An investigation of the relationship between wear and contact force for abradable materials

Abradable linings are frequently used on the inside of aero-engine casings. During the operation of engine, the rotating blades may strike the lining of the casing. The wear mechanisms present during these incursions have been re-produced on a scaled test rig platform. Previously, characterisation of the wear has been performed using a stroboscopic imaging technique in order to identify the different wear mechanisms at the incursion conditions investigated. In the present study, a dynamometer has been included in the test arrangement allowing the measurement of the contact force. This approach has then been combined with sectioning of the abradable test samples, in order to investigate the material response to the different incursion conditions. The wear results, the cutting force and material structure post-incursion show a high degree of correlation. At low incursion rates, significant consolidation and solidification of abradable material was observed, whilst at the same time adhesive transfer to the blade was recorded along with a low tangential to normal force ratio. At high incursion rates, little solidification and consolidation was observed, together with negligible adhesion and a higher tangential force, suggesting a cutting mechanism. Transitions in material behaviour, wear mechanism, and force ratio were observed at the same incursion condition, further highlighting the link between the different experimental measurements.