Failure analysis and life prediction of polymeric rollers for industrial applications

The present study investigates the behaviour of polymeric rollers employed in a cam mechanism of an industrial machine, consisting of two concentrically fitted rings made of polyurethane and short fibre-reinforced PEEK. A cyclic mechanical characterisation of the materials was at first carried out by strain controlled fatigue tests. The safe range of working conditions of the rollers in terms of rotating speed and contact load was then investigated by rolling contact tests carried out on roller prototypes with a dedicated test rig. These tests allowed obtaining important information about the different damage mechanisms occurring in the component: above a critical working temperature, rollers failure resulted from rings unfitting due to excessive deformations, while fatigue crack nucleation in the outer ring at the interface with the inner one was observed below this threshold, at high contact load levels. No contact fatigue damage appeared. FEM models of the roller were also developed, based on cyclic material data, in order to analyse the cyclic stress and strain field and to predict the fatigue life, finding a satisfactory agreement with the experimental rolling contact tests results.