S.-Y. Leu¹, J.T. Chen²

CMES-Computer Modeling in Engineering & Sciences, Vol.14, No.2, pp. 129-140, 2006, DOI:10.3970/cmes.2006.014.129

Abstract Plastic limit angular velocity of rotating hollow cylinders made of the von Mises materials with nonlinear isotropic hardening is investigated numerically and analytically in the paper. The paper applies sequential limit analysis to deal with the rotating problems involving hardening material property and weakening behavior resulted from the widening deformation. By sequential limit analysis, the paper treats the plasticity problems as a sequence of limit analysis problems stated in the upper bound formulation. Rigorous upper bounds are acquired iteratively through a computational optimization procedure with the angular velocity factor as the objective function. Especially, rigorous validation was conducted by numerical… More >

Z. D. Han¹, H. T. Liu¹, A. M. Rajendran², S. N. Atluri³

CMES-Computer Modeling in Engineering & Sciences, Vol.14, No.2, pp. 119-128, 2006, DOI:10.3970/cmes.2006.014.119

Abstract This paper presents the implementation of a three-dimensional dynamic code, for contact, impact, and penetration mechanics, based on the Meshless Local Petrov-Galerkin (MLPG) approach. In the current implementation, both velocities and velocity-gradients are interpolated independently, and their compatibility is enforced only at nodal points. As a result, the time consuming differentiations of the shape functions at all integration points is avoided, and therefore, the numerical process becomes more stable and efficient. The ability of the MLPG code for solving high-speed contact, impact and penetration problems with large deformations and rotations is demonstrated through several computational simulations, including the Taylor impact… More >

J. Ma², H. Lu², B. Wang², R. Hornung³, A. Wissink³, R. Komanduri^2,*

CMES-Computer Modeling in Engineering & Sciences, Vol.14, No.2, pp. 101-118, 2006, DOI:10.3970/cmes.2006.014.101

Abstract A new method for multiscale simulation bridging two scales, namely, the continuum scale using the generalized interpolation material point (GIMP) method and the atomistic scale using the molecular dynamics (MD), is presented and verified in 2D. The atomistic strain from the molecular dynamics simulation is determined through interpolation of the displacement field into an Eulerian background grid using the same generalized interpolation functions as that in the GIMP method. The atomistic strain is consistent with that determined from the virial theorem for interior points but provides more accurate values at the boundary of the MD region and in the transition… More >

Xianwu Ling¹, S.N. Atluri

CMES-Computer Modeling in Engineering & Sciences, Vol.14, No.2, pp. 91-100, 2006, DOI:10.3970/cmes.2006.014.091

Abstract In this paper, a lattice-based cell model is proposed for single wall carbon nanotubes (SWNTs). The finite temperature effect is accounted for via the local harmonic approach. The equilibrium SWNT configurations are obtained by minimizing the Helmholtz free energy with respect to seven primary coordinate variables that are subjected to a chirality constraint. The calculated specific heats agree well with the experimental data, and at low temperature depend on the tube radii with small tubes having much lower values. Our calculated coefficients of thermal expansion (CTEs) are universally positive for all the radial, axial and circumferential directions, and increase with… More >

Chein-Shan Liu¹

CMES-Computer Modeling in Engineering & Sciences, Vol.14, No.2, pp. 77-90, 2006, DOI:10.3970/cmes.2006.014.077

Abstract In this paper we derive the first-order and second-order one-step GPS applied to the estimation of thermophysical properties. Solving the resultant algebraic equations, which usually converges within ten iterations, it is not difficult to estimate the unknown temperature-dependent thermal conductivity and heat capacity simultaneously, if some supplemented data of measured temperature at a time T is provided. When the measured temperature in the conducting slab is contaminated by noise, our estimated results are also good. The new method does not require any prior information on the functional forms of thermal conductivity and heat capacity. Numerical examples are examined to show… More >

Taeyoung Ha¹, Sangwon Seo², Dongwoo Sheen³

CMES-Computer Modeling in Engineering & Sciences, Vol.14, No.1, pp. 57-76, 2006, DOI:10.3970/cmes.2006.014.057

Abstract We present nonoverlapping domain decomposition methods for the approximation of both electromagnetic fields in a three-dimensional bounded domain satisfying absorbing boundary conditions. A Seidel-type domain decomposition iterative method is introduced based on a hybridization of a nonconforming mixed finite element method. Convergence results for the numerical procedure are proved by introducing a suitable pseudo-energy. The spectral radius of the iterative procedure is estimated and a method for choosing an optimal matching parameter is given. A red-black Seidel-type method which is readily parallelizable is also introduced and analyzed. Numerical experiments confirm that the presented algorithms are faster than the conventional Jacobi-type… More >