A probabilistic method for predicting the variability in fatigue behavior of 7075-T6 aluminum

摘要

This paper assesses the applicability of a probabilistic model to estimating fatigue life variability for 7075-T6 aluminum. ^The test specimens for the experimental program were 7075-T6 aluminum single edge notch tension specimens tested under constant amplitude loading. ^The shortest observed fatigue life was 37,000 cycles and the longest 650,000 cycles. ^A plastic replication procedure was used to identify crack nucleation sites and monitor crack growth. ^The initiation sites were identified by examining the plastic replicas and the fracture surfaces of the failed specimens. ^In agreement with previous studies, the fatigue cracks formed in the center of the notch from material inclusions. ^For the prediction model, the distribution of inclusion sizes (0.2-45 sq microns) within the material were used as the distribution of initial flaw sizes. ^The cumulative distributions for the fatigue lives from the experimental work and the numerical model were compared to assess the effectiveness of the model. ^While experimental crack formation lives as long as 50-70 percent of the total life were observed in some of the tests, the model predicted failures well in the shorter life regime. ^(Author)