R.L. Huston¹, C.-Q. Liu²

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.2, pp. 143-152, 2005, DOI:10.3970/cmes.2005.010.143

Abstract This paper presents a summary of recent developments in computational methods for multibody dynamics analyses. The developments are presented within the context of an automated numerical analysis. The intent of the paper is to provide a basis for the easy development of computational algorithms. The principal concepts discussed are: differentiation algorithms, partial velocities and partial angular velocities, generalized speeds, Euler parameters, Kane's equations, orthogonal complement arrays, lower body arrays and accuracy testing functions. More >

Paul R. Dawson¹, Donald E. Boyce², Ronald Rogge³

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.2, pp. 123-142, 2005, DOI:10.3970/cmes.2005.010.123

Abstract Computational mechanics provides a powerful environment for modeling the evolution of material structure during deformation processes and for associating that evolution with changes to the mechanical properties. In this paper, we illustrate a two-scale formulation that links the mechanical loading applied at the scale of a component (the continuum scale) to the responses of the material at the scale of the crystals that comprise it (the crystal scale). Employing the capabilities offered by computational mechanics, we can better understand how heterogeneity of deformation arising at both the continuum and crystal scales influences the behaviors observed More >

George F. Carrier¹, Harry Yeh²

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.2, pp. 113-122, 2005, DOI:10.3970/cmes.2005.010.113

Abstract Sea-bottom displacements associated with seismic events are confined largely to strips of large but finite aspect ratio. We analyze waves that are initiated on such a strip and that propagate across a region of finite depth. We invoke the classical shallow-water-wave theory to obtain rather comprehensive descriptions of the non-dispersive aspects of the waves. The directivity of the energy radiation and the domain of pulse persistence are discussed. More >

J. Bielak¹, O. Ghattas², E.-J. Kim³

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.2, pp. 99-112, 2005, DOI:10.3970/cmes.2005.010.099

Abstract We present a parallel octree-based finite element method for large-scale earthquake ground motion simulation in realistic basins. The octree representation combines the low memory per node and good cache performance of finite difference methods with the spatial adaptivity to local seismic wavelengths characteristic of unstructured finite element methods. Several tests are provided to verify the numerical performance of the method against Green's function solutions for homogeneous and piecewise homogeneous media, both with and without anelastic attenuation. A comparison is also provided against a finite difference code and an unstructured tetrahedral finite element code for a More >

George K. Lea¹

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.2, pp. 97-98, 2005, DOI:10.3970/cmes.2005.010.097

Abstract This article has no abstract. More >

Zhenyu Xue¹, Ashkan Vaziri¹, John W. Hutchinson¹

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.1, pp. 79-96, 2005, DOI:10.3970/cmes.2005.010.079

Abstract A constitutive model for the elastic-plastic behavior of plastically compressible orthotropic materials is proposed based on an ellipsoidal yield surface with evolving ellipticity to accommodate non-uniform hardening or softening associated with stressing in different directions. The model incorporates rate-dependence arising from material rate-dependence and micro-inertial effects. The basic inputs are the stress-strain responses under the six fundamental stress histories in the orthotropic axes. Special limits of the model include classical isotropic hardening theory, the Hill model for incompressible orthotropic solids, and the Deshpande-Fleck model for highly porous isotropic foam metals. A primary motivation is application… More >

P. A. C. Porto¹, A. B. Jorge¹, G. O. Ribeiro²

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.1, pp. 65-78, 2005, DOI:10.3970/cmes.2005.010.065

Abstract This work deals with a numerical solution technique for the self-regular gradient form of Green's identity, the flux boundary integral equation (flux-BIE). The required C^1,α inter-element continuity conditions for the potential derivatives are imposed in the boundary element method (BEM) code through a non-symmetric variational formulation. In spite of using Lagrangian C⁰ elements, accurate numerical results were obtained when applied to heat transfer problems with singular or quasi-singular conditions, like boundary points and interior points which may be arbitrarily close to the boundary. The numerical examples proposed show that the developed algorithm based on the self-regular More >

V.V. Mykhas’kiv¹, O.I. Stepanyuk²

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.1, pp. 45-64, 2005, DOI:10.3970/cmes.2005.010.045

Abstract The 3D elastostatic problem for an infinite remotely loaded matrix containing a finite number of arbitrarily located rigid disk-inclusions and plane cracks is solved by the boundary integral equation (BIE) method. Its boundary integral formulation is achieved by the superposition principle with the subsequent integral representations of superposition terms through surface integrals, which should satisfy the displacement linearity conditions in the inclusion domains and load-free conditions in the crack domains. The subtraction technique in the conjunction with mapping technique under taking into account the structure of the solution at the edges of inhomogeneities is applied More >

Alberto M. Coronado¹, Hanchen Huang²

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.1, pp. 39-44, 2005, DOI:10.3970/cmes.2005.010.039

Abstract Nanostructure fabrication or surface processing in general is predominantly kinetics-limited. One of the kinetics factors is surface diffusion, which involves intricate interplay between the diffusing atoms and substrate atoms. On Cu{111} surfaces, both adatoms and dimers diffuse very fast. Recent studies have shown that adatoms encounter a large facet-facet barrier, even though their conventional Ehrlich-Schwoebel barriers are small. This work examines the facet-facet diffusion barriers of dimers. Our results show that a dimer prefers diffusion through atom-by-atom mechanism, having a barrier of 0.52 eV from {111} to {111} facet and a barrier of 0.55 eV More >

C.-W. Chang¹, C.-S. Liu², J.-R. Chang^1,3

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.1, pp. 13-38, 2005, DOI:10.3970/cmes.2005.010.013

Abstract In this paper, the inverse heat conduction problem governed by sideways heat equation is investigated numerically. The problem is ill-posed because the solution, if it exists, does not depend continuously on the data. To begin with, this ill-posed problem is analyzed by considering the stability of the semi-discretization numerical schemes. Then the resulting ordinary differential equations at the discretized times are numerically integrated towards the spatial direction by the group preserving scheme, and the stable range of the index r = 1/2ν Δt is investigated. When the numerical results are compared with exact solutions, it More >