Perforation process of a novel ceramic/composite panel including alumina-silicon carbide (Al2O3-SiC) nanocomposite as the front plate and ultra-high molecular weight polyethylene laminated composite (Dyneema® HB25) as the back-up impacted by a tip tapered penetrator has been analyzed based on LS-Dyna and HyperMesh codes. In order to balance the competing requirements posed by thickness, weight, cost and performance, a finite element (FE) simulation has been developed with well-developed material models. A two-dimensional, dynamic-explicit and Lagrangian model has been considered. The perforation process has been investigated for three different thicknesses of the ceramic plate. The Johnson-Cook, Johnson-Holmquist and Orthotropic-Elastic material models have been used for the penetrator, ceramic, and composite, respectively. The FE results, which have a good agreement with available experimental data, show that with the increase in the ceramic thickness, ceramic's fracture conoid as well as elasto-plastic deformation of fibers increase while fiber breakage and dishing of the composite layers diminish. In addition to saving cost and time, the FE simulation results can be useful as a fairly accurate prediction tool for the designing of lightweight body protective panels with desired impact resistance performance and eligible blunt trauma of the back-up.

The present study deals with the affected behaviour of SH-wave propagation through a viscoelastic layer sandwiched between an anisotropic porous layer of finite thickness and an isotropic half space. The sandwiched viscoelastic layer is considered as heterogeneous medium of finite thickness and isotropic half-space is considered as initially stressed medium. The method of separation of variables has been applied to obtain the dispersion equation of SH-wave in their respective media. The obtained complex dispersion relation has been separated into real and imaginary parts. Moreover, the dispersion relation has been satisfied with the classical condition of Love waves. The effects of heterogeneity, attenuation constant, dissipation factor of viscoelasticity, initial stress (compressive), thickness ratio of two layers and porosity on the propagation of SH-waves have been shown by number of graphs. Graphs have been plotted for the dimensionless phase and damping velocity on the propagation of SH-waves with respect to the dimensionless real wave number. The results may be useful to explore the nature and peculiarity of SH-wave propagation in the viscoelastic structure.

The present paper examines the thermal buckling of nonlocal magneto-electro-thermo-elastic functionally graded (METE-FG) beams under various types of thermal loading namely uniform, linear and sinusoidal temperature rise and also heat conduction. The material properties of nanobeam are graded in the thickness direction according to the power-law distribution. Based on a higher order beam theory as well as Hamilton's principle, nonlocal governing equations for METE-FG nanobeam are derived and are solved using Navier type method. The small size effect is captured using Eringen's nonlocal elasticity theory. The most beneficial feature of the present beam model is to provide a parabolic variation of the transverse shear strains across the thickness direction and satisfies the zero traction boundary conditions on the top and bottom surfaces of the beam without using shear correction factors. Various numerical examples are presented investigating the influences of thermo-mechanical loadings, magnetic potential, external electric voltage, power-law index, nonlocal parameter and slenderness ratio on thermal buckling behavior of nanobeams made of METE-FG materials.

Acceleration-factor (AF) equations have been developed to rapidly predict product lifetime, and the most widely used equation is Norris-Landzberg (N-L) equation. In recent years, some researchers have found that the current AF equation does not accurately predict the experimental results for thermal cyclic loading at high ramp rates; indeed, it may yield the opposite results, due to the changing effect of the solder strain rate at different ramp rates. Modifying the current AF equation to better assess product reliability has thus become an important task for researchers.

In this study, a novel AF equation was developed from a wafer level chip-scale package (WLCSP) under different thermal cyclic loadings. The frequency term used in the N-L equation was replaced with a new term in the proposed AF equation to distinguish between the effects of ramp rate and dwell time under thermal cyclic loading conditions. Proposed AF equation showed a high level of correlation with the simulation and test results for various thermal cyclic loadings. In addition, the proposed AF equation was validated by confirming the consistency of its results with experimental data on a range of packages and thermal-cycling profiles reported in the literature.

In this study, a methodology to design frame-like periodic solids for isotropic symmetry by appropriate sizing of unit-cell struts is presented. The methodology utilizes the closed-form effective elastic constants of 2D frame-like periodic solids with square symmetry and 3D frame-like periodic solids with cubic symmetry, derived using the homogenization method based on equivalent strain energy. By using the closed-form effective elastic constants, an equation to enforce isotropic symmetry can be analytically constructed. Thereafter, the equation can be used to determine relative unit-cell strut sizes that are required for isotropic symmetry. The methodology is tested with 2D and 3D frame-like periodic solids with some common unit-cell topologies. Satisfactory results are observed.

This paper presents an analytical study on the buckling of cylindrical shells with arbitrary circumferential thickness variations under external pressure. Firstly, based on the thin shell theory and separation of variables, corresponding ordinary differential equations of laterally pressured cylinders are obtained. Secondly, the general asymptotic formula of buckling load, which is in terms of thickness variation parameter up to arbitrary order, is derived by combining the perturbation method and Fourier series expansion. Thirdly, the effects of uniform and circumferential modal thickness variations on the buckling of cylindrical shells under external pressure are investigated, respectively, and the results agree well with those available in literature. Particularly, the buckling load reduction of cylinders with circumferential modal thickness variation obtained by the proposed method coincides with the numerical results presented by Gusic et al. This analytical method is applicable for evaluating the stability of laterally pressured cylindrical shells with arbitrary circumferential thickness variations, once the thickness variation is known.

This paper is devoted to the analytical solution of three-dimensional hyperbolic heat conduction equation in a finite solid medium with rectangular cross-section under time dependent and non-uniform internal heat source. The closed form solution of both Fourier and non-Fourier profiles are introduced with Eigen function expansion method. The solution is applied for simple simulation of absorption of a continues laser in biological tissue. The results show the depth of laser absorption in tissue and considerable difference between the Fourier and Non-Fourier temperature profiles. In addition the solution can be applied as a verification branch for other numerical solutions.

This work examines the magnetohydrodynamic (MHD) flow of second grade fluid due to a stretching cylinder with viscous dissipation. Advance heat transfer technique namely the Newtonian heating is employed to explore the characteristics of heat transfer phenomenon in the presence of Joule heating. Mass transfer is discussed with the combination of both homogeneous and heterogeneous reactions. Diffusion coefficients of species A and B are considered of the same size. Heat production due to chemical reaction is assumed negligible. Appropriate transformations are employed to convert the nonlinear partial differential equations to the nonlinear ordinary differential equations. Convergent solutions of momentum, energy and concentration equations are developed. Characteristics of different involved parameters on the velocity and temperature fields are shown graphically. Numerical values of skin friction coefficient and Nusselt number are computed and analyzed. Higher values of homogeneous reaction parameter results in the reduction of concentration profile while opposite behavior is observed for heterogeneous reaction parameter.

An investigation of unsteady MHD double diffusive natural convection flow of a viscous, incompressible, electrically conducting, heat absorbing, radiating and chemically-reactive fluid past an exponentially accelerated moving inclined plate in a fluid-saturated porous medium, when the temperature of the plate and the concentration at the surface of the plate have ramped profiles, is carried out. Exact solutions for the fluid velocity, fluid temperature and the species concentration, under Boussinesq approximation, are obtained in closed form by the Laplace transform technique. The expressions for the shear stress, rate of heat transfer and the rate of mass transfer at the plate are also derived. Numerical evaluations of the fluid velocity, fluid temperature and the species concentration are performed and displayed graphically whereas those of the shear stress, rate of heat transfer and the rate of mass transfer at the plate are presented in tabular form for various values of the pertinent flow parameters.

The purpose of this study is to highlight the effectiveness and necessity of the computational methods applications for architecture conceptual designs and improve the use of advanced simulation tools in urban planning. The results can provide the urban designers, planners and other decision makers with useful design information for assessing human wind comfort of the surrounding open spaces of public buildings in an urban area. Among different kinds of public buildings, museum architecture is of significant social value and importance for the augmentation of urban image. Using the Guggenheim Museum Bilbao for the case study, this investigation performed CFD simulations of the airflow over the museum to characterize the wind environments around the buildings. The predicted wind speed distributions were used to determine the wind comfort level of the featured spots around the museum for evaluating the suitability allowing visitors to sit or stand at the pedestrian plane for extended periods.

The present study is devoted to electromagnetohydrodynamic (EMHD) flow and heat transfer characteristics of nanofluid inside a parallel plate microchannel. The nanofluid is actuated by Lorentz force which is originated from the interaction of applied electrical field and perpendicular magnetic field. A fully developed assumption with uniform flux at the surface is considered in the analysis, and the influences of viscous dissipation as well as Joule heating are also taken into account. The analytical solutions for velocity and temperature are derived. Moreover, the Nusselt number variations are examined. The results show that the Hartmann number, the dimensionless parameter S and the nanoparticls volume fraction have significant influences on flow and temperature of nanofluid. As Hartmann number increasing, the Nusselt number improves and similar trend can be observed with the augment of nanoparticls volume fraction. A diminishment of heat transfer performance can be seen with increase of the Joule parameter and Brinkman number, while an enhancement in heat transfer can be witnessed with increase of nanoparticls volume fraction.

This paper focuses on the attitude dynamics and control of liquid filled spacecraft, and the large amplitude fuel slosh dynamics is included by using an improved moving pulsating ball model. The moving pulsating ball model is an equivalent mechanical model that is capable of imitating the whole liquid reorientation process, specifically for the occurrence of large amplitude slosh. This model is improved by incorporating a static capillary force and an effective mass factor. The improvements on this model are validated with previously published experiment results. The spacecraft attitude maneuver is implemented by the momentum transfer technique, and the feedback control strategy is designed based on Lyapunov theory. The effects of liquid viscosity, tank location and desired steady time on sloshing torque and control torque are investigated. The attitude control strategy applied in this paper is proved to be applicable for the coupled liquid filled spacecraft system. The obtained conclusions are useful to aid in liquid filled spacecraft overall design.

This study investigated the effect of rarefaction on microchannel gas flow by measuring pressure profiles in microchannels with various aspect ratios. Pressure-sensitive paint (PSP) was applied in rectangular microchannels to obtain the global flow field by using detailed pressure data. The effect of rarefaction on the microchannel gas flow was clearly observed in the microchannels through the pressure data obtained using PSP measurements. A nonlinear pressure distribution was observed inside the microchannels, and this distribution decreased as the Knudsen number (Kn) increased because of the rarefaction effect. The dimensionless pressure deviation from the linear assumption dropped from 0.25 to 0 when the outlet Kn number increased to 0.066 in the 100-μm-wide microchannel, and the dimensionless location of the maximum deviation moved upstream because of the gaseous slip at the wall. The nonlinear pressure distribution also decreased in the 50-μm-wide microchannel as the outlet Kn number increased; however, the peak of the maximum deviation could no longer be identified because of the characteristic of the narrow channel.