Failure Mechanisms in High-Density Polyethylene Rollers

This paper describes failure processes in plastic rollers that undergo rolling contact, and the effect of initial surface roughness upon wear and rolling fatigue. Experiments were performed with mating cylindrical rollers of high-density polyethylene (PE rollers) and chrome-plated cylindrical driving rollers. Surface roughness of the PE roller is affected by three successive transition processes. In the first period, the amount of wear can hardly be measured, although a reduction of surface roughness is noted. During the second period, wear occurs in proportion to the initial surface roughness. In the third period, wear becomes independent of the initial surface roughness, and increases in a manner exponential to load. At the end of this period, small cracks appear randomly, and grow into pits. Roller fatigue Life, defined by the time when cracks appear, is shown by an S-N curve. It is found that fatigue limiting stress, represented by Hertz stresses, is about 10⁷pa.