回位密度を考慮した結晶塑性Cosseratモデルに基づくMg基LPSO相のキンク帯形成に関するメッシュフリー解析

抄録

Kink deformation, which is one of the plastic buckling phenomena for laminated materials, is observed in the long period stacking ordered structure (LPSO) phase of Mg-TM-RE alloys, and it improves mechanical properties of this alloys tremendously. Although the mechanism of kink band formation was conventionally explained by movement and accumulation of dislocations, which are the line defects of crystals, it is recently attempted to express the kinking process from the point of view of rotational line defects of crystals called disclinations. We developted a new model of Cosserat body consistent with the framework of the crystal plasticity by describing the microscopic plastic rotation as a quantity of each slip system. However, finite element method using C⁰ continuous shape function is not applicable for this model since such function is not suitable for the higher-order boundary condition. In this study, a meshfree analysis based on a dislocation-based crystal plasticity Cosserat model considering disclination density is carried out to reproduce the kinking process from the point of view of disclinations, and it is shown that this model can reproduce the kink deformation through quadrupole structure of disclination and array structure of GN dislocation formed in the vicinity of kink-band. Furthermore, a size effect due to the intrinsic length scale of Cosserat model is properly expressed by imposing boundary condition on rotational degree of freedom.