A rapid fatigue life prediction model of butt joints based on energy dissipation

An energy dissipation model for high cycle fatigue linked to anelastic and inelastic behavior of butt joints is developed by introducing α and β variables of the internal state variable (ISV) constitutive model. The crucial stress amplitudes, σ_c0 and σ_c1 (fatigue limit), corresponding to the onset of recoverable anelastic and unrecoverable inelastic behavior, are defined as two characteristic stress amplitudes. The energy dissipation response of butt joints under different stress amplitudes is examined using this energy dissipation model. The results demonstrate that when stress levels are close to the fatigue limit, the energy dissipation exhibits a transition from a linear response to a nonlinear response. On this basis, considering that when the stress amplitude is above the fatigue limit, there is a critical value for the energy dissipation during the fatigue duration, a fatigue life prediction model based on damage accumulation is developed in combination with the damage-related inelastic dissipation, thereby reaching a rapid fatigue life prediction. The results show that the median S-N curve fitted by the predicted data and the test data is in good agreement, and this validates that the proposed model can be utilized to realize a rapid and accurate prediction of the fatigue life of butt joints.