Published: Jan 2000
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Fatigue crack growth rate (FCGR) tests were conducted on Nickel-based uperalloy 718 in the solution annealed and aged condition at room temperature. In each test, the FCGR threshold was measured using the K-decreasing constant R method. Initial testing was at two facilities, one of which used C(T) specimens with W = 127 mm. Previous data at the other facility had been obtained with specimens with W = 50.8 mm. A comparison of test results at R = 0.1 showed that the threshold for the 127 mm specimen was considerably higher than that of the 50.8 mm specimen. A check showed that this difference was not due to a heat-to-heat or lab-to-lab variation. Additional tests were conducted on specimens with W = 25.4 mm and at other R values. Data for the various specimens is presented along with parameters usually used to describe threshold behavior.
Alloy 718, crack propagation, crack closure, specimen size effect, fatigue crack growth rate threshold, Biaxiality ratio, T stress, constraint
Engineering Specialist, The Boeing Company, Rocketdyne Propulsion & Power, Canoga Park, CA
Fracture Systems Research, Allentown, PA