Composite Effects on Tire Mechanics

1. Composite Effects on Tire Mechanics MAE 537: Mechanics of Composites Paul Mayni May 2005 MAE 537 May 2005 Paul Mayni

2. Agenda Pneumatic tire evolution Effects of carcass and belt angles Ply steer phenomenon References MAE 537 May 2005 Paul Mayni

3. Interesting Quotes “The complexity of the structure and behavior of the tire are such that no complete and satisfactory theory has been propounded” Temple, Mechanics of Pneumatic Tires MAE 537 May 2005 Paul Mayni

4. Interesting Quotes “Those of us who are active in research and development as applied to rubber-like materials are well aware of the truly interdisciplinary nature of tire-to-ground traction. Physics, chemistry, metallurgy, dynamics, tribology, thermodynamics, heat transfer elasticity, viscoelasticity, rheology, elastohydrodynamics, … play complex and intertwined roles in determining the magnitude of the frictional coupling that ultimately exists in the contact patch…” D.F. Moore 1973 Symposium on The Physics of Tire Traction MAE 537 May 2005 Paul Mayni

5. Pneumatic Tire Evolution First “modern” tire can be considered a simple ply construction From about 1920-1950 bias tires dominated the market An even number of cross plies of approximately +/- 45° were used as shown in the figure MAE 537 May 2005 Paul Mayni

6. Pneumatic Tire Evolution American tire manufactures hoped to avoid the costly transition to radial tires Typical construction consisted of additional belt layers restricted to the tread summit and using the same angles and materials as the carcass plies Resisting the radial movement in Europe, the belted bias tire was developed in North America MAE 537 May 2005 Paul Mayni

7. Agenda Pneumatic tire evolution Effects of carcass and belt angles Ply steer phenomenon References MAE 537 May 2005 Paul Mayni

8. Bias vs. Bias-belted Unrestricted growth of a bias tire for various cross-ply angles is shown in Figure 5.8 With the addition of belt layers of increased stiffness and cable material the shape of the inflated carcass changed as seen in Figure 5.9 MAE 537 May 2005 Paul Mayni

9. The Radial Tire Superior performance gains in comfort, wear, and handling were achieved with the introduction of the radial tire In a radial tire the carcass plies are oriented at 90°, and the steel belt package acts to distribute the tire’s load more efficiently and maintain a particular summit profile MAE 537 May 2005 Paul Mayni

10. Bias vs. Radial Within the contact patch, a bias tire will undergo extreme lateral deflection as shown in Figure 5.15. In contrast, the radial tire resists this tendency. This greatly reduces tire wear, heat generation, and provides responsive handling characteristics MAE 537 May 2005 Paul Mayni

11. Bias vs. Radial This figure shows the effect of changing the bias angle of a belt-less membrane The shape of the inflated tire is not a simple constant radius. Why is this important? If you can predict the inflated shape you can design the tire mold to have the ideal inflated shape thus reducing residual stress of the inflated tire. MAE 537 May 2005 Paul Mayni

12. Bias vs. Radial Top View The addition of a belt package to a radial sidewall design adds additional complexity to the problem Two interesting behaviors have been observed: For bias-belted tires there exists a special belt angle that in combination with the carcass angle generates a flat summit Radial tires without a belt package are unstable MAE 537 May 2005 Paul Mayni

13. Bias vs. Radial An example of the “flat angle” solution is shown above Regardless of inflation pressure, there will be no tendency for the tire to become “round.” In other words the equilibrium shape is flat. MAE 537 May 2005 Paul Mayni

14. Bias vs. Radial Consider a pure radial tire Remove the belts and inflate Note the characteristic round radial membrane shape Increase the pressure a little MAE 537 May 2005 Paul Mayni

15. Bias vs. Radial MAE 537 May 2005 Paul Mayni

16. Agenda Pneumatic tire evolution Effects of carcass and belt angles Ply steer phenomenon References MAE 537 May 2005 Paul Mayni

17. Conicity & Ply Steer Ply steer can be determined from lateral force variation measurements. An instrumented spindle records lateral force of a tire. Forward and reverse rotations are used in order to separate ply steer from conicity. Ply steer, generated by a coupling of bending and stretching, is dependent on the tire’s rotational direction. Conicity is derived from imagining a tire constructed to take the shape of a truncated cone. Based on geometry this configuration would generate a force towards the apex of the cone regardless of the direction of rotation. MAE 537 May 2005 Paul Mayni

18. Ply Steer The effects of stacking sequence of the tire’s summit plies directly influences the ply steer behavior Example A in the figure graphically depicts the results of an asymmetric stacking sequence Example B has little or no coupling of bending and stretching MAE 537 May 2005 Paul Mayni

19. Ply Steer Typical tire constructions are shown in Figure 8.2.78 Resulting conicity and ply steer values are shown in Figure 8.2.80 MAE 537 May 2005 Paul Mayni

20. Ply Steer The ABD matrix relates membrane loads and moments to strains and curvature The B16 and B26 terms are dependent on the stacking sequence Table 3.10 shows the effect of stacking sequence on ply steer force MAE 537 May 2005 Paul Mayni

21. Ply Steer For reference, some examples of ABD matrices for bias, belted-bias, and a radial tire are provided MAE 537 May 2005 Paul Mayni

22. References Bogdanovich, A. E., Pastore, C. M., (1996). Mechanics of Textile and Laminated Composites. Chapman & Hall, UK Haney, P., (2003). The Racing and High-Performance Tire. TV Motorsports, Springfield Illinois. Clark, S. K., (1981). Mechanics of Pneumatic Tires. US Department of Transportation, Washington, D. C. MAE 537 May 2005 Paul Mayni