Mississippi State University
Newman Jr., James C.
Sullivan, Rani W.
Date of Degree
Graduate Thesis - Open Access
Master of Science (M.S.)
James Worth Bagley College of Engineering
Department of Aerospace Engineering
Fatigue and crack-growth tests were conducted on 7050-T7451 aluminum alloy under a wide range of loading conditions. Crack-growth tests were conducted on compact, C(T), specimens under constant-amplitude loading, single-spike overloads, and a simulated aircraft spectrum loading. Fatigue tests were also conducted on single-edge-notch bend, SEN(B), specimens under constant-amplitude loading and three aircraft load spectra. The FASTRAN, life-prediction code, was used to make crack-growth predictions on the C(T) specimens; and to make fatigue-life calculations using a 12-micrometer initial flaw size at the center of the edge-notch on the SEN(B) specimens. The predictions agreed fairly well with most of the tests, except the model was unconservative on the single-spike overload tests and the severe spectrum Mini-TWIST+ Level 1 tests. The discrepancy was suspected to be caused by a low constraint factor and/or crack paths meandering around overload plastic zones. A roughness- and plasticity-induced crack-closure model would be needed to improve the model.
Shaw, Justin Wayne, "Fatigue and Crack-Growth in 7050-T7451 Aluminum Alloy under Constant- and Variable-Amplitude Loading" (2012). Theses and Dissertations. 2243.