Observations of dry particles behaviour at the tyre/road interface

Abstract

Previous studies highlighted that friction value measured on real road surface textures covered by particles depends on particle sizes. This paper focuses on identification of particles behaviours at the tyre/road interface in the presence of particles. Identification is made by visual observations through high-speed camera, focus-variation microscopy and Scanning Electron Microscopy on the contaminated surface as scratch analysis on the surface. Two particle types were collected into samples picked next to roads. They are composed of clay and quartz which have different behaviours at the interface and affect the friction. Clay has a lasting effect due to its adhesive behaviour. Quartz has a scratching and rolling behaviour and is quickly ejected to the contact area due to a pinching effect.

Modeling of the surface coverage and application to the calculation of friction on surfaces contaminated by particles

“…With fractions 50-80µm and 80-100µm, the cloud of particles is less dense. After Changarnier and coauthors [17], as quartz (predominant element in the composition of the particles) and aluminum are harder than rubber, the slider is the most deformed in the interaction slider / particles / substrate. Just as the particles leave the interface between the slider and the substrate, the slider recovers its initial geometry and there is a pinching effect that throws the particles up a few millimeters behind the slider; once in the air, the particles either settle on the substrate or are entrained by the air flow and leave the substrate.…”

“…Chemical analysis (detailed in [17]) shows that the particles are mainly composed of Si (68%) which is a hard mineral. The other elements are: Na (3.5%), K (4%) and Mg (1.5%) whose presence can be explained by industrial sites located next to the Cheviré bridge; metallic components such as Al (12%) and Fe (6%) whose presence can be attributed to the wear of braking system and tires; and other elements in insignificant amounts [17]. It was shown in [2] that the chemical composition of the particles extracted from sediments is similar to that of particles collected directly from the road surface.…”

“…1:2.8 DG MACRO) was then used to record (6000 frames per second) a close-up view of the contact (30mm in the center part of the sliding distance -126mmof the pad). Calibration tests [17] showed that the size of a pixel is 12μm  12μm. This information enables to measure the distance travelled by particles and their speed Images extracted from a video recorded by the GoPro camera are presented in Figure 6.…”

“…To transpose the developed model to road surfaces, there is a need to not only test actual road surfaces but also evaluate the effect of other factors such as the composition of the particles. In the present paper, particles are composed mainly of quartz whose grains have a rolling / sliding behavior (and scratching as well depending on the radius of curvature of the grains [17]). It has been found in a separate study [17] that the adhesive behavior of clay induces a bonding of the particles to the substrate and, as a matter of fact, has a lasting effect on friction.…”

Sand as a friction coefficient improver on asphalt ice layers

“…8 In addition, depending on the size and type of particles, the characteristics and the rheological behaviour of these sand films and friction mechanisms like rolling, scratching and crushing were observed. 12 Besides, some research works have identified the factors affecting friction coefficient which are young ice or old ice, film water layer, ice temperature, sand grain size, grain morphology, grain distribution, etc.…”