A basic study of friction noise caused by fretting

Fretting may be accompanied by friction noise and preventing or reducing it can be important for designers and operators. In this study, 0.45% carbon steel (Hv730) and mild steel (Hv240) are used as specimens with the crossed cylinder configuration. Friction force, relative movement between the spec imens, friction noise and electrical contact resistance are measured simult aneously during fretting, with normal load 19.6 N, and up to 25,000 cycles in air. Fretting stroke, relative humidity and frequency are varied in the range 25-400 mum, 11-78% RH and 1.0-7.3 Hz, respectively. In addition, the wave signals of the friction noise, together with coefficient of friction a nd relative stroke, are analyzed by FFT analyzer. The main results are as f ollows: certain cycles of fretting are needed to generate friction noise; t here are common features in relation to the occurrence of friction noise; d rastic reduction in coefficient of friction mu; self-excited-vibration and negative gradient of mu, sound level of friction increases with increase in fretting stroke and frequency, and is directly related to average sliding velocity; there is a good correlation between the sound level and amount of wear. Based on the results, the mechanism of the friction noise is discuss ed. (C) 2001 Elsevier Science B.V. All rights reserved.