International Journal of Computational Materials Science and Engineering

Electronic properties of orthorhombic SSM (${\mathrm{\text{Sm}}}_{0.5}{\mathrm{\text{Sr}}}_{0.5}{\mathrm{\text{MnO}}}_3)$ and monoclinic SSM (${\mathrm{\text{Sm}}}_{0.8}{\mathrm{\text{Sr}}}_{0.2}{\mathrm{\text{MnO}}}_3)$ are investigated using the first-principles calculation. The half-metallic behavior that leads to the mixed ionic and electronic conductivity (MIEC) property is identified in orthorhombic SSM. In addition, the strong covalent bonding between $\mathrm{\text{Mn}}$-p and $\mathrm{\text{O}}$-s orbitals of orthorhombic SSM is identified from the PDOS plot. The strong covalent bonding enhances the ${\mathrm{\text{O}}}_2$ molecular adsorption on Mn atom. On the other hand, monoclinic SSM shows the pure conducting behavior and there is no covalent bonding between Mn and O atoms. Thus, the results suggest that the half-metal Sm${}_{0.5}$Sr${}_{0.5}$MnO₃ might be a suitable cathode material for intermediate-temperature solid oxide fuel cells.

In this paper, a micromechanics method is developed to evaluate effective coefficients of piezoelectric fiber-reinforced composites. An exact solution is derived for effective elastic, piezoelectric and dielectric coefficients of such piezocomposites subjected to the applied load in the direction transverse to the fiber orientation. Simultaneously, based on finite element method, a numerical study is performed on a representative volume element of such piezo composite containing fiber in square packing arrangement. The finite element method provides a numerical solution to evaluate effective elastic, piezoelectric and dielectric coefficients for discrete volume fraction of fiber, the range being 0.1–0.6 for this study. The results are interpolated to understand the overall behavior of such piezocomposites. The results obtained from the micromechanics method and the finite element method are compared with the results obtained from other models based on strength of materials method given in the literature. It is observed that the method developed in this study provides better results for effective coefficients susceptible to fiber packing arrangements.

Wood fibers are industrially attractive low-cost natural materials that offer good mechanical properties. It is, however, extremely difficult to experimentally determine the elastic properties of single wood fibers due to the structural complexity and variability of basic properties. We propose a three-step finite element (FE)-modeling algorithm to predict the elastic constants of a single wood fiber. The model is based on calculating the elastic constants of the fiber in three consecutive length scales including nanostructure of cellulose microfibrils (25–30nm), ultrastructure in the fiber wall layers (2–3$\mu$m) and single wood fibers (30–40$\mu$m). The results for a given set of parameters are compared to previous studies with good agreement. The work exhibits its novelty through the model’s robustness and potential for industrial applications. It merely requires three essential inputs — chemical composition and bulk density of fiber and microfibril angle of $S_2$ wall layer, but is capable of predicting reasonably accurately the elastic constants of a wood fiber completely without any required model preprocessing or meshing like common commercial FE method software packages. Furthermore, the validated model is used to perform a parametric study. We have found that cellulose content has positive correlations with almost all the elastic parameters — relatively strong for $E_A,E_T$ and $G_T$, but weaker for ${\nu }_T$. Lignin and hemicellulose have the greatest influence on $G_A$ and ${\nu }_A$. The bulk density of fiber is shown to affect all elastic constants except the longitudinal elastic modulus.

Nickel super alloys like Inconel 718 characterize a significant metal part in the structures of aircraft and engine components. The high reliability levels are the major conditions during the manufacturing of these essential structural components in aerospace production. Surface integrity is the most important factor considered for estimating the quality of machined surfaces in term of finishing as well as strongly effect on the corrosion behavior of the machined surface. In this study, three-dimensional (3D)-finite element (3D-FE) simulations were accomplished to determine induced residual stresses in machined Inconel 718 alloy. 3D simulations were executed in the sequential successive method using the design of experiments (DOEs) based on Taguchi L₉ technique. Subsequently, a veritable turning was implemented based on the selected Taguchi design to validate the simulation results. Also, the efficiency of independent parameters (cutting speed, feed rate, and depth of cut) on the surface integrity (surface roughness, microhardness, induced residual stresses), and corrosion rate of the machined surface were explored experimentally. Based on analysis of variance (ANOVA), it was obtained that the feed rate is the most relevant factor related to surface roughness and corrosion rate while cutting speed is the most relevant factor related to microhardness and induced residual stresses. The analyzed polarization curves confirmed that the reducing surface roughness and increasing induced compressive residual stresses are robustly related to enhancing the corrosion behavior of Inconel 718. Robust agreement was detected between the predicted and measured data. The optimal values of independent parameters that led to optimal surface integrity and minimum value of corrosion rate were found. Based on the revealed simulation results, the 3D-FE simulation of the turning process afforded consistent data as compared to experimental measurements for the wide range of induced residual stresses.

Grain boundary (GB) plane rotation, one of the GB engineering mechanisms, was investigated using the activation–relaxation technique by molecular dynamics simulation. The simulation systems considered in this work are bicrystals with Lennard-Jones-type interatomic potential. The systems of four GB types established are symmetric (SYM), asymmetric (ASYM), symmetric zigzag (SZ), and high-angle zigzag (HZ) models. Of the first two models, $\mathrm{\Sigma }$5 (310) for SYM and $36.87^{\circ }$ tilted for ASYM particularly provided reference atomic potential energy distributions and structures at minimum energy state at 0 K. The characteristic of SYM is the discrete atomistic potential distributions which are distinct from ASYM. The other two models based on zigzag-like GBs were created by rotating GB planes about [001] at the center of a $\mathrm{\Sigma }$5 (310)GB system for the SZ case and a high-angle GB system for the HZ case. Simulation results show that the initially tilted GBs kinetically transferred to relaxed states for shorter-length GBs through a series of curved GBs. The GBs consist of different combinations of order defect segments, amorphous regions, and defect-free regions. A mechanism proposed is the GB plane rotation, the rate of which is structure-dependent. A low-$\mathrm{\Sigma }$ coincidence site lattice boundary section can stabilize the systems at a specified metastable state.

The novel stability solutions of unsupported conical slope in anisotropic and inhomogeneous clays utilizing the lower-bound (LB) and upper-bound (UB) finite-element limit analyses (FELA) are proposed in this paper. The anisotropic undrained shear (AUS) model and linear increasing undrained shear strength are employed to determine the anisotropic and inhomogeneous soil behavior, respectively. The stability factor $N$ is obtained with the variations of dimensionless parameters including the ratio of anisotropic ($r_e)$, the rate of increasing undrained shear strength ($m)$, the ratio between the height and the radius at the bottom slope ($H$/$b)$, and the inclination angle of slope ($\beta )$ provided in sample charts. The failure patterns of conical slope considering the affected parameters are also obtained and described.