V. Sansalone^1,∗, V. Bousson², S. Naili¹, C. Bergot², F. Peyrin³, J.D. Laredo², G. Haïat¹

CMES-Computer Modeling in Engineering & Sciences, Vol.87, No.5, pp. 387-410, 2012, DOI:10.3970/cmes.2012.087.387

Abstract This paper investigates the effects of the heterogeneous distribution of the Haversian Porosity (HP) and Tissue Mineral Density (TMD) on the elastic coefficients of bone in the human femoral neck. A bone specimen from the inferior femoral neck was obtained from a patient undergoing standard hemiarthroplasty. The specimen was imaged using 3-D synchrotron micro-computed tomography (voxel size of 10.13 mm), leading to the determination of the anatomical distributions of HP and TMD. These experimental data were used to estimate the elastic coefficients of the bone using a three-step homogenization model based on continuum micromechanics: (i) At the tissue scale (characteristic… More >

N. Ohba^1,2, S. Ogata², T. Tamura², S. Yamakawa¹, R. Asahi¹

CMES-Computer Modeling in Engineering & Sciences, Vol.75, No.3&4, pp. 247-266, 2011, DOI:10.3970/cmes.2011.075.247

Abstract Understanding the stress dependence of Li diffusivity in the Li-graphite intercalation compound (Li-GIC) that has been used in the Li-ion rechargeable battery as a negative electrode, is important to search for better conditions to improve the power performance of the battery. In the Li-GIC, the Li ion creates a long-ranged stress field around itself by expanding the inter-layer distance of the graphite. To take into account such a long-ranged stress field in the first-principles simulation of the Li diffusion, we develop the hybrid quantum (QM)-classical (CL) simulation code. In the hybrid code, the QM region selected adaptively around the Li… More >

George D. Manolis¹, Stavros Pavlou²

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.3, pp. 399-416, 2002, DOI:10.3970/cmes.2002.003.399

Abstract A free-space Green's function for problems involving time-harmonic elastic waves in variable density materials under plane strain conditions is developed herein by means of Hormander's method in the context of matrix algebra formalism. The challenge when solving problems involving inhomogenous media is that the coefficients appearing in the governing equations of motion are position-dependent. Furthermore, an additional difficulty stems from the fact that these governing equations are vectorial, which implies that coordinate transformation techniques that have been successful with scalar waves can no longer be used. Thus, the present work aims at establishing the necessary background that will allow for… More >

Yu Wang¹, Zhen Luo^1,2, Nong Zhang¹

CMES-Computer Modeling in Engineering & Sciences, Vol.84, No.3, pp. 229-252, 2012, DOI:10.3970/cmes.2012.084.229

Abstract This paper proposes an alternative topology optimization method for the optimal design of continuum structures, which involves a multilevel nodal density-based approximant based on the concept of conventional SIMP (solid isotropic material with penalization) model. First, in terms of the original set of nodal densities, the Shepard function method is applied to generate a non-local nodal density field with enriched smoothness over the design domain. The new nodal density field possesses non-negative and range-bounded properties to ensure a physically meaningful approximation of topology optimization design. Second, the density variables at the nodes of finite elements are used to interpolate elemental… More >

Zhen Luo^1,2, Nong Zhang^1,3, Yu Wang¹

CMES-Computer Modeling in Engineering & Sciences, Vol.83, No.1, pp. 73-96, 2012, DOI:10.3970/cmes.2012.083.073

Abstract This paper aims to present a physically meaningful level set method for shape and topology optimization of structures. Compared to the conventional level set method which represents the design boundary as the zero level set, in this study the boundary is embedded into non-zero constant level sets of the level set function, to implicitly implement shape fidelity and topology changes in time via the propagation of the discrete level set function. A point-wise nodal density field, non-negative and value-bounded, is used to parameterize the level set function via the compactly supported radial basis functions (CSRBFs) at a uniformly defined set… More >

Zhi Yuan Cui¹, Jiu Hui Wu¹, Di Chen Li¹

CMES-Computer Modeling in Engineering & Sciences, Vol.71, No.2, pp. 149-156, 2011, DOI:10.3970/cmes.2011.071.149

Abstract A quantitative rule of the vibrated granular media's energy dissipation is obtained by adopting the turbulence theory in this letter. Our results show that, similar to the power spectrum in fully developed fluid turbulence as described in Kolmogorov's theory, the power spectrum of vibrated granular media also exhibits a k - 5 / 3 (k is the wave number) power which characterizes the local isotropic flow. What's more, the mean energy dissipation rate in vibrated granular media rises with the increase of particle size and volume ratio. The theoretical results in this letter can be verified by the previous experimental… More >

Che-Wun Hong^1,2, Chia-Yun Tsai¹

CMES-Computer Modeling in Engineering & Sciences, Vol.67, No.2, pp. 79-94, 2010, DOI:10.3970/cmes.2010.067.079

Abstract This paper describes the quantum mechanical simulation on the photonic properties of group-III nitride clusters, whose bulk types are common materials for light emitting diodes (LEDs). In order to emit different colors of light using the same semiconductor materials, it is possible to vary the band gap by controlling the quantum dot sizes or doping a third atom theoretically. Density functional theory (DFT) calculations are performed to analyze a set of binary (GaN)_n (3≤n≤32) and ternary In_xGa_1-xN (0≤x≤0.375) clusters to study their photonic characteristics. The ground state structures are optimized to calculate the binding energies using the time-independent DFT. Then… More >

Q.W. Ma^1,2, J.T. Zhou¹

CMES-Computer Modeling in Engineering & Sciences, Vol.43, No.3, pp. 277-304, 2009, DOI:10.3970/cmes.2009.043.277

Abstract Following our previous work, the Meshless Local Petrov-Galerin me -thod based on Rankine source solution (MLPG_R) will be extended in this paper to deal with breaking waves. For this purpose, the governing equation for pressure is improved and a new technique called Mixed Particle Number Density and Auxiliary Function Method (MPAM) is suggested for identifying the free surface particles. Due to complexity of the problem, two dimensional (2D) breaking waves are only concerned here. Various cases are investigated and some numerical results are compared with experimental data available in literature to show the newly developed method is robust. More >

Y. Tomita ¹, M. Uchida ¹

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.3, pp. 239-248, 2005, DOI:10.3970/cmes.2005.010.239

Abstract In this study, we clarified the micro- to mesoscopic deformation behavior of a semicrystalline polymer by employing a large-deformation finite element homogenization method. The crystalline plasticity theory with a penalty method for the inextensibility of the chain direction and the nonaffine molecular chain network theory were applied for the representation of the deformation behavior of the crystalline and amorphous phases, respectively, in the composite microstructure of the semicrystalline polymer. The 3D structure of lamellae in the spherulite of high-density polyethylene was modeled, and the tensile and compressive deformation behaviors were investigated. A series of computational simulations clarified the difference in… More >

A. Arid¹, T. Kousksou¹, S.Jegadheeswaran², A. Jamil³, Y. Zeraouli¹

FDMP-Fluid Dynamics & Materials Processing, Vol.8, No.3, pp. 257-276, 2012, DOI:10.3970/fdmp.2012.008.257

Abstract A two-dimensional numerical model has been developed to investigate the phase-change of ice near 4 °C in a rectangular cavity. The enthalpy-porosity model is reformulated in terms of conservation equations of mass, momentum and heat to account for the evolution the solid/liquid interface. Constant and time-dependent (with sinusoidal law) temperature boundary conditions are considered. Results confirm the possibility to control the typical dynamics of ice melting in a square cavity near the density inversion point by means of a wall temperature which varies in time (with given amplitude and frequency). More >