Stéphane Santucci

Crackling dynamics in material failure as the signature of a self-organized dynamic phase transition

We derive here a linear elastic stochastic description for slow crack growth in heterogeneous materials. This approach succeeds in reproducing quantitatively the intermittent crackling dynamics observed recently during the slow propagation of a crack along a weak heterogeneous plane of a transparent Plexiglas block [K. J. Måløy et al., Phys. Rev. Lett. 96, 045501 (2006)10.1103/PhysRevLett.96.045501]. In this description, the quasistatic failure of heterogeneous media appears as a self-organized critical phase transition. As such, it exhibits universal and to some extent predictable scaling laws, analogous to that of other systems such as, for example, magnetization noise in ferromagnets.

Avalanches and clusters in planar crack front propagation.

We study avalanches in a model for a planar crack propagating in a disordered medium. Due to long-range interactions, avalanches are formed by a set of spatially disconnected local clusters, the sizes of which are distributed according to a power law with an exponent tau{a}=1.5. We derive a scaling relation tau{a}=2tau-1 between the local cluster exponent tau{a} and the global avalanche exponent tau . For length scales longer than a crossover length proportional to the Larkin length, the aspect ratio of the local clusters scales with the roughness exponent of the line model. Our analysis provides an explanation for experimental results on planar crack avalanches in Plexiglas plates, but the results are applicable also to other systems with long-range interactions.

Statistics of fracture surfaces

We analyze the statistical distribution function for the height fluctuations of brittle fracture surfaces using extensive experimental data sampled on widely different materials and geometries. We compare a direct measurement of the distribution to an analysis based on the structure functions. For length scales delta larger than a characteristic scale Lambda that corresponds to a material heterogeneity size, we find that the distribution of the height increments Deltah=h(x+delta)-h(x) is Gaussian and monoaffine, i.e., the scaling of the standard deviation sigma is proportional to delta(zeta) with a unique roughness exponent. Below the scale Lambda we observe a deviation from a Gaussian distribution and a monoaffine behavior. We discuss for the latter, the relevance of a multiaffine analysis and the influences of the discreteness resulting from material microstructures or experimental sampling.

Fracture roughness scaling: A case study on planar cracks

Using a multi-resolution technique, we analyze large in-plane fracture fronts moving slowly between two sintered Plexiglas plates. We find that the roughness of the front exhibits two distinct regimes separated by a crossover length scale

Subcritical Statistics in Rupture of Fibrous Materials: Experiments and Model

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Time-dependent rupture and slow crack growth: elastic and viscoplastic dynamics

. Below

Local dynamics of a randomly pinned crack front during creep and forced propagation: an experimental study.

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Fracture surfaces as multiscaling graphs

, we observe a multi-affine regime and the measured roughness exponent

Thermal activation of rupture and slow crack growth in a model of homogeneous brittle materials

\zeta_{\parallel}^{-} = 0.60\pm 0.05

Rate-dependent elastic hysteresis during the peeling of pressure sensitive adhesives

is in agreement with the coalescence model. Above