Numerical and experimental investigation of rubber-road friction including the effect of flash temperature

Tyres are a critical component for vehicle handling, safety and performance. Vehicles must operate at the limit of friction in the case of emergency manoeuvres in both manual and autonomous driving, while in motorsport, using the whole of the available friction envelope provides a distinct competitive advantage. Therefore, better understanding of the physics of rubber-road friction, together with the development of efficient numerical tools, allows researchers and engineers to predict friction on different surfaces more reliably, and, based on these predictions, to make better design decisions in the form of more effective control systems or a more fine-tuned vehicle set-up. Modeling tyre tread sliding friction on a dry road surface, considering interaction at many roughness levels coupled with the effect of extreme local heating, is the aim of this dissertation and a rather challenging task. The work first focuses on the numerical implementation of Persson’s multi-scale, flash temperature friction model. A mathematical formula is developed to reproduce viscoelastic modulus by means of polynomials. The empirical formulation ensures faster computation time, and allows the effect of hypothetical rubber material models to be assessed. An implicit method for flash temperature calculation is developed using a logistic function adaptation, aiming to further reduce computational time and to offer resolution-free solution of the numerically-solved integrals found in the physical model examined herein. i The bounds of friction in the existence of several ill-defined or difficult-to-measure model parameters are obtained through a systematic sensitivity study of Persson’s model. For the evaluation of the predictions of the aforementioned rubber friction model, a test rig apparatus for in-field operation is designed and built. Unlike existing test setups, the proposed one allows measurements at realistically high speeds, on real road surfaces and with measurement of the temperature near the contact. Measured and predicted friction and local temperature showed promising correlation across a range of operational conditions.