Environmental Effects on Fatigue Crack Initiation.
Final rept. 1 Dec 75-30 Nov 78,
ROCKWELL INTERNATIONAL THOUSAND OAKS CALIF SCIENCE CENTER
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Models of microscopic failure mechanisms important to the crack initiation stage of the fatigue failure of aluminum alloys have been proposed and verified. Included are 1 a model relating rate of nucleation of surface microcracks at intermetallic particles to particle and grain size and ambient humidity 2 and models which relate rate of growth of surface microcracks, with lengths of approximately the grain size, to the alloy microstructure in the region of a nucleation site and to ambient humidity. The models have been used to develop a Monte Carlo simulation of the fatigue failure of aluminum alloys which can be used to predict the effect of alloy microstructure and environmental humidity on 1 mean and scatter in fatigue lifetime 2 microscopic parameters such as numbers and lengths of microcracks, and microcrack closure stresses. Simulated and measured fatigue behavior are compared for several aluminum alloys. Author
- Properties of Metals and Alloys