Defence of dissertation in the field of vehicle engineering, Mona Mahboob Kanafi, M.Sc. (Eng.)
How Road’s Roughness Affect Tyre/Road Friction?
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The public examination of the doctoral dissertation of Mona Mahboob Kanafi, M.Sc. (Eng.), will be held on 7 April 2017 at 12.00 at the Aalto University School of Engineering. The title of the dissertation is Rocky road – surface roughness impacts on rubber friction. Field of the dissertation engineering design and production, vehicle engineering, tyre/road friction.
Opponent: Professor Ion Marius Sivebæk, Technical University of Denmark (DTU), Denmark
Supervisor: Professor Kari Tammi, Aalto University, Finland
Advisor: D.Sc. Ari Tuononen, Aalto University, Finland
Electronic thesis: http://urn.fi/URN:ISBN:978-952-60-7332-3
Contact information: of Mona Mahboob Kanafi, mona.mahboobkanafi@aalto.fi
The research on tyre/road friction is of huge importance due to its direct link to the road safety. The roughness of the road surface plays a major role in the tyre/road friction. In this dissertation, laboratory and field experiments along with the comparison of the experiments with theory predictions were utilised to advance the current understanding about surface roughness impacts on tyre rubber friction.
By monitoring the friction and the roughness of Finnish roads for nine months, it was shown that traditional surface roughness characterisations cannot narrate the actual link that exists between road roughness and friction. However, when surface roughness was characterised at multi-scale and only on the top portion of the road surface profile (where tyre meets the road), a strong correlation was achieved between friction and road roughness. Therefore, road surface roughness analysis for tyre/road friction must be carried out only on the relevant portion of the surface roughness profile.
A big challenge in rubber friction experiments is the reproducibility of the measurements itself, since the surface roughness of the roads are constantly changing during the sliding friction experiments. In this research work, for the first time, the application of 3D printing technology in tyre/road friction studies was introduced. This technology is a powerful tool for creating customised and reproducible surfaces for controlled laboratory rubber friction experiments. With the aid of a high resolution 3D-printer, hard polymer blocks were printed that looked like the surface of road surfaces. By controlling the surface roughness of these prints, polymer blocks with different stone size (macro-roughness) on their surfaces were produced.
Laboratory tyre rubber friction experiments on these surfaces, for the first time, have shown that increasing the size of the stones tend to decrease tyre rubber friction. The results open the path for controlled studies about the surface roughness impacts on tyre rubber friction. In the future, it is desirable that an optimum road surface roughness would be achieved for tyre/road friction, rolling resistance, noise, wear, etc.
Väitöskirjan verkko-osoite: http://urn.fi/URN:ISBN:978-952-60-7332-3
Väittelijän yhteystiedot: Mona Mahboob Kanafi, mona.mahboobkanafi@aalto.fi