Publications

2014

• Inverse Cauchy method with conformal mapping : application to latent flatness defect detection during rolling process
  
  • Weisz-Patrault Daniel
  International Journal of Solids and Structures, Elsevier, 2014, pp.1-33. In this paper a semi-analytical inverse Cauchy problem is presented for a finite cylinder with a cylindrical hole under the surface called the detecting roll. Applications to latent flatness defect detection during rolling process are considered. A steel strip wraps at a known angle around the detecting roll. The presented inverse method aims at evaluating the residual stress profile of the strip. The inputs are the displacements and free surface traction at the hole surface and the outputs are the resultant forces per unit length in the contact between the strip and the roll, thus by equilibrium of the strip the residual stress profile is inferred. This paper is based on plane complex elasticity with conformal mapping techniques. Several 2D-computations are performed at several axial positions. This work is theoretical, the measurement device is not available and technical issues are not broached. Some numerical examples with synthetic data are provided in order to evaluate accuracy and noise sensitivity. Results encourage further investigations and technical developments. (10.1016/j.ijsolstr.2014.11.017)
  DOI : 10.1016/j.ijsolstr.2014.11.017
• Dynamic Stability of Externally Pressurized Elastic Rings Subjected to High Rates of Loading
  
  • Putelat T.
  • Triantafyllidis Nicolas
  International Journal of Solids and Structures, Elsevier, 2014, 51, pp.1 - 12. Of interest here is the influence of loading rate on the stability of structures where inertia is taken into account, with particular attention to the comparison between static and dynamic buckling. This work shows the importance of studying stability via perturbations of the initial conditions, since a finite velocity governs the propagation of disturbances. The method of modal analysis that determines the fastest growing wavelength, currently used in the literature to analyze dynamic stability problems, is meaningful only for cases where the velocity of the perfect structure is significantly lower than the associated wave propagation speeds. As a model structure to illustrate this point we select an elastic ring subjected to external hydrostatic pressure which is applied at different rates epsilon (appropriately non-dimensionalized with respect to elastic axial wave speed). The ring's stability is studied by following the evolution of a localized small perturbation. It is shown that for small values of the applied loading rate, the structure fails through a global mode, while for large values of the applied loading rate the structure fails by a localized mode of deformation. An analytically obtained localization time t(1) is found to be a very good estimate of the onset of instability time at high loading rates (10.1016/j.ijsolstr.2013.08.002)
  DOI : 10.1016/j.ijsolstr.2013.08.002
• Instability of a magnetoelastic layer resting on a non-magnetic substrate
  
  • Danas Kostas
  • Triantafyllidis Nicolas
  Journal of the Mechanics and Physics of Solids, Elsevier, 2014, 69, pp.67-83. 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.
• Statistical inverse method for the multiscale identification of the apparent random elasticity field of heterogeneous microstructures
  
  • Soize Christian
  • Desceliers Christophe
  • Guilleminot Johann
  • Nguyen M. T.
  • Allain Jean-Marc
  • Gharbi H.
  , 2014.
• Editorial
  
  • Bérest Pierre
  Oil & Gas Science and Technology - Revue d'IFP Energies nouvelles, Institut Français du Pétrole (IFP), 2014, 69 (7), pp.1135-1141. No abstract available (10.2516/ogst/2014049)
  DOI : 10.2516/ogst/2014049
• Multi-scale mechanical characterization of sound dentin
  
  • Wang Wenlong
  • Vennat Elsa
  • Puel Guillaume
  • Roubier Nicolas
  • Allain Jean-Marc
  • Attal Jean-Pierre
  , 2014.
• Mathematical modelling of multi conductor cables
  
  • Beck Geoffrey
  • Imperiale Sebastien
  • Joly Patrick
  Discrete and Continuous Dynamical Systems - Series S, American Institute of Mathematical Sciences, 2014, pp.26. This paper proposes a formal justification of simplified 1D models for the propagation of electromagnetic waves in thin non-homogeneous lossy conductor cables. Our approach consists in deriving these models from an asymptotic analysis of 3D Maxwell’s equations. In essence, we extend and complete previous results to the multi-wires case. (10.3934/dcdss.2015.8.521)
  DOI : 10.3934/dcdss.2015.8.521
• Modelling the dynamics of the piano action: is apparent success real?
  
  • Thorin Anders
  • Boutillon Xavier
  • Lozada José
  Acta Acustica united with Acustica, Hirzel Verlag, 2014, pp.10. The kinematics and the dynamics of the piano action mechanism have been much studied in the last 50 years and fairly sophisticated models have been proposed in the last decade. Surprisingly, simple as well as sophisticated models seem to yield very valuable simulations when compared to measurements. We propose here a very simple model, with only 1-degree of freedom, and compare its outcome with force and motion measurements obtained by playing a real piano mechanism. The model, purposely chosen as obviously too simple to be predictive of the dynamics of the grand piano action, appears either as very good or as very bad, depending on which physical quantities are used as the input and output. We discuss the sensitivity of the simulation results to the initial conditions and to noise and the sensitivity of the experimental/simulation comparisons to the chosen dynamical model. It is shown that force-driven simulations with position comparisons, as they are proposed in the literature, do not validate the dynamical models of the piano action. It is suggested that these models be validated with position-driven simulations and force comparisons. (10.3813/AAA.918795)
  DOI : 10.3813/AAA.918795