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Local Plastic Stresses in Sheet Aluminum-Alloy Specimens with Stress-Concentration Factor of 2 Under Constant-Amplitude Loading
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION HAMPTON VA LANGLEY RESEARCH CENTER
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Cyclic plastic stresses at notch roots in specimens under constant-amplitude repeated tension and reversed loading have been studied experimentally. The applied loads were cycled in edge-notched 2024-T3 aluminum-alloy sheet specimens, which had a stress-concentration factor of 2, until local stress conditions stabilized. Determination of local stress histories was made by recording local strain histories during cycling and reproducing these histories in simple unnotched specimens. The fatigue lives for the notched specimens were estimated from the stabilized local stresses and fatigue data for the unnotched specimens. These estimations compared favorably with fatigue-life data for the notch configuration tested. In addition, an expression for calculating local first-cycle plastic stresses is presented. An acceptable correlation is shown between predicted stresses and experimental data within the scope of the investigation.
APPROVED FOR PUBLIC RELEASE