In this work thermal and transient effects on non-conformal lubricated contacts are investigated through experimental analyses. Experiments between a ball and a plane surface of a disc are described. Friction coefficients and film thicknesses are measured (the film thickness only for the glass-on-steel-contact). A paraffin base mineral oil is used as a lubricant. First experiments are carried out under steady-state conditions. To include effects due to different thermal properties of contacting materials, a steel-on-steel and a glass-on-steel contact with different slide-to-roll-ratios are tested. If the contacting materials have different thermal properties, as in the case of a glass-on-steel contact, thermal effects like the temperature viscosity wedge action could clearly be shown. It is found that the friction coefficients are influenced by the slide-to-roll-ratio and the thermal properties of the contacting materials. Under transient conditions the entraining velocity is varied with a sinusoidal law. Squeeze effects explain “loops” of friction- and film thickness found also in previous works. The formation of friction loops is related to the measured film thickness differences. However, also under non-steady-state conditions thermal effects like the temperature viscosity wedge action influence the friction coefficients.
Experimental investigation of Transient and Thermal Effects on Lubricated non-conformal Contacts
BASSANI, ROBERTO;CIULLI, ENRICO;
2007-01-01
Abstract
In this work thermal and transient effects on non-conformal lubricated contacts are investigated through experimental analyses. Experiments between a ball and a plane surface of a disc are described. Friction coefficients and film thicknesses are measured (the film thickness only for the glass-on-steel-contact). A paraffin base mineral oil is used as a lubricant. First experiments are carried out under steady-state conditions. To include effects due to different thermal properties of contacting materials, a steel-on-steel and a glass-on-steel contact with different slide-to-roll-ratios are tested. If the contacting materials have different thermal properties, as in the case of a glass-on-steel contact, thermal effects like the temperature viscosity wedge action could clearly be shown. It is found that the friction coefficients are influenced by the slide-to-roll-ratio and the thermal properties of the contacting materials. Under transient conditions the entraining velocity is varied with a sinusoidal law. Squeeze effects explain “loops” of friction- and film thickness found also in previous works. The formation of friction loops is related to the measured film thickness differences. However, also under non-steady-state conditions thermal effects like the temperature viscosity wedge action influence the friction coefficients.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
