Une condition de déviation des fissures dans les CMC et les multicouches

A crack deflection criterion is proposed on the basis of the Cook and Gordon mechanism. The stress state induced by a crack was computed in an elementary cell of bimaterial using the finite element method. An interface failure criterion was established in terms of strengths and elastic moduli of constituents. A master curve was produced. It allows matrix crack deflection to be predicted with respect to constituents properties and interface strength. The model can be used also to evaluate the strength of interfaces and interphases in ceramic matrix composites and in multilayers. To cite this article: S. Pompidou, J. Lamon, C. R. Mecanique 333 (2005).     

Détection de fissures dans les poutres d'acier : une nouvelle approche par balayage de mesures de vibrations

In the last few years, the techniques of detection and identification of damage in structures benefited from important research efforts. Several methods of non-destructive damage detection, such as techniques based on modal analysis, were developed in addition to the traditional methods. The difficulties encountered by these techniques are their low performance, considering the industrial requirements to detect cracks as early as possible.     

Composites graphite/sel pour le stockage d'énergie à haute température : étude des effets du graphite et de la microstructure des composites sur les propriétés de changement de phase des sels

Thermal energy storage at high temperature is an efficient way for energy saving in the industrial sector, as well as a key component for power generation based on renewable energy resources. Thermal energy storage technology based on phase change materials (mainly salts) has been identified to meet the requirements of investment costs and compactness. However, the low thermal conductivity of salts (1 W/m/K) could be a limiting factor concerning power. To overcome such a drawback, new materials combining salts with graphite have been developed. Nevertheless, it is important to verify that no degradation of the salts storage properties is induced by their thermal conductivity enhancement. In this Note, the effects of the graphite and the composites graphite/salt microstructure on the phase change properties of salts are analysed. To cite this article: J. Lopez et al., C. R. Mecanique 336 (2008).     

Prévision de la répartition de la pression sous des véhicules à chenilles Ilème partie - effects des paramètres de conception du système de suspension des chenilles sur la répartition de la pression sur le sol

The effects of vehicle design parameters on ground pressure distribution and track tension are evaluated quantitatively using the analytical method described in Part I of this paper. The ground pressure distribution of a vehicle is closely related to vehicle sinkage and external motion resistance, while the track tension affects the internal resistance of the track-suspension system. It is found that the number of road wheels on the track has a significant effect on both ground pressure distribution and track tension. On the other hand, the diameter of the road wheels has only a moderate influence on track tension and a rather insignificant effect on ground pressure distribution. The stiffnesses of the suspension and the track tensioning springs have varying degrees of influence on ground pressure distribution and track tension dependent upon terrain stiffness. It is also found that the initial track tension has a significant effect on the actual track tension over a wide range of terrain and a slight to moderate influence on ground pressure distribution, dependent upon terrain stiffness.It should be noted that although individually some of the design parameters have only a slight or moderate effect on ground pressure distribution and track tension, their combined effects may be significant. Therefore, in the selection of design parameters of the track-suspension system, their combined influence must be carefully examined.     

Simulation du front d'écoulement dans les procédés de moulage des composites liquides

This work proposes a procedure of finite difference discretized in a system of curvilinear coordinates adapted to the shape of the saturated zone, to simulate a flow in the LCM (Liquid Composites Molding) process. Formulation and the numerical application of the procedure are described. We describe two configurations of injections. A good agreement is found between numerical, analytical and literature experimental results. To cite this article: M. Hattabi et al., C. R. Mecanique 333 (2005).     

Vérification expérimentale de la relation de réciprocité d'Onsager pour l'électro-osmose et l'électro-filtration dans une argile naturelleExperimental verification of the Onsager's reciprocal relations for electro-osmosis and electro-filtration phenomena on a saturated clay

This Note is devoted to the experimental verification of the Onsager's reciprocal relations in the particular case of electro-osmosis and electro-filtration. A special set up has been designed to carry out the measurements of both the electro-osmotic permeability and the streaming potential. This has been performed by using a natural material i.e., saturated kaolinite. To cite this article: K. Beddiar et al., C. R. Mecanique 330 (2002) 893–898.     

On the impact of anisotropy on dispersion spectra of acoustic waves in platesImpact de l'anisotropie sur les spectres de dispersion des ondes élastiques dans des plaques

A brief overview is given of specific features that can (or cannot) appear in the dispersion spectra of traction-free elastic homogeneous plates due to anisotropy. Its effect on the overall spectral configuration and on the short and long wave trends is illuminated with a link to anisotropic traits of bulk and surface waves. Relevant classical and recent results are put together, and new points are established. To cite this article: A.L. Shuvalov, C. R. Mecanique 334 (2006).     

Combined action of anticonvection and thermocapillarity in two- and three-layer systemsAction simultanée d'anticonvection et de thermocapillarité dans des systèmes multi-couches

Anticonvection generated by the joint action of the external heating and heat sources (sinks) on the interface in the layers with finite thicknesses is studied. Anticonvective structures in fluid systems subject to the anticonvective instability only in the presence of heat sources (sinks) on the interface have been obtained. The nonlinear regimes of anticonvection in the system of three immiscible viscous fluids heated from above are investigated. The specific phenomena caused by direct and indirect interaction of anticonvective and thermocapillary mechanisms of instability are considered. In particular, different oscillatory configurations where anticonvection arises mainly near the upper interface and thermocapillary convection appears mainly near the lower interface, have been studied. To cite this article: I.B. Simanovskii, C. R. Mecanique 332 (2004).