Journal of Computational Applied Mechanics
Volume:54 Issue: 3, Sep 2023

Auxetic materials have a negative Poisson's ratio, which is different from most engineering materials. Auxetic materials are used in various fields such as medicine, sports science, sensors and actuators, etc. An auxetic structure is made of several cells in parallel and series. In this paper, the equivalent stiffness of an auxetic cell and structure are analytically extracted. The effect of the geometrical parameters, such as the angle and beam length of the auxetic cell, on auxetic cell and structure equivalent stiffness, are investigated. The extracted equations are verified using the simulation of the auxetic structure in the Abaqus software. In this study, numerical simulation is used in order to study the effect of the parameters of the auxetic cell on its equivalent mass. The results of this study show that changing the geometrical parameters of the auxetic cell, affect the vibration behavior of the auxetic structure. Also, the effect of geometrical parameters of the auxetic structure on the Poisson's ratio is investigated.

This paper presents an analytical solution for stability analysis of thick rectangular functionally graded plates with porosity subjected to in-plane loadings using the higher-order shear and normal deformation plate theory, for the first time. The plate material and its porosity are assumed to vary along the thickness direction. Also, three types of porosity pattern along the thickness are considered. Since the plate structure is not generally symmetry to the mid-plane it is assumed that the in-plane loads are applied to its neutral plane to remove the bending-stretching coupling. Stability equations are derived and then analytically solved for rectangular plates with simple supports using Legendre orthonormal polynomials and Navier’s method to determine the critical buckling load. The results are then compared with estimates made using higher-order shear deformation (HSDT) and classical plate theories (CPT) available in the literature for FG non-porous plates. It is shown that compared to the HSDT, the HOSNDT yields smaller values for the plate critical buckling load and the effect of HSNDT is more important as the plate thickness increases. In addition, it is demonstrated that compared to the uniaxial load, the effect of HSNDT is greater as the plate is subjected to a biaxial compression load. Finally, the effects of the porosity distribution, porosity, power-law index, loading condition, and thickness ratio are studied in detail using HOSNDT. The results show that the porosity effect is greater in smaller values of the power law index parameter.

This paper presents a new mathematical perfect of fractional order to deal with the response of skin tissue subjected to ramp-type heating based on the refined Lord–Shulman generalized thermoelasticity model. Three different models; the classical, the simple Lord–Shulman as well as the refined Lord–Shulman will be discussed. The governing equivalences of the present three models are attained. The general solution for the initial and boundary condition problem is found by employing the Laplace transform approach and its inverse. Numerical results are represented in figures with a comparison to the different theories with different values of fractional order to discuss the impact of the fractional order on temperature, displacement, and dilatation distributions. The effect of ramp-type heat is studied numerically and graphically on distributions of temperature, displacement, and dilatation according to different theories.

Antibacterial activity of silver nanoparticles with spherical or cubic shapes in medical science will render it attractive. Considering the physical characteristics like thermal features as crucial factors are essential for choosing nanospheres or nanocubes with respect to operating temperature and stability. Therefore, this research probes the melting process, the surface premelting points (Tsm), the complete melting point (Tm), the phase transition, and the specific heat capacity at a constant volume (Cv) of silver nanospheres and nanocubes via a molecular dynamics approach. Regarding these aims, different approaches have been employed to achieve high accuracy. The results indicate that the geometry of nanoparticles dramatically influences the Tsm and Tm, and nanocubes have lower Tsm and Tm than nanospheres. Moreover, the nanocubes are melted from corners toward the cube center while the nanospheres melt in the radius direction. In contrast, Cv of silver nanospheres and nanocubes is almost identical, demonstrating that the Cv is independent of geometry. In addition, the values of Cv for the nanoparticles are close to the bulk value, which indicates that by changing the dimension of silver from bulk to nanoparticles, the specific heat capacity will not change, and this value is an intensive property.

The high intensity focused ultrasound (HIFU) has been proved to be effective in local tumor ablation. Although HIFU utilization in ablation of liver cancer with single layer simulation is studied before, the procedure multi-layer numerical simulation, to the best of author knowledge, has not been conducted. In the present study, computational modeling of the HIFU with multi-layer simulation was carried out to determine the treatment effectiveness. The homogeneous Westervelt equation and bio-heat Pennes equation are solved by COMSOL software to determine the acoustic pressure and temperature distribution respectively. The results show that increasing the transducer frequency by keeping other parameters constant would increase the maximum acoustic pressure and the pressure increase depends on the square of the frequency increase. Also, the maximum tissue temperature increases intensely with respect to the frequency increase. The effect of changing the amplitude of the ultrasonic transducer, the duration of the wave radiation and considering multi-layer tissue were investigated. Amplitude change directly changes the maximum pressure and the maximum temperature increase depends on the square of the amplitude increase.

The Kaup-Newell system describes the pulse propagation in optical fibers. This paper applies the semi-inverse method to construct the system’s variational formulations, two trial-variational formulations with an unknown function are established, and a detailed derivation is given to determine the unknown function. Finally, the Kaup-Newell system with two variables is converted to a partial differential equation with only one variable.

This article delves into the interpretation of the Lorentz force's impact when employing the Carreau hybrid nanofluid model with infinite shear rate viscosity over a stretching sheet, which incorporates porous medium. This model is highly effective in elucidating various non-Newtonian fluid behaviors, encompassing shear thinning and thickening properties. The governing equations consist of coupled nonlinear PDEs, which are transformed into a set of coupled nonlinear ODEs using similarity transformations. These equations are then numerically solved using a MATLAB built-in solver (bvp4c). Different characteristics of the considered flow of various parameters, such as the magnetic parameter, porous media parameter, Weissenberg number, stretching parameter, ratio parameter, coefficients space, and heat source/sinks, on temperature and velocity profiles, which are presented graphically. Additionally, the impacts of these parameters on the skin-friction coefficient and Nusselt number are tabulated. The Key findings suggest that, the higher values of the porous media parameter, magnetic parameter, Weissenberg number, and stretching parameter led to a decrease in velocity by 67.12% and 75.49% on average. Moreover, the velocity profile, Nusselt number, and skin friction coefficient are higher for the Al2O3/KO-based nanofluid compared to the Al2O3+MoS2/KO-based hybrid nanofluid. Also, the boundary layer of the hybrid nanofluid is observed to be hotter than that of the single nanoparticle nanofluid.

Spurs are hydraulic structures used to protect riverbanks from erosion and to concentrate the flow on the river axis. As the flow approach the spurs, discontinuous in the streamlines are occurred and vortices form before the spurs. By placing the spurs in an open channel, scours occur before and after the spurs due to changes in flow conditions and velocities. Determination of velocity distributions around the spur accurately is extremely important for spur design. For a sustainable and hydraulically efficient spur design, flow velocities, flow conditions, sediment characteristics and stream morphology around the spur should be well investigated. In this study, the changing flow velocities and flow patterns on the upstream side of two spurs with were investigated. Two spur which have same geometry placed in an open channel system at an angle of 90o with the side wall. For 2 different discharge values (Q=17.66 lt/sn and Q=15.27 lt/sn), 3-Dimensional velocity measurements were made with ADV (Acoustic Doppler Velocimetry) at 20 different points on the upstream side of the spurs. Velocity values obtained from the experiments were compared with the numerical models and gave consistent results with the numerical models. With these obtained velocity profiles, flow patterns are investigated.

In the present article, the theory of linear thermoelasticity without energy dissipation is addressed from the perspective of the analysis of the spatial evolution of harmonic vibrations in time, in the context of a porous micropolar media. Some preliminary identities are determined that will lead to estimates of the harmonic vibration amplitude, some of these estimates being consequences of the distance influence from the disturbed base, provided that a certain critical value for the vibration frequency is considered.

This paper presented a preventive maintenance scheduling model to optimize the cost and improve the effective age of machines in complex repairable systems. The objective function of the developed model is to minimize the total maintenance costs while maintaining a defined level of availability and reliability. The maintenance costs include random failure cost, repair cost, replacement cost, and total planned downtime cost. Multilevel preventive maintenance actions such as inspection, repair and replacement are considered through the whole planning horizon. A metaheuristic algorithm like genetic algorithm (GA) was developed using a MATLAB program to provide a near-optimal solution for the optimization model. The proposed mathematical model was applied to a Cathodic Protection System of Gas Distribution Steel Network and the results show a reduction in the total maintenance cost by 36%.