Elastomere Friction - The Best Friend international

Experimental and Theoretical Investigations 229
Fig. 6 Time constant of the tangential force ˇ FT (t) after a slippage step Sstart →
Starget. The start level Sstart of the slippage step is represented on the abscissa, the
target value Starget is regarded as a parameter.
by an arrow. Aside from a few outliers the curves run nearly parallely. The
difference between the curves with the start slippage values Sstart = 10%
and Sstart = 50% amounts to approximately Δτ ≈ 0.3 s. The average slope
of the characteristics is mτ, target ≈−2 s. Slippage steps down to a level
of Starget = 10% result in a time constant between τ50, 10 ≈ 1.15 s and
τ20, 10 ≈ 1.45 s. The lowest time constant within the observed measurement
range originates from the step up to the target level Starget = 70%, the values
amount to τ50, 70 ≈ 0.05 s and τ10, 70 ≈ 0.4 s.
To get a more clear image of the dependency on the start value of the
slippage step, Figure 6 shows of time constant τ plotted versus Sstart, here
the target value Starget serves as a parameter.
The already mentioned weak decreasing dependency of the time constant
τ on the start level Sstart can be obviously seen in Figure 6. Within the
observed measurement range this tendency can be regarded as linear. The
accordant slope value is mτ, start ≈−0.8 s. This is clearly below the slope
value mτ,target ≈−2 s describing the dependency on the target value Starget,
which can be seen in Figure 5.
3 Rolling Contact Model
In this section a mechanical model will be shown, which represents the
global dynamics of the rolling contact observed in the measurements, see Sections
2.2 and 2.3. Furthermore it gives insights into the local friction behavior,