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).