• Title, Summary, Keyword: thixotropic behavior

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Assessment of mechanical Properties of Thixotropic Al-Si Materials in Semi-Solid Forming Process (반용융 성형공정에서 Thixotropic Al-Si 소재의 기계적 성질 평가)

  • 허재찬
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.56-62
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    • 2000
  • Semi-solid forming process has some advantages such as successful manufacturing of high quality components with less inner defects suitable for less machining high productivity and energy-saving effect. the thixotropic behavior(solid-like in the unperturbed state and liquid-like during shearing) has been the basis for the semi-solid forming process. The main focus of this article is the investigation of the effect of T6 heat treatment and alloying elements on the mechanical properties in the semi-solid formed products using thixotropic hypoeutectic (A357 and ALTHIX 86S) and hypereutectic(A390) materials. The new methods to produce semi-solid formed components with high quality are also proposed and discussed in terms of a die design and the development of a lubricant.

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Effects of the Ultrafine and Nano-sized Clay on Rheological Behavior of the Matrix of ρ-alumina Bonded Castable

  • Cheon, Sungho;Jun, Byungsei
    • Journal of the Korean Ceramic Society
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    • v.40 no.7
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    • pp.632-636
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    • 2003
  • To prepare the alumina cement free vibrated alumina castable, $\rho$-alumina is employed as a binder material, and nano-sized clay is added to enhance the curing strength and give thixotropic behavior. The rheological behavior of matrix of castable is controlled by investigating the influences of ultrafines, $\rho$-alumina, and nano-sized clay on the viscosity of matrix. The microsilica and ultrafine alumina were added 3 wt% and 4 wt%, respectively to the matrix, which showed that the viscosities tends to be lowest values. The rheological property of the matrix is well established by adding $\rho$-alumina as 8 wt% and clay as 4 wt%. The thixotropic behavior of the $\rho$-alumina bonded castable was appeared by introducing nano-sized clay into the matrix and adjusting the pH near to the PZC of the clay suspension.

Repaired concrete columns with fiber reinforced thixotropic mortar: experimental & FEA approach

  • Achillopoulou, Dimitra V.;Arvanitidou, Konstantinia C.;Karabinis, Athanasios I.
    • Computers and Concrete
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    • v.15 no.1
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    • pp.73-88
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    • 2015
  • Following previous studies, the current paper describes the results of an experimental program concerning the repair of reinforced concrete columns by thixotropic pseudo plastic mortar, preformed to analyze and quantify the influence of initial construction damage to the behavior of the repaired element. Five columns (section scale 1:2) were designed according to the minimum requirements of reinforcement of ductility orientated codes' design with variables the percentages of initial construction damages. All were tested in axial compression with repeated cycles up to failure. For comparison reasons, another one of the same characteristics, yet healthy, was constructed and tested as a reference specimen. A numerical study (Finite Element Analysis) was conducted for further investigation of the behavior of the thixotropic mortar as repair material. The results indicate that: a) surpassing a specific amount of damage, columns even suitably repaired present lower strain capacity, b) finite element analysis present the same way of deboning of the repaired material taking into consideration the buckling of the reinforcement bars.

A Study on the Composition of Silver Paste for Micro Nozzle Dispensing Method (미세노즐 토출에 적용 가능한 은 전극의 조성에 대한 연구)

  • Kim, Do-Hyung;Shin, Dong-Wook;Ryu, Sung-Soo;Chang, Hyo-Sik;Kim, Hyeong-Jun
    • New & Renewable Energy
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    • v.8 no.1
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    • pp.18-23
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    • 2012
  • The screen printing has been widely used to form silver electrodes in solar cell device due to their simplicity of process. However, the wavy and irregular surface which is believed to be originated from a screen mask mesh and thixotropic characteristics of paste on screen printing process is well-known to give a negative effect on solar cell efficiency. The dispensing method that the silver paste is extruded through micro nozzle under a moderate pressure and coated on substrate can form the silver electrode without any wavy surface. In this study, we optimize the composition of silver paste and develop paste blending condition based on the thixotropic behavior of paste. The optimized paste shows a large thixotropic loop area which is related to an aspect ratio of electrode line and has the viscosity of 40 $Pa{\cdot}s$ at 40 s-1. The electrode line we finally obtainis 67.2 ${\mu}m$ in width and has an aspect ratio of 0.277.

Studies on Thermal Oxidation of Soybean Oil : Changes in Some Rheological Properties of a Soybean Oil during Thermal Oxidation (가열산화중의 콩기름의 유동학적 연구)

  • Shin, Ae-Ja;Kim, Dong-Hoon
    • Korean Journal of Food Science and Technology
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    • v.17 no.3
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    • pp.141-145
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    • 1985
  • In the present study, an attempt was made to investigate the characteristics of rheological properties of a themally oxidized soybean oil. Various flow curves of the oxidized oils were obtained using a broad range of shear rate (452-904 rpm). The flow curves showed the characteristics of thixotropic flow, and as temperature decreased (range : 13-$37^{\circ}C$) they demonstrated increasingly stronger thixotropic properties. A thixotropic slope similar to the coefficient of thixotropy as applied to the rheological characteristics of the thermally oxidized soybean oil to predict its rheological properties quantitatively at an equilibrium state. The empirical formula with the thixotropic slope was found satisfactory in predicting the Non-Newtonian behavior of the thermally oxidized soybean oil.

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Development of Transparent Dielectric Paste for PDP

  • Kim, Hyung-Jong;Kyoung Joo;Auh, Ken-Ho
    • Proceedings of the Korea Association of Crystal Growth Conference
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    • pp.79-83
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    • 1998
  • Plasma display panel is a potential candidate for HDTV, due to the fact hat the expansion of screen size is much easier using thick film technology. In this study, transparent dielectric materials using lead borosilicate glasses is developed, which satisfy the requirements of dielectrics for PDP. Paste is made of this glass composition. The paste has thixotropic behavior suitable for screen printing. The paste shows more thixotropic behavior as the particle size decrease. After firing, cross sectional area was analyzed by SEM. The void of fired thick film was removed using bimodal particle system. The dielectric showed good adhesion characteristics.

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Non-Newtonian Rheological Properties of Poly(vinyl alcohol) hydrogel (Poly(vinyl alcohol) hydrogel의 비 뉴톤 유변학적인 성질)

  • Kim, Nam-Jeong
    • Elastomers and Composites
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    • v.44 no.3
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    • pp.323-328
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    • 2009
  • The rheological properties of complex materials such as polymer melts show complicated non-Newtonian flow phenomena when they are subjected to shear flow. These flow properties are controlled by the characteristics of flow units and the interactions among the flow segments. The non-Newtonian flow curves of poly(vinyl alcohol) hydrogel were obtained in various concentrations and temperatures by using a cone-plate rheometer. By applying non-Newtonian flow equation to the flow curves for PVA hydrogel samples, the rheological parameters were obtained. The PVA hydrogel samples are shear thinning under increasing shear rate modes which result in thixotropic behavior.

The Non Newtonian Flow Mechanism and Rheological Properties of Polyurethane Melts (용융 폴리우레탄의 비 뉴톤 유동 메카니즘과 유변학적인 성질)

  • Kim, Nam-Jeong
    • Elastomers and Composites
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    • v.44 no.4
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    • pp.423-428
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    • 2009
  • The non-Newtonian flow curves of polyurethane melts were obtained by using a Physica cone-plate rheometer at various temperatures. The rheological parameters were obtained by applying non-Newtonian flow equation to the flow curves for polyurethane samples. When the polyurethane samples are under increasing-decreasing shear rate modes, the hysteresis loop and thixotropic behavior were shown. Polyurethane melts behave as strong gels when they are subjected to shear flow, but when the applied stress surpasses the yield stress, they exhibit non-linear viscoelasticity. Upon decreasing shear rate, its shear stress remains smaller than the values measured in the increasing shear rate mode, because of broken of its structure.