Manifold adaptive method for thermo -mechanical coupled fatigue phase-field model

Phase-field models can automatically capture crack initiation, propagation, and complex behaviors like branching and coalescence by tracking the evolution of an order parameter. This makes them particularly advantageous for simulating the fatigue fracture of structures. However, the highly nonlinear nature of phase field problems and the high computational cost of fatigue analysis present significant challenges for thermo-mechanically coupled phase-field fatigue simulations. This paper adopts a manifold adaptive finite element based acceleration algorithm. A thermo-mechanically coupled fatigue phase-field model is derived from thermodynamic principles and is used in conjunction with a constant load accumulation method. This approach is then applied to study the behavior of dog-bone specimens, plates with a central hole, and microstructures with spherical defects under thermo-mechanically coupled fatigue loads. The results show that the proposed manifold adaptive thermo-mechanically coupled phase-field model can accurately preserve the curved geometric shapes during mesh refinement and accelerates the computation speed of thermo-mechanically coupled fatigue problems by approximately 90 times. The simulated stress-life curve, when compared with test data, shows that the life prediction error is within a factor of two scatter band. Furthermore, the phase difference of the thermo-mechanically coupled fatigue load significantly affects the fatigue life, with life decreasing as the phase difference decreases.