Experimental investigation of the contact mechanism of solid surfaces with a surface force apparatus

A surface force apparatus was developed by fringes of equal chromatic order technique. The molecule grade smooth surfaces of two cylindrical micas were brought into contact under a controlled load, and the size of contact area and deformed shape were measured. The contact between two solid surfaces can be adhesive or non-adhesive depending on the medium between the contact bodies. Thus different media were used between the two contact surfaces in order to investigate the variations in the normal force with the feeding level under adhesive contact and non-adhesive contact. The test results were compared with that based on Hertz theory (applied to non-adhesive contact) and Johnson-Kendall-Roberts (JKR) theory (applied to adhesive contact). It is found that the test results under the non-adhesive condition agree well with that based on Hertz theory, while the so-called 'neck shrink' phenomenon predicted by JKR theory is observed under the adhesive contact condition.