Ch. Zhang², A. Savaidis³

CMES-Computer Modeling in Engineering & Sciences, Vol.4, No.5, pp. 603-618, 2003, DOI:10.3970/cmes.2003.004.603

Abstract A novel non-hypersingular time-domain traction BEM is presented for three-dimensional (3-D) transient elastodynamic crack analysis. The initial-boundary value problem is formulated as a set of non-hypersingular time-domain traction boundary integral equations (BIEs). To solve the time-domain traction BIEs, a time-stepping scheme based on the convolution quadrature formula of Lubich (1988a,b; 1994) for temporal discretization and a collocation method for spatial discretization is adopted. Numerical examples are given for an unbounded solid with a penny-shaped crack under a tensile and shear impact loading. A comparison of the present time-domain BEM with the conventional one shows that More >

T. Iwasaki¹ and H. Miura¹

CMES-Computer Modeling in Engineering & Sciences, Vol.4, No.5, pp. 551-558, 2003, DOI:10.3970/cmes.2003.004.551

Abstract We have developed a molecular-dynamics technique for investigating migration-induced failures in interconnect films for ULSIs. This technique was used to simulate grain-boundary grooving in Al and Cu films. The simulations showed that the grain-boundary grooves are formed by atomic diffusion at the grain boundary. To clarify what kind of underlay material is effective in suppressing this diffusion, we calculated the dependence of groove depth on the kind of underlay material. The calculation showed that the groove depth of the Al film decreases in the order: Al/Ta, Al/W, and Al/TiN while that of the Cu film More >

S. Okamoto¹, Y. Omura¹

CMES-Computer Modeling in Engineering & Sciences, Vol.4, No.2, pp. 287-300, 2003, DOI:10.3970/cmes.2003.004.287

Abstract The purpose of this study is to develop a procedure for performing a dynamic analysis in the case that a structure undergoes large translational and rotational displacements when moving along a nonlinear trajectory at variable velocity. Finite-element equations of motion that include the inertial force of the structure's motion have been derived. The equations also account for the geometric nonlinearity that has to be considered in a problem of finite translational and rotational displacements. A finite rotational matrix was used to transfer vectors or matrices measured in a certain coordinate frame to those measured in More >

L. Briseghella¹, C. Majorana¹, P. Pavan¹

CMES-Computer Modeling in Engineering & Sciences, Vol.4, No.2, pp. 273-286, 2003, DOI:10.3970/cmes.2003.004.273

Abstract Some aspects of the application of a conservative time integration scheme to the non-linear dynamics of elasto-damaged thin shells are presented. The main characteristic of the scheme is to be conservative, in the sense that it allows the time-discrete system to preserve the basic laws of continuum, namely the balance of the linear and angular momenta as well as the fulfilment of the second law of thermodynamic. Here the method is applied to thin shells under large displacements and rotations. The constitutive model adopted is built coupling the linear elastic model of De Saint Venant-Kirchhoff More >

T. Nishioka¹, F. Stan¹

CMES-Computer Modeling in Engineering & Sciences, Vol.4, No.1, pp. 119-140, 2003, DOI:10.3970/cmes.2003.004.119

Abstract In this paper we investigate the essentially unexplored area of three-dimensional dynamic fracture mechanics. The general objective sought by this investigation is the understanding of three-dimensional dynamic crack propagation and arrest, and, specifically, the effect that the specimen thickness has on the dynamic fracture mechanism. In particular, in the context of the present paper, it is intended to provide a summary of the achievements on the issue of three-dimensional dynamic fracture parameters. Furthermore, the behavior of the three-dimensional field near the crack front is investigated. The issue that will be addressed is the extent of More >

R.Kanapady¹, K.K.Tamma²

CMES-Computer Modeling in Engineering & Sciences, Vol.4, No.1, pp. 103-118, 2003, DOI:10.3970/cmes.2003.004.103

Abstract Of general interest here is the time dimension aspect wherein discretized operators in time may be continuous or discontinuous; and of particular interest and focus here is the design of time discretized operators in the context of discontinuous state-phase for computational dynamics applications. Based on a generalized bi-discontinuous time weighted residual formulation, the design leading to a new unified set of hierarchical energy conserving and energy dissipating time discretized operators are developed for the first time that are fundamentally useful for time adaptive computations for dynamic problems. Unlike time discontinuous Galerkin approaches, the design is… More >

L. M. Hsiung, D. H. Lassila¹

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.2, pp. 185-191, 2002, DOI:10.3970/cmes.2002.003.185

Abstract Initial dislocation structures in as-annealed high-purity Mo single crystals, and deformation substructures of the crystals compressed at room temperature under different strain rates have been examined and studied in order to elucidate the physical mechanisms of dislocation multiplication and motion in the early stages of plastic deformation. The initial dislocation density was measured to be in a range of 10⁶ ~ 10⁷ cm⁻². More importantly numerous grown-in superjogs were observed along screw dislocation lines. After testing in compression, dislocation density (mainly screw dislocations) increased to 10⁷ ~ 10⁸ cm⁻². Besides, the formation of dislocation dipoles (debris) due to More >

L. Gaul, M. Fischer¹, U. Nackenhorst²

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.6, pp. 815-824, 2002, DOI:10.3970/cmes.2002.003.815

Abstract A sequential FEM--BEM approach is employed to calculate the dynamic behavior and sound radiation of rotating wheels. The equations of motion for the wheel are developed in the frame of an Arbitrary Eulerian Lagrangian description with a time-independent formulation for steady state rolling and a spatial description of vibrations. The noise radiation caused by the vibration modes is computed by the symmetric hybrid boundary element method. More >

G.D. Hatzigeorgiou¹, D.E. Beskos¹

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.6, pp. 791-802, 2002, DOI:10.3970/cmes.2002.003.791

Abstract This paper presents a general boundary element methodology for the dynamic analysis of three-dimensional inelastic solids and structures. Inelasticity is simulated with the aid of the continuum damage theory. The elastostatic fundamental solution is employed in the integral formulation of the problem and this creates in addition to the surface integrals, volume integrals due to inertia and inelasticity. Thus an interior discretization in addition to the usual surface discretization is necessary. Isoparametric linear quadrilateral elements are used for the surface discretization and isoparametric linear hexahedra for the interior discretization. Advanced numerical integration techniques for singular More >

R. C. Batra¹, H.-K. Ching¹

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.6, pp. 717-730, 2002, DOI:10.3970/cmes.2002.003.717

Abstract The Meshless Local Petrov-Galerkin (MLPG) method is used to analyze transient deformations near either a crack or a notch tip in a linear elastic plate. The local weak formulation of equations governing elastodynamic deformations is derived. It results in a system of coupled ordinary differential equations which are integrated with respect to time by a Newmark family of methods. Essential boundary conditions are imposed by the penalty method. The accuracy of the MLPG solution is established by comparing computed results for one-dimensional wave propagation in a rod with the analytical solution of the problem. Results… More >