SEDL / STP / STP743-EB / STP28795S

Fatigue Crack Growth Rates as a Function of Temperature

Marci, G
DFVLR—German Aerospace Establishment, Institut für Werkstoff-Forschung, Cologne,

Pages: 20    Published: Jan 1981

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Abstract

The equation dadN=C[(KlG−Klmin)+ΔKT][(Klmax−KIG)−ΔKT]2 had been proposed by the author to predict fatigue crack growth rates. By adopting this functional relation and setting K^IG = 0.5 K^Imax (K^IG ∼ K^Iopen under constant-amplitude cyclic loading), there are the two parameters, C and ΔKI, left to be determined from experimental data.

The parameters C and ΔKT for several structural alloys as a function of temperature between room temperature and 811 K had been analyzed. It was found that the “fatigue tolerance range” ΔKT decreased linearly with increasing temperature. Initially, the parameter C increases nearly linearly with increasing temperature and then increases steeply at higher temperatures. In the present work, this temperature dependence is shown to be found between 4 and 911 K by analyzing low-temperature as well as additional high-temperature data for Inconel 718 and Inconel X-750. By assuming the observed qualitative temperature dependence of C and ΔKT as being correct, available fatigue crack growth rates for Type 304 stainless steel obtained at temperatures ranging from 4 to 922 K were analyzed with respect to C and ΔKT.