Dynamic material characterization under ramp wave compression with GEPI device

GEPI is a pulsed power generator developed by ITHPP for Centre d'Etudes de Gramat (CEG), devoted to Isentropic Compression Experiments in the 1 GPa to 100 GPa range, and to non shocked high velocity flyer plates in the 0.1 km/s to 10 km/s range. The main idea is to generate a high magnetic pressure in a strip line where the samples are located. The whole design is based on low inductance technologies. Depending on the load, the current reaches between 3 and 4 MA in 600 ns. The entire design has been done in a cost effective way and in order to achieve an easy-to-use capability . A description of the generator is shown and typical results of the studies led by CEG are presented. The matters of concern are equations of state, phase transitions, sample recovery and impact of high velocity flyer plate

Soft Recovery Device For Shocked Brittle Materials

A device elaborated to soft recover brittle specimens loaded with a gas gun is presented. The target arrangement has been designed in order to minimize radial release waves in the specimen. A new design of projectile is proposed to avoid parasite recompressions due to further impacts. The optimization of the whole system has been achieved by means of an iterative approach based on both 2D-calculations and experimentation. The efficiency of the system is demonstrated with the soft recovery of quartzite samples for projectile velocities up to 825 m/s.Un dispositif expérimental de récupération d'échantillon après choc est présenté. Le principe du dispositif est de placer l'échantillon dans un boîtier métallique, dimensionné pour minimiser les ondes de détente latérales parasites. Le projectile a été conçu pour éviter les impacts supplémentaires. L'ensemble du système a été optimisé par une approche itérative mettant en oeuvre des simulations numériques et des expériences. L'efficacité du montage est montré à partir d'échantillons de quartzite récupérés après des vitesses d'impact allant de 140 m/s à 825 m/s

Experimental Characterization of Shock Wave Behavior of Porous Aluminum

Experiments of shock wave propagation performed on 9% and 17% porous aluminum are presented and analyzed. The originality of the plate impact set-up and its associated metrology (VISAR interferometry and PVDF piezoelectric gages) exhibits also the influence of local physical mechanisms on shock wave propagation in porous aluminum. More, the variations observed between the rise times of shocks seem to point out a preponderance of the dynamic effects (inertia or strain rate) over the material behavior. This point is confirmed by comparing quasi static and dynamic responses of porous aluminum.On présente une analyse du comportement sous choc de deux aluminium poreux à 9% et 17%. La configuration expérimentale des essais d'impact de plaques ainsi que la métrologie retenue (VISAR et jauges PVDF) révèlent les mécanismes de propagation d'onde dans l'aluminium poreux. Les temps de montée des ondes semblent indiquer une influence des effets dynamiques (inertie ou vitesse de déformation) sur le comportement du matériau. Ce point est confirmé par la comparaison entre les résultats quasi statique et dynamique

Experimental Characterization of Shock Wave Behavior of Porous Aluminum

Experiments of shock wave propagation performed on 9% and 17% porous aluminum are presented and analyzed. The originality of the plate impact set-up and its associated metrology (VISAR interferometry and PVDF piezoelectric gages) exhibits also the influence of local physical mechanisms on shock wave propagation in porous aluminum. More, the variations observed between the rise times of shocks seem to point out a preponderance of the dynamic effects (inertia or strain rate) over the material behavior. This point is confirmed by comparing quasi static and dynamic responses of porous aluminum.On présente une analyse du comportement sous choc de deux aluminium poreux à 9% et 17%. La configuration expérimentale des essais d'impact de plaques ainsi que la métrologie retenue (VISAR et jauges PVDF) révèlent les mécanismes de propagation d'onde dans l'aluminium poreux. Les temps de montée des ondes semblent indiquer une influence des effets dynamiques (inertie ou vitesse de déformation) sur le comportement du matériau. Ce point est confirmé par la comparaison entre les résultats quasi statique et dynamique

Shock Behaviour of 3D Carbon-Carbon Composite

The compressive response of a 3D carbon-carbon composite under shock wave was studied in a plate-impact configuration. Two directions of impact were achieved until a nominal value of longitudinal stress of 2.5 GPa. The measured wave profiles are consistent with previous results on 3D composites and confirm the behaviour of such materials under impact. It is shows that the initial loading is decomposed in two waves. The first one is transmitted by the longitudinal fibres, the second one corresponds to the propagation of a shock wave in the 'matrix'. Macroscopic characteristics of this material are provided.On présente la réponse sous choc d'un composite 3DCC à partir d'essai d'impact de plaques. Deux directions d'anisotropie ont été étudiés jusqu'à une contrainte maximum de 2,5 GPa. La forme des diagrammes de vitesse est cohérente avec les résultats déjà obtenus sur les composites 3D et confirme leur comportement sous choc. On montre que la sollicitation initiale se décompose en deux ondes. La première est transportée par les fibres longitudinales, la seconde par la matrice. On présente des caractéristiques macroscopiques calculées sur ce composite 3DCC

Impact on 3D Carbon/Carbon Composites : a Meso-Scale Approach

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Analysis of temperature measurement at material/LiF interface under moderate shock wave compression

In the field of dynamic high-pressure physics of condensed materials, the accurate knowledge of the thermodynamic state of a material is fundamental to understand its dynamic behaviour under stress. The equation of state of materials is verified in terms of pressure, density and internal energy thanks to the measurements of pressure and velocity under shock wave compression with a satisfying precision. The theoretical temperature evaluated from EOS remains discussed. So; its accurate measurement is of great interest, in particular at low temperature. However, in this range, measurements appear more difficult to perform. Because of this, a high-speed infrared three-wavelength pyrometer has been modified at CEG to perform measurements at very low temperature (<500 K). Besides, an emissive layer has been designed to increase the emissivity of the shocked surface. To reduce the uncertainty of the temperature measurement, it appears necessary to limit its emissivity to a 0.9–1 range