4.2 Proposed model
The existing models are insufficient to describe the experimental
results of FGH96. The purpose of this study was to incorporate the
strengthening effect into the fatigue life evaluation framework. It
should be noted that it is difficult to account for multiple
micro-mechanisms when modeling the strengthening effect. Therefore, a
phenomenological model based on continuum damage mechanics was proposed
here.
It has been pointed out that the strengthening effect is closely related
to the preload stress level and the number of preload
cycles35. According to the characteristics of
strengthening and damaging, the stress level of preload can be divided
into three regions39, including the strengthening and
damaging region(σ>σH), the strengthening
region(σH>σ>σL),
and the useless region (σ<σL).