W. C. Liu, S. Q. Shi, C. H. Woo, Hanchen Huang¹

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.2, pp. 213-218, 2002, DOI:10.3970/cmes.2002.003.213

Abstract Using molecular dynamics method, we study the nucleation of dislocations and their subsequent propagation during the deposition of tungsten thin films under tension. Aiming to reveal the generic mechanisms of dislocation nucleation during the deposition of polycrystalline thin films, the case of tungsten on a substrate of the same material is considered. The substrate is under uniaxial tension along the [111] direction, with the thermodynamically favored (01^ˉˉ1) surface being horizontal. The simulation results indicate that the nucleation starts with a surface step, where a surface atom is pressed into the film along the [111^ˉˉ] More >

Karin Lin¹, D. C. Chrzan²

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.2, pp. 201-212, 2002, DOI:10.3970/cmes.2002.003.201

Abstract The 90° partial dislocation in Si is studied using a combination of Tersoff potentials and isotropic elasticity theory. Both periodic supercells and cylindrical cells are employed and the results compared. The dislocation core radius is extracted by fitting the results of atomic scale calculations to an expression for the elastic energy of the dislocation. The energy differences between two proposed reconstructions of the dislocation core are computed and found to depend systematically on the stress field imposed on the dislocation. It is suggested that hydrostatic stresses may introduce a core transformation. More >

E. Kuramoto, K. Ohsawa, T. Tsutsumi¹

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.2, pp. 193-200, 2002, DOI:10.3970/cmes.2002.003.193

Abstract In order to investigate the interaction of point defects with a dislocation, an interstitial cluster or a SFT (stacking fault tetrahedron), computer simulation has been carried out in model Fe and Ni crystals. The capture zone (the region where the interaction energy is larger than kT) was determined for various interactions. Calculated capture zone for T =500°C for SIAs (crowdion and dumbbell) around a straight edge dislocation is larger than that for a vacancy in both Fe and Ni. Capture zones for Ni are larger than those for Fe, suggesting that Ni (fcc) has a More >

K. Garikipati¹

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.2, pp. 175-184, 2002, DOI:10.3970/cmes.2002.003.175

Abstract The embedding of micromechanical models in the macromechanical formulation of continuum solid mechanics can be treated by a variational multiscale method. A scale separation is introduced on the displacement field into coarse and fine scale components. The fine scale displacement is governed by the desired micromechanical model. Working within the variational framework, the fine scale displacement field is eliminated by expressing it in terms of the coarse scale displacement and the remaining fields in the problem. The resulting macromechanical formulation is posed solely in terms of the coarse scale displacements, but is influenced by the More >

Nasr M. Ghoniem¹, Kyeongjae Cho²

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.2, pp. 147-174, 2002, DOI:10.3970/cmes.2002.003.147

Abstract As a result of surging interest in finding fundamental descriptions for the strength and failure properties of materials, and the exciting prospects of designing materials from their atomic level, an international symposium on Multiscale Modeling was convened at ICES'2K in Los Angeles during August 23 - 25, 2000. In this symposium, 23 speakers with research interests spanning fields as diverse as traditional mechanics, physics, chemistry and materials science have given talks at this symposium. The topics of discussion were focused on sub-continuum modeling of the mechanics of materials, taking into account the atomic structure of solid… More >

T. Nishioka¹, J. Furutuka¹, S. Tchouikov¹, T. Fujimoto¹

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.1, pp. 129-146, 2002, DOI:10.3970/cmes.2002.003.129

Abstract The governing condition of dynamic crack bifurcation phenomena had not been fully elucidated until our recent experimental studies. We found from the experimental results that the energy flux per unit time into a propagating crack tip or into a fracture process zone governs the crack bifurcation. Regarding the numerical simulation of dynamic crack bifurcation, to the authors' knowledge, no accurate simulations have been carried out, due to several unresolved difficulties. In order to overcome the difficulties, for the analysis of dynamic crack bifurcation, we developed a moving finite element method based on Delaunay automatic triangulation. More >

C.C. Tsai¹, D.L. Young², A.H.-D. Cheng³

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.1, pp. 117-128, 2002, DOI:10.3970/cmes.2002.003.117

Abstract This paper describes a combination of the dual reciprocity method (DRM) and the method of fundamental solution (MFS) as a meshless BEM (DRM-MFS) to solve three-dimensional Stokes flow problems by the velocity-vorticity formulation, where the DRM is based on the compactly supported, positive definite radial basis functions (CS-PD-RBF). In the velocity-vorticity formulation, both of the diffusion type vorticity equations and the Poisson type velocity equations are solved by DRM-MFS. Here a typical internal cubic cavity flow and an external flow past a sphere are presented. The results are acceptable. Furthermore, this paper provides a preliminary More >

E. H. Glaessgen¹, W.T. Riddell², I. S. Raju¹

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.1, pp. 103-116, 2002, DOI:10.3970/cmes.2002.003.103

Abstract The effects of several critical assumptions and parameters on the computation of strain energy release rates for delamination and debond configurations modeled with plate elements have been quantified. The method of calculation is based on the virtual crack closure technique (VCCT), and models of the upper and lower surface of the delamination or debond that use two-dimensional (2D) plate elements rather than three-dimensional (3D) solid elements. The major advantages of the plate element modeling technique are a smaller model size and simpler configurational modeling. Specific issues that are discussed include: constraint of translational degrees of More >

Olivier Ricou¹, Michel Bercovier²

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.1, pp. 87-102, 2002, DOI:10.3970/cmes.2002.003.087

Abstract In this article, we present a method of reduction of the dimension of the Stokes equations by one in a quasi-cylindrical domain. It takes the special shape of the domain into account by the use of a projection onto a space of polynomials defined over the thickness. The polynomials are defined to fit as well as possible with the variables they approximate. Hence, this method restricted to the first polynomial, recovers the Hele-Shaw approximation.
The convergence of the approximate solution to the continuous one is shown. Under a regularity hypothesis, we also obtain error estimates. More >

Z. Zhong¹, Y. Dai^1,2, C. C. Mei³, P. Tong^1,4

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.1, pp. 77-86, 2002, DOI:10.3970/cmes.2002.003.077

Abstract In this paper we reexamine the sheet-flow model proposed by Fung and Sobin (1969) for blood flow in capillaries in the pulmonary alveoli from micromechanical point of view. The pulmonary alveolar capillary is assumed to be two parallel membranes connected by periodic tissue posts. Blood is spread out into the very thin layer or sheet between the two membranes. The pulmonary alveolar sheet thus has a microstructure of hexagonal cells. A two-scale theory of homogenization is used to establish the canonical equations for the unit cell. The microscale solution is obtained by means of finite… More >