A simple numerical procedure to calculate the input data of Greenwood-Williamson model of asperity contact for actual engineering surfaces

摘要

Greenwood-Williamson model for asperity contact has been extensively used for prediction of tribological behaviour. However, characterization of the necessary input data, summit asperity height deviation (σ_S), mean radius (β) and density (η) are not available from commercial roughness measuring equipment. A relatively simple numerical method is proposed to calculate the asperities data for actual surfaces. Summits were considered to be the local maximum points above the surface mean line and calculation of the standard deviation, mean radius and density of the summits are directly numerical performed. The method was applied for new and worn ICE cylinder bores. The product σ_S.β.η was found to be between 0.01 to 0.05, lower than the usually accepted range 0.03 to 0.05. The lowest values were found on plateau honing finish, after 15 h test. For all cases, the calculated summit mean radius was found to be lower than previous published values. Some preliminary asperity pressures calculation with the found parameters, suggest that the usual film parameter on the Stribeck curve can lead to wrong conclusions about the tribological severity. Some discussion about the expected asperity pressures of new and worn ICE cylinder bores are also presented.