ACCURATE REAL AREA OF CONTACT MEASUREMENTS ON POLYURETHANE

Theoretical models describing the contact of rough surfaces have been developed for at least three decades. Experimental verification, howev er has not been straightforward up till now since current measurements suffer from large inaccuracies, often 100 percent or worse. In this p aper a new method, based on autofocus techniques, is applied with an a ccuracy better than 15 percent. Measurements are presented for the con tact of a rough polyurethane specimen in contact with a smooth glass p late. Tt was not yet possible to conclude whether the real area of con tact is proportional to the contact load, but the results show the for ming of contact agglomerations, which becomes significant at 10 percen t real area of contact. Asperity interaction appears to be important, even at low loads. However, one or both of these facts are often not c onsidered in present contact models, questioning their reliability.