FATIGUE CRACK PROPAGATION UNDER PROGRAMMED AND RANDOM LOADS
BOEING SCIENTIFIC RESEARCH LABS SEATTLE WA SOLID STATE PHYSICS LAB
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The influence of maximum stress, stress range, and sequence of load application on the rate and mechanism of fatigue crack propagation in 2024-T3 aluminum alloy was studied by means of electron fractography. The macroscopic growth rates were determined on center-notched crack growth panels and the fracture surfaces were examined by electron fractography. An empirical equation relating relative microscopic growth rates at a given crack length to maximum loads and load amplitudes was obtained. It was also found that the advance of a fatigue crack front takes place only during the loading part of a cycle and that in the pseudorandom load case the sequence of load application can markedly influence crack growth rate on any one cycle.
- Metallurgy and Metallography