International Journal of Computational Materials Science and Engineering

The computer analysis of tandem solar cell, c-Si/a-Si:H/$\mu$c-SiGe, is studied within Lumerical FDTD/Device 4.6. The optical characterization is performed in FDTD and then total generation rate is transported into DEVICE for electrical characterization. The electrical characterization of the solar cell is carried out in DEVICE. The design is implemented by staking three sub cells with band gap of 1.12eV, 1.50eV and 1.70eV, respectively. First, single junction solar cell with both a-Si and $\mu$c-SiGe absorbing layers are designed and compared. The thickness for both layers are kept the same. In a single junction, solar cell with a-Si absorbing layer, the fill factor and the efficiency are noticed as $\mathrm{\text{FF}}=78.98\%$, and $\eta =6.03\%$. For $\mu$c-SiGe absorbing layer, the efficiency and fill factor are increased as $\eta =7.06\%$ and $\mathrm{\text{FF}}=84.27\%$, respectively. Second, for tandem thin film solar cell c-Si/a-Si:H/$\mu$c-SiGe, the fill factor $\mathrm{\text{FF}}=81.91\%$ and efficiency $\eta =9.84\%$ have been noticed. The maximum efficiency for both single junction thin film solar cell c-Si/$\mu$c-SiGe and tandem solar cell c-Si/a-Si:H/$\mu$c-SiGe are improved with check board surface design for light trapping.

In the present study, a simplified approach for predicting the deep drawing behavior of adhesive bonded steel blanks using initial geometrical heterogeneities is proposed. In the proposed approach, the influence of adhesive properties on deep drawing behavior of adhesive bonded blanks is predicted by designing and identifying the equivalent geometrical heterogeneities in the base materials constituting adhesive bonded blanks. Thus, the usual practice of representation of adhesive layer and its properties during modeling simulation is eliminated. This approach would help us to overcome the difficulties while incorporating adhesion/adhesive properties during deep drawing simulation. A set of thickness heterogeneity factor ‘$f$’ has been used to predict the effect of hardener to resin (H/R) ratio of adhesive. For instance, in the case of circular-finite groove with diameter of 60mm, it is identified that the cup height during deep drawing evaluated at $f=0.729$, 0.729, 0.666, 0.666 and 0.595 is equivalent to H/R ratios of 0.6:1, 0.7:1, 0.8:1, 0.9:1 and 1:1 of adhesive, respectively. In other words, different adhesive properties are equivalent to different thickness heterogeneity factors ‘$f$’ that should be identified in order to predict the deep drawing behavior of adhesive bonded sheets.

This paper presents the second-order statistics of the nonlinear bending response of elastically supported single-wall carbon nanotube reinforced composite (CNTRC) beam composed of uniformly distributed (UD) and functionally graded (FG) reinforcements in thermal environments with uncertain system properties. The uncertain system properties such as material properties of matrix and SWCNTs, foundation parameters, thermal expansion coefficients are be modeled as uncorrelated Gaussian random variables. The material properties of FG-CNTRCs are assumed to be graded in the beam thickness direction and are evaluated through a micromechanical model. The higher order shear deformation theories (HSDT) with von-Karman nonlinear strain kinematics are used for the mathematical formulation of CNTRCs beam. The thermal effects are also included in the material properties of CNTRCs which are assumed to be temperature dependent and independent. The second-order perturbation technique (SOPT) and Monte Carlo simulation (MCS) via ${\mathrm{\text{C}}}^0$ nonlinear finite element method (FEM) through Newton–Raphason method are proposed to examine the mean, COV and probability density function (PDF) of transverse deflection of the beam. Typical numerical results are presented for the different volume fraction of carbon nanotube, slenderness ratios, boundary conditions, foundation parameters, load parameters, CNTRC distribution, temperature dependent and independent material properties with random system properties. The present outlined approach is validated with the results available in the literature and by employing MCS.

In this paper, the mechanical properties, including elastic properties, deformation mechanism, dislocation formation and crack propagation of graphene/Cu (G/Cu) nanocomposite under uniaxial tension are studied by molecular dynamics (MD) method and the strain rate dependence is also investigated. Firstly, through the comparative analysis of tensile results of single crystal copper (Cu), single slice graphene/Cu (SSG/Cu) nanocomposite and double slice graphene/Cu (DSG/Cu) nanocomposite, it is found that the G/Cu nanocomposites have larger initial equivalent elastic modulus and tensile ultimate strength comparing with Cu and the more content of graphene, the greater the tensile strength of composites. Afterwards, by analyzing the tensile results of SSG/Cu nanocomposite under different strain rates, we find that the tensile ultimate strength of SSG/Cu nanocomposite increases with the increasing of strain rate gradually, but the initial equivalent elastic modulus basically remains unchanged.

To improve efficiency and accuracy of wavelet packet decomposition method modified by simple genetic algorithm (SGA), a novel genetic algorithm, which is based on variance of population and population entropy, is proposed. And then wavelet packet decomposition method is optimized by this algorithm to detect rail cracks. In the optimized method, internal state of population and population diversity are linked up with evolutionary operations to adjust crossover-mutation operators of genetic algorithm. Further, a mathematical model describing fault signal is established, and its parameters are optimized to effectively extract information. The proposed algorithm was tested by test functions and simulated fault signals of rail cracks. The results about simulated fault signals show that convergence probability of proposed algorithm — at best — is 45% higher than that of SGA and 28% higher than that of improved adaptive genetic algorithm (IAGA), and accuracy of crack fault detection reaches above 92%. Meanwhile, the proposed algorithm isn’t prone to stagnation and has fast convergence speed and high accuracy of fault detection. This research not only improves performance of SGA, but also provides a new detection method for fault diagnosis of wheel-rail noise.

Long polymer chains that mainly exhibit thermoplastic properties are recognized to demonstrate excellent thermal and mechanical features at the molecular level. For the purpose of facilitating its study, we present the results of a coarse-grained Molecular Dynamics (MD) and Dissipative Particle Dynamics (DPD) simulations under the Canonical ensemble (NVT) conditions. For each simulation method, the structure, static and dynamic properties were analyzed, with particular emphasis on the influence of density and temperature on the equilibrium of the polymer. We find, after correcting the Soft Repulsive Potential (SRP) parameters used in DPD method, that both simulation methods describe the polymer physics with the same accuracy. This proves that the DPD method can simplify the polymer simulation and can reproduce with the same precision the equilibrium obtained in the MD simulation.

Bitubular structural configurations, where the outer tube is circular, square and curvy square in shape while the inner-tube section is curvy triangular, square and hexagonal in different proposed configurations, are numerically crushed under dynamic axial loading. The crashworthiness effectiveness for changing inner-tube polygonal cross-section for each of the outer tube sections is studied and compared with changing outer tube shape. The deformation plots and energy absorption (EA) parameters such as peak crushing force (PCF) mean crushing force (MCF), energy absorption and crush force efficiency for each case are evaluated. Most of the configurations showed ovalization with low PCF and MCF and moderate crush force efficiency. Afterwards, effects of $L/D$ and $t/R$ on deformation modes and EA are demonstrated by selecting one of the configurations from each group using published experimental results.