Regensburg 2007 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 1: Internal Symposium: Physics of fracture

DY 1.2: Hauptvortrag

Montag, 26. März 2007, 10:00–10:30, H2

Scaling properties of fracture surfaces — •Elisabeth Bouchaud — Fracture Group, SPCSI, CEA-Saclay, France

For very different materials, the morphology of fracture surfaces reveals anisotropic scale invariance properties which can be described with two sets of parameters: roughness exponents and characteristic length scales, measured either along the direction of crack propagation, or perpendicularly to it. If characteristic length scales depend on the material, its microstructure, and the external loading, roughness exponents, on the contrary, are *universal*. The same roughness exponents are indeed observed for metallic alloys and for glasses, for example, albeit at length scales three orders of magnitude smaller in the latter case. An exception, however, was recently found for sintered glasses, which exhibit the same kind of scale invariance properties, but with a different set of roughness exponents. A model depicting fracture in these materials as the quasi static propagation of an elastic line (the crack front) through an array of randomly distributed obstacles (the microstructure) can reproduce these observations. It is suggested that this model is valid when the roughness measurements are performed at length scales much larger than the damaged zone size, which is the case for sintered glasses. On the contrary, roughness measurements for metallic alloys and silicate glasses are performed within the damaged zone. The critical exponents observed in this case, as well as in the case of metallic materials, are hence conjectured to reflect damage screening occurring at length scales smaller than the process zone size.