CMES-Vol. 3, No. 3, 2002

Vol.3, No.3, 2002-Table of Contents

Open Access

ARTICLE

Piecewise Linear Models for Interfaces and Mixed Mode Cohesive Cracks¹
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 comparatively investigated in view of… More >

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ARTICLE

Computer Modeling and Simulation of Stationary-Vane, Rolling Piston Refrigeration Compressors
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 refrigerator test stand provide validation… More >

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1082
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ARTICLE

Numerical Investigation of Creep Damage Development in the Ni-Based Superalloy IN738 LC at 850 °C
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 >

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880
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ARTICLE

Entrance of a Bioartificial Capsule in a Pore
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 to the important number… More >

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819
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ARTICLE

A Geometrically Nonlinear Nine-Node Solid Shell Element Formulation with Reduced Sensitivity to Mesh Distortion
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 >

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838
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Modeling of Electric Double Layer Effects through Pressure-driven Microchannel Flows
E.Y.K. Ng¹, S.T. Poh ²
CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.3, pp. 351-366, 2002, DOI:10.3970/cmes.2002.003.351
Abstract Advances in microfabrication technology have allowed the use of microchannels in ultra compact, very efficient heat exchangers, which capitalize on the channels large surface area to volume ratio, to transport high heat fluxes with small thermal resistances. One example is the cooling of microchips. However, research into microscale flow and heat transfer phenomena conducted by various researchers provided substantial experimental data and considerable evidence that the behaviour of fluid flow and heat transfer in microchannels without phase change may be different than that which normally occurs in larger more conventional sized channels.
This paper describes a numerical analysis with… More >

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772
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ARTICLE

Computational Modeling of Shock and Impact Response of Alumina
A. M. Rajendran¹, D. J. Grove²
CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.3, pp. 367-380, 2002, DOI:10.3970/cmes.2002.003.367
Abstract This paper presents detailed computational analyses investigating the ability of constitutive relationships to describe the response of a 99.5% pure alumina (AD995) subjected to a wide range of stress/strain loading states. Using a shock-wave-propagation-based finite element code, one and two-dimensional simulations were performed for the following shock and impact configurations: plate-on-plate impact; rod-on-rod impact; single-density plate-on-rod impact; graded-density plate-on-rod impact; and rod penetration into a thick plate. The detailed analyses presented in this paper include a model constant sensitivity study through comparisons of computed wave profiles with experimental measurements. More >

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A 2-D Time-Domain BIEM for Dynamic Analysis of Cracked Orthotropic Solids¹
Ch. Zhang²
CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.3, pp. 381-398, 2002, DOI:10.3970/cmes.2002.003.381
Abstract A 2-D time-domain boundary integral equation method (BIEM) for transient dynamic analysis of cracked orthotropic solids is presented in this paper. A finite crack in an unbounded orthotropic solid subjected to an impact loading is considered. Hypersingular time-domain traction boundary integral equations (BIEs) are applied in the analysis. A time-stepping scheme is developed for solving the hypersingular time-domain traction BIEs. The scheme uses a convolution quadrature formula for temporal and a Galerkin method for spatial discretizations. Numerical examples are given to show that the presented time-domain BIEM is highly efficient and accurate. More >

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724
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ARTICLE

A Green's Function for Variable Density Elastodynamics under Plane Strain Conditions by Hormander's Method
George D. Manolis¹, Stavros Pavlou²
CMES-Computer Modeling in Engineering & Sciences, Vol.3, No.3, pp. 399-416, 2002, DOI:10.3970/cmes.2002.003.399
Abstract A free-space Green's function for problems involving time-harmonic elastic waves in variable density materials under plane strain conditions is developed herein by means of Hormander's method in the context of matrix algebra formalism. The challenge when solving problems involving inhomogenous media is that the coefficients appearing in the governing equations of motion are position-dependent. Furthermore, an additional difficulty stems from the fact that these governing equations are vectorial, which implies that coordinate transformation techniques that have been successful with scalar waves can no longer be used. Thus, the present work aims at establishing the necessary background that will allow for… More >

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