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Analysis of local friction between rubber and dry and wet surfaces

Analysis of local friction between rubber and dry and wet surfaces

Led by:  P. Wriggers, R. A. Sauer
Team:  J. Dobberstein
Year:  2009
Is Finished:  yes

A prediction of the friction behavior of a rubber compound sliding over a road surface is an important topic in tire industry.
The high coefficient of friction for a rubber material sliding on a rough surface is mainly attributed to dissipative energy losses inside the material commonly referred to as hysteretic friction. With appropriate material and surface descriptions it is in theory possible to calculate this hysteretic friction.
However a direct finite element computation of the problem is not possible, as a real road surface has a roughness over a wide range of length scales.

To overcome this problem a multiscale approach by Wriggers and Reinelt is adopted, which uses the fact that the surface roughness can be described as self-affine fractal [1].
The idea is to approximate the height correlation function of the self affine road track by a superposition of sinusoidal surfaces on different length scales. The calculations are performed for each scale separately. The scale transition is done by applying the averaged coefficient of friction of one scale onto the surface of the next larger scale.

Essential for the calculations is a proper material model. To describe the rubber material a nonlinear viscoelastic material model for finite deformations is chosen. The viscoelastic material parameters are determined from a fit of the models solution to measurements of the storage and the loss moduli using an evolutionary algorithm.

In order to validate the simulations measurements, where a single tread block was slid over a road surface, were performed by the Institute of Dynamics and Vibration Research (IDS) of Leibniz Universität Hannover.

[1] P. Wriggers and J. Reinelt: Multi-scale approach for frictional contact of elastomers on rough  rigid surfaces. Comput. Methods Appl. Mech. Engrg. 198, pp. 1996-2008, 2009.