Failure Mechanisms

Models for fatigue crack formation and growth

· Deformation produced by (a) monotonic plastic strain, and (b) cyclic plastic strain in a single crystal is compared below.

From: Suresh,
"Fatigue of Materials," Cambridge (1991)

· The same slip systems are active in both but the periodic stress (b) creates persistent slip bands (PSB) that contain both protrusions and intrusions.
· These PSB sites represent stress concentration locations that can form the initial cracks that can lead to fatigue failure.