On the Effect of Longitudinal Vibrations on Dry Friction: Modelling Aspects and Experimental Investigations

High-frequency vibrations have been shown to smooth the effective characteristics of dry friction and overcome undesired effects such as friction-induced vibrations. Although the effect of vibrational smoothing is subject of many theoretical studies and has been applied successfully to metal forming processes, only few publications are known presenting advanced modelling approaches or related experimental results. Using classical Coulomb friction, the agreement between experimental results and related calculations appears not to be sufficient. Therefore, the effect of contact compliance on vibrational smoothing has been discussed recently. Considering a class of dynamic friction models, the effect of high-frequency excitation on a simple 1-DoF friction oscillator has been investigated. The corresponding results show a mostly quantitative impact of compliant contacts on vibrational smoothing, while the qualitative results remain unchanged. Within this contribution, the recent analysis is extended using an elasto-plastic friction model and accounting for stiction and the transition to sliding motion. The corresponding results show similar characteristics, but contain new qualitative aspects and may thus serve as an explanation approach for insufficient agreement between experimental results and classical modelling. In order to validate the advanced approach, an experimental set-up is presented. Measurements are performed showing the hysteretic behaviour of the contact as well as the reduction of average friction forces in presence of vibrational excitation. A comparison of experimental and previously obtained numerical results yields good agreement and thus more insight into relevant aspects of vibrational smoothing.