Begell House Inc.
Nanoscience and Technology: An International Journal
NST
2572-4258
9
4
2018
MODELING OF SUBGRAIN’S CRYSTALLOGRAPHIC MISORIENTATION DISTRIBUTION
283-297
Nikita S.
Kondratev
Research Institute of Mechanics Lobachevsky State University, 6 Gagarin Ave.,
Nizhni Novgorod, 603600, Russia
Peter V.
Trusov
Perm National Research Polytechnic University, 29 Komsomolsky Ave., Perm,
614990, Russian Federation
At present the actual task of various industries is to create products from metal polycrystals and their alloys with the required properties and characteristics. The processing of such products is generally carried out with intense elastoplastic deformation, and is often accompanied by temperature effects. At the same time, the structure of materials undergoes substantial rearrangements, which leads to a significant change in their properties. An effective tool for solving the problem of creating products with the necessary characteristics is the use of multilevel elastoplastic models that allow one to investigate the internal structure of a material in numerical experiments. In the developed two-level statistical model of inelastic deformation, there is the problem of selecting (forming) heterogeneous elements (subgrains) in the initially approximately homogeneous grain. The main source of inhomogeneity is the appearance of crystallographic misorientation of parts (subgrains) of the original grains with respect to one another. The paper considers the problem of determining the orientation of subgrains in the initial stages of inelastic deformation. The mechanism of formation of incidental cell boundaries as a consequence of the appearance of dislocation walls is considered. The method to model boundaries of this type is proposed. In the reference configuration of deformation, flat sections of the cell boundaries (facets) are randomly assigned according
to the uniform law. It is supposed that some of mobile dislocations "settle" on the prescribed incidental boundaries. It is shown that due to the appearance of cell boundaries the angle of the subgrain's crystallographic misorientation is proportional to the dislocation shears in the grain. Calculations are made of the uniaxial stretching of a copper polycrystal. Satisfactory agreement between
numerical results of the subgrains misorientation distribution with respect to the initial grain and experimental data is shown. The model also makes it possible to take into account the decrease in the number of active slip systems in subgrains during rotation.
A VARIANT OF DESCRIBING ADHESION INTERACTION IN THE PROBE–SAMPLE SYSTEM OF AN ATOMIC-FORCE MICROSCOPE
299-323
V. Yu.
Presnetsova
I.S. Turgenev Orel State University, 95 Komsomolskaya Str., Orel, 302026,
Russian Federation
S. N.
Romashin
I.S. Turgenev Orel State University, 95 Komsomolskaya Str., Orel, 302026,
Russian Federation
L. Yu.
Frolenkova
I.S. Turgenev Orel State University, 95 Komsomolskaya Str., Orel, 302026,
Russian Federation
Vladimir S.
Shorkin
I.S. Turgenev Orel State University, 95 Komsomolskaya Str., Orel, 302026,
Russian Federation
S. I.
Yakushina
I.S. Turgenev Orel State University, 95 Komsomolskaya Str., Orel, 302026,
Russian Federation
The paper presents a variant of describing the adhesion interaction in the probe–sample system of an atomic-force microscope constructed within the framework of the deformable solid mechanics. The variant is based on the concept of nonlocal pair and triple potential interactions of particles of a continuous elastic medium with account for the criteria of thermodynamicity and stability of both the discrete system of interacting material points and the system of infinitesimal particles constituting a continuous medium. In this case, the potentials of interaction of continuous medium particles are considered as the limits of analogous potentials of the interaction of particles forming an infinite sequence of discrete systems with distance between them, their masses, momenta, and energy tending to zero. The parameters of the interparticle potentials and
the characteristics of the adhesive interaction between the sample and the probe are expressed in terms of the characteristics of the elastic state — Young's modulus and Poisson's ratio — under the assumption of their homogeneity, linear elasticity, and the isotropy of their materials. In
order to verify the qualitative and quantitative adequacy, the model developed is used to calculate the dependence of the force of the van der Waals interaction between the probe (platinum) and the sample (graphite) on the distance between them. The results of calculation are in satisfactory
agreement with the available data.
EFFECTS OF VISCOUS DISSIPATION AND HEAT GENERATION/ABSORPTION ON NANOFLUID FLOW OVER AN UNSTEADY STRETCHING SURFACE WITH THERMAL RADIATION AND THERMOPHORESIS
325-341
Alok Kumar
Pandey
Department of Mathematics, Statistics and Computer Science, G.B. Pant University of Agriculture and Technology, Uttarakhand-263145, India; Department of Mathematics, Roorkee Institute of Technology, Roorkee, Uttarakhand-247667, India
Manoj
Kumar
Department of Mathematics, Statistics and Computer Science, G.B. Pant University
of Agriculture and Technology, Pantnagar, Uttarakhand, India 263145
Heat and mass transfer that exerts its influence on nanofluid flow through a heated stretching sheet with thermal radiation, viscous dissipation, and heat generation/absorption is analyzed. The transport model is influenced by Brownian motion and thermophoresis. The governing nonlinear PDEs are converted into a system of nonlinear ODEs by means of supplementary transformations
and then handled numerically from the assisting RKF scheme of the 45th order with shooting procedure. The thermal field and concentration field are presented graphically for values of heat generation/absorption parameter, thermal radiation parameter, thermophoresis parameter, and Eckert number. The Nusselt number and Sherwood number are tabulated. The results of this study show that the heat transfer coefficient decreases with increase in the heat generation/absorption parameter and Eckert number, while the reverse trend is observed for mass transfer rate
for the same pertinent parameters.
MHD MIXED CONVECTION IN TRAPEZOIDAL ENCLOSURES FILLED WITH MICROPOLAR NANOFLUIDS
343-372
Sameh Elsayed
Ahmed
Department of Mathematics, Faculty of Science, Abha, King Khalid University, Saudi Arabia; Department of Mathematics, Faculty of Science, South Valley University, Qena, Egypt
Ahmed Kadhim
Hussein
College of Engineering, Mechanical Engineering Department, Babylon University, Babylon City, Hilla, Iraq
M. A.
Mansour
Department of Mathematics, Assuit University, Faculty of Science, Assuit, Egypt
Zehba A.
Raizah
Department of Mathematics, Faculty of Science for Girls, Abha, King Khalid University, Saudia
Arabia
Xiaohui
Zhang
College of Physics, Optoelectronics and Energy, Soochow University, Suzhou 215000, China
A steady laminar two-dimensional magnetohydrodynamic mixed-convection flow in trapezoidal enclosures filled with water-based micropolar nanofluids is investigated numerically by using the finite difference method. The left and right inclined vertical sidewalls of the trapezoidal enclosure
are maintained at a low temperature. The horizontal top wall is considered adiabatic and moves at a uniform lid-driven velocity, while a part of the bottom wall is subjected to a uniform heat source and the remaining parts of it are considered adiabatic. An external magnetic field at different orientation angles is applied on the left sidewall of the enclosure. The fluid inside the enclosure is a water-based micropolar nanofluid containing different types of solid spherical nanoparticles (Cu, Ag, Al2O3, and TiO2). Parametric studies of the influence of various parameters
such as the Hartmann number, Richardson number, the type of nanofluid, magnetic field orientation angle, dimensionless viscosity, dimensionless length, location of a heat source, solid volume fraction in the fluid flow, and the heat transfer rate have been conducted. Comparisons with
previously published numerical works are performed and good agreement between the results is obtained. It is found that the average Nusselt number increases when the Richardson number decreases and the solid volume fraction increases, while it decreases as the heat source length increases. Moreover, it is observed that the Hartmann number, heat source location, and the dimensionless viscosity have a significant effect on the average Nusselt number.
INDEX, VOLUME 9, 2018
373-376