Un modèle couplé discret/continu pour modéliser les impacts sur géostructures cellulaires

International audienceThis article presents a numerical model coupling the finite difference method and discrete element methods (FDM, DEM) for simulating the response of cellular geostructures to impacts. DEM is used in the vicinity of the impacted area while FDM is used far away. The continuity between the DEM and FDM domains is insured using the edge-to-edge method. The numerical parameters are calibrated based on compression and impact experiments conducted on elementary cells. Numerical simulations at the structure scale are compared with real-scale experimental data. The response of the structure is addressed varying the impact conditions. The projectile shape and the position of the impact point appear to be the most influential parameters

Modélisations comparées d'un ouvrage de protection pare-blocs soumis à un impact

National audienceLes ouvrages de protection contre les chutes de blocs à technologie cellulaire sont des assemblages de composants élémentaires fonctionnels. L'intérêt de ces structures réside dans leur emprise au sol réduite et leur réparabilité. Deux approches de modélisation du comportement de ces ouvrages pare-blocs sous impact sont comparées : une modélisation continue et une modélisation discrète. Les paramètres de deux modèles sont calibrés par comparaison à des résultats d'essais statiques et dynamiques sur composants. La comparaison des résultats de simulations d'impact sur ouvrage ne permet pas de statuer sur les avantages d'une approche en particulier. Néanmoins, la prise en compte des interfaces par l'approche discrète semble à privilégier malgré les difficultés d'identification des paramètres agissant. Les modélisations d'un ouvrage type fournissent des informations essentielles pour optimiser la conception de ces ouvrages pare-blocs innovant

MESURE DE LA TEMPÉRATURE RÉSIDUELLE DES MATÉRIAUX SOUMIS À UN CHOC INTENSE

We describe an experimental measurement technique which permits to evaluate the free surface temperature of a shock loaded metallic sample. The radiative infrared emission is carried over from the firing chamber to the pyrometer by a fluoride glass fiber. The pyrometer and the measurement technique are described. The free surface temperature of a shock loaded polished aluminum sample is measured and discussed

Active spectro-polarimetric imaging: signature modeling, imaging demonstrator and target detection

We report on the synthesis of our work on the analysis of active spectro-polarimetric imaging concept of real-world scenes. These synthesis extend from the investigation of depolarization mechanisms up to image analysis and processing. We show in particular that depolarization effects are wavelength dependent and strongly correlated with light absorption of materials. Multi-wavelength images of degree of polarization are recorded and analyzed, evidencing that the polarimetric image must be interpreted in conjunction with its counterpart intensity image in order to extract, the most relevant information from the scene. For real field operation, the noise characteristics of polarimetric images are also investigated under coherent laser illumination. The potential increase of target detection performance brought by properly processing the active polarimetric image is illustrated on a very low contrast scene