Experimental Study on the Fatigue Behavior of Ti‐6Al‐4 V Bolted Joints Containing Burrs

ABSTRACT One‐way assembly accelerates aerospace manufacturing operations but risks leaving drilling burrs within 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 investigation focused on mechanically fastened Ti‐6Al‐4 V single‐lap‐shear joints containing burrs. Fatigue tests showed a severe knock‐down effect. Striation counting confirmed a crack‐growth‐dominated life. Interrupted fatigue test inspected via CT scans and destructive cross‐sectioning revealed the exact failure mechanism. It is not the burr tip condition that drives fatigue failure, as shown in a previous study on open‐hole specimens. In the case of joints, fastener installation and cyclic loading severely crush and crack the burrs, leaving highly damaged regions acting as immediate crack initiators. These findings suggest adopting a damage tolerance approach for the industrial assessment of the effect of burrs.