The Steady State Rheological Behavior of Semisolid AlSi6Mg2 Alloy

2011 ◽  
Vol 339 ◽  
pp. 257-260 ◽  
Author(s):  
Hong Chao Luo ◽  
Shi Pu Chen ◽  
Qin Nie ◽  
En Sheng Xu ◽  
Li Ping Ju
Keyword(s):  
Steady State ◽  
Shear Rate ◽  
Rheological Behavior ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Solid Particles ◽  
Experimental Results ◽  
Present System ◽  
Flow Conditions ◽  
Good Agreement

In the present work, basing on the rheological model of Chen and Fan (CF) [1] of semisolid metal slurries (SSMS), the rheological behavior at steady state of AlSi6Mg2 alloy is investigated. Experimental results on steady state viscosity of the present system in the literature are used to determine the parameters of the CF model by fitting. It has been shown that the steady state viscosity and the average agglomerate size increase with increasing the solid volume fraction and decreasing the shear rate. The theoretical prediction of the CF model is in good agreement with the experimental results in the literatures quantitatively. The importance of the effective solid volume fraction is shown by explaining the strong coupling between the viscosity and the microstructure. Specifically, the external flow conditions such as shear rate influences the viscosity by changing the agglomeration degree of the solid particles, that is, the effective solid volume fraction and then changing the viscosity.

A Steady State Model for the Rheological Behavior of Semisolid Al-6.5wt%Si Alloy

2011 ◽  
Vol 228-229 ◽  
pp. 858-863
Author(s):  
Li Ping Ju ◽  
Hong Chao Luo ◽  
Wei Wang ◽  
Dan Xu
Keyword(s):  
Steady State ◽  
Shear Rate ◽  
Rheological Behavior ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Solid Particles ◽  
State Behavior ◽  
Packing Parameter ◽  
Steady State Model ◽  
Good Agreement

In the present work, The Chen and Fan (CF) model [1] of semisolid metal slurries (SSMS) is improved by modifying the expression of the packing parameter, of the solid particles and then the modified CF (MCF) model is obtained. Subsequently, the MCF model is applied to the Al-6.5wt%Si alloy to investigate its rheological behavior at steady state. The factors which affect the steady state behavior have been studied. It has been shown that the steady state viscosity and the average agglomerate size increase with increasing the solid volume fraction and decreasing the shear rate. The prediction of the model is in good agreement with the experimental results in the literatures qualitatively. The importance of the effective solid volume fraction is shown by explaining the strong coupling between the viscosity and the microstructure. The external flow conditions such as shear rate etc change the agglomeration degree, that is, the effective solid volume fraction and then the viscosity

The Effect of the Microstructure of Semisolid Al Alloy on its Rheology

2014 ◽  
Vol 490-491 ◽  
pp. 109-112
Author(s):  
De Wen Cao ◽  
Jia Huan Wang ◽  
Yu Qing Sun ◽  
Ke Hua Chen ◽  
Cheng Ming Yu ◽  
...  
Keyword(s):  
Particle Size ◽  
Rheological Behavior ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Alloy System ◽  
The State ◽  
Solid Particles ◽  
Al Alloy ◽  
Agglomerate Size ◽  
The One

In the present work, the effect of the microstructure of AlSi6Mg2 alloy on its macro-rheological behavior of the steady AlSi6Mg2 alloy is investigated. Specifically, the effect of particle size, packing mode and degree of the agglomeration of particles are analyzed. It can be seen that the apparent viscosity decreases with increasing the particle size (d) ifdis between a few μm and 200 μm, while the solid particle size does not affect viscosity except this region. This theoretical prediction is in qualitatively agreement with the experimental data. The trend of the variation of the average agglomerate size with the particle size is the same as the one of viscosity. The packing mode of solid particles in agglomerate is closely related to the solid volume fraction and the characteristics of the alloy system. Subsequently, the state of agglomeration of solid particles which determines the rheology of semisolid AlSi6Mg2 alloy, while the external flow conditions (such as shear rate) influence the viscosity by changing the state of agglomeration. Consequently, the particle size, the packing mode and the average agglomerate size have different effect on the rheological behavior of SSMS.

Rheological Behavior of Semisolid Al-6.5wt%Si Alloy under Cyclic Shear Deformation

2011 ◽  
Vol 306-307 ◽  
pp. 104-107
Author(s):  
Hong Chao Luo ◽  
Jun Mei Yang ◽  
Li Yuan Sun ◽  
Li Ping Ju
Keyword(s):  
Experimental Data ◽  
Shear Rate ◽  
Hysteresis Loop ◽  
Shear Deformation ◽  
Rheological Behavior ◽  
Qualitative Agreement ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Cyclic Shear ◽  
The Difference

In the present work, the MCF model for semisolid metal slurries (SSMS) is applied to investigate the thixotropy of the Al-6.5wt%Si alloy under cyclic shear deformation. The study shows that the semisolid Al-6.5wt%Si alloy has the behavior of thixotropy. The area of the hysteresis loop increases with decreasing the up-time, the initial shear rate and increasing resting time, solid volume fraction and maximum shear rate, respectively. These results have qualitative agreement with the experimental data. The origin of the hysteresis loop is atrributed to the difference between the deagglomeration rate and the agglomeration rate.

scholarly journals Quantification of shear viscosity and wall slip velocity of highly concentrated suspensions with non-Newtonian matrices in pressure driven flows

2021 ◽  
Author(s):  
Patrick Wilms ◽  
Jan Wieringa ◽  
Theo Blijdenstein ◽  
Kees van Malssen ◽  
Reinhard Kohlus
Keyword(s):  
Shear Stress ◽  
Liquid Phase ◽  
Shear Rate ◽  
Shear Viscosity ◽  
Slip Velocity ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Wall Slip ◽  
Flow Index ◽  
Concentrated Suspensions

AbstractThe rheological characterization of concentrated suspensions is complicated by the heterogeneous nature of their flow. In this contribution, the shear viscosity and wall slip velocity are quantified for highly concentrated suspensions (solid volume fractions of 0.55–0.60, D4,3 ~ 5 µm). The shear viscosity was determined using a high-pressure capillary rheometer equipped with a 3D-printed die that has a grooved surface of the internal flow channel. The wall slip velocity was then calculated from the difference between the apparent shear rates through a rough and smooth die, at identical wall shear stress. The influence of liquid phase rheology on the wall slip velocity was investigated by using different thickeners, resulting in different degrees of shear rate dependency, i.e. the flow indices varied between 0.20 and 1.00. The wall slip velocity scaled with the flow index of the liquid phase at a solid volume fraction of 0.60 and showed increasingly large deviations with decreasing solid volume fraction. It is hypothesized that these deviations are related to shear-induced migration of solids and macromolecules due to the large shear stress and shear rate gradients.

Investigation on the Rheological Behavior of Polyamide6/Montmorillonite Nanocomposites by Reactive Extrusion

2011 ◽  
Vol 233-235 ◽  
pp. 1998-2001 ◽  
Author(s):  
Ming Zhao ◽  
Xiao Zhong Lu ◽  
Kai Gu ◽  
Xiao Min Sun ◽  
Chang Qing Ji
Keyword(s):  
Activation Energy ◽  
Shear Stress ◽  
Shear Rate ◽  
Rheological Behavior ◽  
Reactive Extrusion ◽  
Shear Thinning ◽  
Experimental Results ◽  
Montmorillonite Nanocomposites

The rheological behavior of PA6/montmorillonite(MMT) by reactive extrusion was investigated using cone-and-plate rheometer. The experimental results indicated that PA6/MMT exhibited shear-thinning behavior. The shear stress of both neat PA6 and PA6/MMT increased with the increase in the shear rate. The reduction of the viscous activation energy with the increase of shear stress reflected PA6/MMT can be processed over a wider temperature.

NMR Technique for Multiphase Fluid Study Involving Melting Phenomena

1999 ◽  
Author(s):  
Q. Ni ◽  
J. D. King ◽  
Y.-X. Tao
Keyword(s):  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Melting Rate ◽  
Analysis Method ◽  
Image Analysis Method ◽  
Equilibrium Conditions ◽  
Multiphase Fluid ◽  
Physical Phenomena ◽  
Non Destructive ◽  
Good Agreement

Abstract Nuclear magnetic resonance (NMR) sensors are used to determine the time variation of solid mass for a packed ice bed in an experiment of convective melting under non-thermal equilibrium conditions. The paper describes the basic experimental technique for NAFTM apparatus and feasibility for determining the solid volume fraction and ultimately the melting rate. The NMR technique provides an effective, non-destructive method for multiphase fluid study where phase change is one of the important physical phenomena. The results show a good agreement of data obtained by the NMR method with those from image-analysis method.

Effects of Solid Volume Fraction on the Gelcasting of Alumina Suspensions

2007 ◽  
Vol 280-283 ◽  
pp. 1041-1044
Author(s):  
Yong Huang ◽  
Li Ming Zhang ◽  
Hai Feng Li ◽  
Tian Ma
Keyword(s):  
Low Temperature ◽  
Rheological Behavior ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
The Other ◽  
Sintered Body ◽  
Green Body ◽  
Microstructure And Properties ◽  
Other Hand ◽  
Alumina Suspensions

The effects of solid volume fraction (SVF) on the gelation of alumina suspensions for gelcasting, debonding and sintering of the green body were studied. It was found that with SVF rising, the gelation of alumina suspension delayed; and the strength of green body decreased. On the other hand, high SVF resulted in that polymerized acrylamide split at a relative low temperature. These phenomena manifest that the fast polymerization of monomers in high SVF alumina suspension was inhibited, and the flexibility of the gelcasting was improved. However, Excessive solid volume fraction was prone to a bad rheological behavior of alumina suspension, and deteriorated the microstructure and properties of sintered body.

scholarly journals Computational investigation of liquid-solid slurry flow through an expansion in a rectangular duct

2014 ◽  
Vol 62 (3) ◽  
pp. 234-240 ◽  
Author(s):  
Gianandrea Vittorio Messa ◽  
Stefano Malavasi
Keyword(s):  
Volume Fraction ◽  
Particle Density ◽  
Fluid Model ◽  
Solid Volume Fraction ◽  
Solid Particles ◽  
Rectangular Duct ◽  
Two Phase ◽  
Horizontal Pipe ◽  
Two Fluid Model ◽  
Two Fluid

Abstract The flow of a mixture of liquid and solid particles at medium and high volume fraction through an expansion in a rectangular duct is considered. In order to improve the modelling of the phenomenon with respect to a previous investigation (Messa and Malavasi, 2013), use is made of a two-fluid model specifically derived for dense flows that we developed and implemented in the PHOENICS code via user-defined subroutines. Due to the lack of experimental data, the two-fluid model was validated in the horizontal pipe case, reporting good agreement with measurements from different authors for fully-suspended flows. A 3D system is simulated in order to account for the effect of side walls. A wider range of the parameters characterizing the mixture (particle size, particle density, and delivered solid volume fraction) is considered. A parametric analysis is performed to investigate the role played by the key physical mechanisms on the development of the two-phase flow for different compositions of the mixture. The main focuses are the distribution of the particles in the system and the pressure recovery

Rheological Behavior of Semisolid AlSi6Mg2 Alloy at Transient State

2012 ◽  
Vol 217-219 ◽  
pp. 369-372
Author(s):  
Li Ping Ju ◽  
Ying Wu ◽  
En Sheng Xu ◽  
Wei Wang ◽  
Hong Chao Luo
Keyword(s):  
Shear Rate ◽  
Rheological Behavior ◽  
Rheological Model ◽  
Transient State ◽  
External Flow ◽  
Flow Conditions ◽  
Agglomerate Size ◽  
Resting Time

In the present work, basing on the rheological model of Chen and Fan [1], the rheological behavior of AlSi6Mg2 alloy at transient state is investigated. It has been shown that the deagglomeration of particles is about two orders of magnitude faster than the agglomeration of them. The inequality of agglomeration rate and deagglomeration rate is thought as the origin of the thixotropy of SSMS. Subsequently, the similar trend of the variation of the viscosity and the average agglomerate size with shearing time and resting time shows that the microstructure of SSMS determines its rheological behavior, while the external flow conditions (such as shear rate, shearing time, etc) influence the viscosity by changing its microstructure. The present study predicts that the CF model can describe reliably the transient rheological behavior of AlSi6Mg2 alloy.

MODIFIED GUTH–GOLD EQUATION FOR CARBON BLACK–FILLED RUBBERS

2013 ◽  
Vol 86 (2) ◽  
pp. 218-232 ◽  
Author(s):  
Y. Fukahori ◽  
A. A. Hon ◽  
V. Jha ◽  
J. J. C. Busfield
Keyword(s):  
Carbon Black ◽  
Volume Fraction ◽  
Solid Particles ◽  
Carbon Particles ◽  
Filler Volume Fraction ◽  
Rigid Filler ◽  
Bound Rubber ◽  
Small Volume Fraction ◽  
Filled Rubbers ◽  
Good Agreement

ABSTRACT The modulus increase in rubbers filled with solid particles is investigated in detail here using an approach known widely as the Guth–Gold equation. The Guth–Gold equation for the modulus increase at small strains was reexamined using six different species of carbon black (Printex, super abrasion furnace, intermediate SAF, high abrasion furnace, fine thermal, and medium thermal carbon blacks) together with model experiments using steel rods and carbon nanotubes. The Guth–Gold equation is only applicable to such systems where the mutual interaction between particles is very weak and thus they behave independently of each other. In real carbon black–filled rubbers, however, carbon particles or aggregates are connected to each other to form network structures, which can even conduct electricity when the filler volume fraction exceeds the percolation threshold. In the real systems, the modulus increase due to the rigid filler deviates from the Guth–Gold equation even at a small volume fraction of the filler of 0.05–0.1, the deviation being significantly greater at higher volume fractions. The authors propose a modified Guth–Gold equation for carbon black–filled rubbers by adding a third power of the volume fraction of the blacks to the equation, which shows a good agreement with the experimental modulus increase (G/G0) for six species of carbon black–filled rubbers, where G and G0 are the modulus of the filled and unfilled rubbers, respectively; ϕeff is the effective volume fraction; and S is the Brunauer, Emmett, Teller surface area of the blacks. The modified Guth–Gold equation indicates that the specific surface volume ()3 closely relates to the bound rubber surrounding the carbon particles, and therefore this governs the reinforcing structures and the level of the reinforcement in carbon black–filled rubbers.

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