Influence of vibrations and noise on experimental results of lubricated non-conformal contacts

Dynamic effects are present in both simulated and real contacts. The influence of vibrations and other interferences on experimental results of lubricated non-conformal point contacts have been investigated. Tests with theoretically constant speed and load have been carried out. Friction force and speed signals have been analysed in particular. Signals have been analysed in the time and frequency domains by investigating first some preliminary aspects such as the influence of the sample rate. Peaks in the frequency domain of the measured quantities have been compared with the theoretical ones calculated considering possible defects of moving elements. The analysis has evidenced the presence of some misalignments and bearing problems. The friction fluctuations have been put in relation to the film thickness variations revealed by the interference images recorded by a new high-speed camera. The presence of a part of the friction force generated by dynamic forces directly acting on the load cell, and therefore not related to the lubricated contact, is revealed, evidencing the usefulness of studies combining different methodologies. The detection of the sources of the different signal variations can indicate the ways of possible reduction of the unwanted effects that can also be separated from the effects relevant to the real contacts by opportune filtering methods.