Abstract
To overcome rolling resistance (RR) a typical vehicle on average consumes 4152 MJ/119 L of fuel annually as a result of both vehicle and pavement factors. A slight improvement in surface texture arrangement may therefore decrease fuel consumption bringing substantial long-term socio-economic benefits. This aligns with ever-tighter limits on CO2 in the USA (163 g/km until 2025) fostering sustainable construction/exploitation of tires/pavements. This paper describes a multi-scale 3-D numerical methodology to calculate micro-distortional RR and contact indentations of surface aggregates into visco-elastic tread compound accounting for loading, velocity, temperature, and compound properties. It consists of a micro-scale tread block single aggregate model and a macro-scale car tire finite element model, rolling in steady-state mode over a rigid smooth surface. The surface texture is idealized in terms of hemispherical indenters. The micro-distortional RR estimates are based on contact force and energy lost per single stone. The computed contact/normal forces peak significantly due to visco-elastic effects at the beginning of the tire–surface contact phase, followed by a gradually relaxing stress region with a sudden release at the end of the interaction. The contact forces appear to be of a reasonable distribution and magnitude. It is found that micro-distortional RR is higher on a rougher and sparsely packed surface compared with a smoother and more tightly packed case. To determine the total tire-related RR, macro-distortional RR can then be added. The predictions were qualitatively confirmed and adjusted against real bituminous mixes by experimental testing, showing a reasonable agreement.
Highlights
Air pollution, limited finite fossil fuel and increased price of fuel push tyre and pavement researchers to find ways to produce the tyres and pavements as sustainably and cost-effectively as modern technologies allow
The computations of macro-distortional rolling resistance (RR) agreed reasonably with the results found in the literature for the same tyre type (5)
It was found that irrespective of the indenter shape and size, compressive forces undergo three interaction phases: the peak normal force at the end of the indentation/loading phase, followed by a gradual relaxation of the rubber compound until the start of unloading phase where the indenter releases from the tread surface
Summary
Air pollution, limited finite fossil fuel and increased price of fuel push tyre and pavement researchers to find ways to produce the tyres and pavements as sustainably and cost-effectively as modern technologies allow. It has long been known that pavements affect fuel use, just as tyres do, through rolling resistance (RR), and that decreasing RR by 10 % typically saves 1-4 % of fuel (1). The occurrence of macro-distortional energy loss is a function of compressive, tangential (micro-slippage and shear-induced inertia) and wave-induced inertial deformations. Pavement texture indentations into the viscoelastic tread compound induce micro-distortional energy loss. These contact distortions give rise to local compression which includes a visco-elastic and to a smaller extent inertial component that influence the moment balance in the tyre-pavement contact patch, but a true quantitative understanding is still lacking. In the long-term, this methodology could supplement Life-Cycle Assessment (LCA) tools and be applied for optimisation of road texture to minimise RR without sacrificing drainage and skid resistance functionality
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