Keejoo Lee¹, Chahngmin Cho², Sung W. Lee¹

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.3, pp. 339-350, 2002, DOI:10.3970/cmes.2002.003.339

Abstract A geometrically nonlinear assumed strain formulation is introduced in conjunction with bubble function displacements to improve the performance of a nine-node solid shell element. The assumed strain field has been carefully selected to avoid both element locking and undesirable spurious kinematic modes. The results of numerical tests demonstrate that the present approach leads to an element that is significantly less sensitive to mesh distortion than the existing element. More >

A. Diaz¹, D. Barthès-Biesel²

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.3, pp. 321-338, 2002, DOI:10.3970/cmes.2002.003.321

Abstract This paper deals with the numerical study of the flow of a bioartificial capsule in a long axisymmetric pore with a hyperbolic entrance. The capsule consists of an infinitely thin and hyperelastic membrane filled with a Newtonian liquid. The resolution of the problem is based on an integral formulation of Stokes equations along with a boundary element method. The model allows the study of the influence of various parameters such as the membrane rheology, the membrane elasticity, the viscosity ratio λ between the capsule fluid and the suspending fluid, the capsule shape and size.
Owing… More >

Wolfgang Brocks¹, Weidong Qi²

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.3, pp. 313-320, 2002, DOI:10.3970/cmes.2002.003.313

Abstract Results of a numerical study of creep damage development and its effect on the deformation behavior in the Ni-based superalloy IN 738 LC at 850 °C are reported. A continuum damage mechanics based anisotropic damage model has been coupled with the unified model of Chaboche, and is used for the present study. Numerical computations are performed on a plate containing a circular hole under tension. They show that the applied damage model does not cause damage localization and no significant mesh-dependence of the results are observed. More >

G. Prater, Jr.¹

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.3, pp. 299-312, 2002, DOI:10.3970/cmes.2002.003.299

Abstract A vapor compressor's performance is affected by pressure and mass flow fluctuations resulting from acoustic effects in the suction and discharge manifolds. Through proper geometric design of the manifolds, these pulsations can be modified to increase efficiency and reduce noise. This paper documents the development of a computer simulation program used to tune stationary-vane refrigeration compressors. The program models the mechanical, fluid, thermodynamic, kinematic, and acoustical processes occurring in such compressors, and calculates suction and discharge chamber pressures, mass flow rates, valve displacements, and acoustic input and transfer impedances. Experimental acoustic pressure measurements from a More >

G. Cocchetti², G. Maier², X. P. Shen³

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.3, pp. 279-298, 2002, DOI:10.3970/cmes.2002.003.279

Abstract Interface models mean here relationships between displacement jumps and tractions across a locus of displacement discontinuities. Frictional contact and quasi-brittle fracture interpreted by cohesive crack models are typical mechanical situations concerned by the present unifying approach. Plastic-softening multidissipative interface models are studied in piecewise linear formats, i.e. assuming linearity for yield functions, plastic potentials and relationships between static and kinematic internal variables. The properties and the pros and cons of such simplified models in a variety of formulations (fully non-holonomic in rates, holonomic and in finite steps), all mathematically described as linear complementarity problems, are More >

P. Zhang¹, P. Klein², Y. Huang^1,3, H. Gao⁴, P. D. Wu⁵

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.2, pp. 263-278, 2002, DOI:10.3970/cmes.2002.003.263

Abstract The recently developed virtual-internal-bond (VIB) model has incorporated a cohesive-type law into the constitutive law of solids such that fracture and failure of solids become a coherent part of the constitutive law and no separate fracture or failure criteria are needed. A numerical algorithm is developed in this study for the VIB model under static loadings. The model is applied to study three examples, namely the crack nucleation and propagation from stress concentration, kinking and subsequent propagation of a mode II crack, and the buckling-driven delamination of a thin film from a substrate. The results More >

Chengyu Wei^{1, 2}, Deepak Srivastava ², Kyeongjae Cho¹

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.2, pp. 255-262, 2002, DOI:10.3970/cmes.2002.003.255

Abstract The temperature dependence of the plastic collapse of single-wall carbon nanotubes under axial compression has been studied with classical molecular dynamics simulations using Tersoff-Brenner potential for C-C interactions. At zero temperature, an (8,0) single-wall carbon nanotube under axial compression collapses by forming fins-like structure which remains within the elastic limit of the system, in agreement of previous molecular dynamics study. At finite temperatures, however, we find that temperature dependent fluctuations can activate the formation of sp3 bonds, in agreement with a recently proposed plastic collapse mechanism of the same nanotube with a generalized tight-binding molecular More >

Robb Thomson, Retired¹, L. E. Levine¹, Y. Shim E. ², M. F. Savage¹, D. E. Kramer¹

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.2, pp. 245-254, 2002, DOI:10.3970/cmes.2002.003.245

Abstract A conceptual theoretical scheme for single crystal metal deformation is presented consisting of multi-scale models from dislocation dynamics to the continuum constitutive relations. The scheme rests on the fundamental observations that deformation is characterized by partially ordered internal dislocation wall structures, discontinuous strain bursts in time, and strain localization in a surface slip band structure. A percolation strain model corresponds to elementary slip line burst events, with percolation parameters to be supplied from experiments and dislocation dynamics studies of wall structures. A model for localization of the slip lines into bands is proposed (for suitable More >

R. Martinez¹, N. M. Ghoniem²

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.2, pp. 229-244, 2002, DOI:10.3970/cmes.2002.003.229

Abstract We focus here on the direct coupling of Dislocation Dynamics (DD) computer simulations with the Finite Element Method (FEM) to simulate plastic deformation of micro-scale structures, and investigate the influence of crystal surfaces on dislocation motion. A series of three-dimensional (3-d) DD simulations of BCC single crystals with a single shear loop in the (101)-[111] slip system are first presented. The purpose of these simulations is to explore the relationship between loop force distributions and the proximity of the loop to the crystal boundary. Traction boundary conditions on a single crystal model are satisfied through… More >

Ju Li¹, Sidney Yip¹

CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.2, pp. 219-228, 2002, DOI:10.3970/cmes.2002.003.219

Abstract We examine the role of atomistic simulations in multiscale modeling of mechanical behavior of stressed solids. Theoretical strength is defined through modes of structural instability which, in the long wavelength limit, are specified by criteria involving elastic stiffness coefficients and the applied stress; more generally, strength can be characterized by the onset of soft vibrational modes in the deformed lattice. Alternatively, MD simulation of stress-strain response provides a direct measure of the effects of small-scale microstructure on strength, as illustrated by results on SiC in single crystal, amorphous, and nanocrystalline phases. A Hall-Petch type scaling More >