The actual contact area of moving surfaces

Hertzian contact is generally assumed when calculating the actual contact area of two surfaces. However, Hertz's formula is strictly only valid when there is no tangential stress in the region of contact. If the two surfaces are moving relative to one another then there will be frictional stress so that the assumption of Hertzian contact cannot be entirely valid. The twodimensional problem of contact with tangental stress is very difficult even for asperities with spherical symmetry. However, for shapes uniformly infinite in one direction it is tractable. The dependence of contact area on load is examined in this case and found to be generally dependent on the frictional force except for the case of circular cross section in which it is the same as for the frictionless problem. The significance of these results is discussed.