scholarly journals Viscosity Models Based on the Free Volume and Entropy Scaling Theories for Pure Hydrocarbons over a Wide Range of Temperatures and Pressures

2020 ◽  
Author(s):  
Hseen O. Baled ◽  
Isaac K. Gamwo
Keyword(s):  
Free Volume ◽  
Viscosity Models ◽  
Wide Range

Free volume based nonlinear viscoelastic model for polyurea over a wide range of strain rates and temperatures

2021 ◽  
Vol 152 ◽  
pp. 103650
Author(s):  
Chencheng Gong ◽  
Yan Chen ◽  
Ting Li ◽  
Zhanli Liu ◽  
Zhuo Zhuang ◽  
...  
Keyword(s):  
Free Volume ◽  
Viscoelastic Model ◽  
Strain Rates ◽  
Nonlinear Viscoelastic ◽  
Wide Range ◽  
Nonlinear Viscoelastic Model

Viscosity Models Based on the Free Volume and Frictional Theories for Systems at Pressures to 276 MPa and Temperatures to 533 K

2012 ◽  
Vol 51 (51) ◽  
pp. 16721-16733 ◽  
Author(s):  
Ward A. Burgess ◽  
Deepak Tapriyal ◽  
Isaac K. Gamwo ◽  
Bryan D. Morreale ◽  
Mark A. McHugh ◽  
...  
Keyword(s):  
Free Volume ◽  
Viscosity Models

Mathematical Modeling of Thickness Dependent Physical Aging in Polymeric Membranes

2016 ◽  
Vol 701 ◽  
pp. 275-280 ◽  
Author(s):  
Serene Sow Mun Lock ◽  
Kok Keong Lau ◽  
Irene Sow Mei Lock ◽  
Azmi Mohd Shariff ◽  
Yin Fong Yeong ◽  
...  
Keyword(s):  
Free Volume ◽  
Physical Aging ◽  
Small Deviation ◽  
Dual Mode ◽  
Lattice Contraction ◽  
Volume Relaxation ◽  
Implementation Challenges ◽  
Wide Range ◽  
Dimensional Finite Element ◽  
Complex Differential Equations

The drawback of membrane process that reduces its competitive edge with the conventional separation technologies is ascribed to its decline separative performance over time due to the aging nature of polymeric material. The most widely accepted mechanism that has been thought of governing the volume relaxation process over the course of aging is the dual mode mechanism, whereby it is comprised of two components. The first is the “Lattice contraction” mechanism that describes the uniform collapse of free volume throughout the unrelaxed polymer matrix. The second is the “Diffusion of free volume” mechanism from the interior to the surface of the glassy polymer. Albeit acknowledgement of the dual mode mechanism as the contributing factor, previous aging model renders high implementation challenges to characterize the complicated nature of aging evolution, which requires adaptation of high end computational tools to solve the relatively complex differential equations. In this work, the dual mode mechanism governing the physical aging process has been modelled employing a simple one dimensional finite element numerical solution whereby the film has been divided into many finite slices with equal thickness along the depth of the membrane. The applicability of the mathematical model has been validated with experimental aging data, whereby a small deviation is observed between the two over a wide range of film thicknesses and reasonable intuitive explanation pertaining to the parameters is obtained.

Parametric Analysis of Effective Viscosity Models for Nanofluids

2012 ◽  
Author(s):  
J. P. Meyer ◽  
P. N. Nwosu ◽  
M. Sharifpur ◽  
T. Ntumba
Keyword(s):  
Heat Transfer ◽  
Parametric Analysis ◽  
Effective Viscosity ◽  
Rheological Behaviour ◽  
High Variability ◽  
Heat Transfer Fluids ◽  
Viscosity Models ◽  
Important Benefit ◽  
Wide Range ◽  
Model Predictions

Viscosity is an important consideration in the application of nanofluids as heat transfer fluids. Various models have been developed to predict the viscosity of nanofluids. The accuracy of these models is of important benefit in determining the rheological performance of nanofluids, particularly in conditions which vary continuously. In this paper, a parametric analysis is undertaken to investigate the degree of variability between empirical data and model predictions. It was found that there is high variability in the compared results, which suggests that a wide range of constitutive factors need to be incorporated into the models in order to account adequately for the rheological behaviour of nanofluids.

scholarly journals Viscoelastic properties of hydroxyl-terminated poly(butadiene) based composite rocket propellants

2014 ◽  
Vol 68 (4) ◽  
pp. 435-443 ◽  
Author(s):  
Sasa Brzic ◽  
Ljiljana Jelisavac ◽  
Jela Galovic ◽  
Danica Simic ◽  
Jelena Petkovic
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Free Volume ◽  
Loss Modulus ◽  
Mechanical Analysis ◽  
Thermal Coefficient ◽  
Fractional Free Volume ◽  
Rocket Propellants ◽  
Wide Range

In the present study, the viscoelastic response of three composite solid propellants based on hydroxyl-terminated poly(butadiene), ammonium perchlorate and aluminum has been investigated. The investigation was surveyed by dynamic mechanical analysis over a wide range of temperatures and frequencies. The mechanical properties of these materials are related to the macromolecular structure of the binder as well as to the content and nature of solid fillers. The storage modulus, loss modulus, loss factor and glass transition temperature for each propellant sample have been evaluated. The master curves of storage (log G' vs log ?) and loss modulus (log G'' vs log ?) were generated for each propellant. A comparison of logaT vs temperature curves for all propellants indicate conformance to Williams-Landel-Ferry equation. Choosing the glass transition as the reference temperature, WLF equation constants are determined. Fractional free volume at the glass transition temperature and thermal coefficient of free volume expansion values are in accordance with the consideration that Al is reinforcing filler.

Comparison of 1D vs 3D viscosity models for glacial isostatic adjustment

2020 ◽  
Author(s):  
Paoline Prevost ◽  
Jeffrey Freymueller
Keyword(s):  
Finite Element ◽  
3D Structure ◽  
Earth Model ◽  
Earth Structure ◽  
Glacial Isostatic Adjustment ◽  
Element Analysis ◽  
Isostatic Adjustment ◽  
Viscosity Models ◽  
Test Region ◽  
Wide Range

<p><span>Accurate calculation of displacements due to glacial isostatic adjustment (GIA) are essential for studies of tectonics, sea level projection, and the estimation of recent ice melting or other mass transport. However, most GIA studies to date have used a 1D viscosity model, with earth parameters varying only in the radial direction, while surface geology and seismic tomography show that the thickness of the lithosphere and the structure of the mantle also varies laterally. Therefore, models with 3D earth structure are needed. Using a 3D earth model requires finite element models, which are computationally expensive and hence make it difficult to compute a wide range of potential parameter values. Consequently, the question is for which application is a 3D model necessary, and for which parameters (and where) do 1D models give sufficiently accurate predictions?</span></p><p> </p><p><span>In this study, we investigate the sensitivity of the GIA modeling to the earth structure, using the Abaqus finite element analysis software, an ice model assumed to be known, and various viscosity models. We start with Patagonia as a test region, because the 3D structure of the mantle is complex due to the proximity of the subduction of the Antarctic plate below South American and the Chile triple junction. In this region, the GIA contributes significantly to the regional recent rapid uplift.</span></p>

Plastic Deformation and Mechanical Softening of Pd40Cu30Ni10P20 Bulk Metallic Glass During Nanoindentation

2005 ◽  
Vol 20 (10) ◽  
pp. 2719-2725 ◽  
Author(s):  
A. Concustell ◽  
J. Sort ◽  
G. Alcalá ◽  
S. Mato ◽  
A. Gebert ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Free Volume ◽  
Loading Rate ◽  
Shear Bands ◽  
Control Mode ◽  
Displacement Control ◽  
Softening Effect ◽  
Wide Range

Nanoindentation tests of Pd40Cu30Ni10P20 bulk metallic glass were performed over a wide range of indentation rates (from 0.04 up to 6.4 mN s−1) under the standard load control mode. New results using the feedback displacement control mode are also presented. The dependence of the pop-in formation on the loading rate is investigated. Variations in hardness and reduced elastic modulus as a function of the indentation rate are observed. A softening effect occurs when increasing the loading rate. This is explained by the differences in plastic deformation achieved at different indentation rates. The displacement control mode was used to avoid the shear localization of the free volume, leading to the almost complete absence of pop-ins along the loading curve. The obtained results suggest that plastic flow in bulk metallic glasses is governed by the rate of creation of free volume, which depends on the strain rate and its localization into shear bands.

scholarly journals Positron Annihilation Lifetime Spectroscopy Insight on Free Volume Conversion of Nanostructured MgAl2O4 Ceramics

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3373
Author(s):  
Halyna Klym ◽  
Ivan Karbovnyk ◽  
Sergei Piskunov ◽  
Anatoli I. Popov
Keyword(s):  
Positron Annihilation ◽  
Free Volume ◽  
Ceramic Materials ◽  
Positron Annihilation Lifetime Spectroscopy ◽  
Positron Annihilation Lifetime ◽  
Positron Trapping ◽  
Multiple Components ◽  
Wide Range ◽  
Decay Positron ◽  
Positronium Decay

Herein we demonstrate the specifics of using the positron annihilation lifetime spectroscopy (PALS) method for the study of free volume changes in functional ceramic materials. Choosing technological modification of nanostructured MgAl2O4 spinel as an example, we show that for ceramics with well-developed porosity positron annihilation is revealed through two channels: positron trapping channel and ortho-positronium decay. Positron trapping in free-volume defects is described by the second component of spectra and ortho-positronium decay process by single or multiple components, depending on how well porosity is developed and on the experimental configuration. When using proposed positron annihilation lifetime spectroscopy approaches, three components are the most suitable fit in the case of MgAl2O4 ceramics. In the analysis of the second component, it is shown that technological modification (increasing sintering temperature) leads to volume shrinking and decreases the number of defect-related voids. This process is also accompanied by the decrease of the size of nanopores (described by the third component), while the overall number of nanopores is not affected. The approach to the analysis of positron annihilation lifetime spectra presented here can be applied to a wide range of functional nanomaterials with pronounced porosity.

Recent Applications of High Resolution Electron Microscopy to Crystalline Arrays of Virus Particles

1978 ◽  
Vol 36 (3) ◽  
pp. 470-482 ◽  
Author(s):  
R.W. Horne
Keyword(s):  
Electron Microscopy ◽  
Image Processing ◽  
Analytical Techniques ◽  
Staining Technique ◽  
High Resolution Electron Microscopy ◽  
Optical Diffraction ◽  
Full Potential ◽  
Virus Particles ◽  
Resolution Electron ◽  
Wide Range

The technique of surrounding virus particles with a neutralised electron dense stain was described at the Fourth International Congress on Electron Microscopy, Berlin 1958 (see Home & Brenner, 1960, p. 625). For many years the negative staining technique in one form or another, has been applied to a wide range of biological materials. However, the full potential of the method has only recently been explored following the development and applications of optical diffraction and computer image analytical techniques to electron micrographs (cf. De Hosier & Klug, 1968; Markham 1968; Crowther et al., 1970; Home & Markham, 1973; Klug & Berger, 1974; Crowther & Klug, 1975). These image processing procedures have allowed a more precise and quantitative approach to be made concerning the interpretation, measurement and reconstruction of repeating features in certain biological systems.

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