Nonreciprocal Elasticity and Nonuniform Thickness of Curved Spokes on the Top-Loading Ratio, Vertical Stiffness, and Local Stress of Nonpneumatic Wheels

The nonreciprocal elastic behavior of flexible spokes is essential for designing a top-loading condition of nonpneumatic wheels to distribute the vehicle load throughout the upper circumferential region of a wheel to replicate the loading mode of their pneumatic counterparts. However, most ad hoc spoke designs had been conducted without considering the top-loading mechanics. Moreover, minimizing the stress concentration on the spokes is also significant for preventing potential failures; however, modification of the geometry to reduce the local stress on the spokes has not yet been studied. In this work, we investigate the effect of nonreciprocal elastic behaviors of curved spokes on the top-loading distribution of nonpneumatic wheels. We also study the geometric effect of nonuniform curved spokes on reducing the local stress concentration. Curved beam spokes with greater curvature can contribute to a high top-loading ratio of nonpneumatic wheels. The nonuniform thickness of curved spokes with the spoke’s ends and center regions can reduce the local stress level by up to 24%. Our design method with varying curvature and nonuniformity of the curved spokes can provide significant design guidelines for nonpneumatic wheels for determining the top-loading ratio, tuning the vertical stiffness, and minimizing local stress on the spokes.