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Periodic Collinear Circular-Hole Cracks in an Infinite Plate in Tension
Get PDFThis paper is concerned with periodic collinear circular-hole cracks in an infinite plate in tension. A numerical approach to this type of circular-hole cracks is presented. Numerical examples are included to illustrate the accuracy of the numerical approach. By means of a generalization of Bueckner's principle and by using a displacement discontinuity method, periodic collinear circular-hole cracks in an infinite plate in tension are investigated in detail by using the numerical approach. Many numerical results are given and discussed
A New Modified Adomian Decomposition Method for Higher-Order Nonlinear Dynamical Systems
Get PDFIn this paper, we propose a new modification of the Adomian decomposition method for solution of higher-order nonlinear initial value problems with variable system coefficients and solutions of systems of coupled nonlinear initial value problems. We consider various algorithms for the Adomian decomposition series and the series of Adomian polynomials to calculate the solutions of canonical first- and second-order nonlinear initial value problems in order to derive a systematic algorithm for the general case of higher-order nonlinear initial value problems and systems of coupled higher-order nonlinear initial value problems. Our new modified recursion scheme is designed to decelerate the Adomian decomposition series so as to always calculate the solution’s Taylor expansion series using easy-to-integrate terms. The corresponding nonlinear recurrence relations for the solution coefficients are deduced. Next we consider convergence acceleration and error analysis for the sequence of solution approximations. Multistage decomposition and numeric algorithms are designed and we debut efficient MATHEMATICA routines PSSOL and NSOL that implement our new algorithms. Finally we investigate several expository examples in order to demonstrate the rapid convergence of our new approach.
On the Continuum Modeling of the Tire/Road Dynamic Contact
Get PDFThe continuum modeling of tire/road vibro-contact dynamics is developed in this paper by assuming continuum relationship between the contact force and the deformation. An important aspect of this model is that the damping depends on the indentation. In the continuum approach, no difference is made between impact and contact, and the friction law can be other than the Coulomb’s law. Since the road is rocky, a bristle model was chosen to take into account the effect of the road irregularities. The identification of the contact domain is performed by checking the minimum distance between bodies
Application of a Hybrid Mesh-free Method Based on Generalized Finite Difference (GFD) Method for Natural Frequency Analysis of Functionally Graded Nanocomposite Cylinders Reinforced by Carbon Nanotubes
Get PDFIn this article, the effects of carbon nanotubes distributions on natural frequency are studied for a functionally graded nanocomposite thick hollow cylinder reinforced by single-walled carbon nanotubes using a hybrid mesh-free method. The FG nanocomposite cylinder is excited by a shock loading, which is applied on the inner surface of cylinder. The first natural frequency is obtained for various nonlinear grading patterns of distributions of the aligned carbon nanotubes. The effects of various nonlinear grading patterns on natural frequency are obtained and discussed in details. The presented hybrid mesh-free method is based on the generalized finite difference (GFD) method for spatial coordinates and Newmark finite difference (NFD) for time domain. To obtain the dynamic behavior and also first natural frequency, time histories of displacements are transferred to frequency domain by fast Fourier transformation (FFT) technique. Numerical results demonstrate the efficiency of the proposed method in frequency domain analysis for functionally graded nanocomposites reinforced by carbon nanotube (FGNRCN)
Novel Graph-based Adaptive Triangular Mesh Refinement for Finite-volume Discretizations
Get PDFA novel graph-based adaptive mesh refinement technique for triangular finite-volume discretizations in order to solve second-order partial differential equations is described. Adaptive refined meshes are built in order to solve timedependent problems aiming low computational costs. In the approach proposed, flexibility to link and traverse nodes among neighbors in different levels of refinement is admitted; and volumes are refined using an approach that allows straightforward and strictly local update of the data structure. In addition, linear equation system solvers based on the minimization of functionals can be easily used; specifically, the Conjugate Gradient Method. Numerical and analytical tests were carried out in order to study the required execution time and the data storage cost. These tests confirmed the advantages of the approach proposed in elliptic and parabolic problems
Exact Elasticity Solution for Natural Frequencies of Functionally Graded Simply-supported Structures
Get PDFThis paper gives an exact three-dimensional elastic model for the free vibration analysis of functionally graded one-layered and sandwich simply-supported plates and shells. An exact elasticity solution is proposed for the differential equations of equilibrium written in general orthogonal curvilinear coordinates. The equations consider a geometry for shells without simplifications, and allow the analysis of the cases of spherical shell panels, cylindrical shell panels, cylindrical closed shells and plates. The main novelty is the possibility of a general formulation for these geometries. The coefficients in equilibrium equations depend on the thickness coordinate because of the radii of curvature for the shell geometries and/or the use of functionally graded layers. These equations are solved in a layer-wise form by introducing a number of mathematical layers where the coefficients are constant. An exhaustive 3D overview of the vibration modes is given for a number of thickness ratios, imposed wave numbers, geometries and embedded materials. Results are given for one-layered functionally graded plates and shells and for sandwich structures with external homogenous skins and an internal core made of functionally graded material. These results can also be used as reference solutions for the validation of analytical or numerical two-dimensional models for functionally graded plates and shells
Comparison and Performance Analysis of Multiple CPU/GPU Computing Systems – Resin Infusion Flow Modeling Application
Get PDFThe use of Graphics Processing Units (GPUs) as co-processors for single CPU/GPU computing systems has become pronounced in high performance computing research, however the solution of truly large scale computationally intensive problems require the utilization of multiple computing nodes. Multiple CPU/GPU computing systems bring new complexities to the observed performance of computationally intensive applications, the more salient of which is the cost of local CPU-GPU host and intra-nodal communication. This paper compares and analyzes the performance of a computationally intensive application represented by resin infusion flow during liquid composite molding process for the manufacture of structural composites application via two distinct multiple CPU/GPU computing system architectures. Resin flow infusion modeling during liquid composite molding process is the engineering application of interest in the present study. The global domain is partitioned into a series of sub-domains each of which is solved at the local host and reassembled for the final solution as per the domain decomposition methodology. The candidate application, as with many scientific and engineering applications, uses the Finite Element Method (FEM) to computationally model the governing physics based mass and momentum conversation equations. FEM discretization results in large sparse linear equation systems that are solved iteratively for this class of free surface, moving boundary value problem. Computational analysis software for the GPU environment has been developed using CUDA API for the iterative linear equation system solver based on the preconditioned conjugate gradient method for the solution of linear system of equations. These linear equation systems are solved multiple times with intra-nodal communication utilized, resulting in the converged global system. The interplay of local host CPU/GPU and intra-nodal communication creates mixed performance results for the presented candidate application. The software/hardware factors that affect performance for each architecture are examined and discussed in this paper-understanding how the presented candidate application’s observed performance is effected by both the individual multiple CPU/GPU computing system architecture and algorithmic/software design is critical to optimize many modern high performance applications which employee the GPU as a hardware accelerator
Purmorphamine Promotes Matrix Mineralization and Cytoskeletal Changes in Human Umbilical Cord Mesenchymal Stem Cells
Get PDFHuman Umbilical Cord Mesenchymal Stem Cells (hUCMSCs) were subjected to in vitro osteogenic differentiation using a novel combination of signaling molecules including BMP-2 and purmorphamine. Differentiation outcomes were assessed by calcein staining and by microscopic examination of the cytoskeleton. Calcein staining showed appreciable degree of calcium mineralization in cell culture, and changes in the morphological attributes of differentiating cells were observed vis-a-vis the actin cytoskeleton. Finally, positive calcein staining, altered cytoskeletal profile, and stress fiber formation in treated cells demonstrated, for the first time, a potentially synergistic interplay between BMP-2 and the hedgehog agonist, purmorphamine.
This study lends support to the notion of combining small doses of potent molecules that can act as safe, less toxic inducers of osteogenic differentiation of human umbilical cord mesenchymal stem cells with respect to bone regeneration
Heat Transfer and Entropy Analysis for Mixed Convection in a Discretely Heated Porous Square Cavity
Get PDFThe present study is a numerical investigation of the irreversibility and heat transfer properties of a steady laminar mixed flow in a square cavity, filled with a saturated porous medium and heated by a discrete set of heat sources. The continuity, Navier-Stokes, energy and entropy generation equations have been solved by a finite volume method. Both heat transfer irreversibility and fluid friction irreversibility have been taken into account in the computations of entropy generation. Simulations have bee carried out for Reynolds number Re=20, 40, 80, 100, 200, Darcy number, Da=10-5-10-1, Prandtl number, Pr=0.015, 0.7, 10, 103, and aspect ratio, D/H =0.05, 0.10, 0.15, 0.2, 0.25, expressly considering the influence of such parameters on the entropy generation and heat transfer processes. The effect of the irreversibility distribution function and aspect ratio has been also taken into account. The results are presented in terms of entropy generation, Nusselt and Bejan numbers. Finally, a general correlation between all these parameters is determined on the basis of the present findings
Domain Type Kernel-Based Meshless Methods for Solving Wave Equations
Get PDFCoupled with the Houbolt method, a third order finite difference time marching scheme, the method of approximate particular solutions (MAPS) has been applied to solve wave equations. Radial basis function has played an important role in the solution process of the MAPS. To show the effectiveness of the MAPS, we compare the results with the well known Kansa's method, timemarching method of fundamental solutions (TMMFS), and traditional finite element methods. To validate the effectiveness and easiness of the MAPS, four numerical examples which including regular, smooth irregular, and non-smooth domains are given