EFFECT of FIBRE ADDITIONS to OILS to REDUCE FRETTING DAMAGE in ROPING STEEL WIRE

ABSTRACT

Overcoming fretting damage with conventional lubricants is difficult because of the very low amplitude of movement ( < 25 j/m) and the low sliding velocity. Non-metallic inserts have proved effective in other applications. It was thought that additions of a fibrous material to a carrier oil would be a possible solution . Three paraffinic oils of viscosities between 1 00 and 420 SUS and a naphthenic oil of viscosity 1 00 SUS were chosen as the carrier fluids . Chopped carbon fibre and chopped Kevlar were the sol id fibres . The wires were 5 mm dia. of cold drawn eutectoid steel (UTS 1300 MPa) . The fretting tests were carried out with a cross cylinder arrangement of the wires with a contact load of 3 N, peak-to-peak amplitude of 40 µm and a frequency of 50 Hz. The fretting specimens were immersed in a bath of the lubricant. The coefficient of friction was continuously monitored through tests run for 5.106 cycles. The depth of the wear scars was measured with a profilometer. The results show a degree of scatter depending on whether fibres are trapped in the contact zone. Where entrapment occurs there is a reduction in friction with certain of the oils and a corresponding reduction in wear. The continuance of the effect depends on the stability of the fibres in the contact. The carbon fibre tended to disintegrate. The Kevlar fibres were more resistant but were hard enough to indent the steel surface.