Marco Dondero¹, Adrián P. Cisilino^1,2, J. Pablo Tomba¹

CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.3&4, pp. 225-246, 2011, DOI:10.3970/cmes.2011.078.225

Abstract This paper introduces a numerical methodology for the design of random micro-heterogeneous materials with functionally graded effective thermal conductivities (ETC). The optimization is carried out using representative volume elements (RVEs), a parallel Genetic Algorithm (GA) as optimization method, and a Fast Multipole Boundary Element Method (FMBEM) for the evaluation of the cost function. The methodology is applied for the design of foam-like microstructures consisting of random distributions of circular insulated holes. The temperature field along a material sample is used as objective function, while the spatial distribution of the holes is the design variable. There More >

K.I. Silva¹, J.C.F. Telles², F.C. Araújo³

CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.3&4, pp. 209-224, 2011, DOI:10.3970/cmes.2011.078.209

Abstract In this work the boundary element method is applied to solve 2D elastoplastic problems. In elastoplastic boundary element analysis, domain integrals have to be calculated to introduce the contribution of yielded zones. Traditionally, the use of internal integration cells have been adopted to evaluate such domain integrals. The present work, however, proposes an alternative cell free strategy based on the OMLS (Orthogonal Moving Least Squares) interpolation, typically adopted in meshless methods. In this approach the definition of points to compute the interpolated value of a function at a given location only depends on their relative More >

A. Khosravifard¹, M.R. Hematiyan^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.3&4, pp. 185-208, 2011, DOI:10.3970/cmes.2011.078.185

Abstract An inverse method for optimal control of the freezing front motion in the solidification of pure materials is presented. The inverse technique utilizes the idea of a pseudo heat source to account for the latent heat effects. The numerical formulation of this inverse method is based on a formerly introduced meshless technique. In this method, the flux and the velocity of the liquid-solid interface are treated as secondary variables and the liquid and solid domains are modeled simultaneously. Some numerical examples are provided to demonstrate the efficiency of the presented method. The effects of regularization More >

Eduardo T Lima Junior¹, Wilson S Venturini², Ahmed Benallal³

CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.3&4, pp. 169-184, 2011, DOI:10.3970/cmes.2011.078.169

Abstract Some considerations on the numerical analysis of brittle rocks are presented in this paper. The rock is taken as a poro-elastic domain, in full-saturated condition, based on the Biot's Theory. The solid matrix of this porous medium is considered to be susceptible to isotropic damage occurrence. An implicit boundary element method (BEM) formulation, based on time-independent fundamental solutions, is developed and implemented to couple the fluid flow and two-dimensional elastostatics problems. The integration over boundary elements is evaluated by using a numerical Gauss procedure. A semi-analytical scheme for the case of triangular domain cells is More >

C.T.M. Anflor¹, R.J. Marczak²

CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.3&4, pp. 151-168, 2011, DOI:10.3970/cmes.2011.078.151

Abstract This paper aims to demonstrate the final result of an optimization process when a smooth technique is introduced between intermediary iterations of a topological optimization. In a topological optimization process is usual irregular boundary results as the final shape. This boundary irregularity occurs when the way of the material is removed is not very suitable. Avoiding an optimization post-processing procedure some techniques of smooth are implemented in the original optimization code. In order to attain a regular boundary a smoothness technique is employed, which is, Bezier curves. An algorithm was also developed to detect during More >

N.A. Dumont¹, E.Y. Mamani¹

CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.2, pp. 109-150, 2011, DOI:10.3970/cmes.2011.078.109

Abstract A particular implementation of the hybrid boundary element method is presented for the two-dimensional analysis of potential and elasticity problems, which, although general in concept, is suited for fracture mechanics applications. Generalized Westergaard stress functions, as proposed by Tada, Ernst and Paris in 1993, are used as the problem's fundamental solution. The proposed formulation leads to displacement-based concepts that resemble those presented by Crouch and Starfield, although in a variational framework that leads to matrix equations with clear mechanical meanings. Problems of general topology, such as in the case of unbounded and multiply-connected domains, may More >

Y.C. Shiah¹, C. L. Tan²

CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.2, pp. 95-108, 2011, DOI:10.3970/cmes.2011.078.095

Abstract By differentiating the Green function of Ting and Lee (1997) for 3D general anisotropic elastotatics in a spherical coordinate system as an intermediate step, and then using the chain rule, derivatives of up to the second order of this fundamental solution are obtained in exact, explicit, algebraic forms. No tensors of order higher than two are present in these derivatives, thereby allowing these quantities to be numerically evaluated quite expeditiously. These derivatives are required for the computation of the internal point displacements and stresses via Somigliana's identity in BEM analysis. Some examples are presented to More >

T. Matsumoto¹, T. Yamada¹, T. Takahashi¹, C.J. Zheng², S. Harada¹

CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.2, pp. 77-94, 2011, DOI:10.3970/cmes.2011.078.077

Abstract Shape design and topology sensitivity formulations for acoustic problems based on adjoint method and the boundary element method are presented and are applied to shape sensitivity analysis and topology optimization of acoustic field. The objective function is assumed to consist only of boundary integrals and quantities defined at certain number of discrete points. The adjoint field is defined so that the sensitivity of the objective function does not include the unknown sensitivity coefficients of the sound pressures and particle velocities on the boundary and in the domain. Since the final sensitivity expression does not have More >

P. Maghoul¹, B. Gatmiri^1,2, D. Duhamel¹

CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.1, pp. 51-76, 2011, DOI:10.3970/cmes.2011.078.051

Abstract This paper aims at obtaining boundary integral formulations as well as three dimensional(3D) fundamental solutions for unsaturated soils under dynamic loadings for the first time. The boundary integral equations are derived via the use of the weighted residuals method in a way that permits an easy discretization and implementation in a Boundary Element code. Also, the associated 3D fundamental solutions for such deformable porous medium are derived in Laplace transform domain using the method of Hérmander. The derived results are verified analytically by comparison with the previously introduced corresponding fundamental solutions in elastodynamic limiting case. More >

A. Sellier, N. Ghalia

CMES-Computer Modeling in Engineering & Sciences, Vol.78, No.1, pp. 25-50, 2011, DOI:10.3970/cmes.2011.078.025

Abstract The Green tensor complying with anisotropic slip conditions at the surface of a plane, impermeable, motionless and slipping wall is theoretically obtained and an efficient numerical method is proposed to accurately compute at a very reasonable cpu time cost each of its Cartesian component. The accuracy of the advocated numerical strategy is tested against the Maple Software and the employed procedure makes it possible to calculate the Green tensor for a non-isotropic slip condition at a cpu time cost comparable with the one needed for the less complicated isotropic Navier condition. More >