Mini Project-Assignment 2- Wheel Stud-materials

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 preapplied 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. Chemical composition (% wt) of the steels Sample

C

Si

Mn

P

S

Ni

Cr

Mo

Al

V

Carbon steel 1003

0.03