Study On Tire Mechanical Properties Of Turn Slip Condition

The tire is the only component of a vehicle that makes physical contact with the road, the forces and moments generated in the contact patch between the tire and road not only determine to a great extend dynamic performance of a vehicle, such as handling, ride comfort and safety etc., but also have a significant impact on the development of auto parts and chassis control system. Hence, in vehicle virtual designing and development an accurate representation of these forces and moments are essential. During cornering, there is turn slip with a tire except the phenomenon of side slip and camber, especially turning at low velocity with small radius, the mechanical property of turn slip has a significant effect on low speed turning light. With the development of intelligent and electric vehicle, an accurate description of the mechanical characteristics at the contact patch of turn slip is very necessary for all wheel steering. In view of this, this thesis makes a theoretical and experimental attempt to study the steady and transient behavior of turn slip situation, the main research contents include the following aspects.Firstly, the theoretical analysis of the tread deformation which explains the mechanism to produce side force and moment as a result of turning is based on the modeling idea of brush model while turning in steady condition. A simplified theoretical turn slip mode with parabolic and arbitrary pressure distribution is established on the basis of this analysis. The effect of the pressure distribution on the lateral forces and moments is analyzed through this model which describes the changed trend of resultant force and moment with regard to turn slip. A model considering tire width is established according to the simplified tire model, which leads to the peek value of lateral force decrease and the maximum value of aligning moment increase due to the longitudinal force generated on the both sides of the contact patch.Secondly, according to the simplified theoretical model, further considering the complex carcass deformation, a complex discrete simulation model of turn slip is established while the elastic tread on the contact area is divided into finite number of elements, which is used to analyze the effect of carcass deformation on the resultant force and moment under the turn slip condition.Furthermore, according to the mechanical properties expressed by theoretical model, a steady semi-empirical tire model for turn slip is established. Several factors, which include cornering stiffness, sideways shift, peek side force, peek aligning moment and residual torque, are used to analyze the effect of turn slip on the side force and aligning moment by adding them in the Uni Tire semi-empirical tire model of pure side slip respectively. Designing and completing the steady turn slip test, the steady semi-empirical tire model for turn slip can be perfectly fitting the experimental result.Finally, first-order and two-side model are established respectively by studying on the boundary conditions of E functions in the non-steady tire model for turn slip which is established through considering the relaxation effect of tire carcass. Designing and completing the step turning test, the resultant curves simulated by the two models are in good agreement with the experimental results, but the two-side model expresses more accurately than the first-order model.