Effects of asperity shape and summit height distributions on friction and wear characteristics

Assuming that hard asperities are conical or hemispherical, the total cross -sectional areas SI, plowed by them and mean friction coefficient were comp ared theoretically for the normal distributions of three dimensional summit and two dimensional surface heights on a profile curve. Moreover, when abr asive grains are conical, the ratio cu, of volume removed as a debris to vo lume of grooves plowed by abrasive grains was obtained experimentally for v arious metals against an abrasive paper. The wear rate of metals was also e stimated by using the mean cross-sectional areas of micro-grooves on worn s urfaces and the ac, values. As a result, the following facts were found, (I ) The total cross-sectional areas Sp plowed by hard conical asperities with various slopes are independent of the both distributions of three dimensio nal summit heights and two dimensional surface heights on a profile curve. (2) The SI, value plowed by hard conical or hemispherical asperities with t he transferred wear particles of various lengths are smaller than those plo wed by the asperities without transferred particles and the friction coeffi cient for the hemispherical asperities are smaller than those for the conic al ones except for high contact pressure. (3) The longer the lengths of har d hemispherical asperities in the sliding direction, the smaller the SI, va lue becomes. This trend can be observed during running-in of abrasive wear and so on. (4) The specific wear rate for abrasive wear of various metals c an be estimated from the relationship between cub values and tan theta/p(f) (tan theta; mean slope of asperities, p(f); mean flow pressure of metal) a nd a, values and that between tan theta/p(f) and Sp/n values on the basis o f a hard conical asperity. (C) 1999 Elsevier Science S.A. All rights reserv ed.