Study of geometric effects on nonpneumatic tire spoke structures using finite element method

This research aims to develop a finite element model of nonpneumatic tires (NPTs) with different spoke shapes to study the geometric effects on the NPT for the maximum stiffness and minimum local stress. Four types of spoke structure were classified from reviewed articles and intellectual property. These were based on a few criteria including (1) manufacturability using polyurethane or engineering polymer as the material and (2) simplicity of the shape, the shape with less complexity and simple patterns. The finite element models of NPTs with different four spoke types were created using the same tread, shear band and the overall dimension. The spoke component of each model was created using 2D elements, with the different thickness to give the same mass. The hyperelastic constitutive equations were used to model behavior of NPT tread and spokes. The finite element analysis of vertical stiffness testing was performed on the NPT models using the maximum load required for skid-steer loaders. The analysis results were then compared to give an overview of load capacity of each model along with each advantage/disadvantage. The model with highest vertical stiffness by weight ratio was selected for the optimum number of spoke. Parabolic trends in vertical stiffness and maximum local stress at different spoke numbers were observed. This study found that the upper design limitation of spoke number was 24 spokes. Thus, the optimized number of spokes can be observed and the finite element model can be used to define the optimum geometry for a novel NPT.