From NASGRO to fractals: Representing crack growth in metals

This paper presents the results of an extensive experimental analysis of the fractal properties of fatigue crack rough surfaces. The analysis of the power-spectral density functions of profilometric traces shows a predominance of the box fractal dimension D = 1.2. This result leads to a particularization of the fatigue crack growth equation based on fractality proposed by the last two authors which is very close to the generalized Frost-Dugdale equation proposed by the first three authors. The two approaches, albeit based on different initial modelling assumptions, are both very effective in predicting the crack growth rate of short cracks.