Numerical Investigation of the Influence of Residual Stresses after Additive Manufacturing on the Fatigue Crack Propagation in 5xxx Aluminum Alloys

This work investigates the influence of initial residual stresses after additive manufacturing, specifically directed energy deposition, in 5xxx aluminum alloys on the fatigue crack propagation behavior. For this purpose, initial plane stress states (compressive as well as tensile) are introduced along the crack path on a C(T)50 specimen via eigenstrains, mimicking possible residual stress states after both directed energy deposition and possible post-processing. The evolution of the stress intensity factor difference is determined and used to calculate the crack propagation rate via Walker’s equation. The stress state of the vicinity of the crack tip dictates the crack behavior: Compressive stresses perpendicular to the crack path exhibit crack closure, resulting in slower propagation rates. Finally, the influence of a more local distribution of the residual stresses on the fatigue crack propagation is investigated, highlighting the importance of the position of compressive stresses relative to the crack tip for effective crack growth retardation.