The effect of transverse roughness on the pressures and stresses in EHL line contacts

An experimental method of checking the pressures and stresses predicted by EHL theory for rough contacts is presented. Essentially it involves running a soft, rough disc against a harder counter face for a limited period. This running modifies the original surface and if the modified profile is measured and used as the input to an EHL solver theoretical predictions of pressure and stress may be obtained. After allowing for the build up of residual stress, the maximum calculated stress should be equal to the yield strength of the soft disc material. This approach is applied in the present paper to a rolling line contact with transverse roughness run at constant load but decreasing speed. The low speed results show close agreement between the calculated stresses and the yield strength of the material, suggesting that the EHL theory is accurate under these conditions. At higher speeds the agreement is less satisfactory indicating that the EHL analysis is inadequate. It is suggested the dynamic forces produced by the surface waviness need to be considered if accurate results are to be obtained.