Polycrystalline kinematics: An extension of single crystal kinematics that incorporates initial microstructure

Single crystal FeFP kinematics are widely used as the basis for many crystal plasticity models. Within this kinematic framework, geometrically necessary dislocations (GNDs) initially do not exist and then they evolve as needed in the material. A shortcoming of this kinematic model is that there is no rigorous way to define the initial and evolving GND state in the same manner. By augmenting the single crystal FeFP kinematics with a geometric argument, a consistent methodology for determining the initial and evolving GND state has been derived. The augmented kinematics describe GND related microstructural features in the undeformed material like low angle sub-grain boundaries and high angle grain boundaries. Therefore these kinematics are particularly applicable to polycrystalline materials.