Bin GU, LC Zhang

The International Conference on Computational & Experimental Engineering and Sciences, Vol.18, No.3, pp. 89-90, 2011, DOI:10.3970/icces.2011.018.089

Abstract Bridging the atomic and continuous analyses is an important aspect in multi-scale mechanics. This paper develops a computational method to integrate the atomic potential of a material with the finite element method. The novelty of this method is that the strain energy is calculated from the atomic potential without the assumption in the Cauchy-Born rule that deformation in a virtual atomic cell is homogeneous. In our new method, the virtual atomic cell deformation is interpolated according to the continuum displacements constructed associated with the shape functions. The applications of the method to single crystal Si and Ge bars under uniaxial… More >

George Fitzgerald, Michael Doyle

The International Conference on Computational & Experimental Engineering and Sciences, Vol.17, No.1, pp. 1-2, 2011, DOI:10.3970/icces.2011.017.001

Abstract Molecular modeling can provide a detailed understanding of structures, properties, and processes for materials as diverse as organic molecules, polymer blends, or alloys. Yet, these methods have generally been restricted to length scales of 100 nm and time scales of 10^-6 seconds, which limits their usefulness for research problems on the engineering scale. In this work, we discuss several approaches for extending their domain of applicability to the macro-scale.

Enhancements to atomistic modeling methods make it possible to apply accurate atomistic models to problems in electronics materials, alloys, and polymers. Statistical methods such as Quantitative Structure-Activity Relationships (QSAR) extend… More >

Yohei Inoue, Taishi Nakamura, Shuji Ogata, Ryo Kobayashi, Toshiyuki Gotoh

The International Conference on Computational & Experimental Engineering and Sciences, Vol.20, No.2, pp. 49-50, 2011, DOI:10.3970/icces.2011.020.049

Abstract No proper simulation method exists in between the molecular simulation method at nanometer scale using the first principles or empirical inter-molecular interaction and the continuum simulation method at micrometer-plus scale. The nanotechnology deals principally with those systems whose characteristic scales reside in such a scale-gap. Considering this, we develop a sequential scale-up scheme starting from the atomistic up to micrometer-plus scales. In the present paper we take, as an example, the system of graphenes that may or may not be fluttering in airflow, and apply to it our sequential scale-up scheme to see its capability.

The graphene is unique… More >

Qin Siwei, Shen SP

The International Conference on Computational & Experimental Engineering and Sciences, Vol.19, No.2, pp. 53-54, 2011, DOI:10.3970/icces.2011.019.053

Abstract Among many multiscale methods ,we choose the quasicontinuum method to understand the mechanical response at the nanocrystalline of grain boundaries(GBs) under tension. The energetic and mechanical strength of 6 i?"<110> symmetric tilt GBs are investigated in nanocrystalline Cu and Ni. We focus on discussing the interaction of the structural units of symmetric tilt GB for the initial deformation mode and the strength of model. At the basis of the previous, We study the nanocrystalline Cu/a-Al2O3 interface and analyze the relationship during the grains orientations, GB energy and interface. Special emphasis is placed on the crystal slip from the interface across… More >

Baolin Wang¹

The International Conference on Computational & Experimental Engineering and Sciences, Vol.8, No.2, pp. 81-84, 2008, DOI:10.3970/icces.2008.008.081

Abstract When the size of a physical system is smaller than its characteristic dimensions, the macroscopic viewpoint may not be applicable. In addition, experiments at micro/nanometer scale are difficult and the analysis of nano-experimental data is far from simple. This is mostly due to the lack of effective models that are able to study the structural characteristics and mechanics behavior of the micro/nanometer physical systems. Atomic simulation simulation has been used extensively in the investigation of nanoscale phenomena. However, the size limit of atomic simulation is far short to reach the macroscale because of the limitation in computer capacity. Therefore, the… More >

Yuzhou Sun¹, Yuchao Mu²

The International Conference on Computational & Experimental Engineering and Sciences, Vol.22, No.1, pp. 115-115, 2019, DOI:10.32604/icces.2019.05304

Abstract Due to its double-structure property, the higher-order continuum theory is adopted to study the constitutive behavior of expansive soil. The higher-order strain and scale factor are considered to describe the effect of the microscale structural property on the macroscale behavior, and a higher-order multiscale constitutive model is developed for expansive soil. The effect of the microscale structural property is investigated through the theoretical and experimental studies based on the developed model. In virtue of a representative elementary volume, the double-structure property is better studied for expansive soil. A variational equation is developed with the contribution of the liquid and gas… More >

Hiroshi Kadowaki¹, Wing Kam Liu²

CMES-Computer Modeling in Engineering & Sciences, Vol.7, No.3, pp. 269-282, 2005, DOI:10.3970/cmes.2005.007.269

Abstract A method to derive governing equations and elastic-plastic constitutive relations for the micropolar continuum model is proposed. Averaging procedures are operated over a surrounding sub-domain for each material point to bridge a discrete microstructure to a macro continuum model. Material parameters are determined by these procedures. The size of the sub-domain represents the material intrinsic length scale, and it is passed into the macroscopic governing equation so that the numerical solution can be regularized for analyses of failure phenomena. An application to a simple granular material model is presented. More >

Shengping Shen¹, S. N. Atluri¹

CMES-Computer Modeling in Engineering & Sciences, Vol.7, No.1, pp. 49-68, 2005, DOI:10.3970/cmes.2005.007.049

Abstract The main objective of this paper is to develop a multiscale method for the static analysis of a nano-system, based on a combination of molecular mechanics and MLPG methods. The tangent-stiffness formulations are given for this multiscale method, as well as a pure molecular mechanics method. This method is also shown to naturally link the continuum local balance equation with molecular mechanics, directly, based on the stress or force. Numerical results show that this multiscale method quite accurate. The tangent-stiffness MLPG method is very effective and stable in multiscale simulations. This multiscale method dramatically reduces the computational cost, but it… More >

Shengping Shen¹, S. N. Atluri¹

CMES-Computer Modeling in Engineering & Sciences, Vol.6, No.1, pp. 91-104, 2004, DOI:10.3970/cmes.2004.006.091

Abstract An atomistic level stress tensor is defined with physical clarity, based on the SPH method. This stress tensor rigorously satisfies the conservation of linear momentum, and is appropriate for both homogeneous and inhomogeneous deformations. The formulation is easier to implement than other stress tensors that have been widely used in atomistic analysis, and is validated by numerical examples. The present formulation is very robust and accurate, and will play an important role in the multiscale simulation, and in molecular dynamics. An equivalent continuum is also defined for the molecular dynamics system, based on the developed definition of atomistic stress and… More >

Peter W. Chung¹, Raju R. Namburu², Brian J. Henz³

CMES-Computer Modeling in Engineering & Sciences, Vol.5, No.1, pp. 45-62, 2004, DOI:10.3970/cmes.2004.005.045

Abstract A method is developed based on an additive modification to the first Lagrangian elasticity tensor to make the finite element method for hyperelasticity viable at the atomic length scale in the context of lattice statics. Through the definition of an overlap region, the close-ranged atomic interaction energies are consistently summed over the boundary of each finite element. These energies are subsequently used to additively modify the conventional material property tensor that comes from the second derivative of the stored energy function. The summation over element boundaries, as opposed to atom clusters, allows the mesh and nodes to be defined independently… More >