Development of Comprehensive Experimental, Analytical and, Numerical Methods for Predicting Rubber Friction and Wear under Thermomechanical Conditions

Viscoelastic materials have been used widely in different applications, such as constructing tires, artificial joints, shoe heels, and soles. A study on the different characteristics of viscoelastic materials has always been a matter of interest in order to improve their properties for various applications. In the automotive industry, rubber, as a viscoelastic material, has been used in several subsystems, such as vehicle interior, suspension, steering joints, and tires. The tire and terrain's contact characteristics are among the essential factors for assessing the performance of the tire and the vehicle in general. Friction and tread wear are two of these contact characteristics. Considering the tire's functionality, for most applications, it is desired to have higher friction to have better traction and a lower wear rate to minimize the material loss of the tread. The friction coefficient and the rubber's wear rate depend on various parameters such as rubber material properties, terrain characteristics, temperature (tread and the environment), and the load. To obtain the wear rate and friction of a viscoelastic material, three approaches have been used for this study: Experimental, Analytical, and Numerical. The results obtained using these approaches have been compared and validated. Several test setups have been designed and implemented to study the wear and friction of the rubber experimentally. Also, a new linear friction tester has been designed and manufactured by the author to achieve this project's objectives. The new test setup has several advantages over existing test setups in this field, such as covering a higher range of velocities while maintaining high precision. The designed Linear Friction tester and the modified dynamic friction tester at the CenTiRe laboratory at Virginia Tech were used to measure the rubber's friction and wear for different testing conditions such as different normal loads, different velocities, and various surfaces such asphalt and sandpaper. The data collected by the experiment will later be used for the validation of the developed models. In order to obtain the wear rate of the rubber using the analytical approach, the real contact area and friction of the rubber were calculated using Persson's model. The simulation has created the surface to obtain the friction coefficient and the real contact area. After obtaining the friction coefficient and the real contact area, the rubber's wear rate was calculated using a novel approach by combining the Persson Powdery Rubber Wear model with the Crack Propagation model. The results from the improved model compare well with the results from the original model. For the last step of this project, a Finite Element approach was used for modeling a tread block and round rubber sample. A new semi-empirical model for wear was developed by improving the Archard wear model. The novel approach was implemented to Abaqus by using the Umeshmotion subroutine and adaptive mesh motion (ALE) and subroutine UFric and UFric_Coef in two categories: The Node base method and the Ribbon base method. For finite element modeling, the visco-hyper elastic material model has been used to define the rubber's material properties.