In-situ observation of the friction/water depth relationship
CEREZO ; BOUTELDJA ; PREVOST ; DO
Type de document
COMMUNICATION PAR AFFICHE (AFF)
Langue
anglais
Auteur
CEREZO ; BOUTELDJA ; PREVOST ; DO
Résumé / Abstract
Accidents are more likely on just wet roads than on flooded ones. Indeed, slight road wetness entails a decrease of tire/road friction, which can have dramatic consequences. Thus, accidents are mainly due to an inadequate vehicle speed linked to a bad estimation of real friction available with thin water film on pavement surfaces. Research has been conducted in laboratory to better understand the thin film traction process. Now, additional works are needed to investigate in-situ water/friction relationship and influence of factors like surface texture or test speed.
This paper deals with in-situ observation of water/friction relationship and the influence of texture on wet friction. The study is based on experimental approach and friction tests are realized on Ifsttar test tracks on classic pavement surfaces and specific painted surfaces. Thus, the Longitudinal Friction Coefficient with a blocked wheel is measured for water depth ranging from 0.10 to 1.25 mm.
First, these experimentations allow obtaining inverse S-shape Stribeck curve for surfaces presenting a high level of microtexture, whereas classical exponential functions are measured the rest of the time. Then, classic results such as the fact that increasing macrotexture limits the decrease of friction with water depth are refund. Other more original results such as existence of boundary lubrication regime on pavements presenting a high level of microtexture are obtained. Moreover, elasto-hydrodynamic lubrication regime is observable on surfaces with low macrotexture. Lastly, a critical water depth WDcrit is defined as the transition between boundary and mixed lubrication regime. Influence of texture and speed parameters on WDcrit is studied. WDcrit ranges from 0.10 to 0.45 mm. WDcrit values seem to be higher at 90 km/h than at 60 km/h. It seems that WDcrit highly increases for surfaces presenting high microtexture/low macrotexture levels, as if microtexture asperities compensate the lack of drainability of pavement surfaces.
