What makes tires grip the road on a rainy day?

October 19, 2011

A team of scientists from Italy and Germany has recently developed a model to predict the friction occurring when a rough surface in wet conditions (such as a road on a rainy day) is in sliding contact with a rubber material (such as a car tire tread block) in an article to be published shortly in the Springer journal EPJE¹.

In their study, B.N.J. Persson from the Jülich Research Center in Germany and M. Scaraggi from the Polytechnic of Bari in Italy examined the flow of liquid at the contact between randomly rough surfaces. The contact interface looks like a labyrinth with vertically narrow void channels intersecting randomly. This causes channels to be either filled with water or not when in wet conditions.

For the first time, the authors applied a statistical analytical method to determine the average fluid flow at the interface of rough surfaces. Understanding this flow is important because it is inherently linked to the phenomenon of friction at the contact between the two surfaces.

Previous attempts to understand friction in such conditions used numerical approaches that required large computing power. They were based on calculating real roughness contacts by singling out each individual portion of the overall rough surface under study. Often, heavy approximations in the description of the simulated surface were applied to decrease the computational time.

The model presented in this paper provides theoretical predictions of friction as a function of the surface sliding velocity. It confirms previous experimental friction measurements made with a smooth steel ball sliding on a rough rubbery surface patterned with parallel grooves. The authors' model confirmed the experimental observation of a changing friction level related to a change in the angle between the direction of movement of the ball and the parallel to the grooves.

Potential applications would require that such a model be used to help create surfaces, such as microstructured tyres, which do not lower their grip when it rains.
-end-
Reference
1. Persson BNJ, Scaraggi M (2011). Lubricated sliding dynamics: flow factors and Stribeck curve. European Physical Journal E. 34: 113, DOI 10.1140/epje/i2011-11113-9

The full-text article is available to journalists on request.

Springer

Related Friction Articles from Brightsurf:

Cartilage-Inspired, Lipid-Based and Super Slippery Synthetic Hydrogels
Drawing inspiration from the mechanisms that lubricate the cartilage in our joints over a lifetime of wear, researchers designed extremely slippery hydrogels with self-renewing, lipid-based boundary layers, which result in a near 100-fold reduction in friction and wear over other hydrogels.

Talc and petroleum jelly among the best lubricants for people wearing PPE
Talcum powder, a coconut oil-cocoa butter beeswax mixture, and petroleum jelly provide the best skin protection for long-term PPE use, say scientists.

Trade friction: Adaptiveness of swarms of complex networks
Network analysis revealed power-law properties of core and peripheral networks.

Why is ice so slippery
The answer lies in a film of water that is generated by friction, one that is far thinner than expected and much more viscous than usual water through its resemblance to the 'snow cones' of crushed ice we drink during the summer.

How to control friction in topological insulators
Topological insulators are innovative materials that conduct electricity on the surface, but act as insulators on the inside.

Solving the longstanding mystery of how friction leads to static electricity
A Northwestern University team developed a new model, which shows that rubbing two objects together produces static electricity, or triboelectricity, by bending the tiny protrusions on the surface of materials.

Robot control system for grasping and releasing objects under both dry and wet conditions
A control system for deformable robot-fingertips was developed for grasping and releasing objects.

Identifying the origin of macroscopic friction between clay mineral surfaces
NIMS, the University of Tokyo and Hiroshima University jointly discovered for the first time, through theoretical calculation and experiment that macroscopic frictions occurring between clay mineral surfaces originate from interatomic electrostatic forces between these surfaces.

A new model of ice friction helps scientists understand how glaciers flow
Despite the looming ecological consequences, glacier motion remains poorly understood.

New method automatically computes realistic movement with friction from 3D design
Researchers from Inria, the French National Institute for computer science and applied mathematics, have developed a novel algorithm that computes the shape of the surface at rest, that is, without any external force, and when this shape is deformed under gravity, contact and friction, it precisely matches the shape the user has designed.

Read More: Friction News and Friction Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.