COEFFICIENT OF FRICTION AND DAMAGE TO CONTACT AREA DURING THE EARLY STAGES OF FRETTING II - STEEL, IRON, IRON OXIDE, AND GLASS COMBINATIONS

摘要

Experiments were conducted to study the start of fretting and the cause of damage during the early stages (up to 400 cycles) of fretting of steel-steel combinations at a frequency of 5 cycles per minute an amplitude of 0.006 inch, a load of 150 grams, in air with relative humidity of less than 10 percent. Pure iron, glass, and iron oxide powder compacts were used in supplementary experiments. The results of microscopic observation of the contact area and measurements of coefficient of friction lead to these conclusions:n1. Fretting starts with severe adhesion between surfaces. The adhesion varies with the material combination, as shown by the initial coefficient of friction, but is of primary importance because it precedes and initiates the other phenomena observed.n2. In the early stages of fretting, several other wear phenomena in addition to adhesion occur. Their relative importance varies with the materials fretted, and they can occur simultaneously at different points within a contact area. They are:n(a) Plowing by protruding transferred material: The plowing is more pronounced when adhesion is greater.n(b) Formation of debris (loose fragments): Oxide debris is not evident when large wear fragments are produced, whereas oxide debris (Fe203) is evident in a very few cycles if the wear frag¬ments are small.n(c) Formation of films by compacting small particles into clearances in the contact area: The formation occurs readily if one of the surfaces is hard. These films can plow the opposing metal surface.