Topological structure and experimental investigation of a novel whole tire bead

Tire quality is a crucial determinant of automobile maneuverability and safety. As such, improving tire performance, safety and durability have become an important research topic. Tire damage around the bead area is one of the main causes of critical tire failure. The trade-off effects of these two areas (bead and shoulder) on each other account for over 75% of the total tire damages reported. In addition, the bead problem alone causes instant tire deflation or bursts and overall accounts for about 30% of the tire damages. Therefore, more research should be devoted to finding a lasting solution to the bead problem.

The tire bead comprises different components, including the reinforcement, apex and anti-abrasive areas. Lately, the design of the tire structure towards the low section has been adopted by several tire makers. To this end, the bead shape has been developed from round to pagoda or quadrangle to hexagon with an inclination towards the inner cavity to enhance the bead support strength and minimize the tire bead deformation. Similarly, a smooth transition of the carcass, as well as a reduction in the concentration of stress on the cord, could be reduced through a circular cross-section. These mark the main bead improvement goals. Unfortunately, most studies on the bead area concentrate on the turnup and carcass structure of the wrapper, while the new bead structure remains underexplored. This can be attributed to the research confidentiality of the manufacturers. Therefore, a thorough understanding of the new tire bead structure is significant in facilitating its development for future use.

On this account, Professor Yong Li, Mr. Xunhua Sun, Mr. Shoudong Zhang, Mr. Julan Song and Professor Shanling Han from Shandong University of Science and Technology, developed a new topological structure for a whole tire bead to improve the safety and performance of the tire. The authors commenced their research work by analyzing the latest trend in tire bead structure development. The main objectives of the study included enhancing the bead strength by modifying the cross-sectional shape, maintaining the shape stability by changing the line contact to surface contact and to reduce the sliding between the rim and bead improve the bead’s bending and torsional stiffness by increasing the filament area. Additionally, the boundary line was modified to obtain a smooth carcass transition. Finally, the applicability of the new structure was experimentally investigated via indoor tests and finite element analysis. The work is currently published in the journal, Materials and Design.

Results demonstrated a preliminary approval of the applicability of the new structure. Compared to the normal tires, the durability of the whole tire bead was enhanced by more than 50% while its temperature was reduced by 5 °C. The performance of the whole tire bead was also superior in terms of grounding footprint, tightening force between the rim and the tire carcass cord stress, etc. It was noted that the damage point of the rubber commenced at the endpoint of the cord attributed to the interlaminar and thermal-oxidative aging shear stress. Furthermore, it was worth noting that the structure could reduce the Von Mises stress at the tire bead area by up to 40%.

In summary, the study analyzed the development trends of the tire bead and proposed a novel topological structure of the whole tire bead. Based on the results, the performance of the whole tire bead was far much superior to the normal tires. For instance, the designed production systems comprising bead processing up to the tire inspection were successfully achieved. The feasibility of the proposed bead structure was also verified experimentally. In a statement to Advances in Engineering, the authors noted that the proposed topological structure would contribute to the development of the next generation tires for various applications, including heavy-duty tires.