FRACTAL MODEL OF CONTACT INTERACTION FOR UNDERLOADED SURFACES

An adequate assessment of the contact interaction of rough surfaces at low nominal contact pressures (up to 2 MPa) is impossible without taking into account the microgeometry of the mating surfaces, and the complex pattern of formation of actual contact spots requires the use of simulated modeling of the contact interaction of real 3D maps of engineering surfaces or their models, which are fractal surfaces. The description of a fractal surface requires knowledge of the fractal dimension of the profile D (surface DS = D + 1) and the fractal roughness parameter G. These fractal parameters determine such structural features of the surface model as the radius of curvature of the upper part of the protrusion and the criterion for the transition from plastic deformation of the protrusion to elastic. The contact interaction of a fractal surface with a smooth, rigid, flat surface suggests that due to the presence of sub-roughness at the nanoscale, plastic deformation of the submicron surfaces occurs first, and then, as the normal load increases, an elastic contact spot forms. The article considers the case when the description of the surface model required the use of another parameter – the dimension DXY of the contact spots, which includes the number of irregularities in contact with an area greater than the selected one. The well–known fractal models of Majumdar-Bhushan (M-B) and others assume that the dimension of the surface and DXY numerically coincide with each other, which is not true. The article provides a comparison of the simulation results for cases when the fractal dimensions under consideration have different and identical values, and shows the magnitude of the error in estimating the load capacity of the contact of the conjugate surfaces.