R.Kanapady¹, K.K.Tamma²

CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.2, pp. 189-208, 2004, DOI:10.3970/cmes.2004.006.189

Abstract An integrated design of generalized single step LMS methods for applications to nonlinear structural dynamics is described. The design of the mathematical framework encompasses all the traditional and new and recent optimal algorithms encompassing LMS methods, and readily permits the different a-form, v-form and d-form representations in a unique mathematical setting. As such, the theoretical developments and implementation aspects are detailed for subsequent applications to nonlinear structural dynamics problems. The developments naturally inherit a consistent treatment of nonlinear internal forces under the present umbrella of predictor multi-corrector generalized single step representations with a wide variety of algorithmic More >

Z. D. Han¹, S. N. Atluri¹

CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.2, pp. 169-188, 2004, DOI:10.3970/cmes.2004.006.169

Abstract Three different truly Meshless Local Petrov-Galerkin (MLPG) methods are developed for solving 3D elasto-static problems. Using the general MLPG concept, these methods are derived through the local weak forms of the equilibrium equations, by using different test functions, namely, the Heaviside function, the Dirac delta function, and the fundamental solutions. The one with the use of the fundamental solutions is based on the local unsymmetric weak form (LUSWF), which is equivalent to the local boundary integral equations (LBIE) of the elasto-statics. Simple formulations are derived for the LBIEs in which only weakly-singular integrals are included More >

T. Furumura¹, L. Chen²

CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.2, pp. 153-168, 2004, DOI:10.3970/cmes.2004.006.153

Abstract Recent developments of the Earth Simulator, a high-performance parallel computer, has made it possible to realize realistic 3D simulations of seismic wave propagations on a regional scale including higher frequencies. Paralleling this development, the deployment of dense networks of strong ground motion instruments in Japan (K-NET and KiK-net) has now made it possible to directly visualize regional seismic wave propagation during large earthquakes. Our group has developed an efficient parallel finite difference method (FDM) code for modeling the seismic wavefield and a 3D visualization technique, both suitable for implementation on the Earth Simulator. Large-scale 3D… More >

Y. Bei¹, B.J. Fregly¹, W.G. Sawyer¹, S.A. Banks^1,2, N.H. Kim¹

CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.2, pp. 145-152, 2004, DOI:10.3970/cmes.2004.006.145

Abstract Mild wear of ultra-high molecular weight polyethylene tibial inserts continues to affect the longevity of total knee replacements (TKRs). Using static finite element and elasticity analyses, previous studies have hypothesized that polyethylene wear can be reduced by using a thicker tibial insert to decrease contact pressures. To date, no study has taken this hypothesis to the next step by performing dynamic analyses under in vivo functional conditions to quantify the relationship between contact pressures, insert thickness, and mild wear. This study utilizes multibody dynamic simulations incorporating elastic contact to perform such analyses. \textit {In vivo} fluoroscopic… More >

Z.Y. Qian¹, Z.D. Han¹, P. Ufimtsev¹, S.N. Atluri¹

CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.2, pp. 133-144, 2004, DOI:10.3970/cmes.2004.006.133

Abstract The weak-form of Helmholtz differential equation, in conjunction with vector test-functions (which are gradients of the fundamental solutions to the Helmholtz differential equation in free space) is utilized as the basis in order to directly derive non-hyper-singular boundary integral equations for the velocity potential, as well as its gradients. Thereby, the presently proposed boundary integral equations, for the gradients of the acoustic velocity potential, involve only O(r⁻²) singularities at the surface of a 3-D body. Several basic identities governing the fundamental solution to the Helmholtz differential equation for velocity potential, are also derived for the further More >

S.Aoki¹, K.Amaya², M.Urago³, A.Nakayama⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.2, pp. 123-132, 2004, DOI:10.3970/cmes.2004.006.123

Abstract The Fast Multipole Boundary Element Method(FMBEM) which is suitable for a large scale computation is applied to corrosion analysis. Many techniques of the FMBEM on the potential problems can be usefully employed. Additionally, some procedures are developed for corrosion analysis. To cope with the non-linearity due to the polarization curve, the Bi-CGSTAB iterative method which is commonly used in the FMBEM is modified. To solve infinite domain problems, the M₀⁰ which is obtained naturally in the multipole expansion is conveniently used. A pipe element for the FMBEM is developed. A couple of example problems are More >

Z.Y. Qian¹, Z.D. Han¹, S.N. Atluri¹

CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.1, pp. 115-122, 2004, DOI:10.3970/cmes.2004.006.115

Abstract This article has no abstract. More >

Haiyi Liang¹, C.H. Woo^1,2, Hanchen Huang³, A.H.W. Ngan⁴, T.X. Yu⁵

CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.1, pp. 105-114, 2004, DOI:10.3970/cmes.2004.006.105

Abstract Molecular dynamics (MD) simulations are performed to study crystalline plasticity during nano-indentation by comparing the elastic-plastic response of three copper substrates with surfaces (001), (110), and (111) crystallographic planes. The effects of elastic anisotropy and crystallographic symmetry on the reduced modulus, dislocation nucleation, and subsequent microstructure evolution, are investigated. The reduced modulus of (111) surface is found to be the largest, while that of (001) surface is the smallest. Elastic stress distribution calculated from finite element method (FEM) is qualitatively consistent with the MD simulation results. Significant differences exist in the deformation behavior in the More >

Shengping Shen¹, S. N. Atluri¹

CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.1, pp. 91-104, 2004, DOI:10.3970/cmes.2004.006.091

Abstract An atomistic level stress tensor is defined with physical clarity, based on the SPH method. This stress tensor rigorously satisfies the conservation of linear momentum, and is appropriate for both homogeneous and inhomogeneous deformations. The formulation is easier to implement than other stress tensors that have been widely used in atomistic analysis, and is validated by numerical examples. The present formulation is very robust and accurate, and will play an important role in the multiscale simulation, and in molecular dynamics. An equivalent continuum is also defined for the molecular dynamics system, based on the developed More >

E. Pan¹, X. Jiang¹

CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.1, pp. 77-90, 2004, DOI:10.3970/cmes.2004.006.077

Abstract It is of great importance to understand the factors that contribute to the strain and electrical distributions, which are induced by the misfit strain between a buried quantum wire (QWR) and its surrounding matrix. One of the important factors is the shape or geometry of cross section of the QWR. Utilizing a recent exact closed-form solution [Pan (2004)], we study the model system of QWRs with different shapes and calculate both the surface and internal elastic and piezoelectric fields induced by QWRs embedded in semiconductor GaAs substrates by properly setting the size and location of More >