A laboratory study of force transmission in radial truck tires is described. The experiments are conducted with the tire‐wheel assembly attached to a fixed, nonrotating axle. Contact with the tire is provided by a flat surface. Single frequency displacement cycles are applied to the loaded tire footprint, and the dynamic force transmitted through the tire is measured at the fixed axle. Fourier transform signal analysis is used to extract the cyclic displacement and force amplitudes. The amplitude ratio force/displacement is defined as the force transmissibility. The experiments show inflation pressure and tire load to have little effect on force transmissibility. A single degree of freedom tire model for force transmissibility is described. The model uses easily measured tire parameters and is intended for use in vehicle models to include the effect of tire dynamics.
Specimens cut from a 40 × 14 nylon cord aircraft tire were subjected to cyclic strain tests to measure the viscoelastic behavior. Spectral analysis was used to quantify nonlinearity in the stress response. Preliminary studies were made to ascertain the effects of specimen length and width on the test results. A bolted end constraint was developed to uniformly distribute the imposed strain through the thickness of the multiply carcass specimens. Test results show the effects of temperature, frequency, and strain level on the viscoelastic properties. Results are generally in agreement with earlier findings made using tubular test specimens.
In this paper we report on an experimental investigation on the friction of tire tread sections sliding over a variety of surfaces. The Texas A&M friction tester was used to measure sliding friction at various speeds and contact pressures. The friction test machine is also described. Actual bituminous and concrete road pavements and artificial 3M Safety Walk were used as surface samples. Tread rubber sections taken from passenger car, truck, and aircraft tires were tested. The influence of major test parameters such as sliding speed, surface texture and contact pressure on friction are discussed.
A finite element tire model, based on nonlinear shell of revolution elements, has been developed to investigate tire‐pavement interaction. The basic characteristics of this relatively comprehensive model are reviewed here, with attention focused on its ability to calculate the effect of tire design variables on tire performance data. A four‐ply bias tire is used to show the ability of the model to predict the different effects that nylon and polyester cords have on tire deformation, contact pressure distribution, and traction.
Uniaxial stress tests were conducted on composite specimens cut from two different locations on a bias tire carcass. These data together with cord data, the Halpin‐Tsai “micromechanics” equations, and the linear laminate constitutive equations are used to derive the in‐situ rubber modulus as a function of time and to check for consistency among the specimens tested. The main purpose of the first part of the study was to obtain constituent material properties for use in a finite element model of a tire. This model is then employed in the investigation of the influence of uniform rubber modulus on the shape of an inflated tire carcass, and it is concluded that the strain and time dependence of the rubber modulus will introduce some error in a tire structural analysis that uses linear elastic stress‐strain equations and permits geometric nonlinearity. It appears that the error will be minimal in a low strain region such as in the sidewall.
Energy dissipation is calculated from the contact deformation of a rolling toroidal membrane tire model. The method of dissipation analysis developed here can be used with other structural representations, including those based on the finite element method. The membrane tire model is inflated, loaded, and rolling on a frictionless, flat surface. The membrane material is assumed to be isotropic and neohookean under static loads and to exhibit a low loss tangent. The assumption of a low loss material permits viscoelastic power loss to be calculated from load transfer functions derived from the elastic response of the tire model. The power loss calculation is used to predict rolling resistance and contact patch shift.