A method for determining the non-Gaussian probability density functions of asperity heights for two contact surface conditions

Most statistical contact analyses assume that asperity height distributions (g (z(center dot))) follow a Gaussian distribution. However, engineered surfaces are frequently the non-Gaussian with a character dependent upon the material and surface state being evaluated. When two rough surfaces experience contact deformations, the original topography of the surfaces varies with different loads. Two kinds of topographies are considered in the present study. The first kind of topography is obtained during the contact of two surfaces under a normal load. The second kind of topography is obtained from a rough contact surface after the end of the elastic recovery. The g (z(center dot)) profile is quite sharp and has a large value at its peak if it is obtained from the surface contacts under a normal load. The g (z(center dot)) profile defined for a contact surface after the elastic recovery is quite close to the g(z(center dot)) profile before contact deformations occur if the plasticity index is a small value. However, the g(z(center dot)) profile for the contact surface after the end of elastic recovery is closer to the g (z(center dot)) profile shown in the contacts under a normal load if a large plasticity index is assumed. Skewness (Sk) and kurtosis (Kt), which are the parameters in the probability density function, are affected by the change in the mean separation of two contact surfaces, or the initial skewness (the initial kurtosis is fixed in this study), or the plasticity index of the rough surface are also discussed on the basis of the topography models mentioned above.