International Journal of Computational Materials Science and Engineering

In this work, we report the combined experimental and theoretical study on molecular structure and vibrational spectra of nonlinear optical crystal L-alanine cadmium chloride (LACC). The single X-ray diffraction studies have revealed that the compound crystallizes in monoclinic system C2 space group with cell parameters $a=16.270$, $b=7.358$, $c=7.887$ and $Z=4$. FTIR and Raman spectra of the nonlinear optical materials LACC have been recorded and analyzed. The optimized geometric bond length and bond angles are obtained with the help of density functional theory (DFT) (B3LYP) calculation. The optimized geometric bond lengths and bond angles obtained by using DFT show good agreement with the experimental data. Using the natural bond orbital analysis the electronic effect and hydrogen bonding were confirmed. The HOMO–LUMO energy gap and the first order hyperpolarizability were calculated and it supports the nonlinear optical activity of LACC crystal.

Using molecular-dynamics simulation, we study the phase transformations in Fe thin films induced by uni- and biaxial strain. Both the austenitic transformation of a body-centered cubic (bcc) film at the equilibrium temperature of the face-centered cubic (fcc)–bcc transformation and the martensitic transformation of an undercooled fcc film are studied. We demonstrate that different strain states (uni- or biaxial) induce different nucleation kinetics of the new phase and hence different microstructures evolve. For the case of the austenitic transformation, the direction of the applied strain selects the orientation of the nucleated grains of the new phase; the application of biaxial strain leads to a symmetric twinned structure. For the martensitic transformation, the influence of the strain state is even more pronounced, in that it can either inhibit the transformation, induce the homogeneous nucleation of a fine-dispersed array of the new phase resulting in a single-crystalline final state, or lead to the more conventional mechanism of heterogeneous nucleation of grains at the free surfaces, which grow and result in a poly-crystalline microstructure of the transformed material.

A molecular structural mechanics method has been implemented to investigate the vibrational characteristics of single-layer graphene (SLG) with defects. By adopting the lumped mass unit to replace carbon atoms, and the beam element with circular cross-section to mimic C–C covalent bonds, SLG is modeled as a space framework. The simulation results show that the chirality almost has no effect on the natural frequency and the vibration mode of SLG, while boundary conditions have great influences. The influences of defects with different number and location on the natural frequencies are also studied. It is concluded that vibration mode is insensitive to the vacancy defect, small hole and short flaw, but large holes and long flaws can affect the vibration characteristics. So the graphene sheet even with small defect effects might be selected as the nanosensor material as well as pristine graphene. The conclusions in this paper may provide some references for the design of nanosensor.

This paper develops a model to identify the effects of thermal stress on temperature distribution and damage in human dermal regions. The design and selection of the model takes into account many factors effecting the temperature distribution of skin, e.g., thermal conductance, perfusion, metabolic heat generation and thermal protective capabilities of the skin. The transient temperature distribution within the region is simulated using a two-dimensional finite element model of the Pennes’ bioheat equation. The relationship between temperature and time is integrated to view the damage caused to human skin by using Henriques’ model Henriques, F. C., Arch. Pathol. 43 (1947) 489–502]. The Henriques’ damage model is found to be more desirable for use in predicting the threshold of thermal damage. This work can be helpful in both emergency medicines as well as to plastic surgeon in deciding upon a course of action for the treatment of different burn injuries.

Ceramic has a great broad application in high-temperature environment due to its favorable mechanical, antioxidant and corrosion resistance properties. However, it tends to exhibit severe crack or fail under thermal shock resulting from its inherent brittleness. Microstructure property is a vital factor and plays a critical role in influencing thermal shock property of ceramic. The present study experimentally tested and characterized thermal-shock crack and residual strength of ceramic under different quench temperature, while two kinds of alumina ceramics with different grain size are employed. A two-dimensional (2D) numerical model based on statistical mesoscopic damage mechanics is introduced to depict the micro-crack propagation of ceramic sheet under water quenching. The effects of grain size on critical thermal shock temperature, crack characteristics and residual strength are studied. And the microscopic mechanism of the influence of grain size on thermal shock resistance of ceramic is discussed based on the crack propagation path obtained from experimental and simulation results. The qualitative effect and evolution change of grain size on thermal shock property of alumina ceramic will be summarized.

An analysis of the equations used for modeling thermal arsenic diffusion in silicon has been carried out. It was shown that for arsenic diffusion governed by the vacancy-impurity pairs and the pairs formed due to interaction of impurity atoms with silicon self-interstitials in a neutral charge state, the doping process can be described by the Fick’s second law equation with a single effective diffusion coefficient which takes into account two impurity flows arising due to interaction of arsenic atoms with vacancies and silicon self-interstitials, respectively. Arsenic concentration profiles calculated with the use of the effective diffusivity agree well with experimental data if the maximal impurity concentration is near the intrinsic carrier concentration. On the other hand, for higher impurity concentrations a certain deviation in the local regions of arsenic distribution is observed. The difference from the experiment can occur due to the incorrect use of effective diffusivity for the description of two different impurity flows or due to the formation of nonuniform distributions of neutral vacancies and neutral self-interstitials in heavily doped silicon layers. We also suppose that the migration of nonequilibrium arsenic interstitial atoms makes a significant contribution to the formation of a low concentration region on thermal arsenic diffusion.

In the present work, experimental investigation and the numerical analysis are carried out for strength analysis of A356 alloy matrix composites reinforced with alumina, fly ash and hybrid particle composites. The combined strengthening effect of load bearing, Hall–Petch, Orowan, coefficient of thermal expansion mismatch and elastic modulus mismatch is studied for predicting accurate uniaxial stress–strain behavior of A356 based alloy matrix composite. The unit cell micromechanical approach and nine noded isoparametric finite element analysis (FEA) is used to investigate the yield failure load by considering material defect of porosity as fabrication errors in particulate composite. The Ramberg–Osgood approach is considered for the linear and nonlinear relationship between stress and strain of A356 based metal matrix composites containing different amounts of fly ash and alumina reinforcing particles. A numerical analysis of material porosity on the stress strain behavior of the composite is performed. The literature and experimental results exhibit the validity of this model and confirm the importance of the fly ash as the cheapest and low density reinforcement obtained as a waste by product in thermal power plants.