Fatigue crack propagation of AA2024-T3 in panels produced by Refill Friction Stir Spot Welding: A numerical and experimental investigation.

Refill Friction Stir Spot Welding (Refill FSSW) or also known as friction spot welding has been considered as a potential alternative to substitute riveted connections in aircraft structures enabling weight savings and productivity gains. Based on that fact, this work aims to study the fatigue crack propagation in panels with triple-spot weld rows, and five spot weld in each row in lap joint configuration produced by Refill FSSW in aluminum alloy 2024-T3 2 mm thickness. This investigation combines the fatigue crack growth numerical model using eXtended Finite Element Method (XFEM) and the experimental investigation from fatigue crack growth, where the crack length is constantly measured and recorded. In order to perform a fully analysis, the numerical model was calibrated and used to optimize the distance between spot weld rows. Then the numerical model was validated using experimental tests for specific geometries and the results were compared considering the crack length vs. fatigue life. The results show a good agreement between the numerical model and experiments. In this way, the XFEM model enables to minimize the number of experimental tests and maximize the information from each joint configuration. In addition, considering the model developed it is possible to analyze different initial crack and stress ratio.