Effect of Burrs on the Fatigue Strength of Metallic Structures: Experimental Study on Open Hole Ti‐6Al‐4V Specimens With Burrs

ABSTRACT One‐Way‐Assembly accelerates aerospace manufacturing but risks leaving drilling burrs at the interfaces of mechanical joints. The detrimental impact of burrs on fatigue strength is widely recognized in the literature, but the mechanisms driving this “knock‐down” remain unclear. This study investigates this phenomenon using open‐hole Ti‐6Al‐4V specimens. The experimental campaign systematically decouples the effects of macrogeometric stress concentration, residual stresses, and burr tip microgeometric features. Results revealed a non‐monotonic relationship between burr size and the fatigue “knock down,” leading to rejecting the macroscopic stress concentration hypothesis. Similarly, stress‐relief heat treatments failed to mitigate the fatigue “knock‐down,” ruling out residual stresses as a governing factor. Instead, a unified failure mechanism was identified. All detrimental configurations collapsed into a single S‐N cluster. Striation counting confirmed this cluster aligns with the material's pure crack propagation behavior, demonstrating that sharp burr tip features severely shorten the crack nucleation phase.