Wear Effect on the Contact between a Metallic Pin and a Rotating Polymeric Specimen

Debris formation is a crucial aspect that determines the lifespan of prosthetic joints. The wearing contact between ultra-high molecular weight polyethylene (UHMWPE) and a Ti alloy surface has been studied in the literature. However, when measuring mass loss, potential errors can arise due to the very small values involved (on the order of some units of 0.1 mg in experiments lasting several hours) and be caused by the absorption of humidity in the specimen, in addition to the lack of accuracy typical of weight scales. These errors can hardly be avoided, but accurate cleaning and drying processes can minimize them. With these premises, the present work aims to determine, by pin-on-disc test, the wear effect in the UHMWPE rotating sheet and Ti6Al4V pin produced by Electron Beam Melting (EBM) under dry and lubricated conditions. The morphology of the worn surface was documented by optical microscopy, and the volume loss of both the rotating specimens and the pin was accurately calculated through the detection of the wear track observed by optical microscopy. In particular, the present work proposes a method for directly determining the volume loss of the polymer to compare it with that obtained with the weight measurement. For both procedures, the uncertainty in evaluating the specific wear rate was analyzed, demonstrating that volume measurement allows for avoiding any possible error associated with weighing the polymeric specimens.