In this paper,a semi-analytical calculation model for the coefficient of friction(COF)of single spherical protrusions is presented.It allows the prediction of the deformative friction part(μ_(def))and adhesive friction part(μ_(def))of the friction pairings steel|polyethylene with ultra-high molecular weight(PE-UHMW)and polyoxymethylene(POM)|PE-UHMW.The experimental studies included unlubricated friction tests,which served to determine the total COF(μ_(def)),as well as tests being lubricated with silicone oil,from whichμ_(def)is obtained.Based on the verification tests,it could be shown that both states of lubrication result in the same deformation and that the relationship between the rear angle(w)andμ_(def)postulated in the calculation model is valid.Therefore,friction tests with segmented spheres were carried out,which allow a specific variation of thew.It can be concluded that for both pairings theμ_(def)is generally of minor significance(approx.1/3μ_(tot))and the influence of theμ_(adh)predominates(approx.2/3μ_(tot))the friction process.Furthermore themtot decreases with increasing contact pressure especially in the low pressure range and depends on the form of motion(continuous and discontinuous).
André BERGMANNJens SUMPFNiels DALLINGERMartin MONEKEMarkus GOLDER
