Fatigue Life Prediction Method for Gas Turbine Rotor Disk Alloy FV535

A rotor disk of jet engine and/or gas turbine is subjected to the intermittent stress waves, that is, the repetition of centrifugal stress at the start and stop of machine with superimposed vibrating stress. The serrated part and bolt hole of the rotor disk are important parts needed for fatigue strength evaluation. A number of studies have been conducted on the fatigue strength under the intermittent stress wave and the fatigue strength estimation of notched specimens. The fatigue strength evaluation method under the intermittent stress proposed by authors is being used for the fatigue life prediction of piston crown of a diesel engine. However, the adaptability of the method to the rotor disk has not been verified yet. The present paper aims at the verification of the adaptability of the method for a rotor disk made of martensite stainless steel FV535. The following conclusions were obtained from this experimental study. 1) The fatigue crack initiation life of a notched specimen under constant stress amplitude was well predicted by Koe's or Neuber's method. 2) The fatigue life prediction method proposed by the authors may well predict the fatigue life of a smooth specimen in the region of higher stress level than the fatigue limit by using the interaction coefficient C of 0.3. However, in the region of stress near the fatigue limit, the method predicted very conservative life and the coefficient C was more than 5.