To save this undefined to your undefined account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you used this feature, you will be asked to authorise Cambridge Core to connect with your undefined account.
Find out more about saving content to .
To save this article to your Kindle, first ensure email@example.com is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below.
Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Propagation of harmonic Lamb waves in plates made of functionally graded materials (FGM) with transverse inhomogeneity is studied by combination of the Cauchy six-dimensional formalism and matrix exponential mapping. For arbitrary transverse inhomogeneity a closed form implicit solution for dispersion equation is derived and analyzed. Both the dispersion equation and the corresponding solution resemble ones obtained for stratified media. The dispersion equation and the corresponding solution are applicable to media with arbitrary elastic (monoclinic) anisotropy.
Finite element analysis is carried out to investigate the characteristics of Rayleigh, Sezawa and Love surface acoustic modes travelling along c-axis tilted ZnO layer on Si (001) half-space. The phase velocity dispersion curves, electromechanical coupling, reflectivity and mass loading sensitivity are studied for different electroacoustic coupling configurations and c-axis tilt angles θ. The behavior of Rayleigh and Sezawa modes operating as gas sensor, was simulated under the hypothesis that the ZnO free surface is covered with a thin polyisobutylene (PIB) film, 0.2 μm thick, able to selectively adsorb volatile gases at atmospheric pressure and room temperature. The sensor sensitivity to gas concentration in air, i.e. the frequency shifts per unit gas concentration, is studied and compared to some common materials used in literature. The obtained results, demonstrate the feasibility of high-frequency multimode micro-sensor based on the c-axis tilted ZnO piezoelectric thin film and operating in both liquid and gaseous environments.
A simple numerical model has been proposed for laser cladding. The model does not involve complex techniques such as cell addition, moving mesh, or prescribing a clad profile with a certain polynomial function. Instead, a mass function has been introduced to register the clad mass deposition on substrate, and from which the clad-track height can be estimated. The model takes several operational parameters, laser power, laser-head speed, and clad powder feeding rate, into consideration and predicts clad-track geometry, dilution, and substrate temperature. Experiments using two different combinations of substrate and clad powder materials to lay single and multiple clad tracks were conducted to provide data for model validation. The results show that the present model returns good agreement with experimental clad profiles for single and multiple tracks.
In this paper, we develop the isogeometric analysis of the dual boundary element method (IGA-DBEM) to solve the potential problem with a degenerate boundary. The non-uniform rational B-Spline (NURBS) based functions are employed to interpolate the geometry and physical function. To deal with the rank-deficiency problem due to the degenerate boundary, the hypersingular integral equation is introduced to promote the full rank for the influence matrix in the dual BEM. Finally, three numerical examples are given to verify the accuracy of our proposed method. Both circular and square domains subjected to the Dirichlet boundary condition are considered. The engineering problem containing a degenerate boundary is considered, e.g., a seepage flow problem with a sheet pile. Numerical results of the IGA-DBEM agree well with these of the exact solution and the original dual boundary element method.
Thermosonic wire bonding is a common fabrication process for connecting devices in electronic packaging. However, when the free air ball (FAB) is compressed onto the I/O pad of the chip during bonding procedure, chip cracking may occur if the contact pressure is too large. This study proposes an effective simulation technique that can predict the wire ball geometry after bonding in an accurate range. The contact force obtained in the simulation can be used for possible die cracking behavior evaluation. The simulation in this study used the explicit time integration scheme to deal with the time marching problem, and the second-order precision arbitrary Lagrangian-Eulerian (ALE) algorithm was used to deal with the large deformation of the wire ball during the bonding process. In addition, the equilibrium smoothing algorithm in LS-DYNA can make the contact behavior and geometry of the bonding wire almost the same as the experiment, which can also significantly reduce the distortion of the mesh geometry after remeshing.
The stress field induced by an edge dislocation or a point force located near a coated triangle-like hole in an infinite plate is provided in this paper. Based on the method of analytical continuation and the technique of conformal mapping in conjunction with the alternation technique, a series solution for the displacement and stresses in the coating layer and the matrix is obtained analytically. Examples for the interaction between an edge dislocation and a coated triangle-like hole for various material constant combinations, coating thicknesses and shape factors are discussed. The analysis discovers that the so-called trapping mechanism of dislocations is more likely to exist near a coated triangle-like hole. The result shows that the dislocation will first be repelled by the coating layer and then attracted by a hole when the coating layer is slightly stiffer than the matrix. However, when the coating layer is sufficiently thin, the dislocation will always be attracted by a hole even the coating layer is stiffer than the matrix.
The elastoplastic behavior of a Functionally Graded Material (FGM) simply supported beam consisting of elastic material A and elastoplastic material B under uniformly distributed load is investigated. A power function is used to describe the volume fractions of the constituent materials, and the average stress of the FGM beam is obtained by using the averaging method. This method can avoid the assumption of the varying properties of the whole material, and can consider the different Possion’s ratios of the different constituent materials. What’s more, only the elastoplastic material B in the FGM beam will yield, and the yield function is determined by the stress of material B only, rather than the average stress of the whole material. The method used in this work is more closer to the real material than the method by assuming the variation of the whole properties of FGM. The theoretical results show a good agreement with the finite element results, which indicates that the method provided in this work is valid. With this method, the variation of the elastic and plastic areas, the stress distribution on the cross section, variation of the curvature and neutral layer, and the residual stress distribution of the FGM beam are discussed through numerical results. This work can provide a new way for the design and in-depth investigation of FGM material.
This study proposed the application of a novel immersed boundary method (IBM) for the treatment of irregular geometries using Cartesian computational grids for high speed compressible gas flows modelled using the unsteady Euler equations. Furthermore, the method is accelerated through the use of multiple Graphics Processing Units – specifically using Nvidia’s CUDA together with MPI - due to the computationally intensive nature associated with the numerical solution to multi-dimensional continuity equations. Due to the high degree of locality required for efficient multiple GPU computation, the Split Harten-Lax-van-Leer (SHLL) scheme is employed for vector splitting of fluxes across cell interfaces. NVIDIA visual profiler shows that our proposed method having a computational speed of 98.6 GFLOPS and 61% efficiency based on the Roofline analysis that provides the theoretical computing speed of reaching 160 GLOPS with an average 2.225 operations/byte. To demonstrate the validity of the method, results from several benchmark problems covering both subsonic and supersonic flow regimes are presented. Performance testing using 96 GPU devices demonstrates a speed up of 89 times that of a single GPU (i.e. 92% efficiency) for a benchmark problem employing 48 million cells. Discussions regarding communication overhead and parallel efficiency for varying problem sizes are also presented.
This paper is intended for dealing with the peristaltic flow of an electrically conducting Williamson nanofluid in a tapered asymmetric channel through a porous medium with heat and mass transfer. In the current paper, temperature-dependent electrical conductivity formulation was introduced for the first time in peristaltic literature. The flow is pervaded by an oblique uniform magnetic field. The present investigation includes the influences of thermal radiation, Joule heat, viscous dissipation, Hall Current, 1st order chemical reaction, and Dofour and Soret numbers. Current problem is reformulated under the molds of low Reynolds number and long wavelength approximation. Afterwards, semi analytical solutions have been evaluated for the distributions of velocity, temperature, nanoparticle concentrations as well as longitudinal pressure gradient. Solutions can be obtained by using multi-step differential transform method (MS-DTM), a reliable and powerful technique that improve accuracy and overcome drawbacks raised in using the standard differential transform method (DTM). Detailed comparisons have been made at different values of 𝑥 through graphs by Ms-DTM. The graphically results were prepared to visualize the effects of various physical parameters of interest. The semi-analytical results had shown that, as the thermal radiation increases, the nanoparticles diameter and concentration of fluid increase (thermal radiation is a decreasing function in temperature when the temperature decreases the diameter of the nanoparticles increases i.e. the volume of nanoparticle and its concentration increases and become more effective near to tumor tissues). Consequently, it can be used as agents for radiation therapy, generate localized raises in radiation doses and selectively target tumor cells for localized damage (Radiotherapy of oncology).
The neuro-endoscopy is a surgical technique that allows the neurosurgeon to maintain a visual contact while operating inside the brain of a patient. A special instrument called the neuro-endoscope is inserted in the brain until the neurosurgeon reaches his/her target. Its manipulation requires a high level of training for neurosurgeons. To enforce both quality and safety of neuro-endoscopy, we propose a robotic manipulator based on a Spherical Decoupled Mechanism. This mechanical architecture has been modified from a 5-Bar Spherical Linkages and adapted to this medical application. It is able to generate a Remote Center of Motion of 2 Degrees of Freedom. It merges the advantages of parallel mechanisms with the kinematic and control simplicity of decoupled mechanisms, while having a very simple architecture. Motion capture experiments using a brain simulation model have been performed with a team of neurosurgeons to obtain the kinematic data of the neuro-endoscope during brain exploration. Based on the identified workspace, the mechanism has been optimized using kinematic performance and architectural compactness as criteria. An optimum mechanism has been selected, showing better kinematic performances than the original 5-bar spherical linkage mechanism.