Modélisation du comportement mécanique des verres silicatés à l'échelle micronique.

Les verres silicatés rompent de manière fragile aux échelles supérieures au micron mais présentent une réponse plastique aux échelles inférieures. Plus particulièrement, ils se densifient de façon irréversible sous des sollicitations de contact. Dans cet article, nous présentons une loi de comportement mécanique permettant de reproduire ce phénomène. Nous proposons ensuite une identification des paramètres matériaux par comparaison entre des résultats de simulations numériques par éléments-finis de l'essai de nanoindentation et des résultats expérimentaux tels que la courbe force-enfoncement et une cartographie de densification obtenue par spectroscopie raman. Une simulation numérique de rayure est ensuite effectuée

Sedimentation-consolidation of a double porosity material

This paper studies the sedimentation-consolidation of a double porosity material, such as lumpy clay. Large displacements and finite strains are accounted for in a multidimensional setting. Fundamental equations are derived using a phenomenological approach and non-equilibrium thermodynamics, as set out by Coussy [Coussy, Poromechanics, Wiley, Chichester, 2004]. These equations particularise to three non-linear partial differential equations in one dimensional context. Numerical implementation in a finite element code is currently being undertaken

Influence of the ionic strength on the deposit phenomenon and transport dynamic of microparticles through saturated porous medium

In this paper, the influence of ionic strength on the dynamics transport of silt micro particles through saturated sand texture is studied in the presence of repulsive interactions. The deposition phenomenon is investigated through column experimental trials. Four ionic strengths are applied by adjustment of suspension salinity (0, 5.13, 10.26 and 13.68 mM). Through this experimental study, the ionic strength influence on deposition phenomenon is shown at the micro particle scale. Ionic strength variation is the primal parameter which predicts attachment and detachment particles at constant flow. These experiments are simulated and reproduced through a numerical model based on an original deposit kinetic which is proposed in this study. This model is the coupling of two multiphasic problems describing conservative salt and micro particles transport. The proposed kinetic formulations are founded on experimental tests constitutions with respect to literature trends. They are based on functional relationships between model parameters and the suspension ionic strength. In addition, the transient blocking phenomena is taken into account through a retention function Langmuir type. The suggested model shows a good match to reproduce the experimental description of the suspended particles transport under the influence of ionic strength variation. It permits to predict deposition phenomenon

Role of contact couples and couple stress in the behaviour of granular media

This paper analyses the interest of taking into account contact couples in the granular material description as well as considering the inadequacy of the micropolar description. The study is made on two types of samples : One which takes into account contact couples, and the other which does not. The response of these two media, which are submitted to a biaxial test, is analysed from both the micromechanic and macroscopic viewpoints. A numerical study which is performed on these two samples shows the influence of the presence of couples on the local static variables as well as on the macroscopic behaviour. A statistical homogenization approach is analysed to simulate the effects of couples. Due to the presence of an internal variable, a numerical study proves that this approach is relevant. This internal variable allows the taking into consideration of the influence of contact couples. A first step in the description of couples versus contact orientation is made by the introduction of the standard deviation. Finally, the inadequacy of the micropolar description which takes into account micropolar stresses is pointed out

Influence of the ionic strength on the deposit phenomenon and transport dynamic of microparticles through saturated porous medium

In this paper, the influence of ionic strength on the dynamics transport of silt micro particles through saturated sand texture is studied in the presence of repulsive interactions. The deposition phenomenon is investigated through column experimental trials. Four ionic strengths are applied by adjustment of suspension salinity (0, 5.13, 10.26 and 13.68 mM). Through this experimental study, the ionic strength influence on deposition phenomenon is shown at the micro particle scale. Ionic strength variation is the primal parameter which predicts attachment and detachment particles at constant flow. These experiments are simulated and reproduced through a numerical model based on an original deposit kinetic which is proposed in this study. This model is the coupling of two multiphasic problems describing conservative salt and micro particles transport. The proposed kinetic formulations are founded on experimental tests constitutions with respect to literature trends. They are based on functional relationships between model parameters and the suspension ionic strength. In addition, the transient blocking phenomena is taken into account through a retention function Langmuir type. The suggested model shows a good match to reproduce the experimental description of the suspended particles transport under the influence of ionic strength variation. It permits to predict deposition phenomenon

Modélisation du comportement mécanique des verres silicatés à l'échelle micronique.

Colloque avec actes et comité de lecture. Internationale.International audienceLes verres silicatés rompent de manière fragile aux échelles supérieures au micron mais présentent une réponse plastique aux échelles inférieures. Plus particulièrement, ils se densifient de façon irréversible sous des sollicitations de contact. Dans cet article, nous présentons une loi de comportement mécanique permettant de reproduire ce phénomène. Nous proposons ensuite une identification des paramètres matériaux par comparaison entre des résultats de simulations numériques par éléments-finis de l'essai de nanoindentation et des résultats expérimentaux tels que la courbe force-enfoncement et une cartographie de densification obtenue par spectroscopie raman. Une simulation numérique de rayure est ensuite effectuée