Long Distance Fracture Surface Roughness on a Dendritic Aluminum Alloy

Abstract

The long distance roughness of the fracture surface of a dendritic aluminum alloy is studied over a wide range of length scales. Self-affinity analysis was performed over samples broken in Charpy impact tests. Simultaneous use of Atomic Force Microscopy, SEM and stylus profilometry allowed us to cover a wide spectrum of length scales, spanning over seven decades, from a few nanometers up to one centimeter. The roughness exponent and correlation length were obtained using the variable bandwidth method. For the roughness exponent, a value of 0.8 was obtained, corresponding to the reported universal exponent. Correlation length was found to correspond well to the characteristic length of the largest heterogeneities in the complex microstructure. Our results provide information that can help to improve our understanding of the role of microstructural parameters on crack propagation mechanisms.

Scaling properties of fracture surfaces on glass strengthened by ionic exchange

“…6a and b, which corresponds to the non-treated and treated specimens, respectively. In both cases the roughness exponent has values consistent with the claimed universal value z $0.8 [5][6][7][8][9]. This implies that the ionic exchange treatment does not modify the exponent characterizing the self-affine regime.…”

“…It is now accepted that fracture surfaces are selfaffine objects, that is to say, they are anisotropic fractals whose self-affine character can be quantified by one roughness exponent z. Different workers [5][6][7][8] conclude that this exponent reflects a somehow ''universal'' behavior and the existence of a characteristic regime with z $0.8 is accepted for rapid crack propagation conditions. Now a question immediately arises: If the roughness exponent has a universal value, what is the role of microstructure in determining the self-affine behavior?…”