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# How temperature and frequency effects the tire behavior ?

Tires and piston rings are the two components which are abused to the greatest extent. What happens between the tire and road at time of braking,acceleration ,maneuvering etc , is extremely important thing to understand .

Tire's are the elastomers and show a property called viscoelasticity. Elastomers are the long chain molecules and their viscous behavior led to the hysteresis loss in them.

Note:- In metals deformation on application of load happens due to the lattice deformation.As shown below:-

- But in elastomers the deformation takes place without the change in bonds. As you can see the below figure we are having and long chain molecule of length L1 and on stretching the molecule we are deforming and increasing the length to L2 without change in bonds or deforming lattice. In long chain molecule their is the entropy drop on stretching them.

### Effect of frequency on interaction of tire long chain molecules:-

Frequency means that how fast or at which rate you are compressing and expanding these long chain molecules.

• At high frequency the molecules don't get the enough time to regain their shape as time between compression and expansion is too less so that's why the molecules behave as the stiff or rigid material. You can see the the curve that at high frequency the modulus is also very high behaving as rigid material.

• At low frequency molecules have enough time to regain their shape so, they behave as spring or elastic material. You can see in the curve at low frequency the modulus is low and behavior is like spring.

• At moderate range the molecules behave as the combination of springs and dashpot ,which will show the behavior of molecule as the viscous material. This is the region where the tires are operated.

### Effect of temperature on interaction of tire long chain molecules:-

Note:- Frequency and temperature are inversely related . This realtion is shown by WLF equations(Williamsâ€“Landelâ€“Ferry Equation).

• At Low temperature the molecules don't get the enough time to regain their shape and behave as the stiff or rigid material. You can see the the curve that at low temperature the modulus is also very high behaving as rigid material.

(This behavior is similar to the behavior at high frequency)

• At high temperature molecules get the support to regain their shape so, they behave as spring or elastic material. You can see in the curve at high temperature the modulus is low and behavior is like spring.

• At moderate range of temperature the molecules behave as the combination of springs and dashpot ,which will show the behavior of molecule as the viscous material. This is the region where the tires are operated.

As the molecules are having the viscous behavior at moderate range of frequency and temperature , this is the region where the tires are operated.

- As the tire molecule behave as the viscoelastic material at moderate frequency and temperature , their is the maximum energy loss at the moderate range due to hysteresis loss.

This is the region where tire is operated.

- In the curve of energy loss vs temperature, the temperature at the peak is Tg which is the glass transient temperature ,below this temperature tire behave as the vitreous material i.e brittle type and above this they behave as soft material .

- Tires are generally operated in the moderate range of temperature & frequency.

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