The bending inertia of a circular cross section is derived within the couple-stress theory where only the gradient of the rate of rotation is taken into account.
The bending inertia of a circular cross section is derived within the couple-stress theory where only the gradient of the rate of rotation is taken into account.
L'astérosismologie est l'étude de l'intérieur des étoiles variables par l'intermédiaire de leurs oscillations, et offre la possibilité de testa la théorie de l'évolution stellaire. Les étoiles variables de type δ Scuti permettent, en particulier, l'analyse des phénomènes de convection dans les régions centrales et de ceux de rotation Les réseaux d'observation terrestres ont considérablement amélioré la qualité des données, et des missions spatiales sont élaborées, dont COROT qui sera lancée en 2001. Un des principaux problèmes de l'astérosismologie concerne l'identification des modes observés, qui reste ambiguë dans la grande majorité des cas, et est compliquée par lu rotation. Les effets non linéaires et non adiabatiques sont également importants, et doivent être mieux pris en compte pour comprendre les mécanismes de sélection des modes et de la saturation de leur amplitude. L'astérosismologie offre un formidable potentiel pour l'élude des phénomènes physiques qui régissent l'évolution des étoiles, et les missions spatiales constituent un nouveau tremplin.
Asterosismology is the study of the interiors of stars by means of their pulsations, and offers the possibility to use the theory of stellar evolution δ Scuti-type stars an particularly attractive fur studying convective phenomena in the deep interior and notation. Ground-based networks have greatly improved the data, and space missions an elaborated, such COROT. One of the main problems is the identification of the observed modes, vhich is ambiguous and is complicated by the effects of rotation. Nonlinear and nonadiabatic effects an also important, and must be taken into account for the understanding of the mechanisms of the selection of modes and of the saturation of their amplitudes. Asteroseismology is a powerful toot for the study of processes which regulate the stellar evolution, and space missions open a new area in that field.
We are interested in the study of the bonding of two parts of an elastic solid by a thin elastic layer of glue. Using matched asymptotic expansions, we show that, at order 1, the glue behaves like a line segment across which displacements and stresses undergo jump discontinuities and the end points of which are submitted to concentrated forces.
A ridge of sand, with initial angles ± θi (smaller than the angle of repose θr) is fed by a source of flux 2Q. We discuss here the theoretical profile achieved after a time t, using the equations of Bouchaud et al. in their original form, and also in a modified form which might apply for strong flows. The result is a central heap, steeper than the original ridge, of slope close to θr. The horizontal span is predicted to be xm = (2Dt)1/2, with an apparent diffusion coefficient D = Q/(θr − θi).
The purpose of Fracture Mechanics is to predict and prevent the initiation and propagation of cracks in solid materials. It splits into two sub-disciplines. Mechanics of Brittle Fracture and Mechanics of Ductile Fracture, the basic origin of the difference lying in the different physical mechanisms governing fracture. One expounds here the foundations of each of them and evokes some present problems which arise in their context.
Starting from a mixed modelling of a matrix material reinforced by regularly embedded inclusions regarded as straight beams, and through a homogenization procedure making use of the virtual work method, a micropolar description is obtained for the homogenized composite medium. The model is implemented within the context of the yield design theory, the strength properties of the reinforced matrix material being simply deduced from those of its individual components. The upper bound kinematic method is then applied to the stability analysis of a reinforced vertical excavation.
The fundamental derivative of the cross section of a conduit partly filled by a flowing liquid is used in order to solve the problem of finite amplitude hydraulic jumps.
The uniqueness of mechanical response can be lost for a material with softening. For a non-viscous material, two methods are widely used to predict this phenomenon: the linear perturbation method and the bifurcation analysis. In this paper we prove that the latter method should be considered as a limit case of the former one, as already observed in some particular cases.
The present work deals with a two-fluid model for blood flow through deformable tubes of small diameter. The two-fluid flow consists of a core (suspension of red cells) and a peripheral red cell free plasma layer. From this model, taking into account the two-phase pulsatile flows, the non-Newtonian behaviour of core and the wall deformability of pipes, a wall shear-stress expression was elaborated for the Womersley numbers regarding the microcirculation. This relation allows the direct resolution of the equations governing such flows without numerical methods.
A new justification of the two-dimensional linear Kirchhoff-Love plate model is given by asymptotic expansion of the nonlinear equilibrium equations. For weak level forces, the asymptotic analysis leads to the two-dimensional linear Kirchhoff-Love model, whereas for moderate level forces, it leads to the usual nonlinear two-dimensional plate model.
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