Roughening of Fracture Surfaces: the Role of Plastic Deformations

TL;DR

This paper investigates the roughness of fracture surfaces across different materials and scales, revealing that plastic void formation and coalescence influence the anomalous scaling exponents observed, which cannot be explained by elasticity theory alone.

Contribution

It introduces a model linking plastic void formation to the anomalous roughness scaling of fracture surfaces, providing a new explanation beyond elasticity theory.

Findings

Plastic void formation correlates with higher roughness exponents.

Elasticity theory alone predicts lower exponents (~0.5).

Void coalescence influences surface roughness scaling.

Abstract

Post mortem analysis of fracture surfaces of ductile and brittle materials on the $\mu$m-mm and the nm scales respectively, reveal self affine graphs with an anomalous scaling exponent $\zeta\approx 0.8$. Attempts to use elasticity theory to explain this result failed, yielding exponent $\zeta\approx 0.5$ up to logarithms. We show that when the cracks propagate via plastic void formations in front of the tip, followed by void coalescence, the voids positions are positively correlated to yield exponents higher than 0.5.