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Xi Chen - One of the best experts on this subject based on the ideXlab platform.

  • Buckling behavior of single-walled carbon nanotubes and a targeted molecular mechanics approach
    Physical Review B, 2006
    Co-Authors: Xi Chen
    Abstract:

    During the general (conventional) molecular mechanics (GMM) simulation of the buckling of single-walled carbon nanotubes (SWCNTs), the load is Displacement controlled and the calculated critical buckling strain is very sensitive to the specific Displacement Increment and convergence threshold chosen in molecular dynamics (MD) simulations, which may have led to the contradictory and diverged results in the previous studies. In this paper, a targeted-molecular mechanics (TMM) simulation method is proposed to study the buckling behavior of SWCNTs under axial compression, bending, and torsion. Comparing with the GMM method, the TMM technique is independent of the Displacement Increment and thus the solution is converged. The critical buckling strain computed from the TMM is higher than that from the GMM under axial compression and torsion, and the TMM results are similar to the GMM results upon bending. The TMM result approaches to the intrinsic critical buckling strain of a perfect tube; in addition, the TMM significantly reduces the computational cost and thus may be more efficient to study larger systems with atomistic simulations.

  • The effect of the Displacement Increment on the axial compressive buckling behaviours of single-walled carbon nanotubes
    Nanotechnology, 2006
    Co-Authors: Xi Chen
    Abstract:

    We carry out systematic molecular mechanics (MM) analyses to study the effect of the Displacement Increment on the critical buckling strain of single-walled carbon nanotubes (SWCNTs) under axial compression. The SWCNT geometric parameters, such as the tube length, diameter, and chirality, are varied in the numerical studies. The results show that the critical buckling strain of the SWCNTs deduced from the atomistic analyses is highly sensitive to the Displacement Increment used in the numerical simulation, and such an effect is more obvious for tubes with smaller diameters. Therefore, a reasonable compressive Displacement Increment should be selected in the atomistic simulations in order to obtain the intrinsic values of the critical buckling strain, which is suggested in this paper. The studies in this paper may be used to explain the contradicting results of the critical compressive buckling strains computed by other MM analyses in the literature.

Leo Rothenburg - One of the best experts on this subject based on the ideXlab platform.

  • a strain Displacement fabric relationship for granular materials
    International Journal of Solids and Structures, 2019
    Co-Authors: Nicolaas P Kruyt, Leo Rothenburg
    Abstract:

    Abstract In this micromechanical study of the behaviour of granular materials, relationships are investigated between deformation at the continuum macro-scale and at the micro-scale of interparticle contacts. Special attention is paid to the role of the microstructure, or fabric, as it is well known to have a strong influence on the behaviour of granular materials. Two-dimensional Discrete Element Method simulations of isobaric tests have been used to formulate truncated Fourier series representations for suitably-averaged relative Displacement Increment vectors at interparticle contacts and of parameters that describe the fabric. Based on a micromechanical expression for the average strain tensor that is valid in the two-dimensional case considered here and on these Fourier series representations, a Strain–Displacement–Fabric relationship has been derived that links the macro-scale dilatancy rate to the micro-scale relative Displacements and fabric. Results of the Discrete Element Method simulations, using samples with different densities, have been employed to verify the accuracy of the proposed relationship for the dilatancy rate.

  • A strain–Displacement–fabric relationship for granular materials
    International Journal of Solids and Structures, 2019
    Co-Authors: Nicolaas P Kruyt, Leo Rothenburg
    Abstract:

    Abstract In this micromechanical study of the behaviour of granular materials, relationships are investigated between deformation at the continuum macro-scale and at the micro-scale of interparticle contacts. Special attention is paid to the role of the microstructure, or fabric, as it is well known to have a strong influence on the behaviour of granular materials. Two-dimensional Discrete Element Method simulations of isobaric tests have been used to formulate truncated Fourier series representations for suitably-averaged relative Displacement Increment vectors at interparticle contacts and of parameters that describe the fabric. Based on a micromechanical expression for the average strain tensor that is valid in the two-dimensional case considered here and on these Fourier series representations, a Strain–Displacement–Fabric relationship has been derived that links the macro-scale dilatancy rate to the micro-scale relative Displacements and fabric. Results of the Discrete Element Method simulations, using samples with different densities, have been employed to verify the accuracy of the proposed relationship for the dilatancy rate.

Cemal Basaran - One of the best experts on this subject based on the ideXlab platform.

  • Damage Mechanics of Carbon Nano Tubes Under Uniaxial Tension
    ASME 2009 InterPACK Conference Volume 1, 2009
    Co-Authors: Cemal Basaran, Tarek Ragab
    Abstract:

    A procedure is proposed for computing the stresses in an armchair Single-Walled Carbon NanoTube (SWCNT) under uniaxial tension. Computation is based on molecular dynamics simulations and the virial stress theorem. The proposed approach is compared with other methods used in the literature for calculating the stresses in CNTs. The loading is applied under two different boundary conditions and different strain rates and the results are compared. It is shown that the method commonly used in the literature for calculating the stresses in CNTs under estimates the ultimate strength by around 35%. It is shown that the value of the Displacement Increment used to apply the tensile strain is crucial.Copyright © 2009 by ASME

  • A framework for stress computation in single-walled carbon nanotubes under uniaxial tension
    Computational Materials Science, 2009
    Co-Authors: Tarek Ragab, Cemal Basaran
    Abstract:

    A procedure is proposed for computing the stresses in an armchair single-walled carbon nanotube (SWCNT) under uniaxial tension. Computation is based on molecular dynamics simulations and the virial stress theorem. The proposed approach is compared with other methods used in the literature for calculating the stresses in CNTs. The loading is applied under two different boundary conditions and different strain rates and the results are compared. It is shown that the method commonly used in the literature for calculating the stresses in CNTs under estimates the ultimate strength by around 35%. It is shown that the value of the Displacement Increment used to apply the tensile strain is crucial. A convergence study is done to eliminate the computational error due to large Displacement Increments.

Nicolaas P Kruyt - One of the best experts on this subject based on the ideXlab platform.

  • a strain Displacement fabric relationship for granular materials
    International Journal of Solids and Structures, 2019
    Co-Authors: Nicolaas P Kruyt, Leo Rothenburg
    Abstract:

    Abstract In this micromechanical study of the behaviour of granular materials, relationships are investigated between deformation at the continuum macro-scale and at the micro-scale of interparticle contacts. Special attention is paid to the role of the microstructure, or fabric, as it is well known to have a strong influence on the behaviour of granular materials. Two-dimensional Discrete Element Method simulations of isobaric tests have been used to formulate truncated Fourier series representations for suitably-averaged relative Displacement Increment vectors at interparticle contacts and of parameters that describe the fabric. Based on a micromechanical expression for the average strain tensor that is valid in the two-dimensional case considered here and on these Fourier series representations, a Strain–Displacement–Fabric relationship has been derived that links the macro-scale dilatancy rate to the micro-scale relative Displacements and fabric. Results of the Discrete Element Method simulations, using samples with different densities, have been employed to verify the accuracy of the proposed relationship for the dilatancy rate.

  • A strain–Displacement–fabric relationship for granular materials
    International Journal of Solids and Structures, 2019
    Co-Authors: Nicolaas P Kruyt, Leo Rothenburg
    Abstract:

    Abstract In this micromechanical study of the behaviour of granular materials, relationships are investigated between deformation at the continuum macro-scale and at the micro-scale of interparticle contacts. Special attention is paid to the role of the microstructure, or fabric, as it is well known to have a strong influence on the behaviour of granular materials. Two-dimensional Discrete Element Method simulations of isobaric tests have been used to formulate truncated Fourier series representations for suitably-averaged relative Displacement Increment vectors at interparticle contacts and of parameters that describe the fabric. Based on a micromechanical expression for the average strain tensor that is valid in the two-dimensional case considered here and on these Fourier series representations, a Strain–Displacement–Fabric relationship has been derived that links the macro-scale dilatancy rate to the micro-scale relative Displacements and fabric. Results of the Discrete Element Method simulations, using samples with different densities, have been employed to verify the accuracy of the proposed relationship for the dilatancy rate.

Tarek Ragab - One of the best experts on this subject based on the ideXlab platform.

  • Damage Mechanics of Carbon Nano Tubes Under Uniaxial Tension
    ASME 2009 InterPACK Conference Volume 1, 2009
    Co-Authors: Cemal Basaran, Tarek Ragab
    Abstract:

    A procedure is proposed for computing the stresses in an armchair Single-Walled Carbon NanoTube (SWCNT) under uniaxial tension. Computation is based on molecular dynamics simulations and the virial stress theorem. The proposed approach is compared with other methods used in the literature for calculating the stresses in CNTs. The loading is applied under two different boundary conditions and different strain rates and the results are compared. It is shown that the method commonly used in the literature for calculating the stresses in CNTs under estimates the ultimate strength by around 35%. It is shown that the value of the Displacement Increment used to apply the tensile strain is crucial.Copyright © 2009 by ASME

  • A framework for stress computation in single-walled carbon nanotubes under uniaxial tension
    Computational Materials Science, 2009
    Co-Authors: Tarek Ragab, Cemal Basaran
    Abstract:

    A procedure is proposed for computing the stresses in an armchair single-walled carbon nanotube (SWCNT) under uniaxial tension. Computation is based on molecular dynamics simulations and the virial stress theorem. The proposed approach is compared with other methods used in the literature for calculating the stresses in CNTs. The loading is applied under two different boundary conditions and different strain rates and the results are compared. It is shown that the method commonly used in the literature for calculating the stresses in CNTs under estimates the ultimate strength by around 35%. It is shown that the value of the Displacement Increment used to apply the tensile strain is crucial. A convergence study is done to eliminate the computational error due to large Displacement Increments.