Fatigue Experiments, Damage Evolution and Multiscale Modeling for AA 7075-T651
Xue, Y., Jordon, J. B., Horstemeyer, S., & Horstemeyer, M. (2005). Fatigue Experiments, Damage Evolution and Multiscale Modeling for AA 7075-T651. Proceedings of the 2005 SEM Annual Conference and Exposition on Experimental Mechanics. Portland, OR, United States: Society for Experimental Mechanics Inc.. 30(2), 139-152.
The fatigue life for 7075-T651 aluminum alloy is sensitive to stress concentrations in regions with its widespread micron-plus-sized intermetallic inclusion particles. The strain-life was estimated based on constant amplitude strain-controlled tests. Tension after cyclic loading, low cycle followed by high cycle fatigue, and interrupted fatigue tests were performed to estimate the particle effects and damage initiation and propagation at various fatigue stages. In the strain-life tests, different surface finishes of the specimens demonstrated differences in residual stresses that caused fatigue life scatter by approximately eight times. A special polishing technique was chosen to reduce the surface residual stresses for a reliable fatigue life estimation. The low cycle fatigue damage was quantified using tensile to failure following a number of cycles at extremely high amplitude loading. It deserves mentioning that the fatigue damage was found to initiate at fractured inclusion particles by examining the specimen cross sections after cyclic loading at different strain levels. Microstructure based multiscale fatigue modeling is used to estimate the fatigue behavior for AA 7075-T651 in terms of damage incubation, microstructurally small crack growth, and long crack growth.