An experiment investigation on dual rotary fretting of medium carbon steel

A test rig of dual rotary fretting, which combined with the torsional and rotational fretting modes has been developed, based on a low-speed reciprocating rotary motor system. As two extreme cases for the dual rotary fretting, when the tilt angle (alpha) equals 0 degrees or 90 degrees, the fretting transforms to simple mode of torsional fretting or rotational fretting, respectively. The dual rotary fretting tests of medium carbon steel (1250) flats against AISI52100 steel balls have been carried out under normal load of 50 N, varied tilt angles (alpha = 5 degrees, 10 degrees, 20 degrees, 40 degrees) and varied angular displacement amplitudes (theta = 0.125 degrees, 0.25 degrees, 0.5 degrees, 1 degrees, 2 degrees, 10 degrees). Kinetic analyses of the fretting running behaviours have been performed in combination with microscopic examinations through optical microscopy, surface profilometer, scanning electric microscopy (SEM) and energy dispersive analysis of X-ray (EDX). The results showed that the running and damage behaviours of the dual rotary fretting were mainly dependent upon the tilt angle a, the angular displacement amplitude theta and the number of cycles, which were obviously different from the two simple fretting modes. The evolutions of the kinetic curves, fretting running regimes, tangential force against normal load curves of contact interfaces and asymmetric morphologies of wear scars as a function of the tilt angle a and the angular displacement amplitude theta have been discussed in detail. Finally, the wear mechanism was summarized. (C) 2011 Elsevier B.V. All rights reserved.