Towards quantifying horizontal stresses of free-polling pneumatic rubber tyres on road surfaces

Abstract

Multi-dimensional forces (and stresses) inside the contact patch of a freerolling pneumatic rubber tyre generally occur as a direct result of a complex interaction between flexible rubber and a rigid test surface or road surface. These forces, transformed to stresses, were measured in three dimensions (3D) with the Stress-In-Motion (SIM) device on four (4) full-scale truck test tyres with the Heavy Vehicle Simulator (HVS), as well as on a 1/3rd scale test tyre using the Model Mobile Load Simulator (MMLS3). In this paper the focus is on the tangential lateral and tangential longitudinal stresses or, more simply referred to in this paper as horizontal stresses (X, Y - Stresses) within the contact patch. A limited number of tests were also carried out in which the horizontal stresses on a relatively rough-textured (RT) test surface were compared with those on a relatively smooth (S) test surface, representing nominal positive textured road surfaces and nominal smooth (zero texture) road surfaces, respectively. In this study the main characteristics and magnitudes of these X, Y – Stresses are described for the purpose of improving the engineering understanding of these. It is anticipated that better understanding of these stresses will lead to the development of improved and more rational mechanistic design of road surfacings including, for example, chip seals, asphalt overlays and asphalt surfacings with or without rolled-in chips. It is important to note that the findings in this study relate solely to relatively slow-moving, free-rolling pneumatic rubber tyres on these two types of test surfaces. Further it is important to note at this stage that for especially those results from the “smooth” (S) surface testing and are meant to merely act as a primer for future research on the effect of surface texture and tyre tread patterns on contact stresses