A Novel Multiscale Numerical Model for Prediction of Texture-Related Impacts on Fuel Consumption
It is estimated that to overcome rolling resistance (RR) a typical vehicle, on average, consumes 4152 MJ/119 L of fuel annually, depending not only on vehicle-related factors but also on pavement-related factors. A slight improvement in surface properties may thus decrease fuel consumption, bringing substantial long-term socioeconomic benefits per capita per country. This aligns with ever-tighter limits on CO2 in the European Union (95 g/km until 2021), fostering sustainable construction and exploitation of tires and pavements. This paper outlines a newly developed multiscale three-dimensional numerical methodology to quantify texture-dependent RR due to indentation of aggregates into viscoelastic tread compound. It consists of a microscale tread block single-aggregate model and a macroscale car tire finite element model, rolling in a steady-state mode over a rigid smooth surface. Microscale interaction rates are deduced from the macroscale model. Tread compound is simulated by application of a time-dependent, linear, viscoelastic model. The microscale simulations enabled quantification of RR induced by an arrangement of surface aggregates. The outlined texture-dependent RR estimates are based on contact force moment around the contact patch center. The computed contact force results show a significant peak of normal force due to viscoelastic and inertia effects at the onset of the tire–surface contact phase, followed by a gradually decreasing/relaxing stress region with a sudden release at the end of the interaction. The contact forces seem to be of a reasonable distribution and magnitude. The proposed approach allows prediction of RR losses due to compressive forces at the microscale. Macro-distortional RR (which is not the subject of this paper) would then have to be added to find the total tire-related RR.ABSTRACT
Close-up of multi-indentation effects as a result of array of stones (not to scale).
Example output of RF1 and RM2 balance pair for derivation of the RR and contact force distribution at the end of time step at 3300 N, 200 kPa, 0.7 coefficient of friction, 100 kph rolling speed (left), and finite element–discretized tire structure (right).
RRF vs Velocity for Coulomb friction model for soft and stiff compound at 3300 N.
Illustration of a microscale model and mesh configuration.
Vertical velocity throughout contact phases adopted from a macroscale model.
Typical compressive contact force distribution for a hemisphere of 5 mm indenting into a tread compound by 0.5 mm.
Microdistortional RR when rolling over 140 hemispheres (tight packing) with 5 mm radius.
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