Alien Registration- Maillet, Laurent (Madison, Somerset County)

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A new test methodology based on structural resonance for mode I fatigue delamination growth in an unidirectional composite

A specific device has been set up to test by vibration resonance the mode I fatigue delamination growth onset of composite laminates. This test system, based on the DCB test specimen, is a mass-spring-specimen dynamic system designed to resonate. The defined operating conditions allow performing delamination propagation tests under imposed load and stopping the test under reproducible conditions, identical to the ones recommended in the ASTM-D6115 standard. This system allows fatigue tests to be driven up to 100Hz, reducing the time taken by a factor of ten without detrimental heat being generated in the material. The effect of frequency on the fatigue delamination growth on mode I has been investigated through a comparison with standard tests performed at 10Hz. A decrease in resistance to the propagation of delamination is observed with the increase in frequency for the composite studied. This frequency effect seems to be a strain rate effect and was taken in consideration by using dynamical critical energy restitution rate for the G-N curve plotting

Les missions d’Adam de Perseigne, émissaire de Rome et de Cîteaux (1190-1221)

Adam succède en 1188 à Érard et devient le second abbé de Perseigne, fille de Cîteaux et première abbaye cistercienne du Maine fondée en 1145 par Guillaume Talvas, comte de Ponthieu et d’Alençon. Durant son abbatiat (1188-1221), Adam apparaît comme l’un des chefs de file de Cîteaux et sa réputation dépasse largement le cadre de son ordre. L’abbé de Perseigne est un maître spirituel qui jouit d’une grande autorité, comme le prouve son abondante correspondance et ses illustres destinataires. C’est notamment cette haute réputation qui lui vaut d’être appelé par Rome ou Cîteaux pour remplir des missions délicates. Au regard de la personnalité d’Adam de Perseigne, de ses réseaux d’influence, et plus particulièrement des liens qu’il entretient avec Richard Cœur de Lion et Innocent III, cet article vise à expliquer pourquoi Rome et Cîteaux ont eu recours à ses bons offices.Adam succeeded Érard in 1188, becoming the second abbot of Perseigne, daughter of Cîteaux and the first Cistercian Abbey in Maine, founded in 1145 by Guillaume Talvas, count of Ponthieu and Alençon. During his abbacy (1188-1221), Adam appears to be one of the leaders of the Cistercians, and his fame went well beyond the limits of his Order. The abbot of Perseigne was a spiritual leader with considerable authority, as is shown by his broad letter-collection and the eminence of his correspondents. His high reputation partly explains why he was called upon by Rome or Cîteaux to undertake delicate missions. With regard to the personality of Adam of Perseigne, his influence networks, and more specifically his relationship with Richard the Lionheart and with Innocent III, this paper aims to explain why Rome and Cîteaux sought his assistance

Porosity measurement by comparison of air volumes

International audienceA method for measuring the volume of a solid with arbitrary shape and the open porosity ͑volume fraction of the open pores͒ of air-saturated porous materials is proposed. The experimental principle is inspired from Beranek's method based on the application of the ideal gas law to the gas surrounding the solid. The originality of the proposed method lies in the comparison of the volume of a measurement chamber containing the sample with that of an empty reference chamber. During a measurement, the reduction of volume in the measurement chamber due to the introduction of the solid is compensated by increasing the volume of a piston connected to the measurement chamber. An important aspect of this experimental system is that the influence of temperature can be considerably reduced as nearly the same variations of temperature apply simultaneously to the measurement and the reference chambers. A preliminary calibration experiment without sample in the measurement chamber is carried out in order to equalize the volumes of the two chambers. The calibration can be performed once and for all, thus minimizing the number of operations in the measurement process. The porosities of several materials are measured and compared to reference values. The precision and possible future improvements are discussed

Automatic Generation of Schedulings for Improving the Test Coverage of Systems-on-a-Chip

International audienceSystemC is becoming a de-facto standard for the early simulation of Systems-on-a-chip (SoCs). It is a parallel language with a scheduler. Testing a SoC written in SystemC implies that we execute it, for some well chosen data. We are bound to use a particular deterministic implementation of the scheduler, whose specification is non-deterministic. Consequently, we may fail to discover bugs that would have appeared using another valid implementation of the scheduler. Current methods for testings SoCs concentrate on the generation of the inputs, and do not address this problem at all. We assume that the selection of relevant data is already done, and we generate several schedulings allowed by the scheduler specification. We use dynamic partial-order reduction techniques to avoid the generation of two schedulings that have the same effect on the system's behavior. Exploring alternative schedulings during testing is a way of guaranteeing that the SoC description, and in particular the embedded software, is scheduler-independent, hence more robust. The technique extends to the exploration of other non-fully specified aspects of SoC descriptions, like timing

On the link between mechanics and thermal properties: mechanothermics

We report on the theoretical derivation of macroscopic thermal properties (specific heat, thermal conductivity) of an electrically insulating rod connected to two reservoirs, from the linear superposition of its mechanical mode Brownian motions. The calculation is performed for a weak thermal gradient, in the classical limit (high temperature). The development is kept basic as far as geometry and experimental conditions are concerned, enabling an almost fully analytic treatment. In the modeling, each of the modes is subject to a specific Langevin force, which enables to produce the required temperature profile along the rod. The theory is predictive: the temperature gradient (and therefore energy transport) is linked to motion amplitude cross-correlations between nearby mechanical modes. This arises because energy transport is actually mediated by mixing between the modal waves, and not by the modes themselves. This result can be tested on experiments, and shall extend the concepts underlying equipartition and fluctuation-dissipation theorems. The theory links intimately the macroscopic size of the clamping region where the mixing occurs to the microscopic lengthscale of the problem at hand: the phonon mean-free-path. We believe that our work should impact the domain of thermal transport in nanostructures, with future developments of the theory toward the quantum regime

Propagation de délaminage par fatigue vibratoire dans un matériau composite

Dans le domaine aéronautique les structures sont soumises à de la fatigue sonique due aux phénomènes aéro-acoustiques. Le dimensionnement statique actuel des avions composites couvre les cas de charge en fatigue. Mais avec le besoin de toujours plus réduire la masse de l avion et l augmentation des connaissances dans le comportement matériau, les marges statiques vont être réduites dans un futur proche et la propagation par fatigue deviendra un enjeu majeur. Il sera donc nécessaire d évaluer la possibilité de propagation d un délaminage dû à une erreur de fabrication ou un impact dans une structure composite. Dans ce contexte, une méthode a été proposée pour étudier la propagation de délaminage sous chargement vibratoire. Tout d abord, des essais de caractérisation de la propagation de délaminage sous chargement vibratoire ont été mis en place et validés pour les deux principaux modes de rupture. Les effets induits par la fréquence élevée de sollicitation, auto-échauffement induit et vitesse de chargement élevée, ont été pris en compte dans la mise au point et le traitement de ces essais. Ensuite, des outils numériques ont été développés pour permettre la simulation d une structure délaminée sous chargement vibratoire et l étude de la propagation du délaminage. A l aide des approches expérimentales et numériques mises en place et des données matériau identifiées, l analyse a pu être conduite sur un cas réel de structure aéronautique. Un essai de fatigue vibratoire sur une structure de reprise de plis a ainsi été réalisé. L évolution du délaminage pendant l essai est représenté de façon satisfaisante par le modèle numérique.Because of their lightness, stress adaptive design and strong stiffness, composite materials are more and more used in aeronautics. Aeronautical structures are submitted to vibrations during their service life due to aerodynamic turbulent flow around the structure. The current static design of composite aircraft covers fatigue loading cases. But with the need to more and more lighten the structure, and the knowledge increase in material behavior, the static reserve factors will be reduced in the near future and sonic fatigue will become a major issue. It will be necessary to evaluate the possibility of a delamination propagation in a composite structure due to a manufacturing error or to an impact. In this context, a method has been proposed to study the propagation of a delamination under vibratory loading. Firstly, tests to characterize the propagation of delamination under vibration loading have been developed and validated for the two main failure modes. The effects induced by the highfrequency loading, self-heat generation and high speed loading, were considered in the elaboration of these tests and in the data reduction. Then, numerical tools have been developed to allow the simulation of a delaminated structure under vibratory loading in order to study the delamination propagation. Using experimental and numerical approaches and the material data identified, the analysis could be conducted on a real case of aircraft structure. A vibration fatigue test on a ply-drop structure has been achieved. The evolution of delamination during the test is adequately modelized by the numerical model.TOULOUSE-ISAE (315552318) / SudocSudocFranceF

Constant entropy sampling and release waves of shock compressions

We present several equilibrium methods that allow to compute isentropic processes, either during the compression or the release of the material. These methods are applied to compute the isentropic release of a shocked monoatomic liquid at high pressure and temperature. Moreover, equilibrium results of isentropic release are compared to the direct nonequilibrium simulation of the same process. We show that due to the viscosity of the liquid but also to nonequilibrium effects, the release of the system is not strictly isentropic

Introduction

L’ouest du royaume de France du xiie au xve siècle Lorsque les premiers établissements cisterciens s’installent dans le nord-ouest de la France, cette partie du royaume connaît une importante recomposition politique. En 1128, Geoffroi V le Bel, comte d’Anjou et du Maine, épouse Mathilde, héritière de la Normandie par son père le roi d’Angleterre Henri Ier Beauclerc qui meurt en 1135. Ce mariage doit clore l’affrontement biséculaire entre Normands et Angevins. Cependant, de 1135 à 1153, Étienn..

Mode II fatigue delamination growth characterization of a carbon/epoxy laminate at high frequency under vibration loading

A fatigue crack propagation test under mode II has been set up for unidirectional composite laminate characterization at high frequency. The specimen is clamped on a shaker and loaded on its first bending resonance mode. This dynamical test allows an accurate delamination extension monitoring based on the resonance frequency shift. Dynamical tests are conducted at 260 Hz and 400 Hz and their results are compared to those obtained with 10 Hz 3-ENF tests. Fatigue crack propagation results are presented taking into consideration the loading ratio difference between both test configurations. All results are collapsed in a unique propagation rate curve