Abstract
Fatigue is one of the most destructive processes leading to the failure of mechanical components under cyclic loading. Traditionally, continuum methods have been used to predict and simulate fatigue, but they struggle to simultaneously capture crack nucleation and propagation under large deformations, as well as the physics of crack closure under compression. Recently, Molecular Dynamics (MD) has shown promising results in fracture mechanics; however, its application is limited by the scale of the models, making it more suitable for studying crack nucleation rather than full crack propagation. In this work, we used a coarse-grained molecular dynamics approach to model crack nucleation, propagation, and closure under cyclic loading in FCC metals. By coarse graining the dislocation plasticity, this approach enables the simulation of crack nucleation and propagation within an atomistic framework while significantly reducing computational costs. A crack-free surface identification method was also implemented to trace crack surfaces and prevent crack Fatigue is one of the most destructive processes leading to the failure of mechanical components under cyclic loading. Traditionally, continuum methods have been used to predict and simulate fatigue, but they struggle to simultaneously capture crack nucleation and propagation under large deformations, as well as the physics of crack closure under compression. Recently, Molecular Dynamics (MD) has shown promising results in fracture mechanics; however, its application is limited by the scale of the models, making it more suitable for studying crack nucleation rather than full crack propagation. In this work, we used a coarse-grained molecular dynamics approach to model crack nucleation, propagation, and closure under cyclic loading in FCC metals. By coarse-graining the dislocation plasticity, this approach enables the simulation of crack nucleation and propagation within an atomistic framework while significantly reducing computational costs. A crack-free surface identification method was also implemented to trace crack surfaces and prevent crack closure during unloading. The method is applied to simulate fatigue crack processes in single-crystal aluminum, as well as cases with pre-existing grain boundary and bi-crystal. It is also extended to large-scale polycrystalline aluminum samples. The crack trajectory and the Paris law exponent were examined, demonstrating good agreement with experimental data. Overall, the proposed method, combined with the crack-free surface identification technique, provides a robust numerical approach for simulating fatigue behavior in metallic materials with reasonable computational efficiency.closure during unloading. The method is applied to simulate fatigue crack processes in single-crystal aluminum, as well as cases with preexisting grain boundary and bi-crystal. It is also extended to large-scale polycrystalline aluminum samples. The crack trajectory and the Paris law exponent were examined, demonstrating good agreement with experimental data. Overall, the proposed method, combined with the crack-free surface identification technique, provides a robust numerical approach for simulating fatigue behavior in metallic materials with reasonable computational efficiency