Cycle Sequence of Fatigue Crack Initiation and Growth at the Submicron Scale

I recently used focused ion beam to fabricate some small structures, such as free-standing micro-beams, in LIGA Ni thin films and applied cyclic loads to those small micro-beams. In such a way, dynamics of fatigue crack initiation and growth can be revealed. Part of my results has been attached with this post.

The description of the attached picture is as follows,

(a) grain structure in the near-notch region; (b) dislocation slip band structure at the load cycles of 60,000; (c) dislocation slip band structure at the load cycles of 140,000  and (d) fatigue crack morphology at the load cycles of 180,000