An elastoplastic phase-field model for dynamic fracture of nickel-based super-alloys

This paper presents a elastoplastic phase-field model for predicting crack nucleation, propagation, and branching, among other things, in elastoplastic solids subjected to dynamic loading. During the entire fracture process of the nickel-based super-alloys, with the accumulation of plastic strain, to some extent the elastic response of the material is reduced and the rate of phase-field evolution is affected, this means that the elastic strength and phase-field evolution of the material will be influenced by the yield surface and the hardening function. Therefore, we construct elastic and plastic energy degradation functions to more accurately reflect the effects of mechanical fields on the damage field, which distinguish between two successive failure mechanisms: (i) elastic strain and (ii) simultaneous elastoplastic localization deformation. In a variational framework, we derive the governing equations and the corresponding weak forms. Then, damage evolution criterion combining elastoplastic and resistance energies and a plastic yielding criterion are derived. From a numerical point of view, we give model parameters' selection criteria. Finally, the proposed model is applied to some impact scenarios with varying impact velocities or pre-existent cracks. The comparison of numerical and experimental results shows it can be easily used for identifying material gradation profiles that manipulate crack propagation.