• Title/Summary/Keyword: residual Si

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Research on residual stress in SiCf reinforced titanium matrix composites

  • Qu, Haitao;Hou, Hongliang;Zhao, Bing;Lin, Song
    • Steel and Composite Structures
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    • v.17 no.2
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    • pp.173-184
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    • 2014
  • This study aimed to theoretical calculate the thermal residual stress in continuous SiC fiber reinforced titanium matrix composites. The analytical solution of residual stress field distribution was obtained by using coaxial cylinder model, and the numerical solution was obtained by using finite element model (FEM). Both of the above models were compared and the thermal residual stress was analyzed in the axial, hoop, radial direction. The results indicated that both the two models were feasible to theoretical calculate the thermal residual stress in continuous SiC fiber reinforced titanium matrix composites, because the deviations between the theoretical calculation results and the test results were less than 8%. In the titanium matrix composites, along with the increment of the SiC fiber volume fraction, the longitudinal property was improved, while the equivalent residual stress was not significantly changed, keeping the intensity around 600 MPa. There was a pronounced reduction of the radial residual stress in the titanium matrix composites when there was carbon coating on the surface of the SiC fiber, because carbon coating could effectively reduce the coefficient of thermal expansion mismatch between the fiber and the titanium matrix, meanwhile, the consumption of carbon coating could protect SiC fibers effectively, so as to ensure the high-performance of the composites. The support of design and optimization of composites was provided though theoretical calculation and analysis of residual stress.

X-ray Diffraction Analysis of Residual Stress in Laminated Ceramic

  • Jin, Young-Ho;Chung, Dong-Yoon
    • Journal of the Korean Ceramic Society
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    • v.48 no.5
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    • pp.458-462
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    • 2011
  • The strength of ceramic was improved by lamination by suppressing the propagation of cracks with compressive residual stress in the face layer of the laminate. Hot pressed SiAlON+SiC/SiC/SiAlON+SiC laminate discs were fabricated for tailored residual stress. The residual stress in this laminate was studied by X-ray diffraction (XRD). There was considerable compressive residual stress in the face layer. A Finite Element Analysis (FEA) was performed to support the measured XRD results and to determine the stress field in the laminate. The residual stress measured by XRD had satisfactory agreement with the analytically calculated and FEA values. The measured value by XRD was -385 ${\pm}$ 20 MPa over most of the face layer. The calculated and FEA values were -386 MPa and -371MPa, respectively. FEA also showed significantly modified stresses and the maximum tensile stress near the edge region which are possible crack generators in the presence of flaws or contact damage.

A Study on the Relationship between Residual Stress and Wear Peroperty in Hypereutectic Al-Si Alloys (과공정 Al-Si 합금의 마모 특성에 미치는 잔류응력의 영향에 관한 연구)

  • Kim, Heon-Joo;Kim, Chang-Gyu
    • Journal of Korea Foundry Society
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    • v.20 no.2
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    • pp.89-96
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    • 2000
  • The effects of modification processing on the refinement of primary Si and the wear behavior of hyper-eutectic Al-Si alloys have been mainly investigated. Refining effects of primary Si in Al-17%Si alloy was more efficient than that of B.390 alloy. Optimum condition of getting the finest primary Si microstructure was when AlCuP modifier is added into the melt at $750^{\circ}C$ and held it at $700^{\circ}C$ for 30 minutes. Wear loss in the specimens of as-cast condition decreases as the size of primary Si decreases, in the order of B.390 alloy, B.390 alloy with AlCuP addition, Al-17%Si alloy and Al-17%Si alloy with AlCuP addition. Wear loss in the aged condition of Al-17%Si alloy, B.390 alloy and B.390 alloy with AlCuP addition decreased due to the increase of compressive residual stress in the matrix by the aging treatment. While, wear loss increased in the aged specimens of Al-17%Si alloy with AlCuP addition and Hepworth addition in which compressive residual stress decreases by the aging treatment. Therefore, it is assumed that higher compressive residual stress in the matrix can reduce the wear loss in composite materials such as hyper-eutectic Al-Si alloys.

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Thickness Effects of Coupling Agent on Residual Bending Stress in $Polyimide/SiO_2$ Joints ($Polyimide/SiO_2$ 접합체에서 잔류굽힘응력에 미치는 Coupling Agent 두께의 영향)

  • Kong, Do-Il;Park, Chan-Eon;Hong, Seung-Taek;Yang, Hoon-Chul;Kim, Ki-Tae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.23 no.7 s.166
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    • pp.1085-1093
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    • 1999
  • Thickness effects of coupling agent on residual bending stress were investigated in $Polyimide/SiO_2$ joints during thermal cycling. Thickness and peel strength of $\gamma$-APS coupling agent were measured and correlated with solution concentration and residual bending stress. The variation of residual bending stress with temperature was also measured for various thicknesses of the coupling agent. Finite element results were compared with experimental data for residual bending stress in $Polyimide/SiO_2$ joints.

A Study on the Residual Stress Analysis of a-Si Thin Film Solar Cell (a-Si 박막형 태양전지의 잔류응력 해석에 관한 연구)

  • Hur, Jang-Wook;Kim, Dong-Wook;Choi, Sung-Dae
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.12 no.2
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    • pp.14-19
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    • 2013
  • The size and distribution of residual stresses and the effect of the minimum mesh size were investigated by the a-Si thin film solar cell. Attributed to the difference in coefficient of thermal expansion of the a-Si and Ag concentrated residual stresses at the joint interface of dissimilar materials. The ${\sigma}y$ and ${\tau}xy$ didn't appear in the central part, but ${\sigma}x$ existed. However, ${\sigma}x$, ${\sigma}y$ and ${\tau}xy$ appeared in the edge part and concentrated residual stresses at the interface between a-Si and Ag. Minimum mesh size gets smaller, the concentration of ${\sigma}y$ was significantly and existence area was reduced. As a result, the failure of thin film solar cells during the cutting process can be explained by the residual stresses.

Evaluation of Strength and Residual Stress in $Si_3N_4/SUS304$ Joint ($Si_3N_4/SUS304$ 접합재의 잔류응력 및 강도평가)

  • 박영철;오세욱;조용배
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.1
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    • pp.101-112
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    • 1994
  • The measurement of residual stress distribution of $Si_3N_4/SUS304$ joint was performed on 23 specimens with the same joint condition using PSPC type X-ray stress measurement system and the two-dimensional elastoplastic analysis using finite element method was also attempted. As results, residual stress distribution near the interface on the ceramic side of the joint was revealed quantitatively. Residual stress on the ceramic side of the joint was turned out to be tensional near the interface, maximum along the edge, varying in accordance with the condition of the joint and variance to be most conspicuous for the residual stress normal to the interface characterized by the stress singularities. In the vicinity of the interface, the high stress concentration occurs and residual stress distributes three-dimensionally. Therefore, the measured stress distribution differed remarkably from the result of the two-dimensional finite-element analysis. Especially at the center of the specimen near the interface, the residual stress, $\sigma_{x}$ obtained from the finite element analysis was compressive, whereas measurement using X-ray yielded tensile $\sigma_{x}$. Here we discuss two dimensional superposition model the discrepancy between the results from the two dimensional finite element analysis and X-ray measurement.

FEM Residual Stress Analysis and Mechanical Properties of Silicon Nitride/Stainless Steel Joint with Multi-Interlayer (다층중간재를 사용한 질화규소/스테인레스 강 접합체의 잔류응력 해석 및 기계적 특성)

  • 박상환;김태우;최영화
    • Journal of the Korean Ceramic Society
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    • v.33 no.2
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    • pp.127-134
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    • 1996
  • The thermal residual stresses were estimated for brazed Si3N4/S.S.316 joints with Cu/Mo multi-interlayers using FEM, and their bending strengths at room temperature were measured for various interlayer configura-tions. The Cu, Mo multi-interlayer decreased the maximum residual stress in Si3N4 and caused the residual stress redistribution rsulting in the high residual stress at Mo interlayer. The stress distribution in the joints as well as the maximum residual stress in silicon nitride were found to be main factors for determining bending strengths and Weibull modulous of the joints. The bending strength of the brazed Si3N4/S.S.316 joints with specific Cu, Mo multi-interlayer system were found to be above 400 MPa.

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Effect of Primary Si Size and Residual Stress on the Mechanical Properties of B.390 Al Alloys (B.390 알루미늄 합금의 기계적 특성에 미치는 초정 Si 입자크기와 잔류응력의 영향)

  • Kim, Heon-Joo;Park, Jeong-Wook
    • Journal of the Korean Society for Heat Treatment
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    • v.18 no.3
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    • pp.157-163
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    • 2005
  • Effects of refinement of primary Si and residual stress on the mechanical properties of Aluminum B.390 alloy have been examined. Calcium was found to have an effect on the size of primary silicon particles. Primary silicon particle was refined as Ca content decreased. Refinement of primary Si particles led to an improvement in mechanical properties of the alloy; increase of elongation was prominent, above all. By the increase of compressive residual stress in the matrix alloy, tensile strength increased but elongation decreased.

A Study for Predictions of In-Cylinder Residual Gas Fraction in SI Engines (SI 엔진 내부의 잔류가스 추정 기법에 관한 연구)

  • Kim, Sung-Cheol;Lee, Sang-Jin;Kim, Duk-Sang;Ohm, In-Yong;Cho, Yong-Seok
    • Proceedings of the KSME Conference
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    • 2001.11b
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    • pp.903-908
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    • 2001
  • Residual gas acts as a diluent which results in reducing the in-cylinder temperature as well as the flame speed, significantly affecting fuel economy, NOx emissions and combustion stability. Therefore it is important to determine the residual gas fraction as a function of the engine operating parameters accurately. However, the determination of the residual gas fraction is very sophisticated due to the unsteady state of induction and exhaust process. There has been little work toward the development of a generally applicable model for quantitative predictions of residual gas fraction. In this paper, a simple model for calculating the residual gas fraction in SI engines was formulated. The effects of engine operating parameters on the residual gas were also investigated. The amount of fresh air was evaluated through AFR and fuel consumption. After this, from the intake temperature and pressure, the amount of total cylinder-charging gas was estimated. The residual fraction was derived by comparing the total charging and fresh air. This results coincide with measured value very well.

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Synthesis of Si3N4 using Residual Organics Trapped in the Silica Gel by Sol-Gel Method (졸-겔법으로 제조된 실리카겔중의 잔류유기물을 이용한 $Si_3N_4$의 합성)

  • 김병호;신현호;이재영
    • Journal of the Korean Ceramic Society
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    • v.29 no.5
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    • pp.357-366
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    • 1992
  • Residual organics were considered as impurity in Sol-Gel method. The purpose of this study was to find the conditions to contain as much residual organics as possible in silica gel prepared from TEOS(tetraethylortho-silicate) by Sol-Gel method. Residual organics are to be expected to have reduction effect on synthesizing Si3N4 from silica gel. The results of this study are follows: 1) The maximum content of entrapped carbon was 19.8 wt.%(C/SiO2=0.25 wt.ratio) in silica gel synthesized under the conditions 1.5 fold mole water for incomplete hydrolysis, 2.5 fold mole phenol as a solvent and 0.1 fold mole HCl as a catalyst to TEOS. 2) Silica gel with organics entrapped by Sol-Gel method had a positive effect on the formation of Si3N4 compared with commercial silica gel. 3) Sintered body of synthesized $\alpha$-Si3N4 with Y2O3 and Al2O3 as additives at 175$0^{\circ}C$ in N2 atmosphere showed bending strength, 602$\pm$20 MPa and frature toughness 4.45$\pm$0.15 MPa.m1/2.

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