By Ummen Sabu13ETMMO8M.Tech. Materials Engineering

School of Engineering Sciences and Technology UNIVERSITY OF HYDERABAD

NON PNEUMATIC TYRES A RECENT DEVELOPMENT IN TYRE INDUSTRY

CONTENTS

Introduction

Evolution of tyres

Pneumatic tyres

Non-Pneumatic tyres

Constructional features of non pneumatic tyres

Material study

Conclusions

References

INTRODUCTION

Wheel ?

A circular object that revolves on an axle and is fixed below a vehicle or other object to enable it to move over the ground.

Tyre ?

A rubber covering, typically inflated or surrounding an inflated inner tube, placed round a wheel to form a soft contact with the road.

Tyres are mounted onto wheels

EVOLUTION OF TYRES

The design and materials used for wheels got advanced with time due to developments in the field of materials engineering.

Ancient times wooden logs were used for moving heavy objects

Wooden wheels were developed later and further it was modified with outer steel bands

Solid rubber tyres were the next major invention

Pneumatic Tyres were the next development in this field, which later got modified into different types

for softening the ride and reducing the power required to propel the carriages

EVOLUTION OF TYRES

Charles GoodyearE’douardDiscovered vulcanization of rubber 1839Pneumatic tyres 1895

The first practical pneumatic tyre was made by the Scot, John Boyd Dunlop, in 1887

FUNCTIONS OF TYRES

Vehicle to road interface

To support vehicle load

To maintain road surface friction

To absorb road irregularities : key benefit of the pneumatic tire

Lower rolling resistance

better high speed performance and control

Lesser heat generation

REQUIREMENTS OF A GOOD TYRE

Pneumatic tyres : Tyres which are used in vehicles today

The material components of modern pneumatic tyres are :

synthetic rubber(Styrene-butadiene copolymer)natural rubberfabrics and wirecarbon blackSulphur and other chemical compounds.

They consist of a tread and a body.

The tread provides traction while the body provides containment for a quantityof compressed air.

PNEUMATIC TYRES

PARTS OF PNEUMATIC TYRES

The main parts are :

Treads

Side wall

Ply

Treads:The tread is the part of the tire which comes in contact with the road surface Designed to not wear away too quickly.

The tread contains grooves and lugs.

Bead:The bead is that part of the tyre that contacts the rim on the wheel

Side wall:Sidewall is that part of the tyre that bridges between the tread and bead

Ply:Plies are layers of relatively inextensible cords embedded in the rubber. The orientations of the plies play a large role in the performance of the tyre and is one of the main ways that tyres are categorized

PNEUMATIC TYRES

TYPES OF PNEUMATIC TYRES

PROBLEMS WITH PNEUMATIC TYRES

Pneumatic tyres becomes flat i.e. They gets punctured by sharp objects in its path

Cross ply tyres: Tyres where the cords run at an angle with respect to the centre line of the tyre

Radial tyres: cords radiate from one bead to another in radial direction. They are softer and offer a more comfortable ride.

Tube tyres and Tubeless tyres

Tweel® is a registered Trademark of Michelin North America

The non-pneumatic tyre (NPT) is getting more attention now due to itsadvantages over the pneumatic counterpart.

Many design studies are still needed from the viewpoint of material, pattern,and structures.

However, no systematic research for such important design issues has beenreported in the literature up to now.

Tweel tyres were recently developed by Michelin

[Integrated tyre and wheel combination called the Tweel™]

The Tweel™ promises performance levels beyond those possible withconventional pneumatic technology because of its decreased rolling resistanceand non requirement of compressed air.

NON PNEUMATIC TYRES

As it has no pressurized air cavity, it cannot be punctured.

The Tweel tyre is a structure designed to mimic the critical characteristics of the pneumatic tyre without the requirement of inflation pressure.

The tyre can flex to absorb road shock and impacts yet can return to their original shape instantly to provide traction again

The flexible design acts like an air filled tyre with similar ride and comfort

Made up of a rubber tread, bonded to the hub through flexible spokes made from high density Polyurethane.

FEATURES OF TWEEL TYRE

When mounted on a car, the Tweel is a single unit consisting of four parts:

1. The hub

2. Polyurethane spokes.(Made from high density PU )

3. A "shear band" surrounding the spokes

4. The tread band.

1

2

4

3

htpps://www.michelintweel.com

PARTS OF TWEEL TYRE

htpps://www.michelintweel.com

TWEEL TYRE

When the Tweel moves on the road, the spokes absorbs road impacts the same way air pressure does in pneumatic tires.

The tread and shear bands deform temporarily as the spokes bend, then quickly spring back into shape.

In the shear layer viscoelastic energy losses occurs as the shear layer deforms at the contact zone.

The spokes determine stiffness.

WORKING OF TWEEL TYRE

Development of the Michelin Tweel®Tire Steven M. Cron Michelin Research and Development Company

If the spokes act as like weak springs, the upper portion of the inextensiblering can easily increase in diameter at higher speeds of rotation and the contactpatch can be short. This represents the low stiffness case.

If the spokes act as stiff springs, it is difficult for the ring to increase indiameter and the contact length must be greater.

Therefore the spokes must have an optimum stiffness and this is determinedusing Abaqus simulation tools and Python scripts

WORKING OF TWEEL TYRE

ADVANTAGES OF NPT

One of the basic shortcomings of a tyre filled with air is that the inflation pressure is distributed equally around the tire, both up and down (vertically) as well as side-to side (laterally).

That property keeps the tyre round, but it also means that raising the pressure to improve cornering -increasing lateral stiffness - also adds vertical stiffness, making the ride harsher.

The Tweel has a unique capability to have different vertical and lateral stiffness. Vertical stiffness affects ride comfort, and lateral stiffness affects handling and cornering.

The ability to tune these two parameters differently allows the best of both worlds, ride comfort and superb handling

ADVANTAGES OF NPT

Rolling resistance is defined as the amount of force needed to roll a vertically loaded tyre at a constant speed.

Rolling resistance is simply the manifestation of all of the energy losses associated with the rolling of a tyre under load.

Since most of the energy is dissipated through hysteretic losses as the materials of the tyre are deformed.

Non pneumatic tyres have lesser rolling resistance compared to conventional tyres

Therefore we get better fuel efficiency by using non pneumatic tyres

MANUFACTURING OF TWEEL TYRES

The tread is constructed by a similar method as the conventional tyre tread manufacturing process where the tread layer is extruded and is then mated to layers of belts and the plies are embedded and entire assembly is vulcanized.

The steel hub is produced by casting process.

The hub and the tread are secured concentrically and polyurethane ispoured into a spoke and shear band mold while the entire assembly spins so that the polyurethane will sufficiently fill the mold in the radial direction

The final solidification is done at 100°C degrees for 4 hours in an oven so that the polyurethane solidification process is accelerated and to assure all the Tweel™ components are securely bonded together.

MANUFACTURING OF TWEEL TYRES

Shear band Tread Spokes Hub Total weight

Raw material Wt % Wt % Wt % Wt % Wt %

Synthetic

rubber

0 41 0 0 1.15

Natural rubber 0 4 0 0 .10

Carbon black 0 10 0 0 .26

Silica 0 28 0 0 .77

Sulfur 0 1 0 0 .02

Zno 0 1 0 0 .03

Oil 0 11 0 0 .29

Stearic acid 0 1 0 0 .04

Recycled

rubber

0 0 0 0 0

Coated wires 10 0 0 0 .62

Polyurethane 90 0 100 0 8.44

Steel 0 0 0 100 4.0

Total% 100 100 100 100

Weight 6.35 2.75 2.65 4 15.75

MATERIAL AND WEIGHT DISTRIBUTION

WHY RUBBER ????

Rubber is a fascinating elastomer material, with unique properties that make it an essential component of a pneumatic tire.

All rubbery materials consist of long chain-like polymer molecules.

The original elastomeric material (raw rubber) is basically a highly-viscous liquid but it can show elasticity because the long molecules are held together, at least temporarily, by being intertwined and entangled.

The basic reaction in rubber processing is the joining of long molecules together by a few chemical bonds (crosslinks) to form a loose three-dimensional permanent molecular network.

The shape becomes fixed and the material is transformed from a high-viscosity liquid into an elastic solid.

This joining reaction is often termed “vulcanization” and is carried out with reagents that introduce sulphur crosslinks between the molecules

CONCLUSIONS

The Tweel is now a conceptual state, but it will hit the market soon

Michelin should find some way to eliminate those gaping see-through holes forthe final production model. May be with a covered sidewall.

Things like checking tire pressure, fixing flat tires, and balancing betweentraction and comfort could all fade into memory.

Non pneumatic tyres are now considered for vehicles used in Lunar and Marsterrain.

REFERENCES

[1].Rhyne, T. B., and Cron, S. M., “Development of a Non-Pneumatic Wheel,”Tire Science and Technology, Volume 34, Number 3, July-September 2006

[3]. Dr.Joshi.C.Haran, “Static analysis of airless tyres “,International Journal ofScientific and Research Publications, Volume 3, Issue 8, August 2013

[3]. htpps://www.michelin.com last visited on 26/03/14 at 8 am