Begell House Inc.
Nanoscience and Technology: An International Journal
NST
2572-4258
10
1
2019
MULTILEVEL MODELS OF POLYCRYSTALLINE METALS: COMPARISON OF RELATIONS DESCRIBING THE CRYSTALLITE LATTICE ROTATIONS
1-20
Alexey I.
Shveykin
Perm National Research Polytechnic University, 29 Komsomolsky Ave., Perm,
614990, Russian Federation
Peter V.
Trusov
Perm National Research Polytechnic University, 29 Komsomolsky Ave., Perm,
614990, Russian Federation
Multilevel models of materials give an explicit description of the physical mechanisms, evolution of material structure, and physical and mechanical properties in inelastic deformation. This allows one to apply such models to improve the existing technologies of mechanical treatment (including
the ones for submicrocrystalline and nanocrystalline materials) and develop some new ones. A key point in multilevel modeling of polycrystalline metals and alloys is the formulation of kinematic and constitutive relations at the mesolevel (the level of individual crystallites),
which would apply to large displacement gradients peculiar to most processes of thermomechanical treatment of metals and alloys. Various formulations of the constitutive mesolevel models used in multilevel models of polycrystalline metals and alloys are considered. These are the relations in the unloaded configuration in the finite form, which are based on the motion decomposition
with an explicit separation of the motion of the moving coordinate system, and the relations written in the rate form in the current configuration. The relationships used in these formulations to describe the rotations of the crystallite lattices are analyzed and compared. The
analysis reveals the equivalence or closeness (in the sense of the response to be estimated) of the spins under consideration (with the exception of the logarithmic spin). The results of numerical calculations carried out for a polycrystal under arbitrarily chosen kinematic impacts lend support to the analytical conclusions.
THERMODYNAMIC ANALYSIS OF THE STABILITY OF NANOBUBBLES IN WATER
21-27
Semen I.
Koshoridze
Institute of Applied Mechanics of Russian Academy of Sciences, 7
Leningradsky Ave., Moscow, 125040, Russia
Yu. K.
Levin
Institute of Applied Mechanics of Russian Academy of Sciences, 7
Leningradsky Ave., Moscow, 125040, Russia
Taking into account the influence of the chemical potential of the components in the gas phase and water, the characteristic parameters of stable nanoscale bubbles (charge, pressure, density of adsorbed ions) in an aqueous medium are determined. It is shown that on reduction of a charge of a nanobubble the radius of its steady state decreases. The adsorbed ions occupy 0.1% of the
surface area of a nanobubble with a radius of 100 nm. The main contribution to the pressure gives water vapor. The total pressure of nitrogen and water vapor in it does not exceed a fraction of a percent at 1 atm.
NUMERICAL INVESTIGATION OF NANOFLUID HEAT TRANSFER IN AN INCLINED STRETCHING CYLINDER UNDER THE INFLUENCE OF SUCTION/ INJECTION AND VISCOUS DISSIPATION
29-49
Shikha
Kandwal
Department of Mathematics, Statistics and Computer Science, G.B. Pant University
of Agriculture and Technology, Pantnagar, Uttarakhand, India 263145
Ashish
Mishra
Department of Mathematics, Statistics and Computer Science, G.B. Pant University of
Agriculture and Technology, Pantnagar, Uttarakhand, India-263145
Manoj
Kumar
Department of Mathematics, Statistics and Computer Science, G.B. Pant University
of Agriculture and Technology, Pantnagar, Uttarakhand, India 263145
The objective of the current analysis is to study the influence of heat generation/absorption and viscous dissipation on MHD flow of a water-based nanofluid containing silver nanoparticles in an inclined porous cylinder in the presence of suction/injection. The basic PDEs are converted into nondimensional ODEs by utilizing suitable transformations and described numerically by
fourth-fifth-order Runge–Kutta–Fehlberg (RKF) procedure via the shooting method. The influence of related parameters on momentum and thermal behavior is scrutinized through the graphs. The values of Nusselt number and skin friction are presented in tabular form. The upshots show that
the thermal boundary layer thickness increases on increase in the values of the Eckert number and heat generation/absorption parameter, whereas the opposite trend is detected for the suction/injection parameter.
EFFECT OF SURFACE TENSION FORCES ON CHANGES IN THE SURFACE RELIEF OF THE ELASTOMER NANOCOMPOSITE
51-66
Roman I.
Izyumov
Institute of Continuous Media Mechanics, Ural Branch of the Russian Academy
of Sciences, Perm, Russian Federation
A. L.
Svistkov
Institute of Continuous Media Mechanics, Ural Branch of the Russian Academy
of Sciences, Perm, Russian Federation
It is proposed to simulate the action of surface tension forces by creating a thin elastic layer on the surface of the material. It is shown that the layer should be considered as an incompressible medium. The changes in the volume of the elastic material are possible only artificially by changing the value of a special parameter that allows one to get the desired effect of the material surface. It is shown that the mechanical properties of the elastic layer should be determined by the refined Neo–Hookean potential. It has been established how the parameters of the potential and the layer thickness are related to the value of the surface tension coefficient. An example of computational modeling the influence of the surface effects on changes in the relief of an elastomeric
sample is given. Solid particles of spherical shape covered by a thin layer of a binder are located near the sample boundary. It has been established that the curvature of the material surface leads to the deformation of the elastomeric matrix at the nanoscale level of the material near its boundary with the environment. This deformation is the result of the action of the surface tension forces. This phenomenon should be taken into account during the atomic force microscopy analysis of the structure and properties of elastomeric nanocomposites.
THE POSSIBILITY OF FORMATION OF SURFACE AND BULK NANOBUBBLES
67-77
Semen I.
Koshoridze
Institute of Applied Mechanics of Russian Academy of Sciences, 7
Leningradsky Ave., Moscow, 125040, Russia
Yu. K.
Levin
Institute of Applied Mechanics of Russian Academy of Sciences, 7
Leningradsky Ave., Moscow, 125040, Russia
A thermodynamic analysis of changes occurring in the Gibbs potential of the system during the formation of surface and bulk equilibrium nanobubbles is carried out. The roughness of the water–solid interface, the charge of nanobubble, and Kelvin's capillary formula are taken into account.
It is shown that the Gibbs potential is always positive and increases monotonically with the bubble radius. This means that in the nanoscale range neither critical nor equilibrium
nanobubbles can be present.
ON ANTIPLANE DEFORMATIONS OF AN ELASTIC MATERIAL WITH RIGID FIBERS CONSIDERING SURFACE ENERGY AND NONPERFECT CONTACT
79-87
Daria
Andreeva
Aberystwyth University, Ceredigion SY23 3BZ, Wales, UK
Wiktoria
Miszuris
Aberystwyth University, Ceredigion SY23 3BZ, Wales, UK
Gennady
Mishuris
Institute of Mathematics and Physics
Aberystwyth University, Ceredigion SY23 3BZ, Wales, UK
Victor A.
Eremeyev
Gdansk University of Technology, 80-233 Gdansk, Poland
Within the linear Gurtin–Murdoch model of surface elasticity we consider the antiplane deformations in an elastic matrix with a rigid cylindrical fiber influenced by external force. The influence of the surface elastic moduli on the stress distribution and adhesion force is analyzed.
FORMATION OF CARBON NANOTUBE ROPES AND THEIR EFFECT ON THE PROPERTIES OF POLYMER NANOCOMPOSITES
89-95
Georgii V.
Kozlov
Kh.M. Berbekov Kabardino-Balkarian State University, 173 Chernyshevsky
Str., Nal'chik, 360000, Russia
Yulia N.
Karnet
Institute of Applied Mechanics, Russian Academy of Sciences,
7 Leningradsky Ave., Moscow, 125040, Russian Federation
I. V.
Dolbin
Kh.M. Berbekov Kabardino-Balkarian State University, 173 Chernyshevsky
Str., Nal'chik, 360000, Russia
A. N.
Vlasov
Institute of Applied Mechanics, Russian Academy of Sciences,
7 Leningradsky Ave., Moscow, 125040, Russian Federation
Carbon nanotubes represent a unique nanofiller with exceptional mechanical properties and a high degree of anisotropy. These characteristics determine the presence of two types of aggregation for such a nanofiller, namely, the formation of ropes (bundles) of individual nanotubes and
formation of their annular structures. Estimates made within the percolation model have shown that each rope of carbon nanotubes in polyamide-6-based nanocomposites consists of several hundred individual nanotubes. In turn, the formation of such ropes has a critical effect on formation of annular structures of carbon nanotubes, since an increase in the diameter of ropes results in an increase in the radius of these annular structures. This effect determines both the level of interfacial adhesion in polymer nanocomposites and their final mechanical characteristics. It has been shown that an increase in the number of carbon nanotubes per one rope reduces its specific surface and the fractal dimensionality of the surface of ropes, which ultimately determines the decrease in the reinforcement degree of polymer/carbon nanotubes nanocomposites. The thermodynamic
analysis of carbon nanotubes interactions has shown that these interactions are significantly higher than similar interactions between polymer macromolecules. This effect determines the formation of carbon nanotube ropes already at the stage of their production. The obtained results suggest that individual carbon nanotubes with a large radius of their annular structures can produce the greatest effect in reinforcement of polymer nanocomposites.