Mechanical Analysis of a Non-Pneumatic Tire’s Spokes

Mechanical analysis was performed of a non-pneumatic tire, specifically a Michelin Tweel size 8x8.55 N10, that can be used up to a speed of 30 mph (48.3 km/h). A Parylene-C coating was added to the rubber spoke specimens before performing both microscopic imaging and cyclic tensile testing. Initially, standard ASTM D412 specimens type C and A were cut from the wheel spokes, and then the specimens were subjected to deposition of a nanomaterial. The surfaces of the specimens were prepared in different ways to examine the influence on the material behavior including the stiffness and hysteresis. Microscopic imaging was performed to qualitatively compare the surfaces of the coated and uncoated specimens. Both coated and uncoated spoke specimens of each standard type were then subjected to low-rate cyclic tensile tests up to 500% strain. The results showed that the Parylene-C coating did not affect the maximum stress in the specimens, but did increase the residual strain. Type C specimens also had a higher maximum stress on average than the Type A specimens. These mechanical tests provide useful data to determine material properties, such as Ogden material parameters, for future simulation of both the hyperelastic and hysteresis behavior of the rubber spokes.