Editing Dislocation (section)

==== Persistent slip bands ====
{{Main articles|Persistent slip bands}}
Repeated cycling of a material can lead to the generation and bunching of dislocations surrounded by regions that are relatively dislocation free. This pattern forms a ladder like structure known as a ''[[persistent slip bands]]'' (PSB).<ref name="suresh04">{{cite book |last1=Suresh |first1=S. |year=2004  |title=Fatigue of Materials |publisher=Cambridge University Press |isbn=978-0-521-57046-6}}</ref> PSB's are so-called, because they leave marks on the surface of metals that even when removed by polishing, return at the same place with continued cycling.

PSB walls are predominately made up of edge dislocations. In between the walls, plasticity is transmitted by screw dislocations.<ref name="suresh04"/>

Where PSB's meet the surface, extrusions and intrusions form, which under repeated cyclic loading, can lead to the initiation of a [[fatigue (material)|fatigue]] crack.<ref name="forsythe">{{cite journal |year=1953 |last=Forsythe |first=P. J. E. |s2cid=4268548 |title=Exudation of material from slip bands at the surface of fatigued crystals of an aluminium-copper alloy |volume=171 |issue=4343 |periodical=Nature |pages=172–173 |bibcode=1953Natur.171..172F |doi=10.1038/171172a0 }}</ref>