MATERIALS SELECTION PROCESSING OF WHEEL STUD

INTRODUCTION

The materials processing of wheel stud to choose good material for design the wheel stud is a

relatively common problem. The problem of wheel fixing failure occurs across a range of vehicle types

and manufacturers but is predominantly a problem relating to heavy goods vehicles. Materials

selection processing of a large number of failed the wheel studs have revealed that all had failed from

fatigue rather than over tightening. The wheel stud as shown in Figure 1, are used widely in cars and

tights wheels of cars by cycle load.

Figure 1. Wheel stud

Mechanical properties of materials such as strength, lightness, fracture toughness - determine

the product performance. Materials costs and environmental properties impact the bottom line and the

ability to comply with regulations.

Some consider the cause of the problem to be due to a relaxation of the tension in the studs

due to settling between the numbers of interfaces involved in the wheel assembly. Use of locking

devices will not prevent relaxation and since the wheel integrity is dependent upon the friction grip

provided by the stud tension, the relative looseness of the wheels will damage the studs and result in

eventual wheel loss due to failure of the fixing.

PROBLEM STATMENT

In this assignment, we had used the selection processes to choose good material for design of wheel

stud and which a manufacturer by experiencing problems with the bad materials chose for design of a

wheel stud on a vehicle. There were two problems:

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1. On some, but not all vehicles, the wheel stud was slipping resulting from fretting. The relative

movement which was occurring between the nuts and the bolts was causing elongation of the wheel's

holes and necking of the shanks of the bolts. This was happening even with the bolts being pre-

applied with thread locking adhesive. Inspection of the bolts on failed units confirmed that the nuts

were not rotating loose, as shown Figure 2 the fracture of bolts.

Figure 2. The Fracture of Bolts

2. During assembly, on certain batches of bolts, proportions were failing on initial torque-up. This was

despite a torque wrench being used to ensure consistency of the torque value. It has corrosion on the

surface (fretting).

FUNCTION

The function of the wheel stud is to tighten the rim with the car so that the car can be driven safely and

comfortable.

OBJECTIVE

The objective of this assignment to know the materials selection processing of wheel stud must also

have corrosion resistant properties in order to avoid corrosion from occur in the wheel stud.

DESIGN SYNTHESIS

The primary design requirement that is required to design a wheel stud are fracture toughness,

fatigue, stress and corrosion resistance for the wheel stud through the process for design it, to

become more strong to use in safety ways, but about secondary materials properties that required to

strain hardening and impact loading from the move on the wave rod, the wheel stud will be fracture,

that is when need to avoid this problems in the design it.

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MICROSTRUCTURE OF WHEEL STUD

The material of wheel stud, it is because for the crack will be initiated in the material, and then it has

fretting occurs on the surface of wheel stud, to investigate the microstructure of wheel stud as shown

in Figure 3.

Figure 3 Microstructure of wheel stud

MATERIAL SELECTION PROCESS OF WHEEL STUD

After the materials selection processes of wheel stud have been made, it is recognize that the best

material for wheel stud is carbon steel. The reasons of choosing the carbon steel as a material for

wheel stud, because of it chose this material has been specified as compared to other materials. But

there are some of materials that also considered for wheel stud due to its properties not much different

as compared to carbon steel. The table 1 below as shown the chemical composition for wheel stud

Table 1 Chemical composition of wheel stud.

Sample

Chemical composition (% wt) of the steels

C Si Mn P S Ni Cr Mo Al V

Carbon steel

1003 0.03 <0.02 0.22 0.024 0.017 0.02 <0.01 0.01 0.028 <0.01

1004 0.05 0.015 0.32 0.011 0.012 0.008 0.02 0.001 0.001 0.001

1008 0.08 <0.02 0.77 0.009 0.010 0.02 0.01 <0.01 0.043 <0.01

1019 0.19 0.22 0.78 0.011 0.029 0.07 0.06 0.02 <0.005 <0.01

MRB500 0.53 0.25 0.80 0.008 0.016 0.058 0.093 0.03 0.003 0.004

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MATERIAL SELECTION PROCESS

Process: Forging is a metal forming process used to produce large quantities of identical parts, as in

the manufacture of automobiles, and to improve the mechanical properties of the metal being forged,

as in aerospace parts or military equipment. The design of forged parts is limited when undercuts or

cored sections are required.

Forging: Forging changes the size and shape, but not the volume, of a part. The change is made by

force applied to the material so that it stretches beyond the yield point. The force must be strong

enough to make the material deform. It must not be so strong, however, that it destroys the material.

The yield point is reached when the material will reform into a new shape.

Type of forging

Die Forging: Open and closed die operations can be used in forging. In open-die forging the dies are

either flat or rounded. Large forgings can be formed by successive applications of force on different

parts of the material. Hydraulic presses and forging machines are both employed in closed die

forging. In closed-die forging the metal is trapped in recessed impressions, which are machined into

the top and bottom dies. As the dies press together, the material is forced to fill the impressions.

Flash, or excess metal, is squeezed out between the dies. Closed-die forging can produce parts with

more complex shapes than open-die forging.  Die forging is the best method, as far as tolerances that

can be met, and also results in a finished part that is completely filled out and is produced with the

least amount of flashing. The final shape and the improvement in metallurgical properties are

dependent on the skill of the operator. Closer dimensional tolerances can be held with closed die

forgings than with open die forgings and the operator requires less skill.

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CONCLUSION

We selected the processing for the best material to design wheel stud and we found that the best

material for designing the wheel stud is carbon steel. The suitable selection processing for the wheel

stud that we found is by using the forging technique.

REFERENCE

[1] Lecture notes of Materials for manufacturing by Dr. Mohd Zaidi Omar.

[2] Lecture notes of Materials Failure Analysis by Dr. Zainuddin Sajuri.

[3] http://www.boltscience.com/pages/casestdy.htm (28 September 2007)

[4] http://www.forging.com/pages/casestudy.htm (28 September 2007)

[5] Granta Design Corporation. 2002. Cambridge Engineering Selector (CES).

[6] Ashby, M. F. 1992. Materials Selection in Mechanical Design. Oxford: Pergamum Press.

[7] Michael Janssen, Jan Zuidema & Russell Wanhill. Fracture Mechanics 2nd ed. pg

212. Spon Press. London. 2004.

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