Belatti wrote:Here another question to tyre experts regarding tyre temperature.
Can you determine tyre damping coefficients measuring temperature? If not, how does tyre engineers determine it?
Ben is correct, temperature cannot be used to estimate damping coefficient. However, it is possible to estimate tyre damping using a multi-post rig.
The solid lines on
this frequency response function were obtained from measurements of a vehicle being excited by a swept "sine", constant peak velocity input to the tyres. The magnitude represents the gross stiffness of the front tyres of the vehicle (averaged left & right), whilst the phase describes how the gross stiffness is split between "spring" & "damping" (magnitude * cosine(phase) = spring & magnitude * sine(phase) = damping). The response function probably can't be trusted much below 3 Hz.
I have fitted a model spring & damper to the response function over the frequency range 6 - 10 Hz (as it happens). Model parameters are shown in the legends (Ks = spring stiffness (N/mm), Cs = viscous damping coefficent (N/mm/sec), & Cc = hysteretic damping coefficent (N/mm)). As you can see, stiffness varies with frequency (&/or amplitude), and damping is a mixture of both viscous (which can be included in a time-domain model) & hysteretic (which can't). Fortunately, perhaps, the damping component is relatively small compared with the stiffness component. That (in my view) doesn't make it unimportant, because damping is the mechanism that injects heat into tyres on-track.
To provide a "foot-to-earth",
here are two-cycle "snapshots" of load-displacement trajectories (with mean load removed) taken at various times (frequencies) from the same recording. Parameters estimated from the trajectories are shown in the legends. Hopefully, the trajectories will help to understand the response function.
It is probably worth noting that tyre stiffness and damping of tyres varies with almost any parameter you care to think of including pressure, mean load, camber, input amplitude, frequency & temperature. The variation with temperature is interesting because both stiffness & damping decrease with increasing temperature. The reduction in damping with increasing temperature is important, because it explains why race tyres can be "worked" to achieve relatively consistent performance on-track.