Publications

2007

• A novel approach to the heat build up problem of rubber
  
  • Le Chenadec Yohan
  • Stolz Claude
  • Raoult Ida
  • Nguyen Mac Lan
  • Charrier Pierre
  • Delattre Benoit
  , 2008, V, pp.345-350. Rubber is well-known to have a hysteretic behavior and a low thermal conductibility. The main consequences are the heat generation and heat build-up phenomena which occur in a rubber structure when submitted to repeated deformations. The purpose of our work is to estimate the steady-state temperature reached in elastomer structures when submitted to cyclic loadings. A decoupled strategy of the cyclic thermomechanical problem resolution is adopted. First a mechanical analysis is performed with a hyperelastic stabilized behavior of rubber. Then an estimation of the energy converted into heat is given. It is based on an energetic measure of a mechanical cycle and links the hysteretic loss energy to the elastic mechanical variables. It accounts for mean strains. An experimental investigation has been carried out in order to identify the estimation of the heat sources at various temperatures and mean strains. The influence of the Mullins effect on the dissipation is discussed. Finally, the thermal problem is solved and the influence of the geometry deformation on the heat equation in finite strains is taken into account with an approximation based on average values over a cycle. The heat build-up law is validated: heat build-up experiments have been carried out and comparisons with FE calculations have shown the ability of the law to estimate the transient and stationary temperature of an inhomogeneous structure submitted to cyclic loadings.
• Fast multipole boundary integral equation method for 3D seismic wave propagation in alluvial basins
  
  • Chaillat Stéphanie
  • Bonnet Marc
  • Semblat Jean-François
  , 2007.
• Ultrasonic measurement of anisotropy and temperature dependence of elastic parameters by a dry coupling method applied to a 6061-T6 alloy
  
  • Augereau F.
  • Laux D.
  • Allais L.
  • Mottot M.
  • Caes C.
  Ultrasonics, Elsevier, 2007, 46 (1), pp.34-41. A pulse-echo ultrasonic method is presented to measure elastic parameter variations during thermal loading with high accuracy. Using a dry coupling configuration dedicated to high temperature investigation, this technique has been applied on 6061-T6 aluminium samples up to 220 °C. Experimental settings are described to assess the measurement reproducibility estimated at a value of 0.2%. Consequently, the anisotropy of this aluminium between the rolling direction and two orthogonal axes has been clearly detected and also measured versus temperature. As regards the temperature dependence of these elastic parameters, these results are compared with the estimations of the Young's modulus obtained during mechanical tests in conditions of low cycle fatigue (LCF). The same linear variation versus temperature is found but with a shift of 7 GPa. This difference has been classically attributed to systematic experimental error sources and to the distinction existing between dynamic and static elastic modulus. (10.1016/j.ultras.2006.10.002)
  DOI : 10.1016/j.ultras.2006.10.002
• Introducing infrared thermography in soil dynamics
  
  • Luong Minh-Phong
  Infrared Physics and Technology, Elsevier, 2007 (49), pp.306-311. The paper introduces infrared thermography as a non-contact and non-destructive technique that conveniently offers the possibility of evaluating the energy-dissipating ability of soil, generally difficult to be determined using traditional techniques. It allows records and observations in real time of heat patterns produced by the dissipation of energy caused by friction between grains. Such dissipative heat occurs when soil is subjected to vibratory loading exceeding the characteristic threshold, and it evidences the distortion mechanism. This energy dissipation mechanisminfluences the wave propagation, intergranular attenuation, and dispersion through particles contacts. The infrared thermographic technique, which couples mechanical and thermal energy, offers the potential of directly monitoring the stress state of particle rearrangement and predicting the macroscopic mechanical response of soils subjected to cyclic, dynamic or vibratory loading. In addition, infrared thermography evidences the fuse effect of soil, capable to mitigate significantly the earthquake loading on engineering structures. 2006 Elsevier B.V. All rights reserved. (10.1016/j.infrared.2006.06.025)
  DOI : 10.1016/j.infrared.2006.06.025
• A Novel Haptic Interface for Musical Keyboards
  
  • Lozada José
  • Hafez Moustapha
  • Boutillon Xavier
  , 2007, pp.6 p.. A novel haptic interface for musical keyboards is presented. The piano key has an embedded active damping system based on magneto-rheological (MR) fluids that allows to reproduce the dynamic behavior of traditional pianos. The MR fluid is encapsulated into a mechanical sealing to avoid leakage. A slider is attached to the back of the key and shears the MR fluid. When a magnetic field is applied across the MR fluid, chains of particles are aligned along the magnetic field lines. The strain of the chains will create a resistant force that can be controlled on real time. An analytical model of the whole system is presented and compared to experimental results.
• Dérivées de l'énergie potentielle pour la propagation de fissure en 3D : Prise en compte de contraintes résiduelles
  
  • Edeline Gwenael
  • Bonnet Marc
  , 2007.
• Bounds and estimates for the effective yield surface of porous media with a uniform or a nonuniform distribution of voids
  
  • Bilger Nicolas
  • Auslender François
  • Bornert Michel
  • Moulinec Hervé
  • Zaoui André
  European Journal of Mechanics - A/Solids, Elsevier, 2007, 26 (5), pp.810-836. (10.1016/j.euromechsol.2007.01.004)
  DOI : 10.1016/j.euromechsol.2007.01.004
• MODELING COUPLING EFFECTS IN CORD-RUBBER COMPOSITE STRUCTURES
  
  • Hassis H.
  • El Arem Saber
  • Pidaparti Ramana
  JP Journal of Solids and Structures, 2007, 1 (3), pp.http://pphmj.com/abstract/2966.htm. An analytical model is developed to study the coupling effects in cordrubber composite materials. The analytical model takes into account the mismatch of stiffness between the cords and the rubber matrix material, and the twist-extension coupling. The transverse deformation, i.e., normal to the cords direction is based on the normal modes of a special system which describes the orthotropic and the coupling behaviour of cord-rubber composites. The equations of motion for the cord-composite plates are derived using the principle of virtual work. Results of deformation and stresses are obtained for some typical cord-rubber composite plates and are compared to the existing solutions. The results presented illustrate that the coupling effects are significant for nonsymmetrical cord orientations.
• Couplings in salt and salt caverns
  
  • Berest Pierre
  • Bérest P.
  , 2007.
• A discontinuous stabilized mortar method for general 3D elastic problems
  
  • Le Tallec Patrick
  • Hauret Patrice
  Computer Methods in Applied Mechanics and Engineering, Elsevier, 2007, 196 (49-52), pp.4881-4900. First, the present paper is concerned with the extension to linearized elastodynamics of the optimal results known in statics for the mortar method. It also analyzes and tests a new couple of displacements/Lagrange multipliers for the method, as proposed independently by Ben Belgacem [F. Ben Belgacem, A stabilized domain decomposition method with non-matching grids for the Stokes problem in three dimensions, SIAM J. Numer. Anal. 42 (2) (2004) 667–685] and the authors [P. Hauret, Méthodes numériques pour la dynamique des structures non-linéaires incompressibles à deux échelles (Numerical methods for the dynamic analysis of two-scale incompressible nonlinear structures), Ph.D. thesis, Ecole Polytechnique, 2004]. Finally, questions of practical implementation in the presence of curved interfaces are addressed and validated from the numerical point of view. (10.1016/j.cma.2007.06.014)
  DOI : 10.1016/j.cma.2007.06.014
• Field statistics in nonlinear composites. II. Applications
  
  • Idiart Martin
  • Ponte Castañeda Pedro
  Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, Royal Society, The, 2007, 463, pp.203-222. Part I of this work provided a methodology for extracting the statistics of the local fields in nonlinear composites, from the effective potential of suitably perturbed composites. In particular, exact relations were given for the first and even moments of the fields in each constituent phase. In this part, use is made of these exact relations in the context of the ‘variational’, ‘tangent second-order’ and ‘second-order’ nonlinear homogenization methods to generate estimates for the phase averages and second moments of the fields for two-phase, power-law composites with isotropic and transversely isotropic microstructures. The accuracy of these estimates is assessed by confronting them against corresponding exact results for sequentially laminated composites. Among the nonlinear homogenization estimates considered in this work, the second-order estimates are found to be, in general, the most accurate, especially for large heterogeneity contrast and nonlinearity. Thus, these estimates are able to capture, for example, the strong anisotropy in the strain fluctuations that can develop inside nonlinear porous and rigidly reinforced composites. (10.1098/rspa.2006.1757)
  DOI : 10.1098/rspa.2006.1757
• Locking free matching of different three dimensional models in structural mechanics
  
  • Le Tallec Patrick
  • Mani Saloua
  ESAIM: Mathematical Modelling and Numerical Analysis, Société de Mathématiques Appliquées et Industrielles (SMAI) / EDP, 2007, 41 (1), pp.129-145. The present paper proposes and analyzes a general locking free mixed strategy for computing the deformation of incompressible three dimensional structures placed inside flexible membranes. The model involves as in Chapelle and Ferent [Math. Models Methods Appl. Sci. 13 (2003) 573-595] a bending dominated shell envelope and a quasi incompressible elastic body. The present work extends an earlier work of Arnold and Brezzi [Math Comp. 66 (1997) 1-14] treating the shell part and proposes a global stable finite element approximation by coupling optimal mixed finite element formulations of the different subproblems by mortar techniques. Examples of adequate finite elements are proposed. Convergence results are derived in two steps. First a global inf-sup condition is proved, deduced from the local conditions to be satisfied by the finite elements used for the external shell problem, the internal incompressible 3D problem, and the mortar coupling, respectively. Second, the analysis of Arnold and Brezzi [Math. Comp. 66 (1997) 1-14] is extended to the present problem and least to convergence results for the full coupled problem, with constants independent of the problem's small parameters. (10.1051/m2an:2007013)
  DOI : 10.1051/m2an:2007013
• Transient behaviour of salt caverns
  
  • Berest Pierre
  • Karimi-Jafari Mehdi
  • Brouard Benoît
  • van Sambeek Leo
  , 2007, pp.383-390.
• Testing aluminum alloy from quasi-static to dynamic strain rates with a modified Split Hopkinson Bar method
  
  • Othman Ramzi
  • Gary Gérard
  Experimental Mechanics, Society for Experimental Mechanics, 2007, 47 (2), pp.295-299. An aluminum alloy(1) was tested at quasi-static to dynamic strain-rates (from 10(-1) to 5 10(3) s(-1)), using a single measuring device, a modified Split Hopkinson Bar. A wave separation technique [Bussac et al., J Mech Phys Solids 50:321-350, 2002] based on the maximum likelihood method was applied to process the strain and velocity measurements recorded at various points on each bar. With this method, it is possible to compute the stress, strain, displacement and velocity at any point on the bar. Since the measurement time is unlimited, the maximum strain measured in a given specimen no longer decreases with the strain-rate, as occurs with the classical Split Hopkinson Bar method. (10.1007/s11340-006-9023-7)
  DOI : 10.1007/s11340-006-9023-7
• Higher-order topological sensitivity for acoustic and elastodynamic inverse scattering
  
  • Bonnet Marc
  , 2007.
• Inversion of random field models for heterogeneous media from spectral analysis of mechanical waves
  
  • Arnst Maarten
  • Bonnet Marc
  • Clouteau Didier
  • Ta Quang-Anh
  , 2007.