K.W. Luczynski¹, A. Dejaco¹, O. Lahayne¹, J. Jaroszewicz², W.Swieszkowski², C. Hellmich¹

CMES-Computer Modeling in Engineering & Sciences, Vol.87, No.6, pp. 505-529, 2012, DOI:10.3970/cmes.2012.087.505

Abstract A 71 volume-% macroporous tissue engineering scaffold made of poly-l-lactide (PLLA) with 10 mass-% of pseudo-spherical tri-calcium phosphate (TCP) inclusions (exhibiting diameters in the range of several nanometers) was microCT-scanned. The corresponding stack of images was converted into regular Finite Element (FE) models consisting of around 100,000 to 1,000,000 finite elements. Therefore, the attenuation-related, voxel-specific grey values were converted into TCP-contents, and the latter, together with nanoindentation tests,entered a homogenization scheme of the Mori-Tanaka type, as to deliver voxel-specific (and hence, finite element-specific) elastic properties. These FE models were uniaxially loaded, giving access to the macroscopic Young's modulus of the… More >

F. Maceri¹, M. Marino¹, G. Vairo¹

CMES-Computer Modeling in Engineering & Sciences, Vol.87, No.5, pp. 461-482, 2012, DOI:10.3970/cmes.2012.087.461

Abstract The mechanical behavior of biopolymer mo -le -cu -les is herein addressed and a novel predictive model for their elasto-damage response is proposed. Both entropic and energetic elastic mechanisms are accounted for, and coupled by consistent equilibrium conditions. Moreover, through non-smooth mechanics arguments, molecular damage is modeled accounting for failure due to both mechanical and non-mechanical damage sources. The model is applied to collagen molecules and an excellent agreement with available experimental tests and atomistic computations is shown. The proposed predictive theory can be usefully integrated in hierarchical models of biological structures towards a multiscale continuum approach. More >

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 >

L. Godinho¹, D. Soares Jr.²

CMES-Computer Modeling in Engineering & Sciences, Vol.87, No.4, pp. 327-354, 2012, DOI:10.3970/cmes.2012.087.327

Abstract In this work, a coupling strategy between the Method of Fundamental Solutions (MFS) and the Kansa's Method (KM) for the analysis of fluid-solid interaction problems in the frequency domain is proposed. In this approach, the MFS is used to model the acoustic fluid medium, while KM accounts for the elastodynamic solid medium. The coupling between the two methods is performed iteratively, with independent discretizations being used for the two methods, without requiring matching between the boundary nodes along the solid-fluid interface. Two application examples, with single and multiple solid sub-domains, are presented, illustrating the behavior of the proposed approach. More >

A.E. Martínez-Castro¹, I.H. Faris¹, R. Gallego¹

CMES-Computer Modeling in Engineering & Sciences, Vol.87, No.3, pp. 177-206, 2012, DOI:10.3970/cmes.2012.087.177

Abstract In this paper, the identification of hidden defects inside a three-dimen -sional layer is set as an Identification Inverse Problem. This problem is solved by minimizing a cost functional which is linearized with respect to the volume defects, leading to a procedure that requires only computations at the host domain free of defects. The cost functional is stated as the misfit between experimental and computed displacements and spherical and/or ellipsoidal cavities are the defects to locate. The identification of these cavities is based on the measured displacements at a set of points due to time-harmonic point loads at an array… More >

Kentaro Doi^1,2, Ikumi Onishi¹, Satoyuki Kawano^1,3

CMES-Computer Modeling in Engineering & Sciences, Vol.77, No.2, pp. 113-136, 2011, DOI:10.3970/cmes.2011.077.113

Abstract Hydrogen technologies are currently one of the most actively researched topics. A lot of researches have tied to enhance their energy conversion efficiencies. In the present study, numerical analyses have been carried out focusing on hydrogen-storage carbon materials which are expected to realize high gravimetric and volumetric capacities. In particular, dissociative adsorption processes of H₂ molecules above graphene surfaces have been investigated by ab initio molecular dynamics. The present results indicate that a steric graphene surface plays an important role in enhancing the charge transfer which induces dissociation of H₂ and adsorption of H atoms on the surface. The dissociation… More >

Delfim Soares Jr.¹

CMES-Computer Modeling in Engineering & Sciences, Vol.76, No.1, pp. 61-82, 2011, DOI:10.3970/cmes.2011.076.061

Abstract This work proposes an iterative procedure to analyse pore-dynamic models discretized by time-domain Meshless Local Petrov-Galerkin formulations. By considering an iterative procedure based on a successive renew of variables, each phase of the coupled problem in focus can be treated separately, uncoupling the governing equations of the model. Thus, smaller and better conditioned systems of equations are obtained, rendering a more attractive methodology. A relaxation parameter is introduced here in order to improve the efficiency of the iterative procedure and an expression to compute optimal values for the relaxation parameter is discussed. Linear and nonlinear models are focused, highlighting that… More >

Mohammad Mashayekhi¹, Hossein M. Shodja^1,2, Reza Namakian¹

CMES-Computer Modeling in Engineering & Sciences, Vol.76, No.1, pp. 19-60, 2011, DOI:10.3970/cmes.2011.076.019

Abstract A meshless method called reproducing kernel particle method (RKPM) is exploited to cope with elastic-plastic fracture mechanics (EPFM) problems. The idea of arithmetic progression is assumed to place particles within the refinement zone in the vicinity of the crack tip. A comparison between two conventional treatments, visibility and diffraction, to crack discontinuity is conducted. Also, a tracking to find the appropriate diffraction parameter is performed. To assess the suggestions made, two mode I numerical simulations, pure tension and pure bending tests, are executed. Results including J integral, crack mouth opening displacement (CMOD), and plastic zone size and shape are compared… More >

Kazuhiko Suga^1,2, Takahiko Ito¹

CMES-Computer Modeling in Engineering & Sciences, Vol.75, No.2, pp. 141-172, 2011, DOI:10.3970/cmes.2011.075.141

Abstract The multiple-relaxation-time lattice Boltzmann method for micro-scale flows (MRT µ-flow LBM) is extensively evaluated in this study. Following the study of Chai, Shi, Guo and Lu (2010), the diffusive bounce-back wall boundary condition and the collision matrix are modeled. To determine the model parameters, the first-order, 1.5-order and second-order slip-flow models are discussed. Since the mean free path of gas molecules is considered to be influenced by the wall in micro flow systems, the effects of a correction function after Stops (1970) are also evaluated. As the increase of the Knudsen number (Kn), it is necessary to introduce the regularization… More >

L.Q. Moreira¹, F.P. Mariano², A. Silveira-Neto¹

CMES-Computer Modeling in Engineering & Sciences, Vol.75, No.2, pp. 113-140, 2011, DOI:10.3970/cmes.2011.075.113

Abstract Turbulence in fluid flow is one of the most challenging problems in classical physics. It is a very important research problem because of its numerous implications, such as industrial applications that involve processes using mixtures of components, heat transfer and lubrication and injection of fuel into the combustion chambers and propulsion systems of airplanes. Turbulence in flow presents characteristics that are fully nonlinear and that occur at high Reynolds numbers. Because of the nonlinear nature of turbulent flow, an increase in the Reynolds number implies an increase in the Kolmogorov wave numbers, and the flow spectrum becomes larger in both… More >