Shardool U. Chirputkar¹, Dong Qian²

CMES-Computer Modeling in Engineering & Sciences, Vol.24, No.2&3, pp. 185-202, 2008, DOI:10.3970/cmes.2008.024.185

Abstract A multiscale method based on the extended space-time finite element method is developed for the coupled atomistic/continuum simulation of nanoscale material systems. Existing single scale approach such as the finite element method has limited capability of representing the fine scale physics in both the spatial and temporal domains. This is a major disadvantage for directly incorporating FEM in coupled atomistic/continuum simulations as it results in errors such as spurious wave reflections at the atomistic/continuum interface. While numerous efforts have been devoted to eliminating the interfacial mismatch effects, less attention has been paid to developing fine scale, atomistic level representations within… More >

S. Namilae¹, U. Ch,ra², A Srinivasan³, N. Ch,ra⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.22, No.3, pp. 189-202, 2007, DOI:10.3970/cmes.2007.022.189

Abstract Molecular dynamics (MD) simulations play an important predictive role in understanding the behavior of nanoscale systems. In this paper, parallel MD simulations are used to understand the mechanical behavior of interfaces in CNT based composites. We present an algorithm for parallel implementation of MD simulations of carbon nanotube (CNT) based systems using reactive bond order potentials. We then use that algorithm to model the CNT-polymer interfaces with various levels of interaction as (a) described only by long range Van Der Waals interactions (b) chemically bonded with fixed matrix and (c) chemically bonded with matrix explicitly modeled. It is shown that… More >

Atsuya Oishi¹, Shinobu Yoshimura²

CMES-Computer Modeling in Engineering & Sciences, Vol.21, No.2, pp. 93-104, 2007, DOI:10.3970/cmes.2007.021.093

Abstract This paper describes a new local contact search method using a multi-layer neural network and its application to smoothed contact surface consisting of Gregory patches. A contact search process consists of two phases: a global search phase for finding the nearest node-segment pair and a local search phase for finding an exact local coordinate of the contact point within the segment. In the present method, the multi-layer neural network is utilized in the latter phase. The fundamental formulation of the proposed local contact search method is described in detail, and it is applied to smoothed contact surfaces consisting of Gregory… More >

R. Vodička¹, V. Mantič², F. París²

CMES-Computer Modeling in Engineering & Sciences, Vol.17, No.3, pp. 173-204, 2007, DOI:10.3970/cmes.2007.017.173

Abstract An original approach to solve domain decomposition problems by the symmetric Galerkin boundary element method is developed. The approach, based on a new variational principle for such problems, yields a fully symmetric system of equations. A natural property of the proposed approach is its capability to deal with nonconforming discretizations along straight and curved interfaces, allowing in this way an independent meshing of non-overlapping subdomains to be performed. Weak coupling conditions of equilibrium and compatibility at an interface are obtained from the critical point conditions of the energy functional. Equilibrium is imposed through local traction (Neumann) boundary conditions prescribed on… More >

Yaxin Song¹, D. Michael McFarland¹, Lawrence A. Bergman¹, Alexander F. Vakakis²

CMES-Computer Modeling in Engineering & Sciences, Vol.10, No.2, pp. 153-170, 2005, DOI:10.3970/cmes.2005.010.153

Abstract A general interface element is developed for dynamic response analysis of structures with jointed interfaces, which can account for damping due to both impact and friction. Contact effects are included through a segment-to-segment contact model which considers the stick-slip-slap behavior at every point along the joint interface. A nonlinear friction law is adopted at the interface to describe microscopic relative motion due to the deformation of the asperities on the interface. Numerical examples demonstrate that the general joint interface element is capable of accounting for both friction and impact damping in jointed interfaces, as well as capturing the transfer of… More >

L. G. Zhou¹, L. M. Hsiung², Hanchen Huang¹

CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.3, pp. 245-252, 2004, DOI:10.3970/cmes.2004.006.245

Abstract Using molecular dynamics simulations, we study the deformation of polysynthetically twinned (PST) TiAl at room temperature. The simulation cell is pre-strained and thermodynamically relaxed to zero stress, so that no dislocations pre-exist in γ−α₂ interfaces. A uniaxial compression is then applied along one 1/6<112] direction. Our results show that interfacial dislocation pairs nucleate at the γ−α₂ interface under the compression. The glide and agglomeration of these dislocations lead to the nucleation of deformation twins from the interface. Based on our studies, twins may nucleate without pre-existing interfacial dislocations. Further we have monitored the propagation of the deformation twin, specifically its… More >

S. Fashu^{1 *}, M.Tozvireva¹, L.Mudzingwa¹, R.Khan², A. Mukuya¹

FDMP-Fluid Dynamics & Materials Processing, Vol.12, No.4, pp. 173-192, 2016, DOI:10.3970/fdmp.2016.012.173

Abstract This paper outlines the findings in the comparison of the influence of mechanical and electromagnetic stirring on ingot long term purity and uniformity during Ohno Continuous Casting. The magnitude of the average optimum velocity flow field and stirring parameters required to effectively purify aluminum ingots using mechanical stirring of the melt was determined and analyzed. Basing on the determined optimum mechanical flow field, electromagnetic parameters producing almost the same flow field near the interface were obtained through careful adjustments of parameters. Optimum parameters of the mechanical and electromagnetic stirring were obtained by numerically solving the solidification model coupled with either… More >

S. Homma¹, M. Yokotsuka¹, T. Tanaka¹, K. Moriguchi¹, J. Koga¹, G. Tryggvason²

FDMP-Fluid Dynamics & Materials Processing, Vol.7, No.3, pp. 231-240, 2011, DOI:10.3970/fdmp.2011.007.231

Abstract We develop a three-fluid front-tracking method in order to simulate the motion of an axisymmetry compound droplet, which consists of three immiscible fluids separated by two different interfaces. The two interfaces of the compound droplet are represented by two different sets of the front-tracking elements immersed on the Eulerian grid mesh, where the velocities and the pressure are calculated. The density and viscosity profiles with jumps at the interfaces are successfully determined from the location and the connection information of the front-tracking elements. The motion of a compound droplet is simulated on axisymmetric cylindrical coordinates. The results show that the… More >

Yu. Gaponenko¹, I. Ryzhkov², V. Shevtsova³

FDMP-Fluid Dynamics & Materials Processing, Vol.6, No.1, pp. 75-98, 2010, DOI:10.3970/fdmp.2010.006.075

Abstract Gas-liquid flows in annulus are analyzed for fluids in large range of viscosity ratios. The geometry corresponds to a liquid bridge co-axially placed into an outer cylinder with solid walls. The internal core consists of solid rods at the bottom and top, while the central part is a relatively short liquid zone filled with viscous liquid and kept in its position by surface tension. The gas enters into the annular duct and entrains initially quiescent liquid. The flow structures in the liquid and gas are obtained numerically for different shapes of solid rods. Solution for fully developed flow in annulus… More >

Rodica Borcia¹, Michael Bestehorn²

FDMP-Fluid Dynamics & Materials Processing, Vol.6, No.1, pp. 1-12, 2010, DOI:10.3970/fdmp.2010.006.001

Abstract We study numerically the fully nonlinear evolution of thin liquid films on solid supports in three spatial dimensions. A phase field model is used as mathematical tool. Homogeneous and inhomogeneous substrates are taken into account. For flat homogeneous substrates the stability of thin liquid layers is investigated under the action of gravity. The coarsening process at the solid boundary can be controlled on inhomogeneous substrates. On substrates chemically patterned in an adequate way with hydrophobic and hydrophilic spots (functional surfaces), one can obtain stable regular liquid droplets as final dewetted morphology. More >