Frequency Effects in the Elevated Temperature Crack Growth Behavior of Austenitic Stainless Steels—A Design Approach

The fatigue-crack growth behavior of annealed types 304 and 316 stainless steels is determined over a range of cyclic frequencies in an air environment at temperatures of 800°F (427°C), 1000°F (538°C) and 1200°F (649°C). A good portion of the experimental data supports the observation that the fatigue crack growth rates at a given value of ΔK increases with decreasing frequencies. The behavior ot each temperature is normalized relative to the behavior at a “standard” frequency of 40 cpm, and a simple frequency correction factor is derived. This frequency correction factor, more applicable to type 304 than to 316 stainless steels, is further coupled with temperature effects data taken at the “standard” frequency and combined with a stress ratio correction to furnish estimates of the fatigue crack growth behavior of those two steels over a fairly wide range of parameters.