STP945: Overload Effects in Sustained-Load Crack Growth in
Inconel 718      Weerasooriya, T     Research scientist,
University of Dayton Research Institute, Dayton,      Nicholas,
T     Senior scientist, (MLLN) Wright-Patterson Air Force Base,
OH      Pages: 11    Published: Jan 1988       Crack-growth-rate
experiments were conducted on compact tension (CT) specimens of
Inconel 718 in air at 649°C. The loading spectrum consisted of a
single 1 Hz cycle at R = 0.1, where R is the ratio of minimum to
maximum stress-intensity factors, and a hold time which was
applied at various levels of the fatigue cycle. The ratio of the
hold-time amplitude to the maximum amplitude of the fatigue
cycle, Rin, was kept at 1.0, 0.9, 0.8, or 0.5. Hold times were
varied from 0 to 200 s. Tests were performed under computer-
controlled constant-K conditions using values of the maximum of
the fatigue cycle of 40 and 50 MPa m1/2. Data show that for Rin
= 1.0, a linear summation model works well, while at Rin = 0.9
there is a measurable