Abstract

Stresses arising in the belts of radial ply tires, particularly those at the belt edge, are known to be critical to tire durability. Belt edge stresses are commonly calculated using finite element (FE) methods that provide estimates of the levels but do not necessarily give significant insight into the underlying mechanics. In contrast, analytical models can provide physical insight into the mechanisms affecting tire durability but are currently incomplete due to the challenges faced in obtaining closed-form mathematical solutions. Nevertheless, analytical solutions remain important to tire design and development because they can expose the entire design space, show the mathematical relationships between the variables, and allow rapid parameter studies.

This work develops an analytical description of the belt deformations and stresses, particularly at the belt edge. The formulation captures all the first-order mechanics pertinent to finite width, antisymmetric +/− angle belt packages present in radial tires. It incorporates interply shear stresses already recognized in the literature and adds to that a new mechanism controlling the interaction of the plies via a Poisson effect. The analytical model is validated by comparison to FE simulations and is also contrasted with a classical analytical model in the literature. The design space for the belt composite is then explored by parameter variation. Finally, since all these solutions depend on homogenization of the belt layers, the analytical solution is compared to a FE model of discrete cables embedded in rubber to explore the accuracy of the homogenization step.

Abstract

Heat flux is one of a number of parameters, together with pressure, temperature, flow, etc., of interest to tire engineers, engine designers and fluid dynamicists. The ability to measure heat flux magnitude and direction was incorporated into a resistance bridge design fabricated using thin-film techniques to allow fast response. The result is a sensor that does not need the large area and stiff packaging required for the thermopile design, nor does it have a low output, but has nearly as fast response. The development of this sensor offers a new laboratory procedure to establish heat transfer coefficients for different regions of a tire. Testing generated heat transfer coefficients that were within the range reported in the literature, and the numerically predicted temperatures from this data agree well with the experimentally generated values.

Abstract

Much research is being done in the tire industry in order to reduce tire development time as well as cost. One such field of particular importance is that of tread wear, where testing time for indoor tests is measured in days, compared to weeks for outdoor tests. Development time could be further reduced if a “virtual wear test” could be performed using a finite element approach to predict friction energy. The purpose of this study is to investigate the link between indoor tread wear profile and steady-state finite element prediction of friction energy. Blank grooved tires of a common construction with three different tread compounds are run through indoor wear tests of different severities to study severity versus compound interaction. The drive files provide a mix of low-speed cornering maneuvers that simulate city driving as well as highway speed steady-state rolling with acceleration and braking events. One drive file places more emphasis on the city maneuvers while the other places emphasis on the highway driving. Using the steady-state finite element model, a composite friction energy is calculated from friction energy predictions at selected loading conditions taken from the drive file events. The composite friction energy profile is finally compared to laser measurements of the worn tire profile to examine the feasibility of a “virtual wear test.”