Xiang-YangLi¹, Shang-Hua Teng², Peng-Jun Wan³

CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.1, pp. 97-116, 2001, DOI:10.3970/cmes.2001.002.097

Abstract To conduct numerical simulations by finite element methods, we often need to generate a high quality mesh, yet with a smaller number of elements. Moreover, the size of each of the elements in the mesh should be approximately equal to a given size requirement. Li et al. recently proposed a new method, named biting, which combines the strengths of advancing front and sphere packing. It generates high quality meshes with a theoretical guarantee. In this paper, we show that biting squares instead of circles not only generates high quality meshes but also has the following advantages. It is easier to… More >

M.A. Golberg¹, C.S. Chen²

CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.1, pp. 87-96, 2001, DOI:10.3970/cmes.2001.002.087

Abstract The purpose of this paper is to develop a highly efficient mesh-free method for solving nonlinear diffusion-reaction equations in R^d, d=2, 3. Using various time difference schemes, a given time-dependent problem can be reduced to solving a series of inhomogeneous Helmholtz-type equations. The solution of these problems can then be further reduced to evaluating particular solutions and the solution of related homogeneous equations. Recently, radial basis functions have been successfully implemented to evaluate particular solutions for Possion-type equations. A more general approach has been developed in extending this capability to obtain particular solutions for Helmholtz-type equations by using polyharmonic spline… More >

Ru-Min Chao, Yen-Ji Chen, F.C. Lin¹

CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.1, pp. 73-86, 2001, DOI:10.3970/cmes.2001.002.073

Abstract The two-dimensional elasticity problem of an isotropic material, containing a centered-crack with unknown boundary traction is studied by the inverse procedure. The dual boundary integral equations are used to analyze the problem. While solving the ill-posed inverse problem, both of the conjugate gradient method and the regularization method are used. A scaling factor depending upon the material constant μ is introduced into the sensitivity matrix in order to keep the order of magnitude the same throughout the formulation. The result by using the displacement measurement will be compared with those by stress measurement, and an extensive discussion will be given.… More >

A. Le van¹, P. Le Grognec¹

CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.1, pp. 63-72, 2001, DOI:10.3970/cmes.2001.002.063

Abstract Necking is a bifurcation phenomenon observed in round bars under tensile loading and has been investigated in numbers of papers. In the present work, it is modeled within the framework of finite rate-independent plasticity. The theory is based on thermodynamic foundations developed for standard materials and results in a total Lagrangian formulation for finite plasticity, where the total strain is decomposed additively according to [Green and Nagdhi 1965)] and the hardening is characterized by a nonlinear isotropic hardening law of the saturation type.
The discretization and consistent linearization of the elastic-plastic equation set using the standard finite element procedure… More >

António Tadeu, Andreia Pereira, Luís Godinho¹

CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.1, pp. 49-62, 2001, DOI:10.3970/cmes.2001.002.049

Abstract The Boundary Element Method (BEM) is used to compute the three-dimensional variation pressure field generated by a point pressure source inside a flat waveguide channel filled with a homogeneous fluid, in the presence of infinite rigid circular pipelines. The problem is solved in the frequency domain, using boundary elements to model the pipeline and an appropriate Green's function to simulate the free surface and the rigid floor of the channel. Because of the 2 ---1/2 ---D geometry of the problem, the separation of variables has been used, and the solution at each frequency is expressed in terms of waves with… More >

A. Mandolini¹, V. Minutolo¹, E. Ruocco¹

CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.1, pp. 39-48, 2001, DOI:10.3970/cmes.2001.002.039

Abstract Many sloping areas in the world are affected by slow movements. If they are occupied by settlements or are crossed by roads, pipelines or other infrastructures, a correct evaluation of future displacements is crucial for land management and sometimes for men safety. It is widely recognized that rainfall is the main triggering factor, producing an intermittent and delayed recharge of the groundwater; as a consequence, the displacement rate is cyclic, following a seasonal trend. In Italy this problem is particularly relevant since many exploited sloping areas are affected by slowly moving landslides that interact with man-made works. In present paper… More >

A. El-Zafrany¹

CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.1, pp. 27-38, 2001, DOI:10.3970/cmes.2001.002.027

Abstract In a recent publication, the author has introduced boundary integral equations for thick plate bending problems, for cases with generalized types of loading. Internal bending moments and shear forces, required for stress analysis, were calculated by means of a finite difference procedure, which requires fine boundary element meshes to achieve an acceptable degree of accuracy. In this paper, boundary integral equations for internal bending moments and shear forces are presented for thick Reissner plates in bending. Domain loading terms in those boundary integral equations have also been simplified for a variety of loading types including concentrated loading, linearly-distributed loading, and… More >

D. S. Sophianopoulos¹, G. T. Michaltsos²

CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.1, pp. 15-26, 2001, DOI:10.3970/cmes.2001.002.015

Abstract The present work deals with the global stability aspects of a simple two-degrees-of-freedom autonomous initially imperfect damped model, under step (conservative) loading. The proposed system is an extension of the classical limit point one firstly introduced by von Mises, with the addition of a linear rotational spring. The effect of its properties (stiffness and damping) are fully assessed and under certain combinations of the parameters involved a third possibility of postbuckling dynamic response is revealed. This is associated with a point attractor response on a stable prebuckling fixed point, although dynamic buckling has already occurred, a finding validating new relevant… More >

C.M. Müller-Karger¹, C.González², M.H.Aliabadi³, M.Cerrolaza⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.2, No.1, pp. 1-14, 2001, DOI:10.3970/cmes.2001.002.001

Abstract In this paper, a three-dimensional Boundary Element model of the proximal tibia of the human knee is described and stresses and displacements in the tibial plateau under static loading are computed. The geometry is generated via three-dimensional reconstruction of Computerized Tomographies and Magnetic Resonance Imaging. Various models of different lengths from the tibia plateau are calculated. The BEM results are compared with a Finite Element model having the same geometry and tibia FE models available in the literature. Also reported are investigations of some pathological situations, including fractures. The results of the comparisons show that BEM is an efficient and… More >

W.W. Liou¹, Y.C. Fang¹

CMES-Computer Modeling in Engineering & Sciences, Vol.1, No.4, pp. 119-128, 2000, DOI:10.3970/cmes.2000.001.571

Abstract A simple implicit treatment for the low speed inflow and outflow boundary conditions for the direct simulation Monte Carlo (DSMC) of the flows in microelectromechanical systems (MEMS) is proposed. The local mean flow velocity, temperature, and number density near the subsonic boundaries were used to determine the number of molecules entering the computational domain and their corresponding velocities at every sample average step. The proposed boundary conditions were validated against micro-Poiseuille flows and micro-Couette flows. The results were compared with analytical solutions derived from the Navier-Stokes equations using first-order and second order slip-boundary conditions. The results show that the implicit… More >