SYMPOSIA PAPER Published: 01 January 1985

A Model for Creep/Fatigue Interactions in Alloy 718


An experimental investigation was conducted to evaluate the crack growth rates in Inconel 718 at 649°C under symmetric and unsymmetric triangular waveshapes and triangular waves with hold times at maximum load. Data are presented as crack growth rate per cycle as a function of total cycle time. An analytical model is developed which predicts crack growth rate from an integration of the sustained load crack growth rates over the cycle when time-dependent behavior is dominant. The data show that the loading portion of a cycle is the major contributor to the time-dependent crack growth behavior. At low unloading frequencies or high load ratios, however, the unloading portion of the cycle is found to become increasingly important. The model utilizes minimum baseline data and is proposed for predictions of crack growth rate over a variety of loading cycle types.

Author Information

Nicholas, T
Air Force Wright Aeronautical Laboratories (MLLN), Wright-Patterson AFB, OH
Weerasooriya, T
University of Dayton Research Institute, Dayton, OH
Ashbaugh, NE
University of Dayton Research Institute, Dayton, OH
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Developed by Committee: E08
Pages: 167–180
DOI: 10.1520/STP34252S
ISBN-EB: 978-0-8031-4933-5
ISBN-13: 978-0-8031-0225-5