Jia-Liang Le¹, Bing Xue¹

CMC-Computers, Materials & Continua, Vol.34, No.3, pp. 251-264, 2013, DOI:10.3970/cmc.2013.034.251

Abstract It has been recently shown that the nominal structural strength of metal-composite structures depends on the structure size, and such dependence is strongly influenced by the stress singularities. Nevertheless, previous studies only focused on structures that exhibit very strong stress singularities, which are close to the crack-like stress singularity. In the actual engineering designs, due to the mismatch of material properties and complex structural geometries, many metalcomposite structures may contain stress singularities that are much weaker than the crack-like stress singularity. This paper presents a numerical study on the size dependence of scaling of fracture… More >

J. Sladek¹, V. Sladek¹, S. Krahulec¹, M. Wünsche², Ch. Zhang²

CMC-Computers, Materials & Continua, Vol.29, No.1, pp. 75-102, 2012, DOI:10.3970/cmc.2012.029.075

Abstract A meshless method based on the local Petrov-Galerkin approach is proposed, to solve static and dynamic problems of two-layered magnetoelectroelastic composites with specific properties. One layer has pure piezoelectric properties and the second one is a pure piezomagnetic material. It is shown that the electric potential in the piezoelectric layer is induced by the magnetic potential in the piezomagnetic layer. The magnetoelectric effect is dependent on the ratio of the layer thicknesses. Functionally graded material properties of the piezoelectric layer and homogeneous properties of the piezomagnetic layer are considered too. The magnetoelectric composites are analyzed More >

K. Wang¹, S.J. Zhou^2,3, Z.F. Nie⁴

CMES-Computer Modeling in Engineering & Sciences, Vol.73, No.1, pp. 77-102, 2011, DOI:10.3970/cmes.2011.073.077

Abstract The natural neighbour Galerkin method is tailored to solve boundary value problems of the couple-stress elasticity to model the size dependent behaviour of materials. This method is based on the displacement-based Galerkin approach, and the calculation of the global stiffness matrix is performed using gradient smoothing technique combined with the non-Sibsonian partition of unity approximation scheme. This method possesses the following properties: the complex C1-continuous approximation scheme is avoided without using either Lagrange multipliers or penalty parameters; no domain integrals involved in the assembly of the global stiffness matrix; and the imposition of essential boundary More >

W. Wei¹, David C.C. Lam¹

CMES-Computer Modeling in Engineering & Sciences, Vol.64, No.2, pp. 213-226, 2010, DOI:10.3970/cmes.2010.064.213

Abstract Molecular rotation is the elastic deformation mechanism underpinning macroscopic deformation in macromolecular solid. In this investigation, molecular mechanic simulations are used to investigate the effect of size on the higher order material properties macromolecular solid. The rotational behavior of molecular coils embedded in beams was examined as a function of the beam size in tension, and in bending where the strain gradients in the bent direction are size-dependent. Analysis showed that the effective elastic modulus is size dependent when strain gradients are significant in bending, but not in tension. Analysis of the molecular rotation behavior More >

B.K.Raghu Prasad¹, Rabindra Kumar Saha¹, A.R.Gopalakrishnan¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.14, No.3, pp. 65-84, 2010, DOI:10.3970/icces.2010.014.065

Abstract Several different models have been proposed to characterize mode-I crack propagation in concrete. The fictitious crack model proposed by Hillerborg et al. and the blunt crack band theory developed by Bazant & Oh are particularly well suited for a finite element analysis. The two-parameter fracture model proposed by Jenq & Shah is found to be applicable only for beams with s/w=4, where s=span & w=depth of the beam. The general applicability of the model for other testing configurations is not published. In the present study an experimental verification of a one-parameter model based on fundamental… More >

D. C. C. Lam¹, L-H Keung¹, P. Tong²

CMES-Computer Modeling in Engineering & Sciences, Vol.66, No.1, pp. 73-100, 2010, DOI:10.3970/cmes.2010.066.073

Abstract Additional molecular rotations in long chained macromolecules lead to additional size dependence. In this investigation, we developed the higher order viscoelasticity framework and conducted experiments to determine the higher order material length scale parameters needed to describe the higher order viscoelastic behavior in the new framework. In the first part of the investigation of high order deformation behavior of macromolecular solids, the higher-order viscoelasticity theories for Maxwell and Kelvin-Voigt materials, and models of higher-order viscoelastic beam deflection creep are developed in this study. We conducted creep bending experiments with epoxy beams to show that the… More >

Letícia Fleck Fadel Miguel¹, Ignacio Iturrioz², Jorge Daniel Riera³

CMES-Computer Modeling in Engineering & Sciences, Vol.56, No.1, pp. 1-16, 2010, DOI:10.3970/cmes.2010.056.001

Abstract Numerical predictions of the failure load of large structures, accounting for size effects, require the adoption of appropriate constitutive relations. These relations depend on the size of the elements and on the correlation lengths of the random fields that describe material properties. The authors proposed earlier expressions for the tensile stress-strain relation of concrete, whose parameters are related to standard properties of the material, such as Young's modulus or specific fracture energy and to size. Simulations conducted for a typical concrete showed that as size increases, the effective stress-strain diagram becomes increasingly linear, with a… More >

Veturia Chiroiu¹, Ligia Munteanu¹, Pier Paolo Delsanto²

CMC-Computers, Materials & Continua, Vol.16, No.1, pp. 75-100, 2010, DOI:10.3970/cmc.2010.016.075

Abstract Conventional continuum theories are unable to capture the observed indentation size effects, due to the lack of intrinsic length scales that represent the measures of nanostructure in the constitutive relations. In order to overcome this deficiency, the Toupin-Mindlin strain gradient theory of nanoindentation is formulated in this paper and the size dependence of the hardness with respect to the depth and the radius of the indenter for multiple walled carbon nanotubes is investigated. Results show a peculiar size influence on the hardness, which is explained via the shear resistance between the neighboring walls during the More >

B.K. Raghu Prasad¹, T.V.R.L. Rao¹, A.R. Gopalakrishnan¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.9, No.3, pp. 179-196, 2009, DOI:10.3970/icces.2009.009.179

Abstract A simple numerical method namely Initial Stiffness Method using finite element method has been employed to study the size effect which is prominent in concrete structures. Numerous experimental investigations performed on notched plain concrete beams subjected to three point or four-point bending have revealed the fracture process to be dependent on size of the structural member. It was found that, the nominal stress at maximum load decreases as the size of the structure increases. The nominal stress at failure on the characteristic dimension of structure is termed as size effect. This has also been explained More >

Tai-Ming Chang¹, Chien-Chou Weng¹, Mei-Jiau Huang^1,2, Chun-KaiLiu², Chih-Kuang Yu²

CMES-Computer Modeling in Engineering & Sciences, Vol.50, No.1, pp. 47-66, 2009, DOI:10.3970/cmes.2009.050.047

Abstract We employ the non-equilibrium molecular dynamics (NEMD) simulation to calculate the in-plane thermal conductivity of silicon thin films of thickness 2.2nm and 11nm. To eliminate the finite-size effect, samples of various lengths are simulated and an extrapolation technique is applied. To perform the quantum correction which is necessary as the MD simulation temperature is lower than Debye temperature, the confined phonon spectra are obtained in advance via the EMD simulations. The investigation shows the thermal conductivities corrected based on the bulk and thin-film phonon densities of states are very close and they agree excellently with More >