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In an effort to develop tires with low rolling resistance, nonpneumatic tires (NPTs) with low viscoelastic energy loss materials are receiving more attention. For better design of NPTs on fuel efficiency, one may need to analyze rolling energy loss of NPT at a component level. The objective of this study is to develop a tool to quantify rolling energy loss and the corresponding internal heat generation of NPTs at a component level. For varying vehicle loads and rolling speeds, we suggest a thermo-mechanical model of an NPT with hexagonal cellular spokes and investigate temperature distribution of the NPT generated by hysteresis and convection loss into air. Using a hyper-viscoelastic material model developed from uniaxial (tensile and compression) tests and dynamic mechanical analysis (DMA), a thermo-mechanical model is developed by combining a longitudinal shear deformation induced hysteresis and a cooling procedure exposed to air.

Due to the relatively high freedom of selection of materials associated with a simple manufacturing method, a nonpneumatic tire (NPT) can be manufactured with a low viscoelastic energy loss material. A highly increasing demand to reduce greenhouse gases drives engineers to explore NPTs. NPTs consisting of flexible spokes and the shear band are still at an early stage of research and development. An optimization study of NPTs' geometry needs to be conducted, which is the objective of this paper. Parametric studies and design of experiments (DOE) of an NPT are conducted with a hyper-viscoelastic finite element (FE) model to determine the effects of three design variables on rolling resistance: the thickness of cellular spokes, the cell angle, and the shear band thickness. Considering vehicle load carrying capacity and riding comfort, ranges of vertical deflection between 18 and 20mm and contact pressure between 0.6 and 0.8MPa are selected as constraints for the optimization.

An understanding of the flow around a tire in contact with the ground is important when designing fuel-efficient tires as the aerodynamic drag accounts for about one third of an entire vehicle's rolling loss. Recently, non-pneumatic tires (NPTs) have drawn attention mainly due to their low rolling resistance associated with the use of low viscoelastic materials in their construction. However, an NPT's fuel efficiency should be re-evaluated in terms of aerodynamic drag: discrete flexible spokes in an NPT may cause more aerodynamic drag, resulting in greater rolling resistance. In this study, the aerodynamic flow around a non-pneumatic tire in contact with the ground is investigated for i) stationary and ii) rotating cases using the steady state Reynolds-Averaged Navier-Stokes (RANS) method. A sensitivity analysis was carried out with a varying mesh density. The flow into cavity by the discrete spoke geometry of the NPT does not significantly affect the overall aerodynamic drag.

A non-pneumatic tire (NPT) has two advantages over a conventional pneumatic tire; it is flat proof and maintenance free of air-pressure. In this study, while determining other advantages inherent in NPTs, the static contact behavior of NPTs with hexagonal honeycombs is investigated as a function of vertical loading and is compared with that of a pneumatic tire. A finite element based numerical simulation is carried out on the contact pressure of NPTs with cellular spokes and the local deformation of cellular spokes. A commercial finite element code, ABAQUS, is used to vary the vertical forces and lattice spoke geometries. A lower contact pressure is obtained with the NPTs than with the pneumatic tire due to the decreasing spoke stiffness of the NPTs when they are designed to have the same load carrying capability.

A Non-Pneumatic Tire (NPT) appears to have advantages over the conventional pneumatic tire in terms of flat proof and maintenance free. In this study, the static contact pressure of NPTs with hexagonal honeycomb spokes is investigated as a function of vertical loading and is compared with that of a pneumatic tire. Finite element based numerical simulation of the 2D contact pressure of a NPT is carried out with ABAQUS for varying vertical forces and lattice spoke geometries. A lower contact pressure is obtained with NPTs than with the pneumatic tire due to a high lateral spoke stiffness of NPTs when they are designed to be the same load carrying capability. The NPT with the spoke of a low cell angle, Type A spoke in this study, shows a low contact pressure; Type A in this study. On the other hand, the NPT with Type C spoke shows a lower local stress in the spoke cell struts, associated with the flexible cellular structural property in the uni-axial compression.