Marks left on a fatigue fracture surface as a result
of the advance or growth of the fatigue crack
resulting from one load application. To visualize fatigue striation, or
even a
series of fatigue striations requires extremely high
magnifications. Individual striations are often
visible at high magnifications in a scanning
electron microscope (SEM).
An example of fatigue striations is shown in Photograph A below.

Photograph A Example of fatigue
striations
as seen through a SEM at a magnification of
10,000x.