MEASUREMENTS OF REAL CONTACT AREAS USING PET FILMS (THICKNESS, 0.9 MU-M)

A new method of measuring the distribution of real contact areas betwe en two solid surfaces has been developed. A polyethyleneterephthalate (PET) film was inserted at the contact interface and pressed at a give n pressure for 1 min. It was indented by surface asperities at real co ntact points. The indented areas where plastic deformation occurred we re measured automatically by image processing through an optical micro scope which was modified so that its stage could be controlled by a mi crocomputer. A contact microscope which could observe the entire nomin al contact area was used to examine the real contact areas measured by the PET film method. One of the two solids in contact must be transpa rent so that the contact microscope can be used. Thus the real contact areas between the ground surfaces and a right-angled prism were measu red by the PET film method and the contact microscope. The distributio ns of the real contact areas measured by the two different methods wer e in relatively good agreement with each other. However, the PET film method depended on the surface roughness of the specimens. Surfaces sm oother than the thickness of the PET film did not give a sufficient in dentation on the PET film.