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Abstract: The objective of this review is to present the salient features of capsule mechanical behaviour under the influence of viscous deforming forces due to a flowing fluid. We focus on artificial capsules that are initially spherical with an internal liquid core and that are enclosed by a very thin hyperelastic membrane. Different constitutive laws, commonly used to describe the rheological behaviour of thin membranes, are presented. The motion and deformation of a single capsule freely suspended in a simple shear flow is presented as a function of membrane constitutive law and of initial pre-stress. The limitations of classical membrane models that neglect bending effects are discussed. To cite this article: D. Barthès-Biesel, C. R. Physique 10 (2009). [Copyright &y& Elsevier]

The present manuscript is devoted to two works related to the spontaneous formation of patterns in Nature: venation in leaves and evolution of embryos. Morphogenetic processes and growth-induced instability phenomena are modelled through analogue experiments. The organization of veins in leaves is similar to what is expected from growth in a tensorial stress field that governs the formation of fractures, while the change in the shape of embryos is related to the deformation of a shell-like membrane whose properties evolve with time. The approaches resulting from analogue experiments is a way to explore specific properties of the media at a macroscopic scale. Thus the manuscript aims to focus on the analogue experiments, their adaptability to reproduce specific patterns and the relation between both growth-induced instability and mechanical behaviour of the matter. [ABSTRACT FROM AUTHOR]

A finite-element computational strategy is developed to study the viscoplastic deformation mechanisms at work in a nickel foam sample under compression creep. The constitutive law for pure nickel accounts for both diffusional and dislocation creep mechanisms. The finite-element results show the competition between both mechanisms due to the strong heterogeneity of the stress distribution in the foam. The initiation of the viscoplastic buckling phenomenon leading to cell crushing in tertiary creep is illustrated. The overall model prediction is compared to the results of compression creep tests performed in vacuo at 900 °C. [ABSTRACT FROM AUTHOR]

Abstract: In this Note, the phenomenon of cumulative slip of solids under cyclic loads is considered. The topic concerns with the relative displacements of two solids maintained in contact by friction. This problem of the daily-life mechanics can be compared to the shakedown of elastic plastic solids under cyclic loads. A transcription of the plastic shakedown theorems is given here for the problem of frictional contact. The statement of Melan theorem is first given for the cumulative-slip problem under some restrictive assumptions. It suggests again the introduction of a safety coefficient with respect to slips. The safety coefficient can be computed from two static and kinematic approaches in min–max duality and leads again to Koiter theorem. As in plasticity, these results are available only for associated laws and do not hold for Coulomb law of friction, except in some very particular situations. These results can be understood mathematically as a particular case of shakedown theorems in plasticity, when the plastic strain is localized on a surface. For Coulomb friction, numerical simulations by direct step-by-step calculations show that the asymptotic behaviour of the response with or without slip-shakedown could be obtained very quickly after some cycles. To cite this article: N. Antoni, Q.-S. Nguyen, C. R. Mecanique 336 (2008). [Copyright &y& Elsevier]

Local buckling of steel structural members has to be well understood in order to design accurately steel structures in seismic areas. Induced softening moment-curvature law leads to a well known ill-posedness elastoplastic evolution problem. Localization is chosen to be controlled with a gradient plasticity approach. The concept of cross-section behavioural classes, classically adopted in modern rule design, should be substituted by the concept of member behavioural classes. To cite this article: N. Challamel, C. R. Mecanique 331 (2003). [Copyright &y& Elsevier]

Generally, tectonic plates are considered as rigid. Oblique plate convergence favors the development of micro-plates along the converging boundaries. The north–south-trending Philippines archipelago (here named Philippine Mobile Belt, PMB), a few hundreds kilometers wide, is one of such complex tectonic zones. We show here that it is composed of rigid rotating crustal blocks (here called platelets). In Myanmar, the northernmost tip of the Sumatra-Andaman subduction system is another complex zone made of various crustal blocks in-between convergent plates. Yet, contrary to PMB, it sustains internal deformation with platelet buckling, altogether indicative of a non-rigid behavior. Therefore, the two case studies, Philippine Mobile Belt and Myanmar-Andaman micro-plate (MAS), illustrate the complexity of micro-plate tectonics and kinematics at convergent plate boundaries. [ABSTRACT FROM AUTHOR]