Race, Gender and “Personal” Pedagogy: Emotional Encounters in the Post-Apartheid Classroom

Tyres represent one of the most important and complex parts in a vehicle, providing the only connection between the vehicle and the road and being responsible for the motion transfer within the tire-road interface in order to guarantee their optimal use in all the vehicle operating conditions. The invention and the enhancement of a pneumatic tyre has made it possible to realize fast and comfortable road vehicles. The pneumatic tyre is a crucial component of a vehicle: among its main features as low mass and flexibility, the purpose of a good-designed tyre has become not only to sustain the vehicle weight, properly filtering the road unevennesses, but also to ensure the highest possible grip level in the whole of its operating range. A tyre is an integrated multi-physical system: from only a mechanical point of view, tyres are represented by highly composite multi-layered structures, consisting of a multitude of different materials, covering synthetic and natural rubbers, carbon black, steel cords and bead wire, polyester and nylon fibre, mixed with chemicals, waxes, oils, pigments, silicas and clays. During the tyre motion, due to the multi-material interaction and to the viscoelastic rubber matrix compositions, the dynamic characteristics of a tyre may vary considerably, even considering to modify only one parameter among inner pressure, track and ambient temperatures, pavement surface, etc. . Taking into account of the tyre temperature influence upon the tyre characteristics, both of the structural part expressed in terms of interaction stiffnesses and the compound viscoelastic behaviour, function of temperature, sliding speed and road granularity, the approach to a tyre dynamic analysis and therefore to a correct modelling of both transient and steady-state conditions can only be multi-physical. Rubber friction is a topic of huge practical importance, e.g. for tyres. In the latter case, rubber-asphalt friction is influenced by a great number of variables and parameters, particularly hard to control and to measure, as for example macro and micro roughness range of bodies in contact, pressure distribution arising at their interface, materials stiffness characteristics, and their temperature-frequencies dependence, relative motion direction and speed. Another variable to take into account is time. The tyre structure and compound characteristics inevitably change within the life-cycle because of ageing, leading to a modification of cornering characteristics and to a decrease of the level of available grip. These degradation time and ambient dependent phenomena have to be taken into account within the vehicle control logics in order to optimize both safety and performance targets. Tyre model requirements for vehicle dynamics, indeed, have to accurately predict the forces arising at the tyre-road interface to be transmitted to the wheel spindle, remaining easily to characterize from the experimental point of view, requiring low computational efforts and being widely applicable. Since wear affects the tyre thermo-dynamic characteristics, it is absolutely crucial to improve the understanding and to scrutinize all the aspects of ageing. This project is focused on the analysis related to the behaviour of high performance tyres in order to comprehend which physical phenomena are responsible for the wear tread abrasive and compound degradation terms.