• Title/Summary/Keyword: Semi-solid phase

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Collision Behavior of Molten Metal Droplet with Solid Surface (용융금속 액적의 고체표면 충돌거동)

  • 양영수;손광재;강대현
    • Journal of Welding and Joining
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    • v.18 no.4
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    • pp.55-63
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    • 2000
  • This paper presents a study of the solder bumping process. The theoretical model, based on the variational principle instead of solving the Navier-Stokes equation with moving boundaries, was developed to considered the energy dissipation in semi-solid phase and the approximate solidification time of the molten metal droplet. The simulation results revealed that the developed model could reasonably describe the collision behavior of molten metal with solid surface. Simulations were made with variation of initial droplet temperature, substrate metal and initial substrate temerature.

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Fabrication of $Al_2O_3/Al$ Composite Materials by Mashy State Forming and its Hot Extrusion Process (반용융가공에 의한 $Al_2O_3/Al$ 복합재료의 제조 및 열간압출공정)

  • Kang, Chung-Gil;Kang, Sung-Soo
    • Journal of Korea Foundry Society
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    • v.13 no.3
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    • pp.248-258
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    • 1993
  • A semi-solid alloy in which solid and liquid phase are co-existing is obtained by stirring of A17075 molten metal. A semi-solid alloy is dependent on the corresponding temperature within the solid-liquid range, and the process parameters should be controlled accurately to obtain the homogeneous semisolid alloy. The fabrication possibility of fiber-reinforced aluminum alloy containing $Al_2O_3$ short fibers with vigorous agitation of short fibers were obtained by control of stirring time, solid fraction and impeller speed in extrusion billet fabrication processes. The microstructure to extrusion billet fabricated by low pressure casting was investigated for fiber dispersion state. The relationship between the extrustion force and velocity at hot extrustion, the flow strain and extrusion ratio were theoretically described. The surface defects with lubricants and without lubricant after hot extrusion were investigated. The composites materials after hot extrusion were measured by vickers hardness with extrusion ratio. It has become clear that the secondary working such as hot extrusion was very useful to obtained improved the mechanical properties of metal matrix composites.

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The finite difference analysis on temperature distribution by coordinate transformation during melting process of phase-change Material (상변화 물질의 용융과정에 있어서 좌표변환을 이용한 온도분포의 해석적 연구)

  • Kim, J.K.;Yim, J.S.
    • Solar Energy
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    • v.5 no.2
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    • pp.77-83
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    • 1985
  • An analysis is performed to investigate the influence of the buoyancy force and the thickness variation of melting layer in the containment that is filled with phase-change Material surrounding a cylindrical heating tube during melting process. The phase-change material is assumed to be initially solid at its phase-change temperature and the remaining solid at any given time is still at the phase-change temperature and neglecting the effect of heat transfer occuring within the solid. At the start of melting process, the thickness of melting layer is assumed to be a stefan-problem and after the starting process, the change of temperature and velocity is calculated using a two dimensional finite difference method. The governing equations for velocity and temperature are solved by a finite difference method which used SIMPLE (Semi Implicit Method Pressure linked Equations) algorithm. Results are presented for a wide range of Granshof number and in accordance with the time increment and it is founded that two dimensional fluid flow occurred by natural convection decreases the velocity of melting process at the bottom of container. The larger the radius of heating tube, the higher heat transfer is occurred in the melting layer.

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Dynamics Simulation of Solid Particles in Compression Deformation of Rheology Material (레오로지 소재의 압축변형시 고상입자 거동의 동역학 해석)

  • Lee, C.S.;Kang, C.G.
    • Transactions of Materials Processing
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    • v.15 no.5 s.86
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    • pp.395-401
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    • 2006
  • It is reported that semi-solid forming process takes many advantages over the conventional forming process, such as a long die life, good mechanical properties and energy saves. It is important to predict the deformation behavior for optimization of the forging process with semi-solid materials and to control liquid segregation for mechanical properties of materials. But rheology material has thixotropic, pseudo-plastic and shear-thinning characteristics. So, it is difficult for a numerical simulation of the rheology process to be performed because complicated processes such as the filling to include the state of the free surface and solidification in the phase transformation must be considered. General plastic or fluid dynamic analysis is not suitable for the analysis of the rheology material behavior. Recently, molecular dynamics is used for the behavior analysis of the rheology material and turned out to be suitable among several methods. In this study, molecular dynamics simulation was performed for the control of liquid segregation, forming velocity, and viscosity in compression experiment as a part of study on the analysis of rheology forming process.

Static/Dynamic Finite Element Analysis of Lightweight Suspension Part Fabricated by Application of phase Change Process (상변환 응용 경량 Suspension 부품의 정적/동적 유한요소해석)

  • 이정우;신현기;강충길
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2002.05a
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    • pp.848-851
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    • 2002
  • In the field of automobile industry, lightweight problems are very important in terms of reducing fuel and protecting environment. To satisfy these demands, the attempt to substitute aluminum automobile components for cast steel part has been actively carried out. To fabricate the aluminum automobile suspension part that has the same mechanical properties with cast steel part, design conditions such as shape and dimension of part shall be established. Therefore in this study, shape and dimension conditions of suspension part were proposed. Aluminum automobile suspension part was fabricated by semi-solid die-casting process under the obtained design conditions. Moreover to evaluate the possibility of application to the automobile component, stress and fatigue analysis were performed by using ABAQUS S/W and compared with those of conventional automobile suspension part.

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The Solution Treatment on Thixo-extrudates of Semi-solid Al-Zn-Mg Alloy (Al-Zn-Mg 반용융 압출재의 용체화처리)

  • Kim, Dae-Hwan;Kim, Hee-Kyung;Eom, Jeong-Pil;Lim, Su-Gun
    • Journal of the Korean Society for Heat Treatment
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    • v.26 no.4
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    • pp.165-172
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    • 2013
  • In the present study, the microstructure and solution treatment response of Al-Zn-Mg alloys bars by thixo-extrusion was investigated. The alloy bars were solution treated at 400, 430, 460 and $490^{\circ}C$ for various times. In order to examine the microstructures and phase analysis of the samples after solution treatment, it was performed by optical and scanning electron microscopy. And, Vickers hardness and electrical conductivity was measured on the solution treated samples for each condition to investigate the solution treatment response of extruded bars during solution treatment. The results show that the optimum solution heat treatment conditions of thixo-extruded Al-Zn-Mg alloy for minimization of the grain growth and degradation promotion of the second phase is a temperature of $460^{\circ}C$ and holding time of 0.5 to 2 h.

A Finite Element Analysis of Thixoforging Process by using Arbitrarily Shaped Dies (임의 형상의 다이를 이용한 반용융 단조 공정의 유한요소해석)

  • Kang, Chung-Gil;Kim, Nam-Seok
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.9
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    • pp.123-134
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    • 1999
  • A new forming technology has been developed to fabricate near-net shape components by using aluminum alloys with globular microstructure. The estimations of filling characteristic in the forging simulation with arbitrarily shaped dies of SSM are calculated by finite element method with proposed algorithm. The proposed model and various boundary conditions for arbitrarily shaped die are investigated with the coupling calculation between the liquid phase flow and the solid phase deformation. The simulation processes with arbitrarily shaped dies are performed on the isothermal conditions and axisymmetric problems. To analyze the forging process simulation with SSM, new stress-strain relationship for semi-solid behaviour is described, and forging the liquid flow. Furthermore, For the purpose of getting net shape of SSM, it is important to be obtain a solid fraction in forging process with arbitrarily shaped dies. To produce a automotive part which have good mechanical properties, the filling pattern in accordance with die velocity and solid fraction distribution has to be estimated for arbitrarily shaped die.

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The Effect of Fluid Flow on the Primary Particle of Al-7wt%Si Alloy in Electromagnetic Stirring (전자교반시 Al-7wt%Si합금의 초정입자에 미치는 유동의 영향)

  • Lim, Sung-Chul;Yoon, Eui-Pak
    • Journal of Korea Foundry Society
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    • v.16 no.6
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    • pp.565-575
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    • 1996
  • In this study, to gain the semi-solid alloy we employed the electromagnetic rotation by a induction motor of 3-phases and 2-poles for Al-7wt%Si alloy and observed the size of primary solid particle, distribution state of primary solid particle, the degree of sphericity, and fraction of primary solid for the evaluation of its results. The size of primary solid particle increases from $98{\mu}m$ to $118{\mu}m$ as solid fraction increases from 0.2 to 0.5. The degree of sphericity increased as the solid fraction increased. Solid particles obtained from the microstructures of isothermally held sample were coarsened and the degree of sphericity was enhanced as isothermal holding time increased. However, when the sample was stirred for more than 40min, solid particles merged together and liquid phase was entrapped within the cluster of solid particles. The size of primary solid particle was not changed significantly with the variation of input voltages by 160V over which solid particles began to merge together to be a large cluster of about $170{\mu}m$ at 180V. The standard deviation and the degree of sphericity were not changed significantly with the variation of input voltage.

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A Solid-Phase Extraction Method for Analyzing Trace Amounts of Polychlorinated Dibenzo-p-Dioxins and Dibenzofurans in Waste Water

  • Park, Deok-Hie;Youn, Yeu-Young;Choi, Jae-Won;Lim, Young-Hee;Cho, Hye-Sung
    • Mass Spectrometry Letters
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    • v.2 no.1
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    • pp.12-15
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    • 2011
  • The Korean government has regulated emission of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in waste water of manufacturing facilities producing chlorinated compounds since 2009. As this regulation is expected to be reinforced in 2013 to 50 pg I-TEQ/L, a large sample volume is required for the analysis of trace amounts of PCDD/Fs in waste water. Liquid-liquid extraction (LLE) is used to extract PCDD/Fs from aqueous samples; however, its low efficiency makes it inadequate for analyzing large sample volumes. Herein, we present a disk-type solid-phase extraction (SPE) method for the analysis of dioxin at a part per quadrillion level in waste water. This SPE system contains airtight glass covers with a decompression pump, which enables continuous semi-automated extraction. Small (0.5 L) and large (7 L) samples were extracted using LLE and SPE methods, respectively. The method detection limits (MDLs) were 0.001.0.25 and 0.015.4.1 pg I-TEQ/L for the SPE and LLE methods, respectively. The concentrations of detected congeners with both methods were similar. However, the concentrations of several congeners that were not detected with the LLE method were quantified using the SPE method.

Analysis of grain size controlled rheology material dynamics for prediction of solid particle behavior during compression experiment (레오로지 소재의 압축 실험 시 고상입자 거동 예측을 위한 결정립 동역학 해석)

  • Kim H.I.;Kim W.Y.;Kang C.G.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2005.10a
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    • pp.649-652
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    • 2005
  • It is reported that semi-solid forming process takes many advantages over the conventional forming process, such as long die lift, good mechanical properties and energy saves. Rheology material has a thixotropic, pseudo-plastic and shear-thinning characteristic. Therefore, general plastic or fluid dynamic analysis is not suitable for the behavior of rheology material. So it is difficult for a numerical simulation of the rheology process to be performed because complicated processes such as the filling to include the state of the free surface and solidification in the phase transformation must be considered. Moreover, it is important to predict the deformation behavior for optimization of net shape forging process with semi-solid materials and to control liquid segregation for mechanical properties of materials. In this study, so, molecular dynamics simulation was performed for the control of liquid segregation in compression experiment as a part of study on analysis of rheology forming process.

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