Abstract
An initial friction peak typically occurs in a dry self-mated quenched and tempered steel fretting contact in gross sliding conditions. The peak is related to adhesive friction and wear, which causes non-Coulomb friction. An early surface degradation including cracks may occur. To avoid such a peak, different media were studied using a flat-on-flat fretting test device with a large annular contact. All the media decreased the initial friction peak in comparison to the dry reference case, and in one series the peak was completely removed. The peak could often be delayed by lubrication. The steady-state coefficient of friction values mostly remained at similar levels to those of the dry contact, but decreased when oil was applied. Nevertheless, some surface damage occurred in every test, with varying amounts of wear.
Highlights
Fretting is characterised as small amplitude cyclic rubbing between surfaces in contact that can cause fretting fatigue and fretting wear
The curves are presented after 100 loading cycles where the contact is already in gross sliding conditions, though the sliding amplitude continues to increase during the ramping-up phase up to 400 loading cycles
In the dry contact con ditions, the initial coefficient of friction (COF) peaks occur at a value of about 1.4 and decreases over the following ten of thousands of loading cycles until it stabilises at a value of around 0.8
Summary
Fretting is characterised as small amplitude cyclic rubbing between surfaces in contact that can cause fretting fatigue and fretting wear. Fretting fatigue can notably decrease fatigue life and lead to early failure in machines and other applications. The rubbing can be caused by loads being transmitted along the contact interfaces in assemblies, or by vi brations. In a gross sliding condition, the whole nominal contact area is sliding. Only a part of the nominal contact area is sliding, and this is called a partial-slip sliding condition. There is a mixed fretting regime which encompasses both of these conditions during its loading history. Shear tractions increase and stresses in the contact. This can lead to cracking and wear. It is generally acknowledged that nonidealities in fretting [1] make fretting a challenging phenomenon
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