The effect of ‘running-in’ on the tribology and surface morphology of metal-on-metal Birmingham hip resurfacing device in simulator studies

Abstract

Abstract

It is well documented that hard bearing combinations show a running-in phenomenon in vitro and there is also some evidence of this from retrieval studies. In order to investigate this phenomenon, five Birmingham hip resurfacing devices were tested in a hip wear simulator. One of these (joint 1) was also tested in a friction simulator before, during, and after the wear test and surface analysis was conducted throughout portions of the testing. The wear showed the classical running in with the wear rate falling from 1.84 mm³ per 10⁶ cycles for the first 10⁶ cycles of testing to 0.24 mm³ per 10⁶ cycles over the final 2 × 10⁶ cycles of testing. The friction tests suggested boundary lubrication initially, but at 1 × 10⁶ cycles a mixed lubrication regime was evident. By 2 × 10⁶ cycles the classical Stribeck curve had formed, indicating a considerable contribution from the fluid film at higher viscosities. This continued to be evident at both 3 × 10⁶ and 5 × 10⁶ cycles. The surface study complements these findings.