STP677

    Effects of Temperature and Frequency on the Fatigue Crack Growth Rate Properties of a 1950 Vintage CrMoV Rotor Material

    Published: Jan 1979


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    Abstract

    Air environment fatigue crack growth rate data were developed for a 1950 vintage (air cast) chromium-molybdenum-vanadium (CrMoV) rotor steel at temperatures of 24, 121, 260, and 427°C (75, 250, 500, and 850°F) and loading frequencies of 0.0017, 0.017, 0.1, and 1.0 Hz. Results show that the room-temperature fatigue crack growth rate in the 1950 vintage material is on the order of two to eight times faster than that encountered in a more modern vacuum cast forging depending upon the ΔK level of interest. Results also show that the effect of frequency on the fatigue crack growth rate varies with differing test temperatures. At room temperature as well as at 260 and 427°C (500 and 800°F), the rate of crack growth increases with decreasing frequency. At 121° (250°F), there is little effect of loading frequency on fatigue crack growth rate. This temperature dependent frequency effect is attributed to the different mechanisms interacted with fatigue at various temperatures. The effect of temperature on crack growth rates was also found to be frequency dependent with more pronounced temperature effects observed at lower frequencies. However, the general trend is the same for all values of frequency, that the rate of fatigue crack growth initially decreases before increasing at higher temperatures. The fact that fatigue crack growth rates do not increase monotonically with increasing temperature is attributed to the decrease in relative humidity of the test environment with increasing temperature.

    Keywords:

    fatigue (materials), frequency, crack propagation, temperature, rotors, steel-CrMoV


    Author Information:

    Shih, TT
    Senior engineer and senior engineer, Westinghouse Research and Development Center, Pittsburgh, Pa.

    Clarke, GA
    Senior engineer and senior engineer, Westinghouse Research and Development Center, Pittsburgh, Pa.


    Paper ID: STP34910S

    Committee/Subcommittee: E08.06

    DOI: 10.1520/STP34910S


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