Stop drilling procedure for fatigue life improvement

This paper investigated how the stop drilling procedure improved the crack initiation life and the total fatigue life in specimens of 6061-T651 aluminium alloy and AISI 304 stainless steel. The crack initiation life was the number of fatigue cycles initiating a 0.2 mm crack at a stophole edge. The larger the stophole diameter, the longer the crack initiation and total fatigue lives. The 2, 2.5, and 3 mm diameter stopholes improved the nonstop-drilled total fatigue life of the 6061-T651 specimen by 187%, 321%, and 443% and that of the AISI 304 specimen by 72%, 121%, and 174%. At each stophole diameter, the 6061-T651 crack initiation life improved over the AISI 304 counterpart because of lower values of the Kf factor and the ΔJ/ραc ratio.