Abstract
In this work, the phase-field approach to fracture is extended to model fatigue failure in high- and low-cycle regime. The fracture energy degradation due to the repeated externally applied loads is introduced as a function of a local energy accumulation variable, which takes the structural loading history into account. To this end, a novel definition of the energy accumulation variable is proposed, allowing the fracture analysis at monotonic loading without the interference of the fatigue extension, thus making the framework generalised. Moreover, this definition includes the mean load influence of implicitly. The elastoplastic material model with the combined nonlinear isotropic and nonlinear kinematic hardening is introduced to account for cyclic plasticity. The ability of the proposed phenomenological approach to naturally recover main features of fatigue, including Paris law and Wöhler curve under different load ratios is presented through numerical examples and compared with experimental data from the author’s previous work. Physical interpretation of additional fatigue material parameter is explored through the parametric study.
Highlights
Material fatigue is a weakening phenomenon caused by cyclic loading whose failure state is far below the material strength of monotonic loading [1, 2]
The results show clear fracture properties influence on the slope of the Paris law curve, more pronounced in fatigue degradation functions F 2 and F 3
The extension of the phase-field fracture approach to fatigue was presented, recovering its main features like − N and Paris law curves in low- and high-cycle regimes without any additional criteria
Summary
Material fatigue is a weakening phenomenon caused by cyclic loading whose failure state is far below the material strength of monotonic loading [1, 2]. Caputo and Fabrizio [47], as well as Amendola et al [48] adopted the phase-field fracture model with Ginzburg–Landau formalism, where the material degradation under cyclic loadings is introduced by incorporating a fatigue potential. In this direction, Schreiber et al [49] proposed an additional energy density contribution to account for the sum of additional driving forces associated with the mechanism of cyclic mechanical fatigue.
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