For Fatigue Analysis I would rather recommend to use Fe-Safe (an specialized Application for Fracture and Fatigue which comes in bundle of Simulia Abaqus software itself).

Zahra Razi this is not an issue. I will recommend you to utilize the XFEM (Extended Finite Element Method) for modeling fatigue crack propagation, as it allows for discrete crack propagation along an arbitrary path based on linear elastic fracture mechanics principles. Also, implement a method based on digital image correlation to measure full-field displacements and finite element simulations to extract the strain energy release rate of surface cracks, enabling crack initiation analysis without knowledge of specimen geometry and applied loads.

Regarding the lack of clear results in your simulation, potential reasons could include the inadequate representation of material properties or loading conditions in your model setup may lead to inconclusive results. Also, insufficient mesh refinement or improper boundary conditions could affect the accuracy of crack initiation detection.

For the troubleshooting strategies to address these issues and enhance your direct cyclic fatigue simulations, make sure that the material properties, such as fracture criteria parameters are accurately defined and aligned with the behavior of the material being simulated. Also, verify that the mesh is sufficiently refined near potential crack initiation sites to capture the initiation accurately. Along with it, review boundary conditions to confirm they are realistic and representative of the actual loading conditions. Last but least, vonsider refining the analysis configuration, such as adjusting time steps or convergence criteria, to improve the simulation's accuracy and detect crack initiation more effectively.

Incase you are still facing issues, feel free to connect with me on my WhatsApp Https://wa.me/+923440907874 and share your problem to get a quick answer. Good luck!