Contact analysis of non-Gaussian random surfaces

Surfaces produced by machining processes such as grinding, shaping and turning and some magnetic disk texturing processes such as sputtering and laser processing are frequently non-Gaussian. Most of the contact models developed in the past three decades assume Gaussian distribution of surface heights in their analyses. In the present paper, contact analysis of non-Gaussian surfaces has been conducted. A computer program was developed to generate non-Gaussian surfaces with specified standard deviation, autocorrelation length, skewness and kurtosis. Contact area, maximum contact pressure and relative meniscus force as a function of skewness and kurtosis were studied at different values of sigma and beta* In these studies, it is observed that a surface with slight positive skewness and kurtosis in the range of 4-7.5 results in an optimum surface with a minimum contact area and meniscus force. Further, stiction of a surface with high kurtosis is somewhat insensitive to liquid film thickness. A surface with negative skewness and/or kurtosis of less than 3 will lead to severe friction/stiction problems and a surface with very high kurtosis and sigma may lead to plastic deformation. Non-Gaussian surfaces offer promise for the design of interface roughness to provide low friction/stiction and wear.