E.A. de Souza Neto¹, S. Amstutz², S.M. Giusti³, A.A. Novotny³

CMES-Computer Modeling in Engineering & Sciences, Vol.62, No.1, pp. 23-56, 2010, DOI:10.3970/cmes.2010.062.023

Abstract A recently proposed algorithm for micro-structural optimization, based on the concept of topological derivative and a level-set domain representation, is applied to the synthesis of elastic and heat conducting bi-material micro-structures. The macroscopic properties are estimated by means of a family of multi-scale constitutive theories where the macroscopic strain and stress tensors (temperature gradient and heat flux vector in the heat conducting case) are defined as volume averages of their microscopic counterparts over a Representative Volume Element (RVE). Several finite element-based examples of micro-structural optimization are presented. Three multi-scale models, providing an upper and a More >

D. Asprone¹, F. Auricchio², G. Manfredi¹, A. Prota¹, A. Reali², G. Sangalli³

CMES-Computer Modeling in Engineering & Sciences, Vol.62, No.1, pp. 1-22, 2010, DOI:10.3970/cmes.2010.062.001

Abstract Particle methods represent some of the most investigated meshless approaches, applied to numerical problems, ranging from solid mechanics to fluid-dynamics and thermo-dynamics. The objective of the present paper is to analyze some of the proposed particle formulations in one dimension, investigating in particular how the different approaches address second derivative approximation. With respect to this issue, a rigorous analysis of the error is conducted and a novel second-order accurate formulation is proposed. Hence, as a benchmark, three numerical experiments are carried out on the investigated formulations, dealing respectively with the approximation of the second derivative More >

Y.C. Cai^1,2, J.K. Paik³, S.N. Atluri²

CMES-Computer Modeling in Engineering & Sciences, Vol.61, No.3, pp. 273-312, 2010, DOI:10.3970/cmes.2010.061.273

Abstract This paper presents an elementary finite element method for geometrically nonlinear large rotation analyses of built-up plate/shell structures comprising of thin members. The tangent stiffness matrix of the element in the updated Lagrangian co-rotational reference frame is developed, based on the von Karman nonlinear theory of plates, and the Reissner variational principle, allowing for unsymmetric stresses and drilling rotations, useful in the analysis of built-up plate and shell structure. The finite rotation of the co-rotational reference frame relative to a globally fixed Cartesian frame, is simply determined from the finite displacement vectors of the nodes… More >

Ming-Hsiao Lee^1,2, Wen-Hwa Chen^1,3

CMES-Computer Modeling in Engineering & Sciences, Vol.61, No.3, pp. 249-272, 2010, DOI:10.3970/cmes.2010.061.249

Abstract The meshless method has a distinct advantage over other methods in that it requires only nodes without an element mesh which usually induces time-consuming work and inaccuracy when the elements are distorted during the analysis process. However, the element mesh can provide more geometry information for numerical simulation, without the need to judge if the nodes or quadrature points are inside the analysis domain which happens in the meshless method, since the analysis domain is defined by the element's edges or faces and the quadrature points are all inside the elements. Because the analysis model… More >

C. Du¹, H. Bai², J. Qu³, X. Su^1,4

CMES-Computer Modeling in Engineering & Sciences, Vol.61, No.3, pp. 223-248, 2010, DOI:10.3970/cmes.2010.061.223

Abstract Second, or higher, order harmonics have great potential in fatigue life prediction. In this study, the dispersion properties of waves propagating in the nonlinear random media are investigated. An one dimensional nonlinear model based on the nonlinear Hikata stress-strain relation is used. We applied perturbation method, the Liouville transformation and the smoothing approximation method to solve the one dimensional nonlinear stochastic wave equation. We show easily that the dispersion equations for all higher order terms will be the same with the corresponding linear random medium by perturbation method. The linear stochastic equation with two random… More >

Hui-Fen Guo^1,2, Bin-Gang Xu^1,3

CMES-Computer Modeling in Engineering & Sciences, Vol.61, No.3, pp. 201-222, 2010, DOI:10.3970/cmes.2010.061.201

Abstract A numerical method is developed for modeling the dynamics of a flexible fiber immersed in a compressible swirling flow. The modeling approach is based on combining an Eulerian finite volume formulation for the fluid flow and a Lagrangian small-deformation formulation for the dynamics of the fiber. The fiber is modeled as a chain of beads connected through mass-less rods. The bending and twisting deformation of the fiber are represented by the displacements of the successive beads. A computational strategy is proposed for the computation of the fluid parameters at the center of discrete fiber sections. More >

Delfim Soares Jr.¹

CMES-Computer Modeling in Engineering & Sciences, Vol.61, No.2, pp. 177-200, 2010, DOI:10.3970/cmes.2010.061.177

Abstract In this work, meshless methods based on the local Petrov-Galerkin approach are employed for the time-domain dynamic analysis of porous media. For the spatial discretization of the pore-dynamic model, MLPG formulations adopting Gaussian weight functions as test functions are considered, as well as the moving least square method is used to approximate the incognita fields. For time discretization, the generalized Newmark method is adopted. The present work is based on the u-p formulation and the incognita fields of the coupled analysis in focus are the solid skeleton displacements and the interstitial fluid pore pressures. Independent spatial More >

Bart Bergen¹, Bert Van Genechten¹, Dirk Vandepitte¹, Wim Desmet¹

CMES-Computer Modeling in Engineering & Sciences, Vol.61, No.2, pp. 155-176, 2010, DOI:10.3970/cmes.2010.061.155

Abstract The Wave Based Method (WBM) is a numerical prediction technique for Helmholtz problems. It is an indirect Trefftz method using wave functions, which satisfy the Helmholtz equation, for the description of the dynamic variables. In this way, it avoids both the large systems and the pollution errors that jeopardize accurate element-based predictions in the mid-frequency range. The enhanced computational efficiency of the WBM as compared to the element-based methods has been proven for the analysis of both three-dimensional bounded and two-dimensional unbounded problems. This paper presents an extension of the WBM to the application of More >

P.H. Wen¹, M.H. Aliabadi²

CMES-Computer Modeling in Engineering & Sciences, Vol.61, No.2, pp. 133-154, 2010, DOI:10.3970/cmes.2010.061.133

Abstract A meshless local Petrov-Galerkin method, for the micro-mechanical material model of woven fabric composite material is presented in this paper. The material models are based on a repeated unit cell approach and two smooth fibre modes. A unit step function is used as the test functions in the local weak-form which leads to local boundary integral equations. The analysed domain is divided into small sub-domains and the radial basis function interpolation without element mesh is adopted. The woven fabric composite elastic moduli evaluated have been shown to be in good agreement with finite element results. More >

B.Y. Lee¹, Y. Lee², J.K.Kim³, Y.Y.Kim⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.61, No.2, pp. 111-132, 2010, DOI:10.3970/cmes.2010.061.111

Abstract In the present work, a micromechanics-based fiber-bridging constitutive model that quantitatively takes into consideration the distribution of fiber orientation and the number of fibers, is derived and a fiber-bridging analysis program is developed. An image processing technique is applied to evaluate the fiber distribution characteristics of four different types of strain-hardening cementitious composites. Then, the fiber-bridging curves obtained from image analysis are compared with those obtained from the assumption of two- and three-dimensional fiber distributions. The calculated ultimate tensile strains are also compared with experimental results. Test results showed that the tensile behavior of strain-hardening More >