F. Fleissner¹, T. Haag², M. Hanss², P. Eberhard¹

CMES-Computer Modeling in Engineering & Sciences, Vol.52, No.2, pp. 181-196, 2009, DOI:10.3970/cmes.2009.052.181

Abstract In alpine regions human settlements and infrastructure are at risk to be hit by landslides or other types of geological flows. This paper presents a new approach that can aid the design of protective constructions. An uncertainty analysis of the flow around a debris barrier is carried out using a chute flow laboratory model of the actual debris flow. A series of discrete element simulations thereby serves to compare and assess two different barrier designs. In this study, the transformation method of fuzzy arithmetic is used to investigate the influence of epistemically uncertain model parameters. More >

E. Tonti¹, F. Zarantonello¹

CMES-Computer Modeling in Engineering & Sciences, Vol.39, No.3, pp. 201-236, 2009, DOI:10.3970/cmes.2009.039.201

Abstract The theory of elasticity is usually formulated using differential calculus. We will show that it is possible to give an algebraic or discrete or finite formulation, by starting directly from experimental laws, i.e. by avoiding any discretization process of the differential equations. This direct formulation can be immediately used for numerical solution in elasticity problems and, from a theoretical point of view, it shows some interesting features which are hidden in the differential formulation or are not considered at all. More >

Fuping Zhou¹, Suresh G. Advani², Eric D. Wetzel³

CMES-Computer Modeling in Engineering & Sciences, Vol.39, No.1, pp. 49-66, 2009, DOI:10.3970/cmes.2009.039.049

Abstract Slow drag of a cylinder through a confined, pressurized bed of granules is studied using two-dimensional discrete element method (DEM) simulations. The time-dependent total drag force experienced by the circular cylinder is calculated from the normal and tangential contact forces between the surfaces. To evaluate the role of the granule shape and the aspect ratio on the drag force, the simulation is performed for cylindrical granules, dumbbell-shaped granules, and elliptical granules of three different aspect ratios. Simulation results show that the drag in dumbbell-shaped granules is higher than that in cylindrical granules. In contrast, the More >

D.T. Fullwood¹, S.R. Kalidindi², B.L. Adams¹, S. Ahmadi¹

CMC-Computers, Materials & Continua, Vol.9, No.1, pp. 25-40, 2009, DOI:10.3970/cmc.2009.009.025

Abstract Localization relations arise naturally in the formulation of multi-scale models. They facilitate statistical analysis of local phenomena that may contribute to failure related properties. The computational burden of dealing with such relations is high and recent work has focused on spectral methods to provide more efficient models. Issues with the inherent integrations in the framework have led to a tendency towards calibration-based approaches. In this paper a discrete Fourier transform framework is introduced, leading to an extremely efficient basis for the localization relations. Previous issues with the Green's function integrals are resolved, and the method More >

P. Bettini, E. Brusa, M. Munteanu, R. Specogna, F. Trevisan¹

CMES-Computer Modeling in Engineering & Sciences, Vol.33, No.3, pp. 215-242, 2008, DOI:10.3970/cmes.2008.033.215

Abstract Electrostatic microactuator is a paradigm of MEMS. Cantilever and double clamped microbeams are often used in microswitches, microresonators and varactors. An efficient numerical prediction of their mechanical behaviour is affected by the nonlinearity of the electromechanical coupling. Sometimes an additional nonlinearity is due to the large displacement or to the axial-flexural coupling exhibited in bending. To overcome the computational limits of the available numerical methods two new formulations are here proposed and compared. Modifying the classical beam element in the Finite Element Method to allow the implementation of a \emph {Non incremental sequential approach} is… More >

L. Codecasa¹, R. Specogna², F. Trevisan³

CMES-Computer Modeling in Engineering & Sciences, Vol.31, No.3, pp. 129-144, 2008, DOI:10.3970/cmes.2008.031.129

Abstract In the paper we introduce a methodology to construct discrete constitutive matrices relating magnetic fluxes with magneto motive forces (reluctance matrix) and electro motive forces with currents (conductance matrix) needed for discretizing eddy current problems over hexahedral primal grids by means of the Finite Integration Technique (FIT) and the Cell Method (CM). We prove that, unlike the mass matrices of Finite Elements, the proposed matrices ensure both the stability and the consistency of the discrete equations introduced in FIT and CM. More >

Ömer Civalek ¹

CMES-Computer Modeling in Engineering & Sciences, Vol.31, No.1, pp. 25-36, 2008, DOI:10.3970/cmes.2008.031.025

Abstract In this paper, free vibration analysis of curvilinear or straight-sided quadrilateral membranes is presented. In the proposed approach, irregular physical domain is transformed into a rectangular domain by using geometric coordinate transformation. For demonstration of the accuracy and convergence of the method, some numerical examples are provided on membranes with different geometry such as skew, trapezoidal, sectorial, annular sectorial, and membranes with four curved edges. The results obtained by the DSC method are compared with those obtained by other numerical and analytical methods. More >

F. Cosmi¹

CMES-Computer Modeling in Engineering & Sciences, Vol.27, No.3, pp. 187-196, 2008, DOI:10.3970/cmes.2008.027.187

Abstract The Cell Method is a recent numerical method that can be applied in several fields of physics and engineering. In this paper, the elastodynamics formulation is extended to include system internal damping, highlighting some interesting characteristics of the method. The developed formulation leads to an explicit solving system. The mass matrix is diagonal (without lumping) and in the most general case a time-dependent damping coefficient can be defined for each node. \newline Accuracy and convergence rate have been tested with reference to the classical problem of a particle free vibration with viscous damping.
An application More >

C. Xu¹, X. Jia², R. A. Williams², E. H. Stitt³, M. Nijemeisland³, S. El-Bachir⁴, A. J. Sederman⁴, L. F. Gladden⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.23, No.2, pp. 117-126, 2008, DOI:10.3970/cmes.2008.023.117

Abstract Existing theories and computer models for packed columns are either incapable of handling complex pellet shapes or based on over-simplified packing geometry. A digital packing algorithm, namely DigiPac, has recently been developed to fill the gap. It is capable of packing of particles of any shapes and sizes in a container of arbitrary geometry, and is a first step towards a practical computational tool for reliable predictions of packed column properties based on the actual pellet shapes. DigiPac can operate in two modes: a Monte Carlo mode in which particles undergo directional diffusive motions; and… More >

K. Y. Volokh^*, E. Y. S. Chao^†, M. Armand^‡

Molecular & Cellular Biomechanics, Vol.4, No.2, pp. 67-74, 2007, DOI:10.3970/mcb.2007.004.067

Abstract Information about the stress distribution on contact surfaces of adjacent bones is indispensable for analysis of arthritis, bone fracture and remodeling. Numerical solution of the contact problem based on the classical approaches of solid mechanics is sophisticated and time-consuming. However, the solution can be essentially simplified on the following physical grounds. The bone contact surfaces are covered with a layer of articular cartilage, which is a soft tissue as compared to the hard bone. The latter allows ignoring the bone compliance in analysis of the contact problem, i.e. rigid bones are considered to interact through… More >