Abstract
Failure of disordered materials continue to pose significant challenges: Stress enhancements in the vicinity of cracks indeed makes impossible to replace the material by an effective homogeneous material whose toughness or life-time is given by an Ť average ť of the various microstructure components of this material. To understand how to include the local processes occurring at the scale of the material microstructure into a statistical description constitutes then a crucial step toward the setup of predictive macroscopic models. An efficient theory should then be able to predict, a minima, the morphology of fracture surfaces, which encodes the interaction between the propagating crack front and the surrounding microstructure. While resulting from material specific processes, these surfaces were recently shown to exhibit some universal scaling features reminiscent of interface growth problems, characterized by two distinct sets of critical exponents, whether surfaces are examined at scale below or above the size of the damaged zone at the crack front.
We present here a model of crack growth within a disordered linear elastic material describing the development of the roughness of the fracture surface as an ``elastic'' manifold with nonlocal interactions that creeps in a random medium - the spatial coordinate along which the crack globally grows playing the role of time 1. This model captures quantitatively the morphological scaling properties of fracture surfaces observed experimentally at length-scales above the size of the process zone. In this model of crack growth, the onset of crack propagation can be interpreted as a dynamic phase transition while sub-critical crack growth can be assimilated to thermally-assisted depinning. Role of damage at length-scales below the size of the process zone is finally discussed.
1) D. Bonamy, L. Ponson, S. Prades, E. Bouchaud, and C. Guillot, Phys. Rev. Lett. 97, 135504 (2006)
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