Chasseneuil-du-Poitou, France
Chasseneuil-du-Poitou, France

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Bouchoucha F.,University of Sfax | Bouchoucha F.,École Centrale Lyon | Akrout M.,University of Sfax | Fakhfakh T.,University of Sfax | And 2 more authors.
International Journal of Modelling, Identification and Control | Year: 2010

In this paper, we present an inexpensive and robust tool for the vibratory monitoring of cylindrical pipes. The tool will be based on the analysis of the anomalies which affect the elastic waves travelling in the pipe. We develop a numerical approach to study the guided elastic wave propagation in tubular structures. Wave finite element method (WFEM) based on the characterisation of the elastic waves is introduced to investigate the dispersion and wave scattering in pipes. Dynamic reduction technique is employed to improve the computational efficiency. Through WFEM and using a modal decomposition, we develop the dynamical behaviour of the pipe. We study the detection of some defects which affect the junction between two adjacent pipes. The question of the mode sensitivity to the defect's detection is considered. Copyright © 2010 Inderscience Enterprises Ltd.

Dautriat J.,Laboratoire Of Mecanique Des Solides | Dautriat J.,French Institute of Petroleum | Bornert M.,Laboratoire Of Mecanique Des Solides | Bornert M.,ParisTech National School of Bridges and Roads | And 3 more authors.
EPJ Web of Conferences | Year: 2010

The technique of Digital Image Correlation (DIC) has been applied to study the deformation of porous carbonate rocks subjected to uniaxial compression tests. The tests have been performed at two different scales: on cylinders of 10 cm high compressed with a standard press with digital images recorded by optical microscopy at a global and local scale and on smaller parallelepiped samples deformed inside a scanning electron microscope (SEM). The development of localization at different scales is thus recorded as well as the damage and compaction mechanisms in relation with the microstructural heterogeneities. © 2010 Owned by the authors, published by EDP Sciences.

Danas K.,Laboratoire Of Mecanique Des Solides | Aravas N.,University of Thessaly | Aravas N.,Mechatronics Institute
Composites Part B: Engineering | Year: 2012

A new constitutive model for elasto-plastic (rate-independent) porous materials subjected to general three-dimensional finite deformations is presented. The new model results from simple modifications of an earlier model of Kailasam and Ponte Castañeda (1997, 1998) [40,41] so that it reproduces the exact spherical and cylindrical shell solution (composite sphere and composite cylinder assemblage) under purely hydrostatic loadings, while predicting (by calibration) accurately the void shape evolution according to the recent "second-order" model of Danas and Ponte Castañeda [17]. Furthermore, the present model is based on a rigorous homogenization method which is capable of predicting both the constitutive behavior and the microstructure evolution of porous materials. The microstructure is described by voids of arbitrary ellipsoidal shapes and orientations and as a result the material exhibits deformation-induced (or morphological) anisotropy at finite deformations. This is in contrast with the well-known Gurson [32] model which assumes that the voids remain spherical during the deformation process and thus the material remains always isotropic. The present model is implemented numerically in a finite element program where a three-dimensional thin-sheet (butterfly) specimen is subjected to a combination of shear and traction loading conditions in order to examine the effect of stress triaxiality and shearing upon material failure. The ability of the present model to take into account the nontrivial evolution of the microstructure and especially void shape effects leads to the prediction of material failure even at low stress triaxialities and small porosities without the use of additional phenomenological damage criteria. At high stress triaxialities, the present model gives similar predictions as the Gurson model. © 2011 Elsevier Ltd. All rights reserved.

De Saxce G.,Lille Laboratory of Mechanics | Vallee C.,Laboratoire Of Mecanique Des Solides
Mathematics and Mechanics of Solids | Year: 2012

In a previous paper, we proposed an approach for the dynamics of 3D bodies and shells based on the use of affine tensors. This new theoretical frame is very large and the applications are not limited to the mechanics of continua. In the present paper, we show how it can be also applied to the description of the mechanics of freely falling particles and rigid bodies. The mass, the linear and angular momenta are structured as a single object called a torsor. Excluding all metric notions, we define the torsors as skew-symmetric bilinear mappings operating on the linear space of the affine functions. Torsors are a particular family of affine tensors. On this ground, we define an intrinsic differential operator called the affine covariant derivative. Next, we claim that the torsor characterizing the behaviour of a freely falling particle is affine covariant derivative free, that allows recovering both laws of linear and angular momentum. Finally, it is shown how the motion of rigid bodies can be described within this frame. © The Author(s) 2011.

De Saxce G.,Lille Laboratory of Mechanics | Buliga M.,Romanian Academy of Sciences | Vallee C.,Laboratoire Of Mecanique Des Solides
Mathematics and Mechanics of Solids | Year: 2011

In many practical situations, uncertainties affect the mechanical behavior that is given by a family of graphs instead of a single graph. In this paper, we show how the bipotential method is able to capture such blurred constitutive laws, using bipotential convex covers. © 2009 The Author(s).

Danas K.,University of Cambridge | Danas K.,Laboratoire Of Mecanique Des Solides | Deshpande V.S.,University of Cambridge | Fleck N.A.,University of Cambridge
International Journal of Plasticity | Year: 2010

Discrete dislocation plasticity models and strain-gradient plasticity theories are used to investigate the role of interfaces in the elastic-plastic response of a sheared single crystal. The upper and lower faces of a single crystal are bonded to rigid adherends via interfaces of finite thickness. The sandwich system is subjected to simple shear, and the effect of thickness of crystal layer and of interfaces upon the overall response are explored. When the interface has a modulus less than that of the bulk material, both the predicted plastic size effect and the Bauschinger effect are considerably reduced. This is due to the relaxation of the dislocation stress field by the relatively compliant surface layer. On the other hand, when the interface has a modulus equal to that of the bulk material a strong size effect in hardening as well as a significant reverse plasticity are observed in small specimens. These effects are attributed to the energy stored in the elastic fields of the geometrically necessary dislocations (GNDs). © 2010 Elsevier Ltd. All rights reserved.

Boulila A.,Laboratoire Of Biomecanique Orthopedique Lbo Ino Mt Kassab | Jendoubi K.,Laboratoire Of Biomecanique Orthopedique Lbo Ino Mt Kassab | Jendoubi K.,Laboratoire Of Mecanique Des Solides | Zghal A.,Laboratoire Of Mecanique Des Solides | And 2 more authors.
Mecanique et Industries | Year: 2010

Under severe conditions, the prosthetic stresses in Total Hip Arthroplasty (THA) can be amplified and transmitted to bone anchoring. This increases the risk of loosening (B. The et al., J. Biomech. 41 (2008) 100-105). The loading peaks are identified as the factors which lead to the failures of the THA (A. Boulila, Optimisation et aide à la conception d'implants orthopédiques - Itude de l'usure d'implants articulaires de hanche, Travaux non publiés et Rapport d'avancement, INO MT Kassab, décembre 2006, Tunis, 82 p.). This study deals with a numerical simulation of the hybrid hip prostheses which have a different geometry and some materials friction. It is shown that some geometries (28 × 56 mm) and friction materials (alumina/polyethylene), can attenuate the stresses induced after a peak and protect the prosthesis against the premature wear or fractures. In front of panoply of about fifty models of hip prostheses existing on the market (M.R. Urist, Curr. Prob. Surg. 12 (1975) 1-54), some THP diameters (intern and external) are incompatible with a working level of stresses and must be eliminated. A judicious combination of friction materials to support damping (case of the polyethylene/ceramic) can be a solution to absorb the shocks and to cure the problem of loosening. © 2010 AFM, EDP Sciences.

Danas K.,Laboratoire Of Mecanique Des Solides | Triantafyllidis N.,Laboratoire Of Mecanique Des Solides | Triantafyllidis N.,University of Michigan
Journal of the Mechanics and Physics of Solids | Year: 2014

Magnetorheological elastomers (MREs) are ferromagnetic particle impregnated rubbers whose mechanical properties are altered by the application of external magnetic fields. Due to their coupled magneto-mechanical response, MREs are finding an increasing number of engineering applications. One such application is in haptics, where the goal is to actively control surface roughness. One way to achieve this is by exploiting the unstable regime of MRE substrate/layer assemblies subjected to transverse magnetic fields. In this work, we study the response of such an assembly subjected to a transverse magnetic field and in-plane stress. The layer is made up of a transversely isotropic MRE material, whose energy density has been obtained experimentally, while the substrate is a non-magnetic isotropic pure polymer/gel. An analytical solution to this problem based on a general, finite strain, 2D continuum modeling for both the MRE layer and the substrate shows that for adequately soft substrates there is a finite-wavelength buckling mode under a transverse magnetic field. Moreover, the critical magnetic field can be substantially reduced in the presence of a compressive stress of the assembly, thus opening the possibility for haptic applications operating under low magnetic fields. © 2014 Elsevier Ltd. All rights reserved.

Danas K.,Laboratoire Of Mecanique Des Solides | Kankanala S.V.,BD Technologies | Kankanala S.V.,Ford Motor Company | Triantafyllidis N.,Laboratoire Of Mecanique Des Solides | Triantafyllidis N.,University of Michigan
Journal of the Mechanics and Physics of Solids | Year: 2012

Magnetorheological elastomers (MREs) are ferromagnetic particle impregnated rubbers whose mechanical properties are altered by the application of external magnetic fields. Due to their coupled magnetoelastic response, MREs are finding an increasing number of engineering applications. In this work, we present a combined experimental and theoretical study of the macroscopic response of a particular MRE consisting of a rubber matrix phase with spherical carbonyl iron particles. The MRE specimens used in this work are cured in the presence of strong magnetic fields leading to the formation of particle chain structures and thus to an overall transversely isotropic composite. The MRE samples are tested experimentally under uniaxial stresses as well as under simple shear in the absence or in the presence of magnetic fields and for different initial orientations of their particle chains with respect to the mechanical and magnetic loading direction. Using the theoretical framework for finitely strained MREs introduced by Kankanala and Triantafyllidis (2004), we propose a transversely isotropic energy density function that is able to reproduce the experimentally measured magnetization, magnetostriction and simple shear curves under different prestresses, initial particle chain orientations and magnetic fields. Microscopic mechanisms are also proposed to explain (i) the counterintuitive effect of dilation under zero or compressive applied mechanical loads for the magnetostriction experiments and (ii) the importance of a finite strain constitutive formulation even at small magnetostrictive strains. The model gives an excellent agreement with experiments for relatively moderate magnetic fields but has also been satisfactorily extended to include magnetic fields near saturation. © 2011 Elsevier Ltd. All rights reserved.

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