Abstract: The torsional wear tests of polymethylmethacrylate (PMMA) against GCr15 is carried out under the angular displacement amplitudes ranging from 0.5° to 15.0° and the normal load at 100 N on a new developed real time observation system of torsional fretting wear, meanwhile, the fretting process is recorded and at the same time the friction vibration is collected. Based on the analysis of the frictional kinetics of torsional fretting, the torsional fretting behavior of PMMA is analyzed by real time observation and friction vibration analysis. The results show that there are three fretting running regimes, i.e. partial slip regime, mixed fretting regime and gross slip regime; when the fretting is running in the state of partial slip (θ=0.5°), the damage is slight and the vibration statistic is similar to load-free condition because the relative motion is accommodated by elastic deformation. In the state of gross slip (θ=15.0°), the contact zone is damaged intensely, and a great deal of the wear debris is removed from the contact zone, there are some crazes in shape of spindle at the edge of contact zone. Meanwhile, the events of friction vibration per cycle increases and then decreases with the increase of the number of cycles; on the other hand, the amplitude of friction vibration shows an opposite trend. The main damage mechanisms are elastic-plastic deformation, delamination and oxidation wear.

Key words: Friction vibration, Polymethylmethacrylate, Real time observation, Torsional fretting