On the role of internal friction in low-and high-cycle fatigue

•Role of internal friction in fatigue is investigated.•Fatigue fracture entropy (FFE) for low- and high-cycle fatigue is evaluated.•FFE and endurance limit for SS304 and CS1018 are evaluated.•Examples are provided to illustrate the utility of FFE concept. A thermographic methodology is used to determine the fatigue fracture entropy for predicting low- and high-cycle metal fatigue. The associated analysis includes consideration of energy dissipation via microplastic deformation and internal friction. Internal friction is shown to play an important role in high-cycle fatigue. The results of extensive low- and high-cycle bending fatigue experiments on stainless steel 304 and carbon steel 1018 are presented to demonstrate the utility of the proposed approach. It is shown that the proposed approach can successfully capture the material failure during cyclic loadings.