Issue 19

K. Pham et alii, Frattura ed Integrità Strutturale, 19 (2012) 5-19; DOI: 10.3221/IGF-ESIS.19.01 19 experimental viewpoint to identify the right law. From a theoretical viewpoint, the presence of the gradient of damage in the model has a regularizing role as expected and limits the possibility of localization of the damage since the size of a localization zone is necessarily greater than a value fixed by the internal length of the material and the others parameters of the model. Moreover, this non local term induces size effects in the response of the bar with in particular a necessarily discontinuous response and even a brutal onset of the damage after the elastic phase for long bars. When the bar is sufficiently long, our construction gives several solutions for the evolution problem, the number of localizations zones being only restricted by the length of the bar. We could probably construct many other solutions as it was made in [2]. This drastic lack of uniqueness that the introduction of a non local term has not removed needs to add a selection criterion. A good candidate is of course the stability criterion introduced in [2] and used to study the stability of homogeneous responses in [12]. The next challenge is to find which solutions among all those we have constructed satisfy the stability criterion. R EFERENCES [1] Benallal, R. Billardon, G. Geymonat, In: C.S.I.M Lecture Notes on Bifurcation and Stability of Dissipative Systems, Q.S. Nguyen, editor, Springer-Verlag, (1993). [2] Benallal, J.-J. Marigo, Modelling Simul. Mater. Sci. Eng., 15 (2007) 283. [3] Bourdin, G.A. Francfort, J.-J. Marigo, J. Elasticity, 91 (2008) 5. [4] G.A. Francfort, J.-J. Marigo, Eur. J. Mech. A/Solids, 12 (1993) 149. [5] Lasry, Belytschko, Int. J. Solids Structures, 24 (1988) 581. [6] Lorentz, S. Andrieux, Int. J. Solids Struct., 40 (2003) 2905. [7] J.-J. Marigo, Nuclear Engineering and Design, 114 (1989) 249. [8] J.-J. Marigo, In: Continuum Thermodynamics: the art and science of modelling material behaviour, volume 76 of Solids Mechanics and Its Applications: Paul Germain's anniversary, G. A. Maugin, R. Drouot, and F. Sidoroff, editors, Kluwer Acad. Publ., (2000). [9] Q. S. Nguyen, Stability and Nonlinear Solid Mechanics, Wiley & Son, London, (2000). [10] K. Pham, J.-J. Marigo, Comptes Rendus Mécanique, 338(4) (2010) 191. [11] K. Pham, J.-J. Marigo, Comptes Rendus Mécanique, 338(4) (2010) 199. [12] K. Pham, J.-J. Marigo, C. Maurini, J. Mech. Phys. Solids, 59(6) (2011) 1163. [13] G. Pijaudier-Cabot, Z. P. Bažant, J. Eng. Mech., 113 (1987) 1512.