Impact damage on silicon carbide : first results

L'objectif de ce travail est d'identifier les mécanismes d'endommagement d'une céramique lors d'un impact. Dans de nombreux cas, l'amorçage et la propagation de l'endommagement se trouvent localisés dans le cône de fissuration de Hertz [1]. Aussi, les essais d'impact menés sur des carreaux de céramiques ne permettent pas d'obtenir, durant l'essai, d'information sur cette zone. Une nouvelle géométrie de cible dite "allumette" permettant de placer des jauges de fissuration à 1'intérieurs du cône a donc été developpée. Les données expérimentales ainsi obtenues, couplées à une analyse microstructurale permettent de valider les résultats d'une simulation numérique effectuée à l'aide d'un code d'éléments finis tridimensionnel.This paper deals with the damage of ceramic materials after impact. The main information on the phenomenology and the kinetic damage are often localized inside the Hertzian cone crack area [1]. With a ceramic tile target, it is not possible to obtain any information during the test. Therefore a new geometry of ceramic target, called "Match" was developed in order to put crack gauge inside the Hertzian cone. The relationship between collected experimental data and microstructural studies allow to validate the results of a three dimensional finite element simulation

Experimental approach and modeling of the compressive behaviour of two SiC grades

To take into account compressive damage in ceramics during a high-energy impact, we first analysed the degradation mechanisms of two SiC grades under quasi-static uniaxial compression. This paper deals with an experimental approach, post-mortem investigations and a probabilistic treatment of the results. A numerical investigation of these tests is performed to understand the phenomenology and explain the results

Experimental and numerical analysis of the impact behaviour of polycarbonate and polyurethane multilayer

The aim of this work is to validate a numerical model for monolithic polycarbonate or polymeric multilayer material in order to adapt them to different impact conditions (type of threat, striking velocity and test temperature). Thus, this paper deals with the experimental and numerical investigations of PC plates impacted at velocities up to 400 m/s for a temperature range between -20°C and 50°C. in this context, impact tests on 6 and 9.7 mm thick polycarbonate plates have been performed. A high speed camera records the target profile during the interaction and the displacement history of the projectile. Photographs of impact on polycarbonate plates show that rupture occurs either by petalling or plugging depending on the projectile striking velocity and on the target thickness. Numerical simulations after fitting procedures agree well with the experimental results and show the temperature and polycarbonate thickness influence on the capacity to absorb the impact energy by plastic deformation

Soil tillage impact on the relative contribution of dissolved, particulate and gaseous (CO2) carbon losses during rainstorms

Although the impact of water erosion on soil carbon losses has been widely investigated, little is known about the relative contributions of dissolved, particulate and gaseous losses, a prerequisite for understanding the mechanisms of carbon (C) export from soils and designing mitigation procedures. The main objective of this study was to quantify the losses of dissolved organic and inorganic C (DOC, DIC), particulate organic C (POC) and soil CO2 from runoff microplots on tilled (T) and no-tilled (NT) soils. The study was performed in the Beauce region in central France under Luvisols using 45 and 80 mmh(-1) artificial rains. At 45 mm h(-1), T plots produced C erosion at an average of 1189.7 +/- 114.8 mg C m(-2) h(-1) with 76.9% of it being POC (915.0 +/- 100.0 mg C m(-2) h(-1)), 21.7% DOC (258.3.0 +/- 7.6 mg C m(-2)h(-1)), 1.4% (16.3 +/- 7.2 mg C m(-2)h(-1)), DIC and 0.01% CO2. NT decreased total soil C losses by 95% (from 0.8 to 0.038 g C m(-2)h(-1)) and soil C losses were as CO2 only. At 80 mm h(-1) NT surprisingly increased C erosion by 40% compared to T (from 39.4 to 55.3 g C m(2) h(-1)), with 95.5% of the C losses being POC vs 88.7% for T. These results on rainstorm-induced C fluxes from soils controlled by tillage are expected to be of future value: (1) for selecting appropriate land management that will mitigate against C losses from soils and improve soil carbon sequestration and; (2) to better understand the Global Carbon Cycle and further develop the existing models

Composantes hydrologiques des émissions terrestres du gaz à effet de serre N2O

Etude réalisée pour le compte de l’ADEME dans le cadre de la convention 1660C0003. Rapport intermédiaire[Departement_IRSTEA]GMA [TR1_IRSTEA]11 - VERSEAU / TRANSFEA