Strain localization phenomena under cyclic loading: application to fatigue of single crystals

Kinematic hardening plays an important role in strain localization phenomena under cycling loading. A single crystal constitutive model including non-linear kinematic hardening is presented. Using a heterogeneous distribution of kinematic hardening variable in a single crystal plate, a continuum model for the formation of intrusion/extrusion is proposed based on FE simulation. The attention is focused on ratchetting phenomena taking place in the localization band. A second example of strain localization is shown by the strain field at the crack tip in single crystals. 2D and 3D finite element computations of the crack tip field in a CT specimen are provided. They are compared to analytical solutions. The 3D computations show that slip activity is different in the bulk or at the surface of the specimen. The evolution of the crack tip field subjected to cyclic loading is investigated. Ratchetting phenomena are shown to take place in some of the localization bands.