Finite element simulation of the wear of polyoxymethylene in pin-on-disc configuration

The simulation of the wear profile of a pin made of polyoxymethylene (POM), in sliding contact with rotating steel disc was performed using the finite element (FE) software package ANSYS 6.1 implemented with a wear equation that updates the geometry. The modeling procedure was first validated against a theoretical solution developed for a simpler case then the solutions were compared to experimental results obtained at different operating conditions of contact pressures, sliding distances and sliding speeds. The two-dimensional (2D) FE model of the tribo-system included Coulomb friction, a wear algorithm based on the Holm-Archard equation, but did not take the frictionally induced heating into account. Using ideal boundary conditions, which constrained the radial edges of the pin to vertical movement only, the simulation predicted the development of an inclination in the wearing profile of the pin due to uneven pressure distribution at the contact zone. Good agreement was found between the modelling and experimentally observed results. An equilibrium angle of inclination was also predicted, after which the wear profile stabilized. It is speculated that this situation is directly linked to the steady state that generally occurs after the run-in period. The simulation process was used to predict geometrical effects characterized by the aspect ratio (AR) of the pin on the wear and it was found that beyond a critical AR of 1.9 uneven wear drastically increases.