Effect of cold work and overload on fatigue life of notched 2024-T351 aluminium alloy specimens

Abstract

Fatigue life of the notched circular hole 2024-T351 aluminium alloy specimens improves significantly with cold work and the improvement in fatigue life is highest for the 7.6% cold work specimens as compared to un-worked specimens. The improvement in fatigue life with stress ratio, R of 0.1, 0.3, and 0.5 is practically same but it is considerably higher for stress ratio, R of 0.7. The fatigue life improvement has been observed in the case of overloading also and the life improvement increases as overloading increases. The improvement in the high cycle fatigue region is more than 50 times and shows the promise of cold-working as well as overloading process. The fatigue life of 3.6% cold worked group of specimens show the fatigue life improvement of about 3 times as compared to the un-worked samples, for stress ratio, R in the range of 0.1 to 0.5 whereas for the stress ratio of 0.7 the life improvement is more than 50 times and the specimen did not fail at all. For both the overload specimens the improvement in life increases with increase in stress ratio. With 75% tensile overloading, life improvement higher than 65% overloading has been observed. An improvement factor in life is maximum for R = 0.5 for both the overloads and their values are 4.1 and 5.3 for overload of 65% and 75% respectively.