This dissertation aims at improving the understanding of dry and wet friction between a tire and a road surface to improve traffic safety. The goal was reached through examination of some of the key phenomena, including tire-vehicle interaction, wet rubber friction, asphalt surface roughness, and tire deformation during aquaplaning. Test programs were carried out at various locations across Europe and new analysis techniques were developed. It was found that changes in tire inflation pressure, ambient temperature, and tread depth affect the average slip conditions of the tire during ABS braking due to changes in the force-slip characteristics of the tire. This is because an acceleration-based brake controller adjusts the average slip operating range of the tire accordingly. However, this also leads to a change in the sliding speed at the rubber-road contact, which has an effect on the friction. Further results of the work included a new analysis method for asphalt surface roughness. A wavelength-wise correlation between asphalt surface roughness data and wet friction results of a tire was presented for the first time. Good levels of correlation were found even though only locations on the same asphalt surface type were included. In addition, the surface roughness metrics used in the study were physically meaningful and well in line with modern rubber friction theories. The developed method was also applied to dry lab friction experiments, where a good correlation between surface roughness and rubber friction was found as well. To allow detailed repli-cation of tire-road friction in laboratory experiments, a method was developed for manufactu-ring durable laboratory rubber friction test countersurfaces that replicate the roughness of a target asphalt pavement. It was found, that the most suitable samples were built by using epoxy instead of bitumen as a binder for the asphalt mix, by duplicating the aggregate gradation curve of the target asphalt surface, and by initially sandblasting the surface to remove excess binder. Furthermore, the work presented in this dissertation showed that an optical tire sensor can be used for detecting partial and full aquaplaning from within a tire. This tool allows the quantification of the remaining tire footprint length in the presence of water on any given road surface. The advancements made in the understanding of dry and wet friction of tires during ABS braking will be utilized immediately and developed further. The new methods will be put to use in the tire industry and they provide many interesting opportunities for further research.
|Translated title of the contribution||Henkilöauton renkaan kuiva- ja märkäkitka ABS-jarrutuksen aikana|
|Publication status||Published - 2014|
|MoE publication type||G5 Doctoral dissertation (article)|
- tire-road wet friction
- rubber friction
- traffic safety
- asphalt surface roughness