• Title/Summary/Keyword: Semi-solid material

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Process Analysis for Rheology Forming Considering Flow and Solidification Phenomena in Lower Solid Fraction (저고상율 소재의 유동 및 응고현상을 고려한 레올로지 성형공정해석)

  • Jung, Young-Jin;Cho, Ho-Sang;Kang, Chung-Gil
    • Journal of the Korean Society for Precision Engineering
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    • v.18 no.9
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    • pp.156-164
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    • 2001
  • Two-dimensional solidification analysis during rheology forming process of semi-solid aluminum alloy has been studied. Two-phase fluid flow model to investigate the velocity field and temperature distribution is proposed. The proposed mathematical model is applied to the die shape of the two types. To calculate the velocity and temperature fields during rheology forming process, the earth governing equation correspondent to the liquid and solid region are adapted. Therefore, each numerical models considering the solid and liquid region existing within the semi-solid material have been developed to predict the deflect of rheology forming gnarls. The Arbitrary Boundary Maker And Cell (ABMAC) method is employed to solve the two-phase flow model of the Navier-Stokes equation. Theoretical model on the basis of the two-phase flow model is the mixture rule of solid and liquid phases. This approach is based on the liquid and solid viscosity. The liquid viscosity is pure liquid state value, however solid viscosity is considered as a function of the shear rate, solid fraction and power law curves.

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Solidification Analysis for Surface Defect Prediction of Rheology Forming Process Considering Flow Phenomena of Liquid and Solid Region (액상과 고상의 유동현상을 고려한 레오로지 성형공정의 표면결함예측을 위한 응고해석)

  • Seo, Pan-Ki;Jung, Young-Jin;Kang, Chung-Gil
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.10
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    • pp.1971-1981
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    • 2002
  • Two-dimensional solidification analysis during rheology forming process of semi-solid aluminum alloy has been studied. Two-phase flow model to investigate the velocity field and temperature distribution is proposed. The proposed mathematical model is applied to the die shape of the two types. To calculate the velocities and temperature fields during rheology forming process, the each governing equations correspondent to the liquid and solid region are adapted. Therefore, each numerical model considering the solid and liquid coexisting region within the semi-solid material have been developed to predict the defects of rheology forming parts. The Arbitrary Boundary Maker And Cell(ABMAC) method is employed to solve the two-Phase flow model of the Navier-Stokes equation. Theoretical model basis of the two-phase flow model is the mixture rule of solid and liquid phases. This approach is based on using the liquid and solid viscosity. The Liquid viscosity is pure liquid state value, however solid viscosity is considered as a function of the shear rate, solid fraction and power law curves.

A Study on Optimum Reheating Process of Automotive Aluminum Piston using Neural Network and the Taguchi Method in Semi-Solid forming (반용융 성헝에서의 다구찌 방법과 신경망을 이용한 자동차 알루미늄 피스톤의 최적 재가열 과정에 대한 연구)

  • 윤재민;김영호;박준홍;최재찬
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2000.11a
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    • pp.902-905
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    • 2000
  • As the manufacturing processes of automotive engine piston, gravity die-casting, squeeze casting, hot forging and powder forging process are generally used for the various specifications. As the semi-solid forming(SSF) is compared with conventional casting such as gravity die-casting and squeeze casting for the characteristics of its process, the product without inner defects such as gas porosity and segregation can be obtained and its microstructure is globular grain. In SSF process, the materials are heated up to the temperature between the solvus and liquidus line at which the materials exists in the form of liquid-solid mixture. In this time, Discussion is given about reheating process of row material and results are presented regarding accurate temperature and process variables controlling for right solid fractions.

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Fabrication of a Part by Heating and Forming in the Semi-solid State of the SKH51 Material (SKH51의 반응고 상태에서의 가열 및 성형에 의한 부품 제조)

  • Lee, Sang Yong
    • Journal of the Korean Society for Heat Treatment
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    • v.27 no.3
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    • pp.127-132
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    • 2014
  • The semi-solid metal forming process has been applied to realize a near-net shape fabrication of a high speed tool steel. A complicatedly shaped part out of SKH51 was successfully manufactured by introducing pertinent materials, tooling and processing conditions. A SKH51 billet with globular grains was heated at temperatures between 1300 and $1350^{\circ}C$ using high frequency induction heater to get semi-solid microstructure before high rate injection of mushy metal into a die cavity for the forming process. It was necessary to control the preheating of dies between 300 and $400^{\circ}C$ to maintain the homogeneous microstructure during the semi-solid metal forming process. Significant defects such as pores, high fraction of liquid fraction and segregation could be removed from the part by using air vents.

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.

The Effect of Injection Velocity on Liquid Segregation of Grain Controlled Rheological Material Considering Asymmetry Multi Thickness Variation (비대칭 다단 두께 변화를 고려한 결정입 제어 반용융 알루미늄 소재의 캐스팅에서 사출속도가 액상편석에 미치는 영향)

  • Seo P. K.;Jung Y. S.;Kang C. G.
    • Transactions of Materials Processing
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    • v.14 no.4 s.76
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    • pp.338-350
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    • 2005
  • Recently, in the field of automobile industry, to solve the problem of reducing the weight of automobile for the improvement of fuel efficiency and the protection of environment, the aluminum alloy parts have been substituted for the steel parts. However, the aluminum alloy does not have as good mechanical property as the steel part. To improve the mechanical property, the semi-solid die casting process is performed to make automobile parts. In the fabrication of semisolid material the control of the liquid segregation is very important to improve the material properties of aluminum alloy. In the present paper we examine the influence of the liquid segregation by the injection conditions in the semi-solid die casting has been investigated.

Forging Process with Al6061 Alloy Rheology Material by Electromagnetic Stirring System (전자교반을 응용한 Al6061 레오로지 소재의 단조공정)

  • Kang, S.S.;Oh, S.W.;Kang, C.G.
    • Transactions of Materials Processing
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    • v.16 no.6
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    • pp.443-446
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    • 2007
  • The semi-solid process has been developed near net-shape components for kinds of methods. Thixo-forming with reheating prepared billet and rheo-forming with cooled melt until semi-solid state. Material is applied electromagnetic stirring system to slurry with aluminum 6061 alloy. An experiment has variation factors which are pressure, solid-fraction, stirring current and stirring time. The mechanical properties are compared to forge sample with to apply heat treatment T6. This study is researched function a virtual pressure and fine shape zone. Optimum pressure is found to prevent defect of porosity.

Fabrication of Metal Matrix Composites and Development of Forming System in Mashy State (반응고법에 의한 금속복합재료의 제조 및 성형 시스템의 개발)

  • 강충길;김현우;김영도
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.3
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    • pp.581-593
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    • 1990
  • A semi-solid alloy in which solid and liquid phase are co-existing is obtained by strirring of Al7075 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 semi-solid alloy. The possibility o homogeneous fiber-reinforce aluminum alloy by addition of $Al_{2}$O$_{3}$ short fibers with vigorous agitation was investigated. The billet of composite materials was fabricated by squeeze casting, and homogeneous dipersion state of fibers in billet of fabricated metal matrix composites was observed. A slurry of semi-solid short fiber metal matrix composites is used in the direct rolling process, and this process showed the fabrication possibility of metal matrix composite sheets. The fabricated sheet was tested regarding vickers hardness, elongation and micro-structure. It has become clear that mashy state processing and working are very useful to obtain parts of composites material closed to near net shape.

A Cooling Roll Design and Prediction of Initial Conditions for Direct Rolling Process of Molten Metal (용탕직접압연공정의 초기조건예측 및 냉각로울 설계)

  • 강충길;김영도
    • Transactions of Materials Processing
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    • v.4 no.3
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    • pp.233-244
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    • 1995
  • Rolling force in the direct rolling(or twin-roll strip continuous casting) process fo semi-solid material has been computed using rigid-viscoplastic finite element method. Temperature distributions for calculations of rolling force and roll deformation are obtained from thermofluid analysis. Three dimensional roll deformation analysis has also been performed by using commercial package ANSYS. From the results, behavior of metal flow, rolling force and roll deformation have been investigated according to the process conditions of semi-solid direct rolling.

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The Theoretical Study of the Measuring Thermal Diffusivity of Semi-Infinite Solid Using the Photothermal Displacement

  • Jeon, PiIsoo;Lee, Kwangjai;Yoo, Jaisuk;Park, Youngmoo;Lee, Jonghwa
    • Journal of Mechanical Science and Technology
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    • v.18 no.10
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    • pp.1712-1721
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    • 2004
  • A method of measuring the thermal diffusivity of semi-infinite solid material at room temperature using photothermal displacement is proposed. In previous works, within the constant thickness of material, the thermal diffusivity was determined by the magnitude and phase of deformation gradient as the relative position between the pump and probe beams. In this study, however, a complete theoretical treatment of the photothermal displacement technique has been performed for thermal diffusivity measurement in semi-infinite solid materials. The influence of parameters, such as, radius and modulation frequency of the pump beam and the thermal diffusivity, was studied. We propose a simple analysis method based on the zero -crossing position of real part of deformation gradient and the minimum position of phase as the relative position between two beams. It is independent of parameters such as power of pump beam, absorption coefficient, reflectivity, Poisson's ratio, and thermal expansion coefficient.