Scaling properties of slow fracture in glass:: from deterministic to irregular topography

In this work we discuss the morphology and self-affine properties of the slow-fracture surfaces of soda-lime glass obtained by a bending process under the effect of applied water vapor. The fractographic analysis showed the presence of secondary cracks in the mirror ror zone, whereas in the mist-hackle region step-like morphologies were observed and over them we found fine undulations. The self-affine analysis, performed by two methods, showed the existence of two different statistical distributions for the roughness exponent, zeta. At the beginning of the mirror zone zeta = 0.5, in the mist-hackle region we detected the same value for fine length scales, whereas at large length scales we observed zeta = 0.8. This scenario may be described by a qualitative model in which the deterministic mirror-mist-hackle pattern coexists with an irregular topography, the two observed regimes are thus characterized by two different roughness exponents, with the 0.5 value dominating at low-speed/fine-scales and the 0.8 value governing the high-speed/large-scales regimes.