Fatigue fracture

In this chapter, the general aspects of fatigue fracture, such as fatigue life, the three stages of fatigue and the mechanical characteristics of materials’ behavior under cyclic loads, are presented. Once the fatigue phenomenon is understood from the mechanical point of view, the fractographic characteristics of fractured surfaces at each one of the three stages are described in detail. The mechanisms of fatigue crack nucleation and propagation are described, along with the typical macroscopic and microscopic features of fatigue fractures. Emphasis is placed on the description of the origin and characteristics of microscopic fatigue striations, as one of the most distinguishable aspects of fatigue fractures. A description of the fractographic characteristics of Stage II fatigue fractures in the absence of striations is also included. The chapter finishes with a description of corrosion-fatigue fractures.