Development of deformable tire-pavement interaction: contact stresses and rolling resistance prediction under various driving conditions

Even though continuous improvements have been seen in the analysis of flexible pavements, one of the most important factors is still oversimplified: the tire. This can result in costly decisions, such as poor structural road design, incorrect damage prediction, and inappropriate adoption of maintenance/rehabilitation techniques. Moreover, accurate analysis of the tire-pavement system improves predictions of rolling resistance, fuel consumption, and greenhouse gas emissions. The main contribution of this research lies in the evaluation of tire and pavement as a semi-coupled system, assuming both are deformable bodies, while focusing on contact stresses, rolling resistance, and pavement responses. In addition to load and tire inflation pressure, temperature, speed, and rolling conditions were considered. A series of necessary advancements in the tire model, such as appropriate material characterization (hyperelastic and visco-hyperelastic), accurate geometry, and model validation using experimental measurements, were implemented. The experimental program provided information for validation (contact area, tire deflection, and contact stresses/loads). In addition, based on the experimental measurements, a procedure including analytical expression was proposed to predict the variation of the vertical and transverse contact loads along the contact length. Four tire finite element (FE) models having accurate geometry and material characterization were developed to predict contact stresses and rolling resistance force. First, a hyperelastic tire was used on a rigid surface to predict contact stresses under various rolling and loading conditions. Second, the influence of tire speed and temperature was investigated using a visco-hyperelastic tire rolling on rigid surface. Third, hyperelastic tire on deformable elastic body was used to assess the sensitivity of the contact stresses to the body's stiffness. Fourth, the relevance of surface temperature and tire speed was determined using a hyperelastic tire on a deformable viscoelastic body. Finally, the deformable tire and pavement model were integrated to evaluate critical pavement responses, rolling resistance force, and structure-induced rolling resistance. Vertical and transverse contact loads for all conditions and longitudinal contact stresses at full braking were successfully fitted to analytical expressions, thus easing their potential application in pavement analysis. Based on the hyperelastic tire FE results, the vertical contact stresses were unaffected by traveling speed and rolling condition, and the rolling condition mainly modified the longitudinal contact stresses. After altering the rubber component’s material model to visco-hyperelastic, the contact area increased 6.8% due to temperature and decreased 3.8% due to speed. In addition, longitudinal contact stresses were the most affected by temperature and speed: increments in peak value caused by speed were as high as 17%, and the reduction caused by temperature reached 33.1%. On the other hand, temperature and load were the most relevant variables affecting rolling resistance force, and a relatively small effect of tire inflation pressure and speed was observed. Furthermore, an existing ASTM equation for calculating rolling resistance was modified to include the effect of temperature. When simplifying the pavement structure as an elastically supported linear elastic deformable body, the pavement's elastic modulus affected the longitudinal contact stresses the most. Even though pavement flexibility did not affect the total internal energy of the hyperelastic tire, it modified the value in each tire component up to 5.3%. Finally, the semi-coupled tire-pavement model showed that the rolling resistance force for thin pavements was higher than for thick pavement. In general, the higher the viscous behavior of pavement, the higher the rolling resistance. The critical pavement responses most affected were the vertical strain and vertical shear strain in the asphalt concrete layer, mainly caused by an increment of the transverse contact stresses

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