Extended Study of Flaw Growth at Fastener Holes. Volume 2. Data Tabulations
Final rept. 10 Jun 1975-10 Jun 1977
LOCKHEED-GEORGIA CO MARIETTA
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An analytical and experimental investigation was conducted to characterize the fracture and cyclic-growth behavior of cracks emanating from various types of fastener holes, such as open, close-tolerance, interference- fit, and cold worked fastener holes. An analytical approach was developed for estimating stress intensity factors for through cracks emanating from these types of fastener holes. Approximate stress intensity factors for quarter- elliptical cracks emanating from a corner or the same types of fastener holes were derived from corresponding through-crack solutions. Two alloy plates 2219- T851 aluminum and 6Al-4VELI beta annealed titanium with and without intentional initial flaws were tested under constant amplitude cyclic load and flight-by-flight fighter and bomber spectrum loads. Two initial flaw shapes corresponding to a quarter-circular corner crack and a through-the-thickness crack and three inital crack lengths small, intermediate and large were used in the test program. Three levels of cold working and interference and one level of fastener load transfer were included for each alloy. The amount of load transferred through the loaded fastener was maintained uniformly at the level which produced a bearing stress equal to the far-field stress.
- Couplers, Fasteners and Joints