Dhanjoo N. Ghista^1,2, Liang Zhong², Leok P.Chua², Eddie Y-K Ng², Soo T.Lim³, Ru S. Tan³, TerranceS-J Chua³

Molecular & Cellular Biomechanics, Vol.2, No.4, pp. 217-234, 2005, DOI:10.3970/mcb.2005.002.217

Abstract Background: In this paper, the left ventricle (LV) is modeled as a cylinder with myocardial fibers located helically within its wall. A fiber is modeled into myocardial structural units (MSUs); the core entity of each MSU is the sarcomeric contractile element. The relationship between the sarcomere unit's contractile force and shortening velocity is expressed in terms of the LV model's wall stress and deformation, and hence in terms of the monitored LV pressure and volume. Then, the LV systolic performance is investigated in terms of a mechatronic (excitation-contraction) model of the sarcomere unit located within the… More >

Yunfa Zhang¹, Zihui Xia^1,2

CMC-Computers, Materials & Continua, Vol.2, No.3, pp. 213-226, 2005, DOI:10.3970/cmc.2005.002.213

Abstract In the present study, the initiation and evolution of the interphase damage and their influences on the global stress-strain relation of composite laminates are predicted by finite element analysis on a micromechanical unit cell model. A thin layer of interphase elements is introduced and its stress-strain relation is derived based on a cohesive law which describes both normal and tangential separations at the interface between the fiber and matrix. In addition, a viscous term is added to the cohesive law to overcome the convergence difficulty induced by the so-called snap-back instability in the numerical analysis. More >

B. Amaziane¹, A. Naji², D. Ouazar³, A. H.-D. Cheng⁴

CMC-Computers, Materials & Continua, Vol.2, No.2, pp. 85-96, 2005, DOI:10.3970/cmc.2005.002.085

Abstract In this paper the optimization of groundwater pumping in coastal aquifers under the threat of saltwater intrusion is investigated. The aquifer is inhomogeneous and contains several hydraulic conductivities zones. The aquifer data such as the hydraulic conductivities are uncertain, but with their expected mean and standard deviation values given. A stochastic boundary element method based on the perturbation technique is employed as the simulation tool. The stochastic optimization is handled by the chance-constrained programming. Genetic algorithm is selected as the optimization tool. Numerical examples of deterministic and stochastic problems are provided to demonstrate the feasibility More >

D.S. Liu^1,2 , C.Y. Chen² , D.Y. Chiou³

CMES-Computer Modeling in Engineering & Sciences, Vol.9, No.2, pp. 179-192, 2005, DOI:10.3970/cmes.2005.009.179

Abstract A three-dimensional heterogeneous infinite element method (HIEM) for modeling inclusions with interphases in composite materials is presented. This special element is formulated based on the conventional finite element method (FEM) using the similarity stiffness property and matrix condensation operations. An HIE-FE coupling scheme is also developed and implemented using the commercial software ABAQUS to conduct the elastostatic analysis. The proposed approach was validated first to study heterogeneous material containing one spherical inclusion. The displacement and stress variations around the inclusion vicinity are verified against conventional FEM. The proposed approach was next applied to analyze the effective More >

Charles E. Anderson, Jr.¹, Matthew S. Burkins², James D. Walker¹, William A. Gooch²

CMES-Computer Modeling in Engineering & Sciences, Vol.8, No.2, pp. 91-104, 2005, DOI:10.3970/cmes.2005.008.091

Abstract A modification of Wilkins computational ceramics model is used to simulate experiments of the impact of the APM2 bullet against boron carbide/aluminum targets. Flash radiography provides time-resolved penetration histories. The simulation results are compared to the experimental data; generally, agreement is very good, including capturing dwell and then the onset of penetration. Crater width and debris diameter are also reproduced by the simulations reasonably well. A critical discussion of deficiencies of this computational engineering model is provided. More >

R. Matsumoto, M. Nakagaki

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.3, pp. 187-198, 2005, DOI:10.3970/cmes.2005.010.187

Abstract Large-scale molecular dynamics simulations of tensile deformation of amorphous metals containing a nano-crystalline particle were performed in order to clarify the effects of particle size and crystal volume fraction on the deformation mechanism and strength. It became clear that particle size has very little effect, while crystal volume fraction has a substantial influence. Elastic modulus and flow stress intensify as crystal volume fraction increases. Furthermore, the stress in the crystal phase continues to increase, even after yielding in the amorphous phase. Consequently, work-hardening effects appear, preventing localization of plastic deformation. Thus, the dispersed nano-crystalline particles… More >

Paul R. Dawson¹, Donald E. Boyce², Ronald Rogge³

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.2, pp. 123-142, 2005, DOI:10.3970/cmes.2005.010.123

Abstract Computational mechanics provides a powerful environment for modeling the evolution of material structure during deformation processes and for associating that evolution with changes to the mechanical properties. In this paper, we illustrate a two-scale formulation that links the mechanical loading applied at the scale of a component (the continuum scale) to the responses of the material at the scale of the crystals that comprise it (the crystal scale). Employing the capabilities offered by computational mechanics, we can better understand how heterogeneity of deformation arising at both the continuum and crystal scales influences the behaviors observed More >

J. Bielak¹, O. Ghattas², E.-J. Kim³

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.2, pp. 99-112, 2005, DOI:10.3970/cmes.2005.010.099

Abstract We present a parallel octree-based finite element method for large-scale earthquake ground motion simulation in realistic basins. The octree representation combines the low memory per node and good cache performance of finite difference methods with the spatial adaptivity to local seismic wavelengths characteristic of unstructured finite element methods. Several tests are provided to verify the numerical performance of the method against Green's function solutions for homogeneous and piecewise homogeneous media, both with and without anelastic attenuation. A comparison is also provided against a finite difference code and an unstructured tetrahedral finite element code for a More >

J. Bahen¹, O. Gaber¹, K. Behdinan², J. De Beer³, P. Zalzal⁴, M. Papini¹, M. Z. Saghir¹

FDMP-Fluid Dynamics & Materials Processing, Vol.1, No.4, pp. 343-352, 2005, DOI:10.3970/fdmp.2005.001.343

Abstract The penetration of the reamer into the medullary cavity can be compared to a piston entering a cylinder filled with viscous fluid. When the flutes of the reamer are clogged with bone debris, fat and marrow, the piston effect is magnified and larger pressures are usually obtained. This paper considers a reamer with clogged flutes and investigates whether the rotation speed of the reamer has a significant influence on the pressure within the intramedullary cavity. The effect of reamer rotation speed on the pressure distribution within the bone is investigated numerically by solving the full More >

Cosmina S. Hogea¹, Bruce T. Murray¹, James A. Sethian^2,3

FDMP-Fluid Dynamics & Materials Processing, Vol.1, No.2, pp. 109-130, 2005, DOI:10.3970/fdmp.2005.001.109

Abstract A computational framework for simulating growth and transport in biological materials based on continuum models is proposed. The advantages of the finite difference methodology employed are generality and relative simplicity of implementation. The Cartesian mesh/level set method developed here provides a computational tool for the investigation of a host of transport-based tissue/tumor growth models, that are posed as free or moving boundary problems and may exhibit complicated boundary evolution including topological changes. The methodology is tested here on a widely studied "incompressible flow" type tumor growth model with a numerical implementation in two dimensions; comparisons More >