International Journal of Computational Materials Science and Engineering

In this paper, the swirling nanofluid flow which is driven by a rotating bottom disk of a cylindrical container under magnetic field effect and temperature gradient is considered. Effects of electrical conductivity of cylindrical walls on heat transfer enhancement are numerically analyzed. The governing equations that describe the combined problem (magnetohydrodynamics and mixed convection) under the adoptive assumptions are solved numerically by the finite volume technique. Calculations were made for fixed Reynolds number (Re$=$1000), Richardson number (0$\le$Ri$\le$2), aspect ratio ($H/R=2$), Hartmann number (0$\le$Ha$\le$60), and solid nanoparticle (copper) with volume fraction ($\varphi =0.1$). Five cases are considered in this study: (EI-Walls), (EC-Walls), (EC-Bottom), (EC-Top), and (EC-Sidewall). A decrease in the mean Nusselt number was found with the increase of the Richardson number due to stratification layers. These latter limits the heat transfers between the hot and cold zones of the cylinder. The results indicate that the Nusselt number gets bigger within a certain range of Hartmann numbers, and especially when the rotating lid is electrically conducting. Indeed, average Nusselt number decreases while the Hartmann number increase after it exceeds a critical value. Finally, the electrical conductivity of the rotating lid plays an important role in heat transfer enhancement in nanofluid swirling flow.

Hydrogenated amorphous silicon nitride is useful as an anti-reflection coating on solar cells. The addition of hydrogen atoms to amorphous silicon nitride can reduce the dangling bonds that exist on the surface. The objective of this paper is to clarify on the behavior of hydrogen atoms absorbed in silicon nitride during the hydrogenation process at various temperatures. We investigate, in particular, the silicon and hydrogen bonds that are formed by the transfer of electrons from hydrogen to silicon to form ${\text{Si}}^{1-}$, ${\text{Si}}^{2-}$, ${\text{Si}}^{3-}$, and ${\text{Si}}^{4-}$ ions. The conversion of ${\text{Si}}^{1-}$ ions into ${\text{Si}}^{2-}$ ions and then also into ${\text{Si}}^{3-}$ and ${\text{Si}}^{4-}$ occurs during enhancement of the hydrogen atoms absorbed. Hydrogenated amorphous silicon nitride was stabilized through the passivation of dangling bonds of silicon atoms and nitrogen atoms by the absorbed hydrogen atoms. The passivation was indicated by enhancement of over-coordinated silicon and nitrogen atoms as well as the reduction of under-coordinated silicon and nitrogen atoms. It was found that the thermal energy from high hydrogenation temperature was primarily used by hydrogen atoms to diffuse more and to penetrate deeper into silicon nitride rather than being used for the ionization of silicon atoms. Finally, we stress that these reactive molecular dynamic simulations have led to substantial progress in understanding how hydrogen atoms interact with amorphous silicon nitride during hydrogenation.

On account of the significance of entropy generation and bioconvection in biomedical and bioengineering, valuable contributions have been made by scientists in the present decade. The current study explores the impact of entropy generation, bioconvection of microorganisms, and Ohmic heating on the peristaltic transport of Williamson fluid containing molybdenum disulfide and silver nanoparticles through an endoscope with a long wavelength and low Reynolds number assumptions. The second law of thermodynamics is used to examine the entropy generation, and also Ohmic heating effect is used in the system. Between two coaxial tubes, a non-Newtonian Williamson fluid with molybdenum disulfide and silver nanoparticles is considered. The Homotopy perturbation method (HPM) is applied to describe the nonlinear partial differential equations. We were able to arrive at analytical solutions for velocity, nanoparticle concentration, microbes’ density, and temperature. In the end, the impact of distinct physical parameters on temperature, nanoparticle concentration, velocity, microorganism density, entropy generation, Bejan number, and the heat transfer rate was graphically depicted. The significant outcome of the present study is that the impact of the Peclet number enhances the velocity profile. But Peclet number and bioconvection constantly decline the density of motile microorganisms. One more significant outcome is that the Brinkman number declines the entropy generation near the inner tube and in the rest of the part, enhances the entropy generation. Brinkman number enhances the heat transfer rate. These findings have applications in biological sciences, engineering, geothermal energy, and industry, including the construction of microbial fuel cells and bio-convection nanotechnology devices. Microorganisms are beneficial in the degradation of biomaterials, resulting in the production of oxygen and the preservation of human health.

In this paper, geometrical nonlinear flutter analysis of functionally graded carbon nanotube-reinforced composite plates is presented. The governing equations of the system are obtained using the Mindlin plate theory and von Karman geometric nonlinearity. The linear piston theory is utilized to determine the aerodynamic pressure. Applying the Hamilton principle, equations of motion of a system are derived in the matrix form, and then the finite element method is used to obtain the discretized equations. Application of Newmark’s time integration and Newton–Raphson method are used to solve the nonlinear oscillation equations for determining the nonlinear flutter response and critical flow velocity. To check the validity of the present formulation, numerical results are compared with the previous data in the literature. The effects of stiffeners, type carbon nanotube (CNT) and angle of attack of airflow, thickness (ratio h/a) of the plate on critical airflow velocity and nonlinear dynamic response of the SFG-CNTRC plates are studied.

In this paper, a 3D molecular dynamics (MD) simulation is performed to investigate the nanoindentation process, the most frequently used technique to measure mechanical properties such as hardness, of three Al/Mg intermetallic compounds, where Mg is the main element added to pure Al. To further improve the understanding of the mechanical response, in this study, we examine the hardness-strength data for three kinds of typical materials, including $\beta$-Al₃Mg₂ and $\gamma$-${\text{Al}}_{12}$${\text{Mg}}_{17}$ and $𝜀$-${\text{Al}}_{30}$${\text{Mg}}_{23}$ phases with different microstructures. In terms of the observed morphologies around the indentations, the influencing variables of the general link between strength and hardness are described. Accordingly, atomic simulations in this paper are performed under the same loading ($21\times 10^{10}{\mathrm{\text{s}}}^{-1}$) using a spherical diamond indenter. At both the $𝜀$-${\text{Al}}_{30}$${\text{Mg}}_{23}$ and $\gamma$-${\text{Al}}_{12}$${\text{Mg}}_{17}$ phases, we can see that the indenter generates a bigger deformation zone and a greater number of dislocations in the $z$ direction. The simulation findings show that the microstructure has an impact on the shape of the deformation in each phase. After the deformation process, we get the depth-displacement ($P$–$h$) curves to describe the mechanical behavior of $\beta$-Al₃Mg₂, $𝜀$-${\text{Al}}_{30}$${\text{Mg}}_{23}$ and $\gamma$-${\text{Al}}_{12}$${\text{Mg}}_{17}$ phases. From the $P$–$h$ curves, we got the radial distribution function, mechanical properties, such as micro hardness, Yield point and maximum load are determined and presented. According to the findings, the chemical composition of these phases has a considerable impact on their characteristics. These $P$–$h$ curves obtained show a rapid increase in loading up to a maximum. The deformation behavior of −Al₃Mg₂ and −${\text{Al}}_{12}$${\text{Mg}}_{17}$ phases under nanoindentation is slightly identical, and they have also a high elasticity limit, the ability to endure deformation and the characteristic of being very ductile and malleable. While $𝜀$-${\text{Al}}_{30}$${\text{Mg}}_{23}$ phase was shown to be brittle and weak under the same uniaxial nanoindentation loading compared to other phases, it was found that there is a good correlation between the previous simulated studies.

The vibration induced by low-frequency elastic wave reduces the working accuracy of precision instruments. The locally resonant phononic crystal provides a feasible measure for low-frequency vibration isolation because of its bandgap characteristics. In this paper, a locally resonant phononic crystal structure with a broad bandgap is proposed, which consists of a periodic phononic crystal plate with double-sided steel stubs coated by rubber layers. Through finite element analysis, it can be found that the proposed structure can produce a bandgap with 355 Hz bandwidth within the range of 0–500 Hz and isolate vibration in the range of bandgap. By analyzing the local resonance modes of the proposed structure, we further propose the equivalent mass–spring model to predict its bandgap range. The predicted bandgap results from equivalent models of the proposed structure agree well with the results from the finite element analysis. These equivalent models provide an effective and simple method for bandgap optimization of the proposed phononic crystal structure.