Discussion: “Extended Greenwood-Williamson Models for Rough Spheres” (Zhao, T., and Feng, Y. T., 2018, ASME J. Appl. Mech., 85(10), p. 101007)

The authors have dealt with a problem that is quite common when nonconformal rough surfaces come into contact [1]. They state “To our best knowledge, however, no attempt has been reported to solve the contact problem with positive overlap between two rough particles.” This discussion is aimed at highlighting that such work does exist and provide additional insight. Specifically, Ref. [2] deals with two contacting rough surfaces, one flat and the other hemispherical (similar to the case herein). But the work in Ref. [2] deals with real surfaces having the complication that both contain nonhomogeneous and anisotropic roughness properties. A procedure is given [2] where these properties had been reduced to parameters (spectral moments) that the GW model needs. It should be noted that what the authors call “GW, E-GW, and EP-GW” cases, are seamlessly handled in Ref. [2] without...