Tire-ice model development for the simulation of rubber compounds effect on tire performance

The material properties of the rubber compounds, which are highly dependent on temperature, have a vital role in the tire behavior. A comprehensive study on the effect of the rubber properties on tire performance, for different temperatures, as well as different road conditions is required to adequately predict the performance of tires on ice.In this study, a theoretical model has been developed for the tire-ice interaction. The temperature changes obtained from the model are used to calculate the height of the water film created by the heat generated due to the friction force. Next, the viscous friction coefficient at the contact patch is obtained. By using the thermal balance equation at the contact patch, the dry friction is obtained. Knowing the friction coefficients for the dry and wet regions, the equivalent friction coefficient is calculated. The model has been validated using experimental results for three similar tires with different rubber compounds properties. The model developed can be used to predict the temperature changes at the contact patch, the tire friction force, the areas of wet and dry regions, the height of the water film for different ice temperatures, different normal load, etc.     

Sensitivity analysis and Kriging based models for robust stability analysis of brake systems

This paper presents a global strategy for the prediction of brake squeal. This approach is based on the global sensitivity analysis combined with Kriging modeling. The main aim is to assess the pertinence of using this strategy to build suitable and efficient instability predictors that can be potentially associated with numerical optimization schemes and/or robustness analysis algorithms for a robust design of brake systems. Through the use of a simplified brake system, the global sensitivity analysis is, firstly, shown to be essential for obtaining great insight on how design parameters influence individually and/or collectively the stability behavior. The latter is characterized by the distance of all the systems eigenvalues from the imaginary axis. It is shown that the so-called Sobol indices help for an objective quantification of the importance of taking parameter uncertainty into account in the whole design process. Based on these conclusions, Kriging modeling is, secondly, proposed to robustly predict friction induced instabilities. Its efficiency is then demonstrated. Consequently, the global sensitivity analysis and Kriging modeling give a very promising strategy helping for squeal prediction and, more generally, for optimal and robust design of brake systems.