Dynamic Tire Response and the Effect on Roughness-Induced Vehicle Energy Dissipation

Vehicle dynamics models rely on accurate inputs to quantify dynamic loading and energy dissipation to design pavement structures and assess the environmental impacts. The tire’s response to loading is one of the inputs used in these models, and it is typically represented by a linear spring and dashpot connected in parallel. However, tires are made of rubber, a viscoelastic material, so their load response depends on the excitation frequency. Yet, existing models do not incorporate this parameter. This thesis will first examine the load response and its variation with excitation frequency of two truck tires – a dual tire assembly (275/80 R22.5) and a wide-base tire (445/50 R22.5) – in the laboratory. The experimental parameters included load, amplitude, tire inflation pressure, and excitation frequency. A regression analysis based on the experimental results was completed to propose simple equations to calculate the frequency-dependent stiffness and damping. Additionally, the conventional Quarter Car Model (QCM) was modified to include the dynamic parameters observed in the experimental testing. The model was verified using results in the literature. Finally, the modified QCM and values obtained from testing were used to calculate roughness-induced vehicle energy dissipation. The dimensionless energy dissipation of the two truck tires was compared. Experimental testing showed that at constant amplitudes, the damping decreased exponentially with an increase in frequency, while dynamic stiffness exhibited a peak of around 3.14 rad/sec. The experimental testing concludes that dynamic properties vary with excitation frequency and must be considered in energy dissipation models. Through the modified QCM, it was found that the dimensionless dissipation for the WBT is 0.63 to 0.90 times that of the DTA for the same tire pressure and applied load of 689 kPa and 40 kN, respectively