International Journal of Computational Materials Science and Engineering

Modern aerostructures are predominantly of curved construction characterized by a skin and stiffeners. The latest generation of large passenger aircraft also mostly uses composite materials in their primary structure and there is trend toward the utilization of bonding of subcomponents. A stiffener is a simple beam attached to the skin to support the applied load. The stiffeners are provided to improve the bending stiffness of the panel which then improves the structural efficiency. Metals, unlike composites, offer plasticity effects to evade high stress concentrations during postbuckling. Under compressive load, composite structures show a wide range of damage mechanisms. A pre-damaged configuration is loaded to study the effect of delamination location and mode for delamination initiation and propagation. A parametric study is conducted to investigate the effect of the location of the delamination propagation when delamination is embedded inbetween plies of the stiffener, with the cases (i) delamination embedded at front and inbetween plies of the stiffener, (ii) delamination embedded at middle and inbetween plies of the stiffener, (iii) delamination embedded at the end and inbetween plies of the stiffener. Further, the influence of the location of the delamination in between plies of stiffener on load carrying capacity of the panel is investigated. The effect of delamination location on crack growth and collapse behavior is analyzed using analysis tool. The effect of delamination location on crack growth and collapse behavior is analyzed with numerical method of Virtual Crack Closure Technique.

The Grunwald formula is the traditional method to deal with Riemann–Liouville fractional derivative, while its convergence is only $O(h)$. In this paper, a high-order polynomial approximation is presented for the Riemann–Liouville fractional derivative. The quadratic polynomial functions and their fractional derivatives with explicit expressions are constructed to approximate the fractional derivative instead of Grunwald formula or shifted Grunwald formula. We proved that this technique has convergence of $O(h^{3-\alpha })$. Based on the MLS approximation and the high-order polynomial approximation and center difference method, a meshless analysis is proposed for the two-dimensional two-sided space-fractional wave equations (SFWE). The SFWE is found to be very adequate in describing anomalous transport and dispersion phenomena. In the meshless method, the trial function for the SFWE is constructed by the MLS approximation and the Riemann–Liouville fractional derivative is approximated by the high-order polynomial approximation, and the essential boundary conditions can be directly and easily imposed on as finite element method. This technique avoids singular integral, and has high accuracy and efficiency. Numerical results demonstrate that this method is highly accurate and computationally efficient for space-fractional wave equations.

A size-dependent shell model which accounts for geometrical imperfection sensitivity of the axial postbuckling characteristics of a cylindrical nanoshell made of functionally graded material (FGM) is proposed within the framework of the surface elasticity theory. In accordance with a power law, the material properties of the FGM nanoshell are supposed to vary through the shell thickness. In order to eliminate the stretching-bending coupling terms, the change in the position of physical neutral plane corresponding to different volume fractions is taken into account. Based upon the virtual work’s principle, the non-classical governing differential equations are derived and then deduced to boundary layer-type ones. After that, a perturbation-based solution methodology is employed to predict the size dependency in the nonlinear instability of perfect and imperfect axially loaded FGM nanoshells with various values of shell thickness, material property gradient index and different uniform temperature changes. It was seen that for thicker FGM nanoshells in which the surface free energy effects diminish, the influence of the initial geometric imperfection on the critical buckling load is higher than its influence on the minimum load of the postbuckling domain. It is also found that through reduction of the surface free energy effects, the influence of material property gradient index on the critical end-shortening of FGM nanoshell decreases.

Many cells use oscillations in calcium concentration to transmit messages. These oscillations largely depend on the influx of calcium into cytosol from endoplasmic reticulum (ER) and plasma membrane (PM) through various channels and pumps. To analyze the influence of transfer of calcium between different cellular compartments, we develop a mathematical model of calcium dynamics in fibroblast cell. The model involves three important physiological parameters $J_{\mathrm{\text{PM}}},J_{\mathrm{\text{ER}}}$, and excess buffer approximation (EBA). Finite difference method has been employed to obtain the solution. A computer program has been developed in MATLAB 7.10 for the entire problem and numerical results have been used to study the effects of buffers, ER and PM fluxes on spatial and temporal calcium patterns required by the cell to perform specific cell function.

Head impact with bonnet is one of the major causes for pedestrian severe injury or fatality in car accidents. This paper proposes a multidisciplinary design optimization method for bonnet inner based on pedestrian head protection along with bonnet stiffness requirement. A finite element (FE) model of a child headform impactor is developed and verified via simulation according to Global Technical Regulation No. 9 (GTR No. 9). Static stiffness analysis and headform collision simulation against one impact point for a particular bonnet are implemented. Parametric design and optimization analysis are carried out. Optimization solution significantly achieves a better head protection effect, which clearly affirms the feasibility of the proposed multidisciplinary optimization method and provides a reference approach to optimal design of engine bonnet inner.

Using Perdew–Burke–Ernzerhof $+U$ formalism, we present a systematic study of the magnetic phase stability, mechanical properties, electronic density of states and band gaps of actinide dioxides (${\mathrm{\text{AnO}}}_2,\mathrm{\text{An}}=\mathrm{\text{Actinide elements}}$). Relativistic effects are also considered via the spin orbit coupling. The $5f$ electrons behavior has been investigated as a function of the Coulomb repulsion $U$. Lattice parameters, elastic constants and band gaps of ${\mathrm{\text{AnO}}}_2$ are consistently in good agreement with the available experimental data. From $\mathrm{\text{GGA}}+U+\mathrm{\text{SO}}$ calculations, all ${\mathrm{\text{AnO}}}_2$ are found to be semiconductors or insulators. Our results show that the strong correlation treatment by the Coulomb potential and the spin orbit interactions are necessary to predict the accurate electronic structure of this series of materials.

The problem of phase velocities and attenuations of plane body waves and its reflection from a stress-free surface has been investigated in the micropolar porous materials. The amplitude and energy ratios of reflected waves are obtained analytically. The effect of inertial coefficients in the propagation of plane body waves is computed numerically for a particular model.

The temperature variation of phonon drag thermoelectric power $S_{\mathrm{\text{ph}}}^{\mathrm{\text{drag}}}(T)$ is computed within the relaxation time approximation for high temperature MgB₂ superconductors. The phonon drag thermoelectric power ($S_{\mathrm{\text{ph}}}^{\mathrm{\text{drag}}})$ in normal state of MgB₂ superconductors dominates and is an artifact of strong phonon-impurity and phonon scattering mechanism. The carrier diffusive thermoelectric power is explored when heat transfer is limited by the scattering of phonons from defects, grain boundaries, phonons and charge carriers. The carrier diffusion contribution to the thermoelectric power ($S_c^{\mathrm{\text{diff}}})$ is analyzed keeping in mind the inherent two energy gaps. The conductivity within the relaxation time approximation for $\pi$ and $\sigma$ band carriers has been taken into account ignoring a possible energy dependence of the scattering rates. Such an estimate sets an upperbound on $S_{\mathrm{\text{ph}}}^{\mathrm{\text{drag}}}$ and is about 50% of total heat transfer at room temperature. Both these channels for heat transfer are added and $S_{\mathrm{\text{total}}}$ starts departing from linear temperature dependence at about 150K, before increasing at higher temperatures weakly. It is shown that the behavior of the $S(T)$ is determined by competition among the several operating scattering mechanisms for the heat carriers and a balance between carrier diffusion and phonon drag contributions. The numerical analysis of thermoelectric power in the metallic phase of MgB₂ shows similar results as those revealed from experiments. The anomalies reported experimentally are well accounted in terms of the scattering mechanism by phonon drag and carrier scattering with impurities.

The wire mesh of a space mesh reflector antenna is a core component that reflects electromagnetic waves, greatly influencing the functions of the antenna. Due to the complex weaving structure of the wire mesh, there are thousands of contact nodes per square meter. Therefore, modeling and analyzing the wire mesh becomes very difficult. It is both time-consuming and labor-intensive to calculate the contact force of the wire mesh. In this paper, fast contact force calculation for a wire mesh based on support vector machine (SVM) was developed. First, the wire mesh was discretized into small-sized wire meshes with the same shape. Then, the contact forces of the discretized wire meshes with different boundary conditions can be obtained by the finite element method. Afterwards, a (SVM) model was established based on a small part of the contact forces. Finally, the accuracy and efficiency of the fast calculation model was validated through the numerical examples.