Fretting Corrosion and Fatigue Strength: Brief Results of Preliminary Experiments

Abstract

Fretting corrosion, the conditions under which it occurs, and the possibility of its effect on fatigue strength, are discussed. Fretting corrosion always appears in regions of unknown stress concentration, so that an accurate estimate of the weakening effect due to it cannot be made from combined fretting and fatigue tests. It is suggested that fatigue tests of previously fretted test pieces, analogous to determinations of the percentage loss of fatigue strength by prior stressless chemical corrosion, would be useful. Apparatus for making such tests is described, and preliminary results for a medium-carbon steel and for a nickel-chromium-molybdenum alloy stéel are given. The losses of fatigue strength after fairly severe fretting were 13 per cent and 18 per cent respectively. Although these are not necessarily maximum values, reductions of this order are regarded as justifying further investigation, and the suitability of the apparatus and methods used is considered.