Nanoindentation technique has been used to measure the elastic modulus of virus capsids, capsules, vesicles, and tubules. The principle of the nanoindentation technique is based on the elastic solution of an isotropic, homogeneous, semi-infinite material, which limits the use of nanoindentation in measuring the mechanical properties of materials of small scales. To address this limitation, Reissner's thin shell model, which is based on the point indentation on a thin shell, has been used in analyzing the indentation of thin shells. In this work, the indentation of elastic hemispherical shells of various thicknesses by a rigid, spherical indenter is analyzed, using the finite element method. The simulation results reveal the limitation of the Reissner's thin shell model. A semi-analytical relationship between the indentation depth and the indentation load is proposed, which consists of the contributions of the Hertz's local deformation, the Reissner's local flattening, and the Pogorelov's deflection of the shell. This relationship provides an analytical basis of using nanoindentation to determine the nominal contact modulus of spherical shells. The comparison between the numerical results and the experimental results in literature supports the proposed semi-analytical relationship and reveals the effect of viscoelastic characteristic of shell structures on the indentation deformation.

An innovative optimization technique is presented for the design of composite laminated plates subjected to in-plane loads. A list of quasi-homogeneous laminates that can be used as angle-ply materials is proposed as a comprehensive solution for optimum lay-up. Two optimization procedures are performed: Dimensioning of the flexural stiffness and the elastic modulus, which provides the optimal orientations for the layers and offer highest in-plane resistance to composite laminated structures. The polar formalism for plane anisotropy is used to represent the flexural stiffness and elastic modulus tensors. Numerical examples are resolved for two materials with different elastic moduli.

A new approach in meshless methods has been introduced for stress assessment around a crack in two-dimensional elastic solids. This method with the name VDLSM (Voronoi Based Discrete Least Squares Meshless) is a pure meshless method which does not implement nodal mesh for trial and test functions. Rather, it uses a collection of the scattered nodal points and implements the discrete least squares approach to discretize the strong form of the governing differential equations on the domain of interest. This can reduce considerably the pre-processing cost of the analysis. Meshless methods generally are faced with some difficulty to accommodate the stress analysis in the vicinity of sharply concave surfaces such as cracks. Some techniques have been used to fix that problem such as visibility, transparency and diffraction, but these methods require some additional back corrective analyses for those parts of the domain located near the crack, which lengthen the time consumed for the solution and, moreover, do not provide the desired accuracy for the unknowns in these regions. VDLSM as a new, straightforward and easy applicable method has been suggested here for overcoming such deficiency using the algorithm of the Voronoi tessellation for constructing the Moving Least Squares (MLS) shape functions.

Analyses of free vibration and thermal buckling of nanobeams using nonlocal shear deformation beam theories under various boundary conditions are precisely illustrated. The present beam is restricted by vertically distributed identical springs at the top and bottom surfaces of the beam. The equations of motion are derived using the dynamic version of Hamilton's principle. The governing equations are solved analytically when the edges of the beam are simply supported, clamped or free. Thermal buckling solution is formulated for two types of temperature change through the thickness of the beam: Uniform and linear temperature rise. To validate the accuracy of the results of the present analysis, the results are compared, as possible, with solutions found in the literature. Furthermore, the influences of nonlocal coefficient, stiffness of Winkler springs and span-to-thickness ratio on the frequencies and thermal buckling of the embedded nanobeams are examined.

Based on the coordinate transformation method, the formula of the dynamic inhomogeneous isoparametric finite element method is presented for generating element stiffness, damping and mass matrices. First, the global coordinate form and simplified form of dynamic inhomogeneous finite element are given in this paper. Then, the discrete material parameter distributions under the isoparametric coordinate system are obtained by using the transformation relationship between the global coordinates and the isoparametric coordinates. The simplified form with the discrete material parameter distributions is obtained for generating the element stiffness and mass matrices of the dynamic inhomogeneous isoparametric element. The numerical examples show that the scheme proposed in present paper has high precision.

The analysis method is developed to obtain dynamic characteristics of the rotating cantilever plate with thermal shock and tip-rub. Based on the variational principle, equations of motion are derived considering the differences between rubbing forces in the width direction of the plate. The transverse deformation is decomposed into quasi-static deformation of the cantilever plate with thermal shock and dynamic deformation of the rubbing plate under thermal shock. Then deformations are obtained through the calculation of modal characteristics of rotating cantilever plate and temperature distribution function. Special attention is paid to the influence of tip-rub and thermal shock on the plate. The results show that tip-rub has the characteristics of multiple frequency vibrations, and high frequency vibrations are significant. On the contrary, thermal shock shows the low frequency vibrations. The thermal shock makes the rubbing plate gradually change into low frequency vibrations. Because rub-induced vibrations are more complicated than those caused by thermal shock, tip-rub is easier to result in the destruction of the blade. The increasing friction coefficient intensifies vibrations of the rubbing plate. Minimizing friction coefficients can be an effective way to reduce rub-induced damage through reducing the surface roughness between the blade tip and the inner surface of the casing.

This work is to present a formulation of cloaking or concentrating device in acoustics in which the transformed material could be either having uniform bulk modulus or having homogeneous density tensor. The transformed material parameters, depending on the mapping of physical and virtual coordinates, are often position-varying and anisotropic. This often adds substantial complexity in practical implementation. Here we present a theoretical algorithm that allows us to design a transformation field that could have either uniform bulk modulus or constant density tensor. For cloaking devices with constant bulk modulus, analytical and numerical results are presented for circular as well as for non-circular cloaking devices. Specifically, elliptical and twin-cloak devices are exemplified. To achieve the effect of constant density tensor, we consider only circular geometry. Devices with cloaking or concentrating effects can be exactly formulated. We note, however, that it seems unlikely at this moment to have a transformation device that has constant bulk modulus and constant density tensor at the same time. Nevertheless, we remark the present results are of still sufficient merit in that the uniform material parameters, in either set of material parameters, indeed greatly simplify the practice in real implementations.

Geometric model of a lobed mixing exhaust system is created and its flow field is simulated by using the steady Reynolds Averaged Navier-Stokes (RANS) equations under the condition of different core flow inlet swirl angles. According to the numerical simulation results, due to the guidance effect of the lobe parallel side wall, the structure and vorticity of streamwise vortices change little near the lobe exit with inlet swirl angle, and it is the same with the thermal mixing efficiency. As the flow develops, although the inlet swirl angle has limited influence on the streamwise vorticity, it greatly affects the structure of streamwise vortices. It causes the thermal mixing efficiency to increase with the swirl angle. As for the total pressure recovery coefficient, it falls slightly when the inlet swirl strengthens. At the nozzle exit, the total pressure recovery coefficient of CFISA = 30° model is 0.5% lower than CFISA = 0° model. Moreover, as the inlet swirl strengthens, the thrust fall of lobed mixing exhaust system gradually accelerates, especially when the inlet swirl angle is over 15°.

In this paper three-dimensional hyperbolic heat conduction equation in a cubic media with rectangular cross-section under a pulsed heat flux on the upper side has been solved analytically using the method of separation of variables and the Duhamel integral. The closed form solution of both Fourier and non-Fourier profiles are introduced with both modes of steady and pulsed fluxes. The results show the considerable difference between the Fourier and Non-Fourier temperature profiles. Then the answer procedure is used for modeling of interaction of a cubical tissue under a short laser pulse heating. The effects of pulse duration and laser intensity are studied analytically. Furthermore the results can be applied as a verification branch for other numerical solutions or laser treatments of biological tissues.

The results of a numerical simulation of heat and mass transfer during evaporation of a water droplet with solid inclusion in air at temperature as high as 1000K are presented. Typical heating steps of droplet until it reaches the conditions of intensive evaporation (i.e. the interface “solid inclusion – liquid” reaches the boiling temperature) are described. The roles played by the external air temperature and by the main properties of inclusion are detailed. The droplet size, the relation between the sizes of inclusion and a liquid layer during the heating up is determined. The necessary and sufficient conditions of intensive evaporation in the system “water droplet with solid inclusion in high-temperature air” are pointed out.

In order to analyze the boiling and capillary limitations of two-phase heat transport devices, the existing models developed by Chi and Peterson and the existing experimental data carried out with various micro channel wick structures from literature were collected for benchmark. It was found that the dominant parameters for boiling and capillary limitations were the nucleation sites and structure geometries of the micro channels, and important parameters were considered to modify the models empirically. It was also found that for micro channel structures the inclined angle is sensitive to the capillary limitations and not to boiling limitations. By properly estimating the nucleation sites and empirical coefficients for micro channels needed by the newly modified models, the boiling and capillary limitations can be accurately predicted, and hence the applicability of the modified models is confirmed. Based on this, a numerical analysis was then carried out to investigate the trends of boiling and capillary limitations of the micro channel wick structures. Effects of the channel geometries and arrangement were taken into account, including the aspect ratio and structure size of the micro channels. Furthermore, the effects of inclined angle and contact angle were also analyzed. The present results can provide a design reference of performance trends of micro channel wick structures.

This study investigated four electrolytes (tap water, mineral water, seawater, and Al2O3 nanoparticles emulsified in deionized water) to prepare nanofluids for enhancing their microgeneration and heattransfer capabilities by conducting thermoelectric performance experiments on power generation facilities. This study first performed a two-step synthesis process by using emulsion-ultrasonic technology for fabricating an Al2O3 nanofluid to determine the optimal suspended stability for the alumina nanofluid used as an electrolyte according to the Zeta potential, pH value, thermal conductivity, and viscosity. The alumina nanofluid was then compared with the other aqueous solutions to determine the characteristics of the effects of the output currents, voltages, resistances, and temperature distributions at different operating temperatures, distances, and electrode areas. Finally, the emulsifying effect of the alumina nanofluid between 0 wt % and 2 wt % demonstrated the most favorable stability, particle fraction, thermal conductivity, and stable current output.

A new approach for the analysis of stress intensity factors (SIFs) for cracked plane plate is proposed based on the wavelet finite element method using the scaling functions of B-spline wavelet on the interval (BSWI). The performance of the method is investigated through the comparison of the results with the available numerical examples in the literate. It is shown that the solution quality is much better than that of the traditional adaptive finite element method. Though the method is applied to plane structures in this paper, it can be extended to solving problems for other classes of structures.