  Fatigue failure of crystalline materials is a difficult problem in science
and engineering, and recent results have shown that fatigue crack growth can
occur in intermittent jumps which have fat-tailed distributions. As fatigue
crack propagation is known to leave markings -- called striations -- on the
fracture surface, the distances between these should also have fat-tailed
distributions, if the crack propagation is intermittent. Here, we combine
macroscale crack tip tracking in fatigue crack growth measurements of aluminum
5005 samples with \emph{post-mortem} scanning electron microscopy imaging of
the striation lines. We introduce two different methods for extracting the
striation line spacing from the images. What we find is a similar distribution
of striation spacings as jump sizes using one of our methods, but the average
striation spacing does not correlate with the crack growth rate. We conclude
that we observe avalanche-like crack propagation, reflected in both the
macroscale crack tip tracking as well as the analysis of the fracture surfaces.
Our results show that the fracture surfaces can be used to study the
intermittency of fatigue crack propagation and in development of
crack-resistant materials. The advantages and disadvantages of the two methods
introduced are discussed.
