The Effect of Isotropic One-Process and Two-Process Surface Textures on the Contact of Flat Surfaces

Abstract

The contact of random modeled one-and two-process textures with smooth, flat surfaces is discussed in this paper. An elastic-plastic contact model was applied, assuming a distributed radius of summits. A one-process surface was characterized by the standard deviations of height and the correlation length; however, it also had a two-process texture by the standard deviations of the plateau and valley structures, the material ratio at the transition point, and the correlation lengths of the plateau and valley parts. It was found that the contact characteristics depended on the height and spatial properties of the surface texture. The plateau part governs the contact characteristics of two-process surfaces, while the effect of the valley surface portion is smaller. The plastic deformation leads to a smaller effect of the surface texture on the contact characteristics. elastic deformation, but an increase in the correlation length led to a decrease in the maximum contact pressure. It was found [15] that an increase in the plasticity index due to the change in the surface topography of Gaussian ordinate distribution led to increases in the contact area and the contact load for the same separation. The authors of paper [16] analyzed the effect of the correlation length on the real area of contact. It was found that a higher correlation length corresponded to a higher number of contact points and therefore a larger contact area for the same separation based on surface heights.Typically, the contact of surfaces of Gaussian ordinate distribution was analyzed. In Reference [17], the contact of surfaces of different ordinate distribution (the skewness Ssk was in the range from −2 to +2) was studied. It was found that skewness affected the contact load and the contact area. A separation based on asperity heights for the same load or the same contact area is lower for more negative skewness for the same standard deviation of surface height. For surfaces of asymmetric ordinate distribution, similar to Gaussian topographies, the contact load is proportional to the contact area, except for very large loads. Jang and Peng [18] found that the contact of anisotropic surfaces of negative skewness was more elastic than that of surfaces of Gaussian ordinate distribution and the same standard deviation of surface height. A similar tendency was confirmed for isotropic surfaces, considering the asperities' interaction [19].The obtained findings were confirmed experimentally only for the effect of surface height on the rough surface contact; when the roughness height was higher, the deformations were bigger [20,21].The functional properties of two-process surfaces can be better than those of one-process textures [22][23][24][25]. Two-process surfaces can be machined or formed during wear. Only a few publications about the contact of two-process surfaces have been presented so far [26][27][28]. Greenwood and Williamson [1] thought that two-process worn surfaces were characterized by the Gaussian distribution of heights of summits from the ...

Prediction of Parameters of Equivalent Sum Rough Surfaces

“…The density of summits of two-process random surface is higher compared to the asperity density of one-process textures. However, there are opinions that not all the summits should be taken into consideration in the contact analysis of two-process surfaces [16,48]. Because of the difficulty of using Equation (3), areal summit density of the equivalent sum rough surface was predicted using the weighting average method-Equation (12).…”

“…However, the distribution of surface height is often different from Gaussian [20,22,23]. Specifically, two-process surfaces characterized by negative values of the skewness, Ssk, and high values of the kurtosis, Sku, are of high functional importance [16,[24][25][26]. Two-process textures have traces of two processes (machining or wear).…”

“…However, due to the large exponent used, the parameters Ssk and Sku are sensitive to presences of spikes as well as narrow and deep valleys. In addition, for two-process surfaces [16,[24][25][26], these parameters are interrelated. Sp is the maximum peak height and Sz is the maximum surface height.…”

“…This simplification can be used not only in statistical models of the elastic contact [7,9], but also in statistical models of the elastic-plastic contact [10][11][12][13]. The contact parameters such as the number of contacting asperities, the real area of contact, and the contact load, for any given separation between the equivalent sum rough surface and a smooth flat, can be also calculated by summing the contributions of all the contacting asperities using the summit identification model [14][15][16]. Combining two rough surfaces onto one equivalent rough surface and a smooth plane can also be helpful in deterministic contact models considering the Boussinesq problem [17][18][19].…”

Conditions of the Presence of Bimodal Amplitude Distribution of Two-Process Surfaces

“…The plateau-honed cylinder surface is the practical example of machined two-process textures [ 4 , 7 , 11 , 12 ]. The stratified property of the two-process surface substantially affects the contact behavior [ 13 , 14 , 15 , 16 , 17 , 18 ]. The contact stiffness and the normal deformation are governed by the fine part of two-process surface.…”