21-06-2011, 03:33 PM
fatigue analysis of wheel rim complete rerort.doc (Size: 2.76 MB / Downloads: 375)
CHAPTER 1
INTRODUCTION
1.1 History of Wheel/Rim
Several thousand years ago was the start of the history of wheel when the human race began to use the log to transport heavy objects. The original of the wheel were the round slices of a log and it was gradually re-inforced and used in this form for centuries on both carts and wagons.
This solid disc changed to a design having several spokes radially arranged to support the outer part of the wheel keeping it equidistant from the wheel centre. A wooden wheel which used hard wood stakes as spokes was very popular as a wheel for many vehicles up to about 1920.
Afterwards the disc wheel, in which the spokes were replaced with a disc made of steel plate, was introduced and is still being used to this day. Furthermore, a light alloy has come to be used currently as a wheel material for many types of vehicle.
Trucks have been basic backbone of the world's workforce for decades. They're big, powerful, and can really get you through the roughest of terrains. But a truck can't do its job without properly functioning wheels. Truck rims need to be replaced if they're bent or cracked for the sake of your truck's life - and sometimes just for an upgrade. Knowing your truck rim options will greatly assist you in this process.
Most steel truck rims are created in the same way. It starts with a hard cast hub, with 4, 5 or even 6 holes for the bolts. A spun steel rim is then secured around this with a series of welds. The rim is properly balanced and then given a smooth finish. Although some steel rims are available in silver and chrome, most of those finishes are saved for alloy wheels.
Truck wheels need to be durable and able to carry around weight. You won't find many spoke designs with these rims. They're usually as solid as possible. But that doesn't mean your options aren't varied when looking for replacements. The most important thing to remember is to purchase the same size rims you're replacing unless you're also planning on vehicle modifications.
Lighter wheels can improve handling by reducing unsprung mass , allowing suspension to follow the terrain more closely and thus improve grip, however not all alloy wheels are lighter than their steel equivalents. Reduction in overall vehicle mass can also help to reduce fuel consumption
Better heat conduction can help dissipate heat from the brakes , which improves braking performance in more demanding driving conditions and reduces the chance of brake failure due to overheating.
1.2 wheel rim description
The rim of a wheel is the outer circular design of the metal on which the inside edge of the tyre is mounted on vehicles such as automobiles. For example, in a four wheeler the rim is a hoop attached to the outer ends of the spokes-arm of the wheel that holds the tyre and tube.
A standard automotive steel wheel rim is made from a rectangular sheet metal. The metal plate is bent to produce a cylindrical sleeve with the two free edges of the sleeve welded together. At least one cylindrical flow spinning operation is carried out to obtain a given thickness profile of the sleeve — in particular comprising in the zone intended to constitute the outer seat an angle of inclination relative to the axial direction. The sleeve is then shaped to obtain the rims on each side with a radially inner cylindrical wall in the zone of the outer seat and with a radially outer frusto-conical wall inclined at an angle corresponding to the standard inclination of the rim seats. The rim is then calibrated.
To support the cylindrical rim structure, a disc is made by stamping a metal plate. It has to have appropriate holes for the center hub and lug nuts. The radial outer surface of the wheel disk has a cylindrical geometry to fit inside the rim. The rim and wheel disk are assembled by fitting together under the outer seat of the rim and the assembly welded together.
Wheel rim is the part of automotive where it heavily undergoes both static loads as well as fatigue loads as wheel rim travels different road profile. It develops heavy stresses in rim so we have to find the critical stress point and we have to find for how many
number cycle that the wheel rim is going to fail.
1.3 Type of Wheel/Rim (Material)
Steel and light alloy are the main materials used in a wheel however some composite materials including glass-fiber are being used for special wheels.
(1) Wire Spoke Wheel
Wire spoke wheel is a structural where the outside edge part of the wheel (rim) and the axle mounting part are connected by numerous wires called spokes. Today's vehicles with their high horsepower have made this type of wheel construction obsolete. This type of wheel is still used on classic vehicles. Light alloy wheels have developed in recent years, a design to emphasize this spoke effect to satisfy users fashion requirements.
(2) Steel Disc Wheel
This is a rim which processes the steel-made rim and the wheel into one by welding, and it is used mainly for passenger vehicle especially original equipment tires.
(3) Light Alloy Wheel
These wheels based on the use of light metals such as aluminium and magnesium have become popular in the market. These wheels rapidly become popular for the original equipment vehicle in Europe in 1960's and for the replacement tire in United States in 1970's. The features of each light alloy wheel are explained as below;
A) Aluminium Alloy Wheel
Aluminium is a metal with features of excellent lightness, thermal conductivity, corrosion resistance, characteristics of casting, low temperature, machine processing and recycling, etc.
This metals main advantage is reduced weight, high accuracy and design choices of the wheel.
This metal is useful for energy conservation because it is possible to re-cycle aluminum easily.
B) Magnesium Alloy Wheel
Magnesium is about 30% lighter than aluminium, and also, excellent as for size stability and impact resistance. However, its use is mainly restricted to racing, which needs the features of lightness and high strength at the expense of corrosion resistance and design choice, etc. compared with aluminium.
Recently, the technology for casting and forging is improved, and the corrosion resistance of magnesium is also improving. This material is receiving special attention due to the renewed interest in energy conservation.
C) Titanium Alloy Wheel
Titanium is an excellent metal for corrosion resistance and strength (about 2.5 times) compared with aluminum, but it is inferior due to machine processing, designing and high cost. It is still in the development stage although there is some use in the field of racing.
D) Composite Material Wheel
The composite materials wheel, is different from the light alloy wheel, and it (Generally, it is thermoplastic resin which contains the glass fiber reinforcement material) is developed mainly for low weight. However, this wheel has insufficient reliability against heat and for strength. Development is continuing.