Accelerating Phase-Field Fatigue Computations with an Adaptive Cycle Jumping Scheme
Please login to view abstract download link
Phase-field models for fatigue fracture, e.g. [1,2], represent a versatile approach capable of reproducing the main characteristics of fatigue behavior. However, the associated computational effort makes the cycle-by-cycle analysis of components in the high cycle fatigue (HCF) regime with cycle counts n > 10⁴ - 10⁵ practically unfeasible. To overcome this, a cycle-jump acceleration can be adopted, where the explicit cycle-by-cycle resolution of a certain number of cycles Δn is skipped by instead extrapolating selected state variables based on their evolution during only some explicitly computed cycles in between the cycle jumps. To exploit the full potential of this strategy, an adaptive cycle-jump algorithm is proposed for the model presented in [1] which degrades the fracture toughness of the material as a representative fatigue history variable accumulates above a certain threshold. In the proposed scheme, the core idea lies in deciding when and how many cycles can be skipped based on the cycle-wise rate of a scalar variable Λ which is representative of the fatigue lifetime advancement. For this, the fatigue life of a component is divided into three stages: (1) an initial stage before fatigue effects are triggered, (2) the crack nucleation stage, and (3) crack propagation (including the Paris regime) ending with failure of the component. The representative variable Λ is suitably defined within each of the stages according to their specific features. The behavior and reliability of the proposed cycle-jump scheme is first demonstrated by comparing cycle-by-cycle with accelerated results. Then, the adaptive cycle-jump scheme is used to analyze the fatigue life of various virtual specimens. Finally, the obtained accuracy and speedup are compared with those from other available cycle-jump approaches. [1] Carrara, P., Ambati, M., Alessi, R. and De Lorenzis L., A framework to model the fatigue behavior of brittle materials based on a variational phase-field approach. Comp. Meth. App. Mech. Eng. 361 (2020) [2] Alessi, R., Vidoli, S., and De Lorenzis, L., A phenomenological approach to fatigue with a variational phase-field model: The one-dimensional case. Eng. Frac. Mech. 190(1) (2018) 53–73.