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991.
Bilel Ben Boubaker Bernard Haussy Jean-François Ganghoffer 《Comptes Rendus Mecanique》2003,331(4):295-302
The coupling between yarns in a piece of fabric has been analysed at the mesoscopic scale, in terms of its impact on the macroscopic unidirectional behaviour. Starting from a discrete model of a woven structure associated to a variational formulation of the equilibrium of the structure, the coupling between both yarns is introduced, the potential energy of which is calculated. The initial shape of the yarn, represented by a planar undulated beam supposed to be periodic, is described by a Fourier series. The coefficients of the series are expressed vs. the contact force exerted at the top of the undulations, and vs. the mechanical properties of the solicited yarn. The contact force is then expressed vs. the mechanical properties of the transverse yarn and vs. the vertical displacement of the contact point. The potential energy of the coupling is then built, assuming the continuity of the displacement at the contact points. The equilibrium shape of the yarn submitted to unidirectional traction is obtained numerically as the minimum of the total potential energy. The simulated traction curve reproduces in a satisfactorily manner the observed behaviour. The respective contributions of the flexional and extensional effects of the yarn are analysed. The consideration of the coupling enhances the rigidity of the response of the yarn; one demonstrates the effect of the geometrical and mechanical parameters of the transverse yarn. To cite this article: B. Ben Boubaker et al., C. R. Mecanique 331 (2003). 相似文献
992.
Simon Salager Fredéric Jamin Moulay Saïd El Youssoufi Christian Saix 《Comptes Rendus Mecanique》2006,334(6):393-398
This paper concerns the influence of temperature on the water retention curve of porous media. We present a model based on the differential of suction as a function of temperature, water content and void ratio. When adjusted for a given temperature, this model is able to predict the curve for any temperature. The model was validated by several tests on a ceramic (terra cotta) and a clayey silty sand at 20 and 60?°C. The application of the model to data found in the literature confirms its predictive power for a wide range of porous materials. To cite this article: S. Salager et al., C. R. Mecanique 334 (2006). 相似文献
993.
Pierre Ladevèze 《Comptes Rendus Mecanique》2006,334(7):399-407
This Note introduces new strict upper error bounds on outputs of interest for linear as well as time-dependent nonlinear structural problems calculated by the finite element method. Small-displacement problems without softening, such as (visco)plasticity problems, are included through the standard thermodynamics framework involving internal state variables. To cite this article: P. Ladevèze, C. R. Mecanique 334 (2006). 相似文献
994.
Yves-Marie Scolan 《Comptes Rendus Mecanique》2005,333(6):487-492
On the basis of simple conformal mappings, we present a method to describe a two-dimensional potential flow around a rotating obstacle of arbitrary section. As a result, a simplified expression of the matrix of added mass and added moment of inertia is obtained. We also underline the need to determine this perturbation potential all over the fluid domain. Indeed, this is of practical interest in order to express the hydrodynamic moment in incompressible viscous flow. To cite this article: Y.-M. Scolan, C. R. Mecanique 333 (2005). 相似文献
995.
In this Note, we derive a multidimensional drift-flux model for boiling flows. Within this framework, the distribution parameter is no longer a scalar but a tensor that might account for the medium anisotropy and the flow regime. A new model for the drift-velocity vector is also derived. It intrinsically takes into account the effect of the friction pressure loss on the buoyancy force. On the other hand, we show that most drift-flux models might exhibit a singularity for large void fraction. In order to avoid this singularity, a remedy based on a simplified three field approach is proposed. To cite this article: O. Grégoire, M. Martin, C. R. Mecanique 333 (2005). 相似文献
996.
We consider a linear model of a rotating Timoshenko beam, which is clamped at one end to a disk the other being free. The motion of the beam is controlled by the angular acceleration of the disk. We study the minimization problem of mean square deviation of the Timoshenko beam from a given position. For the minimization problem of the first mode we prove that optimal control is the chattering control, i.e., it has an infinite number of switches in a finite time interval. We construct a suboptimal control with a finite number of switches. To cite this article: M.I. Zelikin, L.A. Manita, C. R. Mecanique 334 (2006). 相似文献
997.
The inverse medium problem for a circular cylindrical domain is studied using low-frequency acoustic waves as the probe radiation. To second order in k0a (k0 the wavenumber in the host medium, a the radius of the cylinder), only the first three terms (i.e., of orders 0, ?1 and +1) in the partial wave representation of the scattered field are non-vanishing. This enables the scattered field to be expressed algebraically in terms of the unknown material constants, i.e., the density ρ1, and the real and imaginary parts of complex compressibility κ1 of the cylinder. It is shown that these relations can be inverted to yield explicit, decoupled expressions for ρ1 and κ1 in terms of the totality of the far-zone scattered field. These expressions furnish accurate estimations of the material parameters provided the probe frequency is low and the radius of the cylinder is known very precisely. To cite this article: T. Scotti, A. Wirgin, C. R. Mecanique 332 (2004). 相似文献
998.
The Large Eddy Simulation of closed-loop active flow control applied to a 3D cavity excited by a compressible airflow with a Mach number of 0.6 is presented. The control actuator is an idealized synthetic jet located at the upstream cavity edge, and the control function is supplied by a feedback LMS-type algorithm whose input is a pressure signal measured inside the cavity. The radiated sound, provided directly by the LES simulation, was shown to decrease substantially when active control was applied. A simultaneous reduction of the vertical velocity fluctuations in the shear layer was observed. The intensity of vortical structures inside the cavity was also reduced, although the general aspect of the recirculation zone was not modified. The direct noise computation technique, which supplies the pressure field by solving the fluid mechanics equations, is shown to constitute a powerful tool for studying active aeroacoustic noise control. To cite this article: O. Marsden et al., C. R. Mecanique 331 (2003). 相似文献
999.
Boris Martin Zoubir Ayadi Michel Nivoit André Galtier Christian Cunat 《Comptes Rendus Mecanique》2004,332(11):907-913
A thermodynamic approach of relaxation phenomena called DNLR (Distribution of Non Linear Relaxations) has been employed for about fifteen years to describe the behaviour of materials. In this Note, we show that different DNLR constitutive equations, initially written in a rate formulation, can be put in a time-integrated (hereditary) form which generalises the superposition principle to non linear fields like viscoplasticity or damage behaviours. To cite this article: B. Martin et al., C. R. Mecanique 332 (2004). 相似文献
1000.
Siegfried Maïolino 《Comptes Rendus Mecanique》2005,333(3):279-284
A general smooth and convex yield function is proposed, able to model the particular behavior of geomaterials, particularly rock materials that are characterized by a linear or parabolic Mohr's envelope, and a particular shape in the deviatoric plane. These characteristics are defined by two functions: the equation of the criterion in the meridian plane and the extension ratio, which are integrated in a general equation ensuring convexity and smoothness of the yield function, whatever the characteristic functions. This expression is interesting, because it allows a straightforward development of a constitutive model based on triaxial tests, in extension and compression. It also allows the development of smooth criteria corresponding to the Mohr–Coulomb criterion and the H?k–Brown criterion, the latter typical of rock mechanics. To cite this article: S. Maïolino, C. R. Mecanique 333 (2005). 相似文献