• Title/Summary/Keyword: Thermal expansion parameters

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Measurements of Lattice Strain in $SiO_2/Si$ Interface Using Convergent Beam Electron Diffraction (수렴성빔 전자회절법을 이용한 $SiO_2/Si$ 계면 부위의 격자 변형량 측정)

  • Kim, Gyeung-Ho;Wu, Hyun-Jeong;Choi, Doo-Jin
    • Applied Microscopy
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    • v.25 no.2
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    • pp.73-79
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    • 1995
  • The oxidation of silicon wafers is an essential step in the fabrication of semiconductor devices. It is known to induce degradation of electrical properties and lattice strain of Si substrate from thermal oxidation process due to charged interface and thermal expansion mismatch from thermally grown SiO, film. In this study, convergent beam electron diffraction technique is employed to directly measure the lattice strains in Si(100) and $4^{\circ}$ - off Si(100) substrates with thermally grown oxide layer at $1200^{\circ}C$ for three hours. The ratios of {773}-{973}/{773}-{953} Higher Order Laue Zone lines were used at [012] zone axis orientation. Lattice parameters of the Si substrate as a function of distance from the interface were determined from the computer simulation of diffraction patterns. Correction value for the accelerating voltage was 0.2kV for the kinematic simulation of the [012]. HOLZ patterns. The change in the lattice strain profile before and after removal of oxide films revealed the magnitudes of intrinsic strain and thermal strain components. It was shown that $4^{\circ}$ -off Si(100) had much lower intrinsic strain as surface steps provide effective sinks for the free Si atoms produced during thermal oxidation. Thermal strain in the Si substrate was in compression very close to the interface and high concentration of Si interstitials appeared to modify the thermal expansion coefficient of Si.

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Deformation Analysis Considering Thermal Expansion of Injection Mold (사출금형의 열팽창을 고려한 변형 분석)

  • Kim, Jun Hyung;Yi, Dae-Eun;Jang, Jeong Hui;Lee, Min Seok
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.39 no.9
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    • pp.893-899
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    • 2015
  • In the design of injection molds, the temperature distribution and deformation of the mold is one of the most important parameters that affect the flow characteristics, flash generation, and surface appearance, etc. Plastic injection analyses have been carried out to predict the temperature distribution of the mold and the pressure distribution on the cavity surface. As the input loads, we transfer the temperature and pressure results to the structural analysis. We compare the structural analysis results with the thermal expansion effect using the actual flash and step size of a smartphone cover part. To reduce the flash problem, we proposed a new mold design, and verified the results by performing simulations.

Analysis and Prediction for Abutment Behavior of Prestressed Concrete Girder Integral Abutment Bridges (프리스트레스트 콘크리트 거더 일체식 교량의 교대 거동 해석과 예측)

  • Kim, Woo-Seok
    • Journal of the Korea Concrete Institute
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    • v.23 no.5
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    • pp.667-674
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    • 2011
  • This paper discusses the analysis method of prestressed concrete girder integral abutment bridges for a 75-year bridge life and the development of prediction models for abutment displacements under thermal loading due to annual temperature fluctuation and time-dependent loading. The developed nonlinear numerical modeling methodologies considered soil-structure interaction between supporting piles and surrounding soils and between abutment and backfills. Material nonlinearity was also considered to simulate differential rotation in construction joints between abutment and backwall. Based on the numerical modeling methodologies, a parametric study of 243 analysis cases, considering five parameters: (1) thermal expansion coefficient, (2) bridge length, (3) backfill height, (4) backfill stiffness, and (5) pile soil stiffness, was performed to established prediction models for abutment displacements over a bridge life. The parametric study results revealed that thermal expansion coefficient, bridge length, and pile-soil stiffness significantly influenced the abutment displacement. Bridge length parameter significantly influenced the abutment top displacement at the centroid of the superstructure, which is similar to the free expansion analysis results. Developed prediction model can be used for a preliminary design of integral abutment bridges.

Experimental Study on the Operating Characteristics of the Organic Rankine Cycle (ORC 시스템의 운전 특성에 관한 실험연구)

  • Eom, Hong Sun;Yoon, Cheon Seog;Kim, Young Min
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.25 no.4
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    • pp.208-215
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    • 2013
  • An experimental study of an ORC (Organic Rankine Cycle) system has been performed for small-scale applications in the range of a few kW for low-grade-recovery heat sources. The ORC system was equipped with a scroll expander. Experimental tests were carried out using this system, and showed good performance and reliability for the small-scale system. The effects of various operating conditions were selected as the main parameters for the performance of ORC system, such as the expander speeds and mass flow rates of R-134a for expander inlet temperatures ranging from $100^{\circ}C$ to $190^{\circ}C$, as well as the thermal power, thermal efficiency, expansion efficiency, and volumetric efficiency.

Interrupting Characteristics of 25.8kV Gas Circuit Breaker Using Thermal-Expansion Principle (열팽창분사원리를 이용한 25,8kV급 가스차단기의 차단특성)

  • Chang, K.C.;Shin, Y.J.;Park, K.P.;Jeong, J.K.;Kim, J.K.;Kim, G.S.
    • Proceedings of the KIEE Conference
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    • 1994.07b
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    • pp.1603-1605
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    • 1994
  • Recently, Gas Circuit Breakers are rapidly replacing Vacuum Circuit Breakers in the medium voltage switchgear. This is due to the improved performance of - GCB in interrupting capability, price, weight, size etc., while the countermeasure to suppress the switching surges of VCB has not been satisfactory. Intensive research works on the GCB have been conducted in the world widely since 1980. Nowadays it is well known that the thermal expansion type GCB can provide- better performance than puffer type in the distribution power system. KERI has conducted researches in the GCB rated at 25.8kV 25kA with Jinkwang Co. using the thermal expantion principle since 1993. In this paper, the calculated results of electric and magnetic fields for the model GCB are presented and analyzed. The effect of permanent magnet used to improve the interruption capabilty at the low current level is also investigated. The design parameters for the interrupter inspected through the short-circuit tests conducted at high power laboratory of KERI.

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A Study on the Effects of the Design Parameters and Sealing Mechanism of the Exhaust Gas in Engine Exhaust System (엔진 배기계의 배기가스 누설 메카니즘과 설계인자들의 영향에 관한 연구)

  • Choi, B.L.
    • Journal of Power System Engineering
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    • v.14 no.4
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    • pp.37-42
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    • 2010
  • This paper deals with the sealing mechanism of the gasket component and the effects of design parameters for the exhaust manifold. The finite element model includes hot-end exhaust system and a simplified gasket model supplied by ABAQUS software. The mechanical behaviors of bead and body of a gasket are measured after several times of cyclic loads by gasket supplier. From the finite element analysis due to the cyclic thermal loads, the flange of exhaust manifold shows thermal expansion and contraction in longitudinal direction as well as convex and concave deformations with respect to the engine cylinder head. And, the contact pressures of the gasket beads suddenly changes by normal deformation of inlet flanges. Therefore, the magnitudes of contact pressures could be used to determine the sealing characteristics of the exhaust gas in the exhaust system. The distributions of contact pressures in gasket bead lines shows a good agreement with the engine test results.

가속 시험을 통한 솔더조인트의 건전성 평가

  • 명노훈;이억섭;김동혁
    • Proceedings of the Korean Reliability Society Conference
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    • 2004.07a
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    • pp.221-226
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    • 2004
  • The thermal stresses induced by difference in Coefficient of Thermal Expansion between FR-4 board and 63Sn-37Pb solder joint directly affect the reliability of 63Sn-37Pb solder joint. This research, thus, focuses to investigate the crack initiation and propagation behavior around solder joint by imposing a designed Acceleration Life Test Procedure on solder joint by using a newly manufactured Thermal Impact Experimental Apparatus. The fracture mechanism of the solder joint was found to be highly influenced by thermal stresses. The reliability of solder joint was evaluated by using a failure probability model in terms of varying parameters such as frequency and temperature. The relationship between failure probability and safety factor was also studied.

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Analysis of Thermal Crown of Working Roll in Hot Strip Rolling (열간 압연하에서 작업롤의 Thermal Crown에 관한 연구)

  • Cho, Jin
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.8
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    • pp.1451-1457
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    • 1992
  • In hot strip rolling, the thickness of strip cannot be retained uniform by several irregular parameters. It has been shown that the load distribution can affect only a small fraction of the excess strip crown, whereas the thermal effects of working roll are the major reason on large changes in the strip center crown during hot rolling. In this study, the temperature distribution of working roll is represented by fourier series expansion. The analytical solution of the resulting thermo-elasticity problem is obtained by love's strain function. The results which are compared with those of the finite element method show good agreements.

Thermal Recovery Characteristics of a CO2 Mixture Gas Circuit Breaker

  • Oh, Yeon-Ho;Song, Ki-Dong;Lee, Hae-June;Hahn, Sung-Chin
    • Journal of Electrical Engineering and Technology
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    • v.11 no.4
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    • pp.969-973
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    • 2016
  • Interruption tests were conducted using the same circuit breaker for an initial pressure of SF6 0.5 MPa (gauge pressure) and CO2 mixture 1.0 MPa, 0.8 MPa, and 0.6 MPa. The pressure-rises in the compression and thermal expansion chambers were measured for verifying the computational results using a simplified synthetic test facility. Further, the possibility of the CO2 mixture substituting SF6 gas was confirmed. Moreover, in view of the thermal recovery capability, it has also been confirmed that the pressure of the CO2 mixture can be reduced almost to the same value as that of the SF6 gas by optimizing the design parameters of the interrupter.

Optimum Design of Volute Configuration in a Sirocco Fan using CFD and DOE

  • Jung, Uk-Hee;Choi, Young-Seok;Lee, Kyoung-Yong
    • International Journal of Air-Conditioning and Refrigeration
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    • v.17 no.2
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    • pp.68-73
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    • 2009
  • In this paper, a numerical study has been carried out to investigate the influence of volute geometries on the performance of a sirocco fan. In order to achieve an optimum volute design and explain the interactions between the different geometric configurations in the volute system, three-dimensional computational fluid dynamics and the 'design of experiment' method have been applied. Several geometric parameters, such as the volute expansion angle, the cut-off position and the bell mouth shape, are employed to improve efficiency and performance. $2^k$ factorial designs were performed to screen the most influential parameters and interactions, and showed that the cut-off position and the bell mouth shape are the most significant parameters. The optimum design was selected as a result of the response surface methodology, and effects of these parameters and their interactions were presented. From the results of computational analyses and experimental data, the performance and efficiency of the sirocco fan were successfully improved. Also, detailed effects of geometric variables of the volute system on the fan performance were discussed.