Deformation and Heat Generation in a Nonpneumatic Tire with Lattice Spokes

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. The model on the temperature rise of the NPT is validated through an experiment using a thermal imaging camera. The thermo-mechanical model demonstrates the spokes of NPTs do produce a comparable hysteretic energy loss, which has been ignored at an initial model of NPTs. Our model shows that the loss in the spokes covers ∼28% out of the total hysteretic energy loss of the NPT. High temperature is expected on the shear band due to the low surface area exposed to air compared to the spokes.