SEDL / STP / STP1372-EB / STP13432S

A Size Effect on the Fatigue Crack Growth Rate Threshold of Alloy 718

Garr, KR
Engineering Specialist, The Boeing Company, Rocketdyne Propulsion & Power, Canoga Park, CA

Hresko, GC
Fracture Systems Research, Allentown, PA

Pages: 20    Published: Jan 2000

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Abstract

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.