A Test Rig for the Contact Area Evolution During Pre-Sliding

An experimental test rig was developed in order to investigate elastic-plastic single micro-spherical contact under combined normal and tangential loading. This novel apparatus allows in situ and real time direct optical measurement of the real contact area (RCA) evolution in pre-sliding. It also allows relative displacement measurements under very low rates of tangential loading (down to 0.01N/s) to capture accurately the fine details at sliding inception. The RCA measurement is realized by direct optical observation technique, whereas two different image processing algorithms were implemented for the elastic and the elastic-plastic contact regimes.