Publications

2010

• Topological sensitivity of energy cost functional for wave-based defect identication
  
  • Bonnet Marc
  Comptes Rendus. Mécanique, Académie des sciences (Paris), 2010, 338, pp.377-389. This article is concerned with establishing the topological sensitivity (TS) against the nucleation of small trial inclusions of an energy-like cost function. The latter measures the discrepancy between two time-harmonic elastodynamic states (respectively defined, for cases where overdetermined boundary data is available for identification purposes, in terms of Dirichlet or Neumann boundary data for the same reference solid) as the strain energy of their difference. Such cost function constitutes a particular form of error in constitutive relation and may be used for e.g. defect identification. The TS is expressed in terms of four elastodynamic fields, namely the free and adjoint solutions for Dirichlet or Neumann data. A similar result is also given for the linear acoustic scalar case. A synthetic numerical example where the TS result is used for the qualitative identification of an inclusion is presented for a simple 2D acoustic configuration. (10.1016/j.crme.2010.07.016)
  DOI : 10.1016/j.crme.2010.07.016
• New flow rules in elasto-viscoplastic constitutive models for spheroidal graphite cast-iron
  
  • Szmytka Fabien
  • Rémy Luc
  • Maitournam Habibou
  • Köster Alain
  • Bourgeois Myriam
  International Journal of Plasticity, Elsevier, 2010, 26, pp.905-924. A specific flow rules and the corresponding constitutive elasto-viscoplastic model combined with new experimental strategy are introduced in order to represent a spheroidal graphite cast-iron behaviour on a wide range of strain, strain rate and temperature. A “full model” is first proposed to correctly reproduce the alloy behaviour even for very small strain levels. A “light model” with a bit poorer experimental agreement but a simpler formulation is also proposed. These macroscopic models, whose equations are based on physical phenomena observed at the dislocation scale, are able to cope with the various load conditions tested – progressive straining and cyclic hardening tests – and to correctly describe anisothermal evolution. The accuracy of these two models and the experimental databases to which they are linked is estimated on different types of experimental tests and compared with the accuracy of more standard Chaboche-type constitutive models. Each test leads to the superiority of the “full model”, particularly for slow strain rates regimes. After developing a material user subroutine, FEM simulations are performed on Abaqus for a car engine exhaust manifold and confirm the good results obtained from the experimental basis. We obtain more accurate results than those given by more traditional laws. A very good correlation is observed between the simulations and the engine bench tests. (10.1016/j.ijplas.2009.11.007)
  DOI : 10.1016/j.ijplas.2009.11.007
• Defect identification using elastodynamic topological sensitivity
  
  • Bonnet Marc
  , 2010.
• Fast Multipole Method for 3D Electromagnetic Boundary Integral Equations. Application to Nondestructive Testing on Complex 3D Geometries
  
  • Lim Tekoing
  • Pichenot G.
  • Bonnet Marc
  , 2010.
• A New Cost Effective Well Testing Methodology for Tight Gas Reservoirs.
  
  • Berest Pierre
  • Bérest P.
  Paper SPE 134293 - Proc. SPE Annual Technical Conference,, 2010, pp.134293.
• Effects of atmospheric pressure fluctuations in a closed cavern.
  
  • Berest Pierre
  • Bérest P.
  , 2010, pp.215-231.
• On the existence and uniqueness of a solution to the interior transmission problem for piecewise-homogeneous solids
  
  • Bellis Cédric
  • Guzina B. B.
  Journal of Elasticity, Springer Verlag, 2010, pp.in press. The interior transmission problem (ITP), which plays a fundamental role in inverse scattering theories involving penetrable defects, is investigated within the framework of mechanical waves scattered by piecewise-homogeneous, elastic or viscoelastic obstacles in a likewise heterogeneous background solid. For generality, the obstacle is allowed to be multiply connected, having both penetrable components (inclusions) and impenetrable parts (cavities). A variational formulation is employed to establish \emph{sufficient} conditions for the existence and uniqueness of a solution to the ITP, provided that the excitation frequency does not belong to (at most) countable spectrum of transmission eigenvalues. The featured sufficient conditions, expressed in terms of the mass density and elasticity parameters of the problem, represent an advancement over earlier works on the subject in that i) they pose a precise, previously unavailable provision for the well-posedness of the ITP in situations when both the obstacle and the background solid are heterogeneous, and ii) they are dimensionally consistent i.e. invariant under the choice of physical units. For the case of a viscoelastic scatterer in an elastic solid it is further shown, consistent with earlier studies in acoustics, electromagnetism, and elasticity that the uniqueness of a solution to the ITP is maintained irrespective of the vibration frequency. When applied to the situation where \emph{both} the scatterer and the background medium are viscoelastic i.e. dissipative, on the other hand, the same type of analysis shows that the analogous claim of uniqueness does not hold. Physically, such anomalous behavior of the ``viscoelastic-viscoelastic'' case (that has eluded previous studies) has its origins in a lesser known fact that the homogeneous ITP is not mechanically insulated from its surroundings -- a feature that is particularly cloaked in situations when either the background medium or the scatterer are dissipative. A set of numerical results, computed for ITP configurations that meet the sufficient conditions for the existence of a solution, is included to illustrate the problem. Consistent with the preceding analysis, the results indicate that the set of transmission values is indeed empty in the ``elastic-viscoelastic'' case, and countable for ``elastic-elastic'' and ``viscoelastic-viscoelastic'' configurations.
• A FEM-based topological sensitivity approach for fast qualitative identification of buried cavities from elastodynamic overdetermined boundary data
  
  • Bellis Cédric
  • Bonnet Marc
  International Journal of Solids and Structures, Elsevier, 2010, 47, pp.1221-1242. A time-domain topological sensitivity (TS) approach is developed for elastic-wave imaging of media of arbitrary geometry. The TS, which quantifies the sensitivity of the misfit cost functional to the creation at a specified location of an infinitesimal hole, is expressed in terms of the time convolution of the free field and a supplementary adjoint field as a function of that specified location. Following previous studies performed under (mostly) static or time-harmonic conditions, the TS field is here considered as a natural and computationally efficient approach for defining a defect indicator function. This study emphasizes the implementation and exploitation of TS fields using standard displacement-based FEM approaches, a straightforward task once the correct sensitivity formulation is available. A comprehensive set of numerical experiments on 3-D and 2-D elastodynamic and acoustic configurations is reported, allowing to assess and highlight many features of the proposed TS-based fast qualitative identification such as its ability to identify multiple defects and its robustness against data noise. (10.1016/j.ijsolstr.2010.01.011)
  DOI : 10.1016/j.ijsolstr.2010.01.011
• Sustainable and Realistic Commitments in the Energy Field
  
  • Salençon Jean
  , 2010.
• 1-D non-periodic homogenization for the seismic wave equation
  
  • Capdeville Yann
  • Guillot Laurent
  • Marigo Jean-Jacques
  Geophysical Journal International, Oxford University Press (OUP), 2010, 181 (2), pp.897-910. When considering numerical acoustic or elastic wave propagation in media containing small heterogeneities with respect to the minimum wavelength of the wavefield, being able to upscale physical properties (or homogenize them) is valuable mainly for two reasons. First, replacing the original discontinuous and very heterogeneous medium by a smooth and more simple one, is a judicious alternative to the necessary fine and difficult meshing of the original medium required by many wave equation solvers. Second, it helps to understand what properties of a medium are really ‘seen' by the wavefield propagating through, which is an important aspect in an inverse problem approach. This paper is an attempt of a pedagogical introduction to non-periodic homogenization in 1-D, allowing to find the effective wave equation and effective physical properties, of the elastodynamics equation in a highly heterogeneous medium. It can be extrapolated from 1-D to a higher space dimensions. This development can be seen as an extension of the classical two-scale homogenization theory applied to the elastic wave equation in periodic media, with this limitation that it does not hold beyond order 1 in the asymptotic expansion involved in the classical theory. (10.1111/j.1365-246X.2010.04529.x)
  DOI : 10.1111/j.1365-246X.2010.04529.x
• Éditorial
  
  • Rey Christian
  • Raous Michel
  • Pasquet Philippe
  • Bonnet Marc
  • Feyel Frédéric
  Mécanique et Industries, Elsevier, 2010, 11 (3-4), pp.165-295. Voir la collection <a href="https://hal.science/CSMA2009">Giens 2009</a>. (10.1051/meca/2010059)
  DOI : 10.1051/meca/2010059
• Multi-scale viscoplastic behaviour of Halite : In-situ SEM full field measurements, a micro-mechanical approach, Experimental mineralogy, petrology and geochemistry
  
  • Bourcier M.
  • Dimanov A.
  • Héripré E.
  • Bornert Michel
  • Raphanel J.
  , 2010.