Z. D. Han¹, S. N. Atluri¹

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.6, pp. 699-716, 2002, DOI:10.3970/cmes.2002.003.699

Abstract As shown in an earlier work, the FEM-BEM alternating method is an efficient and accurate method for fracture analysis. In the present paper, a further improvement is formulated and implemented for the analyses of three-dimensional arbitrary surface cracks by modeling the cracks in a local finite-sized subdomain using the symmetric Galerkin boundary element method (SGBEM). The finite element method is used to model the uncracked global (built-up) structure for obtaining the stresses in an otherwise uncracked body. The solution for the cracked structural component is obtained in an iteration procedure, which alternates between FEM solution More >

Liu Yang¹, Jie Han, M. P. Anantram, Richard L. Jaffe

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.5, pp. 675-686, 2002, DOI:10.3970/cmes.2002.003.675

Abstract Bonding geometry and bandgap of carbon nantotubes under uniaxial and torsional deformation are studied computationally for nanotubes of various chiralities and diameters. Bonding geometries are obtained with Tersoff-Brenner potential from molecular mechanics simulations. Bandgaps as function of strain are calculated from the molecular mechanics structures using one (p) and four (2s and 2p_x, 2p_y, 2p_z) orbital tight-binding models. For small strains, the bandgap results are qualitatively consistent with those predicted by the one orbital analytical model. Response of the electronic properties of nanotubes to large strains is characterized by a change in sign of d(bandgap)/d(strain). These originate More >

D.W. Brenner, O.A. Shenderova, D.A. Areshkin, J.D. Schall¹, S.-J. V. Frankland²

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.5, pp. 643-674, 2002, DOI:10.3970/cmes.2002.003.643

Abstract The derivation of a bond-order potential energy function and a self-consistent tight-binding scheme is presented, followed by a survey of the application of these methods to calculating properties of carbon nanostructures. The modeling studies discussed include properties of functionalized and kinked carbon nanotubes, Raman shifts for hydrogen stored in nanotubes, nanotubes in a composite, properties of nanotubes in applied potential (electrical) fields, and structures and properties of nanocones, nanodiamond clusters and rods, and hybrid diamond-nanotube structures. More >

Al Globus¹, Madhu Menon², Deepak Srivastava¹

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.5, pp. 557-574, 2002, DOI:10.3970/cmes.2002.003.557

Abstract A genetic algorithm procedure has been developed for fitting parameters for many-body interatomic force field functions. Given a physics or chemistry based analytic form for the force field function, parameters are typically chosen to fit a range of structural and physical properties given either by experiments and/or by higher accuracy tight-binding or ab-initio simulations. The method involves using both near equilibrium and far from equilibrium configurations in the fitting procedure, and is unlikely to be trapped in local minima in the complex many-dimensional parameter space. As a proof of concept, we demonstrate the procedure for… More >

Leonid V. Zhigilei¹, Avinash M. Dongare¹

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.5, pp. 539-556, 2002, DOI:10.3970/cmes.2002.003.539

Abstract Computational modeling has a potential of making an important contribution to the advancement of laser-driven methods in nanotechnology. In this paper we discuss two computational schemes developed for simulation of laser coupling to organic materials and metals and present a multiscale model for laser ablation and cluster deposition of nanostructured materials. In the multiscale model the initial stage of laser ablation is reproduced by the classical molecular dynamics (MD) method. For organic materials, the breathing sphere model is used to simulate the primary laser excitations and the vibrational relaxation of excited molecules. For metals, the… More >

Deepak Srivastava¹, Satya N. Atluri²

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.5, pp. 531-538, 2002, DOI:10.3970/cmes.2002.003.531

Abstract The current status of the progress and developments in computational nanotechnology is briefly reviewed, from the perspective of its applications. The enabling tools and techniques of physics- and chemistry-based simulations, within a multi-scale context , are briefly reviewed . More >

P. Sainsot¹, C. Jacq², D. Nélias¹

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.4, pp. 497-506, 2002, DOI:10.3970/cmes.2002.003.497

Abstract Pressure distributions calculated in the simulation of rough contacts show high values and induce high stresses just beneath the surface. These stresses often exceed the yield strength of the material, therefore, a purely elastic contact model is restrictive. Plastic flow occurs and modifies the surface shape and consequently modifies the surface pressure.
This paper presents a numerical model for 3D-elastoplastic rough contact. It allows the determination of real pressure and permanent surface displacement (flattening of asperities) as well as residual stresses and plastic strains useful in fatigue analysis. The material is assumed to follow the More >

Michael J. Rodgers¹, Leon M. Keer, Herbert S. Cheng

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.4, pp. 483-496, 2002, DOI:10.3970/cmes.2002.003.483

Abstract The steady-state temperature rise due to frictional heating on the surface of coated halfspaces and halfplanes is described by closed form expressions in the Fourier transformed frequency domain. These frequency response functions (FRFs) include the effects of the coating and the speed of the moving heat source and apply for all Peclet number regimes. Analytical inversion of these expressions for several special cases shows the Green's functions as infinite series of images, which may be costly and slowly convergent. Also, the influence coefficients integrated from these Green's functions are not available in closed form. Applying… More >

Shuangbiao Liu, Michael J. Rodgers, Qian Wang, Leon M. Keer, Herbert S. Cheng¹

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.4, pp. 465-482, 2002, DOI:10.3970/cmes.2002.003.465

Abstract Computing the temperature rise and thermoelastic displacement of a material subjected to frictional heating is essential for the realistic modeling of the performance of mechanical components. This paper presents a novel set of frequency-domain expressions for the surface temperature rise and the surface normal thermoelastic displacement of a moving three-dimensional elastic halfspace subjected to arbitrary transient frictional heating, where the velocity of the body and its direction can be an arbitrary function of time. Frequency response functions are derived by using the Carslaw-Jaeger theory, the Seo-Mura result, and the Fourier transform. General formulas are expressed More >

J.Y. Jang¹, M.M. Khonsari²

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.4, pp. 455-464, 2002, DOI:10.3970/cmes.2002.003.455

Abstract Thermohydrodynamic analysis of journal bearings lubricated with multigrade oils is presented. Design charts are presented that enable one to readily estimate the bearing maximum temperature and the shaft temperature using a series of dimensionless parameters introduced in this paper. More >