opaque powder, Vita Hi-Ceram powder, Vita VMK Paint On-88 powder were used. Chemical composition was evaluated by EDS(Energy Dispersive X-ray Spectrophotometer, Oxford QX-2000, England), particle size was measured by MALVERN Instruments(MALVERN Instruments SB. OC., U.S.A.. ad linear thermal expansion coefficient was measured by dilatometer(Motoyama, Japan). Bond strength was measured by the Universal tsting machine(Istron Co., Ltd., U.S.A.). The Results were as follows : 1. Through recognition of the relative difference in chemical composition between the core powder and the regular opaque powder, the difference in the proportion of $Al_2O_3$ in each type of material is demonstrated ; Duceram Jaket Opaque powder : 30.16%, Duceram Opaque powder : 16.60%, Vita Hi-Ceram : 63.64%, Vita VMK Paint-On 88 : 16.16%. 2. There was no significant difference in the proportion of metal-bonding materials between the core powder and the regular opaque powder. 3. In the regular opaque powder, alkaline materials were incoporated in order to increase the coefficient of thermal expansion. 4. In the particle size analysis, there was no significant difference in mean particle size or in the particle size distribution between the core powder and the regular opaque powder. 5. In the thermal expansion test for temperature range of $25-600^{\circ}C$, the regular opaque powder had higher coefficient of thermal expansion than that of core powder. 6. In the 4 point flexural bending test, there was no statistically significant difference in the mean bond strength between the core powder and the opaque powder among the Duceram products.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 춘계학술대회 논문집
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• pp.251-252
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• 2009