A MECHANICAL MODEL FOR THE PREDICTION OF THE TIRE/ROAD FRICTION
The viscoelastic deformation of tire rubber by road surface asperities was modeled by the rolling contact between a Kelvin solid and a surface motif, which is the part of surface profiles between two peaks. Stress and strain calculations showed that contact losses might occur locally, depending on the rolling speed, the viscoelastic properties of the Kelvin solid and the geometry of the motif. Mean vertical and horizontal forces were calculated, from which a coefficient of friction was derived. The model was successfully coupled with a profile analysis method to predict tire/road friction at low speed from road surface microtexture. The contribution of various texture scales to friction was emphasized. For the covering abstract see ITRD E118503.
Friction of Different Surface Layer of Pavements in Contact With a Rubber
We analyse the physical mechanisms taking place in unlubricated friction between surface layer of pavements and a piece of rubber at low sliding speeds < 200 mm/s. This analysis is based on extensive experimental investigations of the load and velocity dependences of dynamic friction forces. The dynamical behaviour caused by dry friction is studied for a rubber-block system pulled with constant velocity over a surface layer of pavements. The dynamical consequences of a general type of phenomenological friction law (stick-time dependent static friction, velocity-dependent kinetic friction) are investigated. Three types of motion are possible: stick-slip motion, continuous sliding, and oscillations without sticking events. In the last case, we propose values of friction coefficient of different surface layer of pavements.© 2005 ASME
High speed rolling friction on viscoelastic substrates: The determination of the hysteretic damping factor
Abstract High speed rolling friction phenomena on rubber substrate materials were investigated at speeds of up to 73 km h −1 under various loads and temperatures. Tests were conducted on two tyre tread rubber substrates (filled tread rubber and unfilled tread rubber equivalent) using rolling cylinders under approximately plane stress conditions. Rolling friction measurements were converted to a corresponding damping factor; this is a quantitative measure of the energy loss. High speed hydrodynamic pressure drag effects on the unfilled rubber substrate are considered, in addition to the viscoelastic contribution, to be responsible for hysteresis losses. The filled rubber substrate showed a departure from viscoelastic hysteresis behaviour; this is attributed to the temporary breakdown of filler particle agglomerates at elevated temperatures. The characteristic frequency of deformation at a single rolling speed and cylinder size is considered to be independent of the length of contact.