Abstract
Owing to the chosen test procedure, tyre models often represent driving on a sandpaper surface,
thereby diminishing the correlation of vehicle simulations with real data from experimental
tests on road surfaces. The discrepancy between tyre measurements obtained on sandpaper
versus, e.g., asphalt, is a result of the differences in the local tread rubber/ground friction
characteristics. Rubber friction, however, is a complex physical phenomenon for which we
have no complete mathematical theory. Thus, this work took an experimental approach to
capture the tyre friction behaviour in detail. Building on the knowledge obtained from the
friction measurements, a method to transfer tyre shear force characteristics from one surface to
another was developed so that high quality data from indoor testing can be scaled to predict
tyre behaviour on real surfaces.
The frictional behaviour of tread rubber sliding on sandpaper and asphalt surfaces was
measured and corresponding friction master curves were created. The master curves were
integrated with a simple brush-type tyre model that was extended with a thermal model to
simulate longitudinal and lateral forces. Using tyre force measurements obtained on a flat-track
machine – which uses a sandpaper surface – the simple brush-model incorporating the
sandpaper master curve was parameterised and validated over a wide range of slip conditions
demonstrating the importance of accurately capturing the friction characteristics. Furthermore,
by swapping the sandpaper friction master curve for the asphalt one, the parameterised model
was shown to accurately predict tyre forces on an asphalt surface by comparing the simulation
results to vehicle-based measurements obtained on the same surface. Hence, the information
contained within the friction master curve is key to transfer tyre shear forces accurately and
reliably from one surface to another.
Moreover, the validated model was used to create artificial slip curves on asphalt and
sandpaper surfaces. Results show that the investigated tyre consistently produces smaller forces
on asphalt than sandpaper; a behaviour that agrees well with published information. Similarly,
the model was able to capture known effects of different slip rates and longitudinal velocities
on tyre temperatures and forces very well.