Finite Element Analysis Of Temperature Distribution In Steady Rolling Tires

Due to the important influences of tire temperature on tire performance, more attention is focused on tire temperature analysis. Although the study on tire temperature field has lasted for several decades, no efficient analysis method has been established because of the complexities. Now it's still an urgent task to develop analysis method of tire temperature in the science and engineering fields. Aimed to establish a systematic thermo-mechanical solving strategy and analysis method of tire steady temperature field, a series of studies are carried out in this dissertation, especially about the characterization and determination of internal heat sources and thermal boundary conditions for rolling tires. The influences of operating conditions and structure characteristics on tire temperature are also investigated here.A new method for uniaxial tension test of polyester cord, named Minus-Test method, is presented. The experimental results indicate that the end-effect which is obvious in conventional test can be eliminated by this method, and then more reliable tensile modulus of polyester cord will be obtained. The thermal conductivities of tire rubbers are measured. The rubber-steel cord composite structures are treated as homogeneous orthotropic material, and the equivalent orthotropic conductivities are calculated by using the conductivities and volume fractions of the components.The experimental study on the viscoelastic properties of tire rubbers by means of Dynamic Mechanical Thermal Analyzer (DMTA) indicates that the viscoelastic parameters are strongly dependent on dynamic strain and temperature. The ability of the modified Kraus model to characterize the dynamic strain dependence of tire rubber under different temperatures is evaluated by using the experimental results, and then a new model, named non-central-symmetric locally linearized model, is presented. The model takes account of the dynamic strain dependence and temperature dependence of storage modulus and loss modulus explicitly. The fitting results indicate that the model is able to characterize the dynamic strain dependence and temperature dependence of the viscoelastic parameters of tire rubbers accurately. The model also takes account of the effect of static strain implicitly. Based on this model, an equivalent strain formula is deduced to calculate the energy dissipation under three-dimensional harmonic load. Finally, a complete algorithm to calculate the internal heat sources for rolling tires is proposed, and corresponding calculating procedure, named DECAL, is also given.A universal convective heat transfer relationship for outer surface of rolling tires is presented by extending the convective relationship of smooth convex surface of revolution. Based on Mikic model, the formula for calculating the thermal contact conductance between tire tread and road is proposed. Then an equivalent convective heat transfer coefficient for tread surface is given by averaging the convective effect and conductive effect along the tire circumference. On the other hand, a trial and error method is presented to determine the parameters in convective relationship.A systematic thermo-mechanical solving strategy and analysis method of tire steady temperature field is established based on two-way iterative approach. The solving strategy and analysis method is evaluated by using varied means including the combination of analysis and local experiment. It indicates that the solving strategy and analysis method is efficient. It also indicates that the convective heat transfer relationship of outer surface of rolling tires and the approach to determine the relevant parameters are efficient, reliable and universal to some extend.Based on the above analysis method, the influences of operating conditions and structure characteristics on tire temperature are discussed. Under free rolling condition, the tire temperature increases with the increase of speed, load and ambient temperature, but decreases with the increase of inflation pressure. The temperature distribution in the tire doesn't change while varying these parameters. The maximum temperature always exists in tire shoulder. Under inclined rolling condition, the temperature in the inclined side increases with the increase of camber angle, but the temperature in another side decreases. The temperature in crown decreases slightly. With the decrease of aspect ratio, the temperature in tire shoulder and crown decreases obviously, and the temperature in tire side and bead hardly change. With the increase of belt cord angle, the temperature in tire shoulder increases first and then decreases, with a maximum value near 22°. The temperature in tire crown varies non-monotonously, like an inclined"S"shape. The temperature in tire bead changes a little at first, and then increases while the belt cord angle is greater than 22°. The temperature in tire side hardly changes. With respect to the tire with longitudinal grooves, the temperature in tire crown and shoulder decreases obviously, but the temperature in tire side and bead changes slightly.