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 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, ζ. At the beginning of the mirror zone ζ = 0.5, in the mist–hackle region we detected the same value for fine length scales, whereas at large length scales we observed ζ = 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.