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  • A Physically Meaningful Level Set Method for Topology Optimization of Structures
  • Abstract This paper aims to present a physically meaningful level set method for shape and topology optimization of structures. Compared to the conventional level set method which represents the design boundary as the zero level set, in this study the boundary is embedded into non-zero constant level sets of the level set function, to implicitly implement shape fidelity and topology changes in time via the propagation of the discrete level set function. A point-wise nodal density field, non-negative and value-bounded, is used to parameterize the level set function via the compactly supported radial basis functions (CSRBFs) at a uniformly defined set…
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  • Fluid Flow Simulation Using Particle Method and Its Physics-based Computer Graphics
  • Abstract The application of a particle method to incompressible viscous fluid flow problem and its physics-based computer graphics are presented. The method is based on the MPS (Moving Particle Semi-implicit) scheme using logarithmic weighting function to stabilize the spurious oscillatory solutions for the pressure fields which are governed by Poisson equation. The physics-based computer graphics consist of the POV-Ray (Persistence of Vision Raytracer) rendering using marching cubes algorithm as polygonization. The standard MPS scheme is widely utilized as a particle strategy for the free surface flow, the problem of moving boundary, multi-physics/multi-scale ones, and so forth. Numerical results demonstrate the workability…
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  • New Optimization Algorithms for Structural Reliability Analysis
  • Abstract Solution of structural reliability problems by the First Order method require optimization algorithms to find the smallest distance between a limit state function and the origin of standard Gaussian space. The Hassofer-Lind-Rackwitz-Fiessler (HLRF) algorithm, developed specifically for this purpose, has been shown to be efficient but not robust, as it fails to converge for a significant number of problems. On the other hand, recent developments in general (augmented Lagrangian) optimization techniques have not been tested in aplication to structural reliability problems. In the present article, three new optimization algorithms for structural reliability analysis are presented. One algorithm is based on…
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  • Modeling Train Movement for Moving-Block Railway Network Using Cellular Automata
  • Abstract Cellular automata (CAs), model the dynamics of complex systems as the state update of cells restricted from their own neighbors. This paper regards the tempo-spatial constraints as dummy neighborhoods of cells for train movement, such as scheduled movement authority and speed restriction, equivalent to the maximum displacements during the future certain time steps and each time step, respectively. Under the framework of CA modeling, this paper attempts to propose an improved CA model for moving-block railway network which incorporates the tempo-spatial constraints to capture the restrictive, synergistic and autonomous dynamics. We divide the one-dimensional cell lattice into several segments, called…
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  • Creation of Imperfections for Welding Simulations
  • Abstract The welding simulation is carried out by an uncoupled thermal and mechanical analysis or by a coupled thermo-mechanical analysis. For weld-induced distortion and residual stress simulation, nonlinear mechanical analysis is required. Nonlinearities are caused by both nonlinear behaviour of the material and geometrical nonlinearity. Usually, the element birth technique is used to incorporate the filler material in the model. The ideal straight geometry may be altered by imperfections to enable buckling behaviour. Real component shapes contain various imperfections (e.g. geometrical, material). The finite element mesh may contain geometrical imperfections too. When a simple weld model is used, the mode of…
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  • The Superconvergence of Certain Two-Dimensional Hilbert Singular Integrals
  • Abstract The composite rectangle (midpoint) rule for the computation of multi-dimensional singular integrals is discussed and the superconvergence results is obtained. When the local coordinate is coincided with certain priori known coordinates, we get the convergence rate one order higher than the global one. At last, numerical examples are presented to illustrate our theoretical analysis which agree with it very well.
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  • Numerical Simulation of Melt Filling and Gas Penetration in Gas Assisted Injection Molding
  • Abstract The governing equations of two-phase flows including gas and polymer melt are presented, which are solved using finite volume and domain extension methods with SIMPLEC technology. The melt filling and primary gas penetration in gas-assisted injection molding (GAIM) process are simulated, where the Cross-viscosity model is employed to describe the melt rheological behavior, and the CLSVOF(coupled Level Set and Volume of fluid) method is employed to capture the moving interfaces. In order to test and verify the coupled methods, melt filling in a rectangular plate with an insert is simulated, and the numerical results are in good agreement with those…
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  •   Views:533       Downloads:347       Cited by:1        Download PDF
  • Numerical Study of Dynamic Compression Process of Aluminum Foam with Material Point Method
  • Abstract Due to its high strength, low weight and strong anti impact capability, aluminum foam has great potential in the fields of transportation, aerospace and building structures as energy absorbing materials. Due to its complicated microstructures, it is desirable to develop an efficient numerical method to study the dynamic response of the aluminum foam under impact loading. In this paper, the material point method (MPM) is extended to the numerical simulation of the dynamic response of the aluminum foam under impact loading by incorporating the Deshpande Fleck's model and a volumetric strain failure model into our three-dimensional explicit material point method…
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  • A New Homotopy Perturbation Method for Solving an Ill-Posed Problem of Multi-Source Dynamic Loads Reconstruction
  • Abstract In this paper, a new homotopy perturbation method (IHPM) is presented and suggested to solve an ill-posed problem of multi-source dynamic loads reconstruction. We propose a stable and reliable modification, and obtain a new regularization method, then employ it to find the exact solution for the multi-source dynamic load identification problem. Also, this present method only needs easy computations rather than successive integrations. Finally, the performances of two numerical examples are given. Comparisons are performed between the original homotopy perturbation method (HPM) and IHPM. The results verify that the present method is very simple and effective.
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  • 2D Mixed Convection Viscous Incompressible Flows with Velocity-Vorticity Variables
  • Abstract Mixed convection viscous incompressible fluid flows, under a gravitational system, in rectangular cavities are reported using the unsteady Boussinessq approximation in velocity-vorticity variables. The results are obtained using a numerical method based on a fixed point iterative process to solve the nonlinear elliptic system that results after time discretization; the iterative process leads to the solution of uncoupled, well-conditioned, symmetric linear elliptic problems for which efficient solvers exist regardless of the space discretization. Results with different aspect ratios A up to Grashof numbers Gr = 100000 and Reynolds numbers Re = 1000 for the lid driven cavity problem are reported.…
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  •   Views:496       Downloads:401        Download PDF
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