Defence of dissertation in the field of transport engineering, Yi Xiong, MSc

In-plane Tire Deformation Measurement Using a Multi-Laser Sensor System.

The public examination of the doctoral dissertation of Yi Xiong, M.Sc. (Tech.), will be held on 3 June 2016 at 12.00 at the Aalto University School of Engineering. The title of the dissertation is In-plane Tire Deformation Measurement Using a Multi-Laser Sensor System.

The interactions between tires and roads are basic mechanisms that alter the dynamic states of vehicles. A fundamental understanding of tire-road interactions is clearly demanded in tire design to achieve performance improvements. The emergence of various tire sensors provides an opportunity to make accurate measurement of the physical quantities that are involved in tire-road interactions.

This thesis aims to measure and analyze the in-plane deformation of rolling tires through its direct correlations with the steady-state in-plane tire forces. To date, there is no existing tire sensor that can measure both the tread and carcass deformations. A multi-laser sensor system has therefor been developed in the thesis to measure the in-plane deformation of different tire parts, including the tread, carcass, and inner liner.

Measurements on tread deformation were conducted on both passenger car and truck tires. A non-uniform tread deformation was observed in the measurement and was interpreted as follows: the asymmetric deformation in the longitudinal direction is a direct indicator of the rolling resistance and the non-uniform deformation in the lateral direction reflects the contribution of separate parts to the rolling resistance. The evolution and variation of tread deformations were investigated with different tire types, operational conditions, and tire states. The deformation of the carcass was first analyzed with the flexible ring tire model and then validated through tire sensor measurements. Coupled deformations of the tire carcass in the tangential and radial directions were observed. Indicators based on measured radial carcass deformations are proposed for the estimation of the in-plane tire forces. In addition, the partial inner contours were also measured for truck tires under static conditions for various inflation pressures and loads. The measurements can help tire designers to obtain optimum inner tire contours.

In summary, this thesis shows that the tire sensor can act as a powerful tool for tire research and development. The relations between the in-plane deformation and in-plane tire forces that have been obtained are useful in gaining an understanding of the physical mechanism of observed phenomena, e.g., the rolling resistance, and in the design of basic estimation algorithms, e.g., for the estimation of in-plane tire forces, which are important factors in the development of green and intelligent tires.

Opponent: Professor Schalk Els, University of Pretoria, South Africa

Supervisor: Professor Kari Tammi, Aalto University

Electronic dissertation thesis: http://urn.fi/URN:ISBN:978-952-60-6803-9

Contact information: Yi Xiong, tel. +358 469306316 , yi.xiong@aalto.fi