Publications

2012

• Dependence of elastic properties of argillaceous rocks on moisture content investigated with optical full-field strain measurement techniques
  
  • Yang Diansen
  • Bornert Michel
  • Chanchole Serge
  • Gharbi Hakim
  • Valli Pierre
  • Gatmiri Behrouz
  International Journal of Rock Mechanics and Mining Sciences, Pergamon and Elsevier, 2012, 53, pp.45-55. The mechanical behaviour of the argillaceous rock considered in France as a potential host rock for nuclear waste repository strongly depends on water content. In order to quantify the dependence of the mechanical properties on humidity, an experimental setup that combines hydromechanical loadings with optical observations and digital image correlation (DIC) has been developed. It allows investigation of the hydromechanical behaviour of a material from the sample scale (cm) down to micrometric scale (100 mu m). Using this system, the shrinkage and swelling properties of the argillaceous rock at various constant uniaxial stresses, and the linear mechanical behaviour of the material at different moisture levels, were experimentally studied. A quasi-linear relation between the relative humidity, ranging from 39% to 85%, and the deformation during dehydration and rehydration is found at both the sample scale (cm), and a mesoscopic scale of a few hundred micrometres. This relation depends on the applied stress with much less swelling at higher axial compressive stress. In addition, a linear decrease of the axial Young's modulus (normal to bedding plane) with an increase of the relative humidity is observed. (10.1016/j.ijrmms.2012.04.004)
  DOI : 10.1016/j.ijrmms.2012.04.004
• Damage localization and rupture with gradient damage models
  
  • Pham Kim
  • Marigo Jean-Jacques
  Frattura ed Integrità Strutturale = Fracture and Structural Integrity, Università degli Studi di Cassino, 2012, 19, pp.pages 5-19. We propose a method of construction of non homogeneous solutions to the problem of traction of a bar made of an elastic-damaging material whose softening behavior is regularized by a gradient damage model. We show that, for sufficiently long bars, localization arises on sets whose length is proportional to the material internal length and with a profile which is also characteristic of the material. The rupture of the bar occurs at the center of the localization zone when the damage reaches there the critical value corresponding to the loss of rigidity of the material. The dissipated energy during all the damage process up to rupture is a quantity c G which can be expressed in terms of the material parameters. Accordingly, Gc can be considered as the usual surface energy density appearing in the Griffith theory of brittle fracture. All these theoretical considerations are illustrated by numerical examples.
• Mathematical and numerical modelling of piezoelectric sensors
  
  • Imperiale Sébastien
  • Joly Patrick
  ESAIM: Mathematical Modelling and Numerical Analysis, Société de Mathématiques Appliquées et Industrielles (SMAI) / EDP, 2012. The present work aims at proposing a rigorous analysis of the mathematical and numerical modelling of ultrasonic piezoelectric sensors. This includes the well-posedness of the final model, the rigorous justification of the underlying approximation and the design and analysis of numerical methods. More precisely, we first justify mathematically the classical quasi-static approximation that reduces the electric unknowns to a scalar electric potential. We next justify the reduction of the computation of this electric potential to the piezoelectric domains only. Particular attention is devoted to the different boundary conditions used to model the emission and reception regimes of the sensor. Finally, an energy preserving finite element / finite difference numerical scheme is developed; its stability is analyzed and numerical results are presented.
• Optimization of the Effective Shear Properties of a Bidirectionally Corrugated Sandwich Core Structure
  
  • Besse C.
  • Mohr Dirk
  Journal of Applied Mechanics, American Society of Mechanical Engineers, 2012, pp.011012.