A new dwell sensitivity damage parameter

Published dwell-fatigue data were compiled from various sources for a number of materials such as copper alloys (NARloy-Z, AMZIRC), steel alloys (9Cr–1Mo), and nickel based alloys (IN 100, Rene 95, Waspaloy). In general, dwell-times were found to be detrimental to the fatigue life of materials, but the exact extent of the effect varies depending on the material, duration of the dwell, and the direction in which a dwell was applied. In general, a degree of strain saturation occurred which lowered the dwell sensitivity at higher strain ranges (εt>1%). An attempt was made to further develop the models proposed earlier and include such concepts as stress relaxation with respect to a particular dwell time. Very limited data sets are available in the literature showing the test details needed to develop a model for this research. Stress relaxation was used as a damage parameter for dwell cycles that may describe dwell sensitivity. A dwell sensitivity damage mechanistic map was developed and discussed in this paper.