The influence of preloading on the residual fatigue life of nickel-based
superalloys under elevated temperatures was investigated experimentally.
A powder metallurgy nickel-based superalloy FGH96 was preloaded with
different number of cycles, and the residual fatigue life was tested
under subsequent high-amplitude loads. The test results show that the
fatigue life of the material was increased when the preloading cycle
number was within a specific range. At the same time, the fatigue life
of virgin specimens under high-amplitude loads shows little scatter,
which provides the possibility to consider the strengthening effect of
low-amplitude loads. A novel damage accumulation model was proposed to
incorporate the strengthening effect of low-amplitude loads into the
life prediction framework. The proposed model provides better life
prediction than some existing models. Finally, the proposed model was
validated using experimental data for various materials under the
low-high loading sequence.