The fatigue of aluminum alloys subjected to random loading |
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Authors: | G. W. Brown R. Ikegami |
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Affiliation: | 1. University of California, Berkeley, Calif. 2. Structural Dynamics Group, Boeing Aircraft, Seattle, Wash.
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Abstract: | This paper describes an expeirmental investigation which was carried out to determine the fatigue life of two aluminum alloys (2024-T3 and 6061-T6). They were subjected to both constant-strain-amplitude sinusoidal and narrow-band random-strain-amplitude fatigue loadings. The fatigue-life values obtained from the narrow-band random testing were compared with theoretical predictions based on Miner's linear accumulation of damage hypothesis. Cantilever-beam-test specimens fabricated from the aluminum alloys were subjected to either a constant-strain-amplitude sinusoidal or a narrow-band random base excitation by means of an electromagnetic vibrations exciter. It was found that the ε-N curves for both alloys could be approximated by three straight-line segments in the low-, intermediate- and high-cycle fatigue-life ranges. Miner's hypothesis was used to predict the narrow-band random fatigue lives of materials with this type of ε-N behavior. These fatigue-life predictions were found to consistently overestimate the acutal fatigue lives by a factor of 2 or 3. However, the shape of the predicted fatigue-life curves and the high-cycle fatigue behavior of both materials were found to be in good agreement with the experimental results. |
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