In-situ Analysis of Laminated Composite Materials by X-ray Micro-Computed Tomography and Digital Volume Correlation

The complex mechanical behaviour of composite materials, due to internal heterogeneity and multi-layered composition impose deeper studies. This paper presents an experimental investigation technique to perform volume kinematic measurements in composite materials. The association of X-ray micro-computed tomography acquisitions and Digital Volume Correlation (DVC) technique allows the measurement of displacements and deformations in the whole volume of composite specimen. To elaborate the latter, composite fibres and epoxy resin are associated with metallic particles to create contrast during X-ray acquisition. A specific in situ loading device is presented for three-point bending tests, which enables the visualization of transverse shear effects in composite structures

Multiaxial Kitagawa analysis of A356-T6

Experimental Kitagawa analysis has been performed on A356-T6 containing natural and artificial defects. Results are obtained with a load ratio of R = -1 for three different loadings: tension, torsion and combined tension-torsion. The critical defect size determined is 400 \pm 100 \mum in A356-T6 under multiaxial loading. Below this value, the microstructure governs the endurance limit mainly through Secondary Dendrite Arm Spacing (SDAS). Four theoretical approaches are used to simulate the endurance limit characterized by a Kitagawa relationship are compared: Murakami relationships [Y Murakami, Metal Fatigue: Effects of Small Defects and Nonmetallic Inclusions, Elsevier, 2002.], defect-crack equivalency via Linear Elastic Fracture Mechanics (LEFM), the Critical Distance Method (CDM) proposed by Susmel and Taylor [L. Susmel, D. Taylor. Eng. Fract. Mech. 75 (2008) 15.] and the gradient approach proposed by Nadot [Y. Nadot, T. ~Billaudeau. Eng. Fract. Mech. 73 (2006) 1.]. It is shown that the CDM and gradient methods are accurate; however fatigue data for three loading conditions is necessary to allow accurate identification of an endurance limit.Comment: 27 pages, 11 figure

Three-dimensional grain mapping by x-ray diffraction contrast tomography and the use of Friedel pairs in diffraction data analysis

X-ray diffraction contrast tomography (DCT) is a technique for mapping grain shape and orientation in plastically undeformed polycrystals. In this paper, we describe a modified DCT data acquisition strategy which permits the incorporation of an innovative Friedel pair method for analyzing diffraction data. Diffraction spots are acquired during a 360 degree rotation of the sample and are analyzed in terms of the Friedel pairs ((hkl) and (hkl -) reflections, observed 180 degrees apart in rotation). The resulting increase in the accuracy with which the diffraction vectors are determined allows the use of improved algorithms for grain indexing (assigning diffraction spots to the grains from which they arise) and reconstruction. The accuracy of the resulting grain maps is quantified with reference to synchrotron microtomography data for a specimen made from a beta titanium system in which a second phase can be precipitated at grain boundaries, thereby revealing the grain shapes. The simple changes introduced to the DCT methodology are equally applicable to other variants of grain mapping. Copyright 2009 American Institute of Physics

Towards a standardization of biomethane potential tests

8 PáginasProduction of biogas from different organic materials is a most interesting source of renewable energy. The biomethane potential (BMP) of these materials has to be determined to get insight in design parameters for anaerobic digesters. A workshop was held in June 2015 in Leysin Switzerland to agree on common solutions to the conundrum of inconsistent BMP test results. A discussion covers actions and criteria that are considered compulsory ito accept and validate a BMP test result; and recommendations concerning the inoculum substrate test setup and data analysis and reporting ito obtain test results that can be validated and reproduced.The workshop in Leysin, Switzerland, has been financed by the Swiss Federal Office for Energy, and co-sponsored by Bioprocess Control Sweden AB, Lund, Sweden. The authors thank Alexandra Maria Murray for editing the English

Beneficial effect of cysteine supplementation in response to sepsis

International audienc

Influence de la température sur la méthanisation de boues primaires d’épuration

The influence of temperature and organic load on the anaerobic digestion of primary sludge was studied in the range of 28-60°C with organic loads ranging from 2 to 8.5gCOD.L-1.j-1. The work was carried out from a mesophilic inoculum with prior adaptation. The incubation was conducted in 10-L perfectly mixed thermo-regulated digesters which were fed fed daily. Results showed that the daily production of methane was more influenced by the load than by temperature. The performances obtained at 28°, 37° and 49°C were found similar but slightly reduced at 55°C. The digester operated at 60°C with the highest load quickly led to acid inhibition resulting in a drastic drop of methane production. The rise in temperature lead to an accumulation of ammonium NH4+ in the digesters as well as soluble COD (measured after filtration to 0.45 microns). These variations suggested a change in the balance of biodegradation pathway. The effect of temperature on the acceleration of hydrolysis / acidogenesis phases was more acute than on the acetogenic and methanogenic phases, thereby leading to the accumulation of intermediate metabolites.L’influence de la température et de la charge organique sur la méthanisation des boues primaires de station d’épuration a été étudiée dans la plage de 28 à 60°C pour une charge organique allant de 2 à 8.5gDCO.L-1.j-1. Les travaux ont été réalisés à partir d’un inoculum mésophile, préalablement adapté. L’incubation des boues a été conduite dans des digesteurs thermostatés parfaitement agités de 10L alimentés quotidiennement. Les résultats révèlent que la production journalière de méthane est davantage influencée par la charge que par la température. Les performances épuratoires obtenues à 28°, 37° et 49°C s’avèrent similaires. Elles sont légèrement moins bonnes à 55°C, et le digesteur opéré à 60°C avec la charge la plus élevée a rapidement conduit à une inhibition acide avec arrêt de production de méthane. L’élévation de température conduit à une accumulation d’ammonium NH4+ dans les digesteurs, ainsi que de la DCO soluble (après filtration à 0,45µm). Ces variations suggèrent une modification des équilibres de biodégradation. L’effet de la température sur d’accélération des phases hydrolyse / acidogenèse s’avère plus accentué que sur les phases d’acétogenèse et de méthanisation, conduisant ainsi à l’accumulation de métabolites intermédiaires

Increased cysteine requirements and production of cysteine from methionine during the acute phase of sepsis in rats

ESPEN 98, résumé P137International audienc

Recherche d'un marqueur moléculaire de la souche L13 de Microdochium dimerum, agent de lutte biologique contre Botrytis cinerea sur tomate

National audienc