Second‐order work analysis for granular materials using a multiscale approach

Nicot, François; Hadda, Nejib; Darve, Félix

doi:10.1002/nag.2175

Cited by 16 publications

(8 citation statements)

References 34 publications

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“…It was found that the direction of the shear band (around 60°) was the direction of the interparticle second‐order work having the maximum negative value (Figures C and A), demonstrating that the micro slip lines have degenerated into shear band. The simulation results are consistent with those obtained by the discrete element method simulations of a drained biaxial compression test on a dense sample by Nicot et al, which demonstrated that the multiscale approach does explain the localised failure of granular assemblies.…”

Section: Analyses Of the Influence Of Microstructural Instabilities Osupporting

confidence: 88%

A multiscale approach for investigating the effect of microstructural instability on global failure in granular materials

Zhao

Yin

Hicher

2018

Num Anal Meth Geomechanics

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Summary This paper aims to develop a multiscale approach that has the ability to characterise the influence of microstructural instabilities on global failures in granular materials. For this purpose, the Chang‐Hicher multiscale constitutive relation has been implemented into a finite element code, and the expression of the second‐order work, as an indicator of the material instability, has been computed at the interparticle contact scale, at the representative element volume scale, and at the boundary value problem scale. At the global scale, the second‐order work can be obtained through the integration of that obtained at interparticle contacts. Hence, it becomes possible to analyse the range of instability from the microstructure to the macrostructure. Drained and undrained triaxial tests were numerically simulated. With this method, it was demonstrated that the grain‐scale origin of the specimen instability was well captured. Additionally, biaxial tests were conducted and the onsets of localised and diffuse failure in granular assemblies were successfully predicted. The transition from diffuse to localised failure was demonstrated at different scales, whereby the coincidence between the direction of local instabilities and the direction of the shear band became evident. The influence of the boundary conditions and of the heterogeneity of the initial porosity on the failure mode of granular materials was also analysed. All these examples demonstrate that the developed multiscale approach can characterise in a satisfactory manner the influence of instability at the inter‐grain contacts upon the global failure of granular assemblies.

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Section: Analyses Of the Influence Of Microstructural Instabilities Osupporting

confidence: 88%

A multiscale approach for investigating the effect of microstructural instability on global failure in granular materials

Zhao

Yin

Hicher

2018

Num Anal Meth Geomechanics

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“…Complementary to the previous section, the particular role played by rattlers in mitigating plastic strain development can be examined analytically and qualitatively using the micro-formulation of the second-order work introduced for granular materials (Nicot et al, 2007;Hadda et al, 2013). In this section the contact scale necessary condition to observe the vanishing of the second-order work (Nicot and Darve, 2006a;Nicot et al, 2013) is revisited in terms of rattlers influence to provide an analytical proof of the conjecture formulated in Section 2.5. This section is kept qualitative on purpose but a quantitative assessment of the role played by rattlers directly at the contact scale is proposed in Appendix A through DEM simulations.…”

Section: A Contact Scale Explanation For the Stabilizing Role Played mentioning

confidence: 97%

Rattlers' contribution to granular plasticity and mechanical stability

Wautier

Bonelli²,

Nicot

2019

International Journal of Plasticity

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The mechanical behavior of granular materials is widely governed by microstructure reorganizations. This constant evolution of the microscale geometry is often taken into account directly at the macroscale within the plasticity context, and more particularly non-associated plasticity. In this paper we propose to revisit the non-associated plastic behavior of granular materials with respect to material instability assessment in terms of the loss of positiveness of the second-order work. It is shown that large incremental plastic strain is a necessary condition for the existence of mechanical instability. The ability of a material to develop substantial plastic incremental strain is then related to the existence of rattlers, i.e., free particles that get jammed into force chains when existing contact networks fail to adapt to incremental loadings. This link between rattlers, plastic deformation and the vanishing of the second-order work is explicitly derived i) from the micro-formulation of the second-order work and ii) directly from discrete element simulations.

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“…However, it must be emphasized that this force chain deconfinement does not seem to be the triggering mechanism, as was shown in the case of an incremental stress loading corresponding to a nega-tive second-order work [34]. Indeed, for classical stresscontrolled directional analysis under axisymmetric conditions, the vanishing of the second-order work is usually observed for loading directions corresponding to a macroscopic dilation [13,34,41]. At the microscale, this dilation results in some contact loss.…”

Section: Mesoscale Mechanismsmentioning

confidence: 94%

Flow impact on granular force chains and induced instability

Wautier

Bonelli²,

Nicot

2018

Phys. Rev. E

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With today's fully coupled DEM/PFV simulations, the impact of an internal fluid flow on the mechanical stability of a granular material is assessed at the scale of a three-dimensional representative elementary volume. To isolate the specific impact of the fluid on the contact network, a granular sample in which rattlers have been initially removed is considered while a fluid pressure drop is applied under constant mechanical loading. Although the initial state is reputed to be unstable according to the second order work criterion, it is shown that i) an internal fluid flow is able to trigger the underlying instability on its own and ii) the flow direction has no influence because of local fluid force fluctuations. In addition, the microscale mechanisms occurring during the sample collapse are investigated and it is shown that the fluid perturbation induces a decrease in kinematic constraints around force chains, which is characteristic of a local loss of stability.

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Second‐order work analysis for granular materials using a multiscale approach

Cited by 16 publications

References 34 publications

A multiscale approach for investigating the effect of microstructural instability on global failure in granular materials

A multiscale approach for investigating the effect of microstructural instability on global failure in granular materials

Rattlers' contribution to granular plasticity and mechanical stability

Flow impact on granular force chains and induced instability

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