  Recently, it has been shown that while asperity models show correctly
qualitative features of rough contact problems (linearity in area-load,
negative exponential dependence of load on separation which means also
linearity of stiffness with load), the exact value of the coefficients are not
precise for the idealized case of Gaussian distribution of heigths. This is due
to the intrinsic simplifications, neglecting asperity coalescence and
interaction effects. However, the issue of Gaussianity has not been proved or
experimentally verified in many cases, and here we show that, for example,
assuming a Weibull distribution of asperity heigths, the area-load linear
coefficient is not much affected, while the relationships load-separation and
therefore also stiffness-load do change largely, particularly when considering
bounded distributions of asperity heigths. It is suggested that Gaussianity of
surfaces should be further tested in experiments, before applying the most
sophisticated rough contact models based on the Gaussian assumption.
