Study Of Tread Rubber Friction Mechanism And Tire Cornering Properties Under Complex Conditions

Tire characteristics have significant effects on the driving stability, ride comfort, and driving safety of vehicle. While friction characteristics between tire and road surface are the key to study the mechanical properties of tire, because the changes of mechanical properties of tire are closely related to the friction characteristics under complex environmental conditions and driving conditions, such as driving speed, road surface, ambient temperature, etc. The research on the rubber friction characteristics is a cross discipline, including materials science, road surface features statistics, contact theory, engineering mechanics, and so on, which makes it a difficult problem and an urgent issue to be solved in the tire industry and academic field.However, due to a number of complex factors, limitation of objective tire test conditions, the research and modeling of mechanical properties of tire under complex environmental conditions and driving conditions are imperfect. Hence, it is important to study on the friction mechanism of tread rubber and build the tire model under complex conditions with high expression accuracy and the physical meaning. The main contributions of this dissertation are listed as follows.Firstly, the rubber friction mechanism is discussed and a micro analytical friction model of tread rubber is developed. Based on energy conservation in rubber deformation and the mechanism of molecular surface energy, a simplified friction model is built and the relationship between rubber hysteresis, viscous friction and its composite modulus is studied. Then, combined with Persson contact theory, a general friction model for micro analysis of tread rubber is established, including the rubber elasticity, viscoelasticity, time temperature conversion, and other physical parameters, as well as the road surface power spectrum, fractal theory, and other factors. Finally, related experiments are carried out, and the results show that the parameters in this model have definite physical meaning, so it is easy to grasp the macro law of the mechanical properties of rubber friction.Secondly, a theoretical tire model for cornering properties under complex conditions is established considering the rubber friction characteristics and the effect of carcass compliance. The key point is to discuss the influence of the distribution of tread complex stress and strain, slip velocity, friction coefficient at the tread-road interface, and analyze its impact on tire mechanics differences under different speed and road conditions, etc. According to the deformation mechanism of the tire brush, a theoretical model was established, and mechanical properties of tire are analyzed in detail. Then the distribution of tread complex stress and strain, slip velocity, friction coefficient and so on at the tread-road interface is discussed and the phenomenon of tire mechanical properties under several typical complex conditions are explained and analyzed. The results show that the theoretical model can express the influences of different speed, road surface and ice surface on the key mechanical characteristics of tire.Furthermore, based on the theoretical model and combined with the experimental results, a practical Uni Tire semi-empirical tire model under complex conditions is established. On the basis of the theoretical model considering general friction distribution, the concept of equivalent pressure distribution and average friction coefficient are introduced; the results prove that the model considering general friction distribution has the same non-dimensional form as the model with constant friction coefficient. What’s more, the model also satisfies higher order boundary conditions, which guarantees the correctness of the theoretical framework of Uni Tire semi-empirical model. Then a practical Uni Tire semi-empirical tire model considering rubber friction under complex conditions is established and verified by the test data. The result shows that this model has good expression ability and precision.Finally, the prediction ability of Uni Tire under complex conditions is analyzed and some key technologies of tire test equipment are studied. The prediction of tire forces under complex conditions is carried out from two aspects: the conditions easily and difficulty to be obtained. The results show that the Uni Tire semi empirical model under complex conditions based on the theoretical model has good mechanical ductility, predictive ability, and less test effort, at the same time, the prediction accuracy is still high. In addition, it is a way to obtain the prediction of the mechanical properties of the tire under some complex considers, which are difficult to obtain, but often encountered, so it has important engineering significance. Secondly, the research of the domestic and foreign tire test benchs is analyzed. The motion coupling phenomenon of “A” frame structure tire test rig is described, and a new six-degree-freedom structure is proposed which has high attitude control accuracy but no motion coupling. The mechanism of steel strip active and passive deviation and the relevant laws are studied to achieve the desired results of the strip in the middle. The relevant equations are applied to the actual control of high-speed tire test rig, and good control results are obtained. In a word, exploratory studies of some technologies of tire test rig are conducted, which provides test platform for obtaining more accurate tire mechanical properties.The main innovations of this dissertation include:(1) The microscopic mechanism of rubber hysteresis and viscous dynamic friction is analyzed in depth, and an analytical friction model of tread rubber is established which can describe complex factors.(2) A theoretical tire model for cornering properties under complex conditions is established, which consideris the rubber friction characteristics and the effect of carcass compliance, and expresses the influences of different speed and road surface on the key mechanical characteristics of tire.(3) A practical Uni Tire semi-empirical tire model under complex conditions is established, which has good expression power, precision and prediction ability. This model considering general friction distribution has the same non-dimensional form and also satisfies higher order boundary conditions.