Fretting-fatigue behavior of steel wires in low cycle fatigue

Highlights: → The paper presents the fretting-fatigue behavior of steel wires in low cycle fatigue. → Variation modes of the hysteretic loops of tangential force versus displacement are all located in mixed fretting regimes. → Larger strain amplitude corresponds to larger normalized tangential force and reduced fretting fatigue life. → The wear mechanisms for fretting-fatigue at different strain amplitudes are abrasive wear, adhesive wear and fatigue wear. → Acoustic emission technique is used to explain crack nucleation and propagation mechanisms at different strain amplitudes. -- Abstract: The effect of strain amplitude on fretting-fatigue behavior of steel wires in low cycle fatigue was investigated using a fretting-fatigue test rig which was capable of applying a constant normal contact load. The fretting regime was identified based on the shape of the hysteresis loop of tangential force versus displacement amplitude. The variations of the normalized tangential force with increasing cycle numbers and fretting-fatigue lives at different strain amplitudes were explored. The morphologies of fretting contact scars after fretting-fatigue tests were observed by scanning electron microscopy and optical microscopy to examine the failure mechanisms of steel wires. The acoustic emission technique was used to characterize the fretting-fatigue damage in the fretting-fatigue test. The results show that the fretting regimes are all located in mixed fretting regimes at different strain amplitudes. The increase in strain amplitude increases the normalized tangential force and decreases the fretting fatigue life. The abrasive wear, adhesive wear and fatigue wear are main wear mechanisms for all fretting-fatigue tests at different strain amplitudes. The accumulative total acoustic emission events during fretting-fatigue until fracture of the tensile steel wire decrease with increasing strain amplitude. An increase of the strain amplitude results in the accelerated crack nucleation and propagation and thereby the decreased life.