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Composite Effects on Tire Mechanics. MAE 537: Mechanics of Composites Paul Mayni May 2005. Agenda. Pneumatic tire evolution Effects of carcass and belt angles Ply steer phenomenon References. Interesting Quotes.

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composite effects on tire mechanics

Composite Effects on Tire Mechanics

MAE 537: Mechanics of Composites

Paul Mayni

May 2005

MAE 537 May 2005 Paul Mayni

agenda

Agenda

Pneumatic tire evolution

Effects of carcass and belt angles

Ply steer phenomenon

References

MAE 537 May 2005 Paul Mayni

interesting quotes

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

interesting quotes1

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

pneumatic tire evolution

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

pneumatic tire evolution1

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

agenda1

Agenda

Pneumatic tire evolution

Effects of carcass and belt angles

Ply steer phenomenon

References

MAE 537 May 2005 Paul Mayni

bias vs bias belted

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

the radial tire

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

bias vs radial

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

bias vs radial1

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

bias vs radial2

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

bias vs radial3

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

bias vs radial4

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

bias vs radial5

Bias vs. Radial

MAE 537 May 2005 Paul Mayni

agenda2

Agenda

Pneumatic tire evolution

Effects of carcass and belt angles

Ply steer phenomenon

References

MAE 537 May 2005 Paul Mayni

conicity ply steer

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

ply steer

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

ply steer1

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

ply steer2

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

ply steer3

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

references

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