Non-Coulomb friction in gross sliding fretting conditions with aluminium bronze against quenched and tempered steel

A series of fretting tests were performed in gross sliding conditions to study the properties of non-Coulomb friction occurring in the contact of an aluminium bronze sphere against a quenched and tempered steel plane. Measurements were analysed by studying measured fretting loops and the topographies of fretting scars with 3D optical profilometry. Measured fretting loops showed non-Coulomb tangential behaviour, in which the tangential force depended on the tangential displacement. Measurements in which the tangential displacement amplitude was suddenly increased or reduced showed a temporary reduction in the maximum friction force. Fretting wear modified initially polished surfaces producing a tangentially interlocked fretting scar surface profile, which may explain the non-Coulomb increase in the friction force.