Publications

2010

• 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
• Defect identification using elastodynamic topological sensitivity
  
  • 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.
• Fast Multipole Method for 3D Electromagnetic Boundary Integral Equations. Application to Nondestructive Testing on Complex 3D Geometries
  
  • Lim Tekoing
  • Pichenot G.
  • Bonnet Marc
  , 2010.
• Effects of atmospheric pressure fluctuations in a closed cavern.
  
  • Berest Pierre
  • Bérest P.
  , 2010, pp.215-231.
• 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.
• Simulations des verres nucléaires simplifiés par dynamique moléculaire : de l'ajustement des potentiels à la fracturation
  
  • Kieu Le-Hai
  • Delaye Jean-Marc
  • Stolz Claude
  , 2010.
• Thermalization of a driven bi-stable FPU chain
  
  • Efendiev Yalchin
  • Truskinovsky Lev
  Continuum Mechanics and Thermodynamics, Springer Verlag, 2010, 22, pp.679-698. We study Hamiltonian dynamics of a Fermi–Pasta–Ulam (FPU) chain with bi-stable elements. We show, that a quasi-static driving of a ‘cold’ chain beyond the spinodal threshold leads to complex dynamical behavior involving equipartition which suggests thermalization. The subsequent quasi-static cycling between the two energy wells produces reversible temperature oscillations which we link to the release (or absorbtion) of the latent heat. By adopting canonical distribution we obtain a thermodynamical description of the chain which agrees well with numerically computed time-averaged behavior of the corresponding dynamical system. (10.1007/s00161-010-0166-5)
  DOI : 10.1007/s00161-010-0166-5
• On the application of Fast Multipole Methods to Helmholtz problems with complex wavenumber
  
  • Frangi A.
  • Bonnet Marc
  , 2010. see full text
• Coupling of finite element and boundary integral methods for a capsule in a Stokes flow
  
  • Walter J.
  • Salsac A.-V.
  • Barthès-Biesel D.
  • Le Tallec Patrick
  International Journal for Numerical Methods in Engineering, Wiley, 2010, 83 (7), pp.829-850. We introduce a new numerical method to model the fluid-structure interaction between a microcapsule and an external flow. An explicit finite element method is used to model the large deformation of the capsule wall, which is treated as a bidimensional hyperelastic membrane. It is coupled with a boundary integral method to solve for the internal and external Stokes flows. Our results are compared with previous studies in two classical test cases: a capsule in a simple shear flow and in a planar hyperbolic flow. The method is found to be numerically stable, even when the membrane undergoes in-plane compression,which had been shown to be a destabilizing factor for other methods. The results are in very good agreement with the literature. When the viscous forces are increased with respect to the membrane elastic forces, three regimes are found for both flow cases. Our method allows a precise characterization of the critical parameters governing the transitions. (10.1002/nme.2859)
  DOI : 10.1002/nme.2859
• Compliant interfaces: A mechanism for relaxation of dislocation pile-ups in a sheared single crystal
  
  • Danas Kostas
  • Deshpande Vikram S.
  • Fleck Norman A.
  International Journal of Plasticity, Elsevier, 2010, 26, pp.1792-1805. 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). (10.1016/j.ijplas.2010.03.008)
  DOI : 10.1016/j.ijplas.2010.03.008
• Microscopic and macroscopic instabilities in finitely strained fiber-reinforced elastomers
  
  • Michel Jean-Claude
  • Lopez-Pamies Oscar
  • Ponte Castañeda Pedro
  • Triantafyllidis Nicolas
  Journal of the Mechanics and Physics of Solids, Elsevier, 2010, 58 (11), pp.1776-1803. The present work is a detailed study of the connections between microstructural instabilities and their macroscopic manifestations -- as captured through the effective properties -- in finitely strained fiber- reinforced elastomers, subjected to finite, plane-strain deformations normal to the fiber direction. The work, which is a complement to a previous and analogous investigation by the same authors on porous elastomers, (Michel et. al. , 2007), uses the linear comparison, second-order homogenization (S.O.H.) technique, initially developed for random media, to study the onset of failure in periodic fiber-reinforced elastomers and to compare the results to more accurate finite element method (F.E.M.) calculations. The influence of different fiber distributions (random and periodic), initial fiber volume fraction, matrix constitutive law and fiber cross- section on the microscopic buckling (for periodic microgeometries) and macroscopic loss of ellipticity (for all microgeometries) is investigated in detail. In addition, constraints to the principal solution due to fiber/matrix interface decohesion, matrix cavitation and fiber contact are also addressed. It is found that both microscopic and macroscopic instabilities can occur for periodic microstructures, due to a symmetry breaking in the periodic arrangement of the fibers. On the other hand, no instabilities are found for the case of random microstructures with circular section fibers, while only macroscopic instabilities are found for the case of elliptical section fibers, due to a symmetry breaking in their orientation. (10.1016/j.jmps.2010.08.006)
  DOI : 10.1016/j.jmps.2010.08.006