Abstract:In order to obtain the actual contact area and surface morphology of solid rough surface,a measuring device was designed to observe and analyze the nominal contact area and actual contact area of contact interface.The contact images of metal balls and glass plates with different diameters under different loads were obtained by using this measuring device.The edge extraction and gray threshold analysis of contact Newton’s ring were carried out by using Canny image processing method.The change of nominal contact area and actual contact area of the contact interface with the diameter of the ball and load was obtained.The experimental results indicate that the nominal contact area of rough interface is increased with the increase of load.The ratio of the actual contact area to the nominal contact area is also increased nonlinearly with the increase of the load and the diameter of the ball.At the stage of plastic deformation,the nominal contact area of small diameter metal ball is sensitive to the change of load,however,at the elastic deformation stage,the nominal contact area of larger diameter metal ball changes dramatically.The experiment results are in accordance with the Hertz contact theory.The measuring device can also be used to study the tribological properties of the contact interface,such as surface morphology,boundary film thickness,wear debris formation and so on.