An Experimental Evaluation of the Fatigue Behavior of AH36 Weld-Repaired Deck Sockets in a Simulated Marine Atmosphere

: Fatigue testing of specimens removed from weld-repaired deck sockets on the fast sealift ship was conducted to satisfy two objectives. The primary objective was to determine the shift in fatigue initiation behavior due to an intermittent salt spray environment. The secondary objective was to validate the fatigue initiation design curves used in the fatigue analysis of the ship deck structure. No effect of a salt spray schedule was observed within the low stress, high cycle fatigue regime examined (delta sigma = 0.6 sigma(sub y) to 1.0 sigma(sub y), N(sub f) = 2 x 10(exp 5) to 10(exp 7) cycles). However, an effect of the salt spray schedule was observed within the high stress, low cycle regime (delta sigma = 1.2 sigma(sub y) to 1.7 sigma(sub y), N(sub f) = 1.5 x 10(exp 4) to 4 x 10(exp 5) cycles) and an approximate maximum fatigue reduction factor (delta sigma(sub air)/delta sigma(sub salt spray) of 1.4 was observed. Comparison of the fatigue data obtained in this study with the design fatigue curves is consistent with the known effect of specimen size on fatigue behavior. This work verified that the design fatigue curves obtained from large welded specimens represents a lower bound for the fatigue behavior of weld-repaired deck sockets tested in air, as well as under a corrosive salt spray schedule.