Eduardo M. B. Campello^1,2, Tarek I. Zohdi³

CMES-Computer Modeling in Engineering & Sciences, Vol.98, No.2, pp. 221-245, 2014, DOI:10.3970/cmes.2014.098.221

Abstract This work deals with the bombardment of a stream of particles possessing varying mean particle size, velocity and aspect ratio into a cell that has fixed (known) compliance characteristics. The particles are intended to penetrate the cell membrane causing zero or minimum damage and deliver foreign substances (which are attached to their surfaces) to the interior of the cell. We adopt a particle-based (discrete element method) computational model that has been recently developed by the authors to describe both the incoming stream of particles and the cell membrane. By means of parametric numerical simulations, treating the stream’s mean particle size,… More >

Diptiranjan Behera¹, Snehashish Chakraverty²

CMES-Computer Modeling in Engineering & Sciences, Vol.96, No.5, pp. 317-337, 2013, DOI:10.3970/cmes.2013.096.317

Abstract This paper targets to analyse the static response of structures with fuzzy parameters using fuzzy finite element method. Here the material, geometrical properties and external load applied to the structures are taken as uncertain. Uncertainties presents in the parameters are modelled through convex normalised fuzzy sets. Fuzzy finite element method converts the problem into fuzzy or fully fuzzy system of linear equations for static analysis. As such here, two new methods are proposed to solve the fuzzy and fully fuzzy system of linear equations. Numerical examples for structures with uncertain system parameters that are in term of triangular fuzzy number… More >

Fei Yin¹, Deli Gao¹

CMES-Computer Modeling in Engineering & Sciences, Vol.89, No.1, pp. 25-38, 2012, DOI:10.3970/cmes.2012.089.025

Abstract The methods to design the casings used in oilfields, are currently based on the assumptions that the remote crustal-stress-field is axially symmetric, in plane strain. However, most of the failures of the casings are caused by non-uniform and asymmetric far-field crustal stresses, so that it is necessary for a proper design of the casings, to investigate and understand the casing's behavior under non-uniform far-field crustal stresses. A mechanical model is first established for the system, consisting of the casing and formation, by using the plane strain theory of linear elasticity. The non-uniform crustal stress is resolved into a uniform stress… More >

Jeng-Tzong Chen¹, Wen-Cheng Shen², Po-Yuan Chen²

CMES-Computer Modeling in Engineering & Sciences, Vol.12, No.2, pp. 109-119, 2006, DOI:10.3970/cmes.2006.012.109

Abstract In this paper, we derive the null-field integral equation for a circular bar weakened by circular cavities with arbitrary radii and positions under torque. To fully capture the circular geometries, separate forms of fundamental solution in the polar coordinate and Fourier series for boundary densities are adopted. The solution is formulated in a manner of a semi-analytical form since error purely attributes to the truncation of Fourier series. Torsion problems are revisited to demonstrate the validity of our method. Torsional rigidities for different number of holes are also discussed. More >

António Tadeu^1,2, Julieta António¹, Patrícia Ferreira³

CMES-Computer Modeling in Engineering & Sciences, Vol.91, No.3, pp. 153-176, 2013, DOI:10.3970/cmes.2013.091.153

Abstract This paper presents an iterative coupling between a formulation based on the normal derivative of the integral equation (TBEM) and the method of fundamental solutions (MFS) for the transient analysis of acoustic wave propagation problems in the presence of multiple inclusions. The proposed formulation overcomes the individual limitations of each method, requires less computer memory and may use less CPU time than a full direct coupling formulation scheme. In the proposed formulation each inclusion is solved individually, successively, using the TBEM or the MFS and scatters a field that it is seen as an incident field at each of the… More >

P. L. Bishay¹, S.N. Atluri¹

CMES-Computer Modeling in Engineering & Sciences, Vol.84, No.1, pp. 41-98, 2012, DOI:10.3970/cmes.2012.084.041

Abstract Higher-order two-dimensional as well as low and higher-order three-dimensional new Hybrid/Mixed (H/M) finite elements based on independently assumed displacement, and judiciously chosen strain fields, denoted by HMFEM-2, are developed here for applications in macro-mechanics. The idea of these new H/M finite elements is based on collocating the components of the independent strain field, with those derived from the independently assumed displacement fields at judiciously and cleverly chosen collocation points inside the element. This is unlike the other techniques used in older H/M finite elements where a two-field variational principle was used in order to enforce both equilibrium and compatibility conditions… More >

V. Kozulić¹, B. Gotovac¹

CMES-Computer Modeling in Engineering & Sciences, Vol.80, No.3&4, pp. 251-274, 2011, DOI:10.3970/cmes.2011.080.251

Abstract The numerical model for the elasto-plastic analysis of prismatic bars subjected to torsion is developed. The functions implemented in this model are Fup basis functions which belong to the class of atomic functions. The collocation method is used to form a system of equations in which the differential equation of the problem is satisfied in collocation points of closed domain, while boundary conditions are satisfied exactly at the domain boundary. The propagation of plastic zones in the cross-section is monitored by applying the incremental-iterative procedure until failure. An approximate solution of arbitrary accuracy is attained by hierarchically increasing the number… More >

Chein-Shan Liu¹

CMES-Computer Modeling in Engineering & Sciences, Vol.80, No.1, pp. 57-86, 2011, DOI:10.3970/cmes.2011.080.057

Abstract Based-on the ordinary differential equations defined on an invariant manifold, we propose a theoretical procedure to derive a Relaxed Steepest Descent Method (RSDM) for numerically solving an ill-posed system of linear equations when the data are polluted by random noise. The invariant manifold is defined in terms of a squared-residual-norm and a fictitious time-like variable, and in the final stage we can derive an iterative algorithm including a parameter, which is known as the relaxation parameter. Through a Hopf bifurcation, this parameter indeed plays a major role to switch the situation of slow convergence to a new situation with faster… More >

Yongjie Zhang¹, Boyle C. Cheng², Changho Oh¹, Jessica L. Spehar², James Burgess³

CMES-Computer Modeling in Engineering & Sciences, Vol.29, No.2, pp. 55-62, 2008, DOI:10.3970/cmes.2008.029.055

Abstract The spinal column plays a vital biomechanical role in the human body by providing structural support and facilitating motion. As degenerative changes occur in the spine, surgical treatment may be necessary in certain instances. Such treatments seek to address pain, frequently through the restriction of spinal motion. Traditional spinal implant devices are designed to restrict the motion of a functional spinal unit (FSU) but newer device designs allow for semi-constrained motion such as spinal arthroplasty devices. In this study, a sequence of fluoroscopic imaging data was recorded during the flexibility protocol with an interspinous process spacer device placed at L2-L3.… More >

L.K. Keppas¹, G.I. Giannopoulos¹, N.K. Anifantis¹

CMES-Computer Modeling in Engineering & Sciences, Vol.25, No.3, pp. 181-196, 2008, DOI:10.3970/cmes.2008.025.181

Abstract In the present paper a boundary element procedure is formulated to treat two-dimensional time dependent thermo-elastic contact problems incorporating thermal resistance along the contacting surfaces. The existence of pressure-dependent thermal contact leads to coupling of temperature and stress fields. Therefore, the inherent non-linearity of the problem demands simultaneous treating of both thermal and mechanical boundary integral equations while iterative procedures are introduced to ensure equilibrium of mechanical and thermal contact conditions at each step of the process. The transient behavior of interfacial cracks in bimaterial solids when undergo thermal shock in the presence of partial crack closure and thermal contact… More >