DESIGN AND ANALYSIS OF AN

AUTOMOTIVE FRONT WHEEL HUB

B.TECH MECHANICAL ENGINEERING - VI SEMESTER

DESIGN PROJECT

Presented by

Bhoopendra Singh - 07BME064

Kallur Krishnamoorthy Rajesh - 07BME097

SCHOOL OF MECHANICAL & BUILDING SCIENCES

VELLORE INSTUTUTE OF TECHNOLOGY

VIT UNIVERSITY

VELLORE – 632014, TAMIL NADU

APRIL 2010

CERTIFICATE

This is to certify that the design project entitled “Design And Analysis Of An Automotive

Front Wheel Hub” submitted by Bhoopendra Singh - 07BME064 Kallur Krishnamoorthy

Rajesh - 07BME097, doing III Year B.Tech Mechanical Engineering to the School of

Mechanical & Building Sciences, VIT University Vellore is a bonafide record of work

carried out by them under my supervision.

Their performance during the project phase is __________________

Guide Programme Manager

(Prof. Dr. Sunil Bhat) (Prof. P. Kuppan)

Internal Examiner External Examiner

ACKNOWLEDGEMENT

First we would like to thank VIT University and our chancellor, Dr. G. Viswanathan, for

providing us the opportunity to do this project.

We would like to thank our guide, Dr. Sunil Bhat, whose expert guidance in solving the

problem was a prime reason for the successful ideation and completion of the project. He

extended his guidance at all times, and helped us learn in the process through scientific

questioning and reasoning. His in depth knowledge in machine design, fracture mechanics,

strength of materials, and finite element analysis helped us come out of difficult situations.

We would also like to thank Mr. Ravi, PDC Lab assistant, in helping us learn and use the

software ANSYS® 11.0.

Last but not the least, we would like to thank God Almighty, without whom this project

would not have seen the light of the day.

ABSTRACT

Design and analysis of a front wheel hub of a single seater all terrain vehicle was to be

done,to ensure optimum performance, and to finalise the dimensions and material

specifications for manufacturing the same for the above said vehicle. First, the given volume

was obtained within which the component was to be placed. Initial dimensions were set based

on bearings to be used and Wheel rim dimensions. Various materials were studied and

shortlisted for the purpose. The loading conditions were analyzed, and an equivalent

mathematical model was constructed. Mathematical analysis was done for various materials.

Next, a finite element model was setup and analysed for various materials. The actual stress

concentrations were found out. Based on the obtained FEA result, a optimized and enhanced

design for high strength –low weight was obtained. Finally, a weighted matrix method was

used to select the final material to be used. Through this project, we have arrived at a

optimized design of a front wheel hub, that is both strong and light weight, with reduced

material for best performance.

i

LIST OF TABLES

Table No. Table Name Page No.

1. Moment of Inertia of equivalent sections of the Hub 11

2. Material Comparison Table I- Properties 24

3. Material Comparison Table II - Performance 24

ii

LIST OF FIGURES

Fig. No. Figure Name Page No.

1 Hub-Rotor 4

2 Hub-With Suspension 4

3 Vehicle Dimensions 5

4 Front View Suspension Geometry Based On Vehicle Dynamics 5

5 Hub Side View 9

6 Hub Front View 10

7 Vehicle Hitting A Bump 12

8 . Equivalent Cantilever System For A Hub 11

9 Analysis For Steel 17

10 Analysis For Steel 17

11 Analysis For Aluminum 18

12 Analysis For Al-Sic Mmc 18

13 Analysis For Al-C , Mmc 19

14 New, Optimized Design 20

15 Modified Steel Hub Analysis 21

16 Modified Aluminium Hub Analysis 21

17 Modified Al-Sic Mmc Analysis 22

18 New, Optimized Hub Isometric View 25

19 Optimized Hub Side View 25

20 Optimized Hub Front View 26

iii

NOMENCLATURE

u - initial velocity

v - final velocity

a - acceleration

t - time

s - distance

h - height

d - displacement

σ - stress

ε - strain

E - Young’s modulus

G - Shear Modulus

I - Moment of Inertia

J - Polar Moment of Inertia

θ - angular displacement

P - Power

T - Torque

w - Angular Velocity

τ - Shear stress

iv

CONTENTS

Abstract (i)

List of Tables (ii)

List of Figures (iii)

Nomenclature (iv)

PAGE NO

CHAPTER – I INTRODUCTION

1.1 Problem Specification 01

1.2 Significance of the Project 01

1.3 Objectives 02

1.4 Methodology 03

CHAPTER – II LITERATURE REVIEW 04

2.0 Vehicle Overview 05

2.1 Bearings Used 06

2.2 Formulae Used 06

2.3 Materials Considered 07

CHAPTER – III DESIGN OF COMPONENT 08

3.0 Conventional Design 08

3.1 Initial CAD Design 09

CHAPTER – IV STRESS ANALYSIS 11

4.0 Mathematical Model 11

4.0.1 Tensile Stress 12

4.0.2 Bending Stress 12

4.0.3 Torsional Stress 13

4.0.4 Von-Mises Stress 14

4.1 Finite Element Modeling 16

4.1.1 Analysis of initial design 17

4.1.2 Observation and Changes suggested 20

4.1.3 Analysis of New design 21

CHAPTER – V MATERIAL SELECTION 23

CHAPTER – VI CONCLUSION 25

6.0 Final Design Specifications 25

6.1 Observations 27

6.2 Scope for Future work 28

REFERENCES 29

CHAPTER : I

Introduction

While designing a single-seater all terrain recreational vehicle, we were put up with the task

of designing and optimizing the Front Wheel Hub of our vehicle. The vehicle is to negotiate

all kinds of terrain under high performance mode (race purposes). The vehicle runs under a

11 bhp petrol engine, coupled to a gearbox that produces a maximum acceleration of 1g. Also

the front wheel is the steered wheel, hence there will be loads in and about all 3 axes(x,y,z).

Since the terrain is rough, the design is required to be very strong. Also, since it is for racing

purposes, the design is also supposed to be light weight.

1.0 Problem Specification

To design a front wheel hub for an all terrain vehicle on strength and weight basis. The

component is to be modelled mathematically and in finite elements , upon which stress

analysis is to be done. Based on the results, design optimization is to be made for best design.

Also materials have to be analyzed and chosen for the same.

1.1 Significance of the Project

This project has significance to the automotive industry. This project is an example of

optimization of design through FEA. The design procedure used here can be standardised for

automated design processes.

1

1.2 Objectives

The objectives of this design project are summarized as follows:

To analyze the design and improve the design of Front wheel Hub of an

ATV for high strength and light weight.

To understand the loading conditions, boundary conditions and the

environment the component is subjected to.

To formulate a mathematical model, through scientific assumptions and

come up with a theoretical stress-strain model.

Perform Finite element analysis to find out stress concentrations, thereby

finding areas to improve design.

Give final design with dimensions and material specifications.

2

1.3 Methodology

The approach to our design problem is elaborated through the flow-chart given below

3

Understanding the Problem at

hand

Making a time schedule

Literature survey

CAD ModellingMathematical

Modelling

Stress Analysis

Discussion with Guide

Finite Element Analysis

Design Optimization

Discussion with guide

Material Selection

Final Specifications

Compiling a Final Report

CHAPTER : II

Literature Survey

In automotive wheel systems, the suspension is connected to the wheel using a hub-rotor

assembly.

The hub-rotor rotates about the upright(which is connected to the suspension), upon bearings.

There is a base plate with holes for bolts, which is bolted on the wheel rim.

Fig 1. HUB-ROTOR Fig 2. HUB-with suspension

As can be seen, the wheel hub is a symmetric component. All the loads from the wheel to the

shocks are transferred through the hub. Hence the safe design of wheel hub is very important.

The design of hub depends upon the space given to it, which is decided according to the other

suspension components like shock position, arm length, suspension geometry, brakes position

etc.

The positioning of the other suspension assemblies is not discussed in this design project.

Only the design of the hub is discussed here.

4

Bearing

housing

Baseplate

2.0 Vehicle Overview

Dimensions of the vehicle (SAE MINI BAJA ATV)

Weight : 350kg

Track length : 135 cm

Wheelbase : 160 cm

Engine: Lombardini 340cc 11hp

Max. torque on wheels: 1200 N-m

Max. speed: 45 kmph

Maximum Wheel travel :15cm

Rim PCD (for holes of bolts): 102 cm

Fig 3. Vehicle Dimensions

Based on various consideration, the suspension geometry was designed. This gave us the

available space for the wheel hub.

Fig 4.Front View suspension geometry based on Vehicle dynamics

5

Track length

Wheelbase

70kg

70kg

105kg 105kg

40:60 weight

distribution

2.1 Bearings Used

Based on static loads, the bearing was selected with an axial load of 30000N and a radial load

of 10000N and life of ten million revolutions.This was done based on bearing selection

procedure given in Design data books.

The tapered roller bearing , 32005 (25 x 47) suited the purpose with a width of 15mm

2.2 Formulae Used

1. Laws Of Motion

v= u +at eqn 1.1

s= ut+0.5at^2 eqn 1.2

v^2 = u^2 + 2as eqn 1.3

centrifugal force, Fc= mv^2/r eqn 1.4

2. Stress Strain Analysis

a. Stress, σ= F/A eqn 2.1

b. σ=Eε (ε –strain, E-elasticity modulus) eqn 2.2

c. Bending equation , M= EI( d2y/dx

2) eqn 2.3

d. Torsion, T/J = τ/R = Gθ/L eqn 2.4

e. Principal stresses

eqn 2.5

f. Von-Mises Hencky maximum distortion energy theory

eqn 2.6

g. If an impact loading is equalised to a weight W falling from a height H, then,

deflection due to impact loading in terms of height of fall and static deflection for

same weight is,

dmax = dst + ( dst2 + 2Hdst)

1/2 eqn 2.7

6

2.3 Materials Considered

C45 Steel

It is a medium carbon steel with 0.4 -0.5 % carbon, with yield strength o 380 MPa and an

impact strength of 41 N-m. It is used generally in shafts, gears, spindles etc.

Al 6061 T6

6061 is a precipitation hardening aluminum alloy, containing magnesium and silicon as its

major alloying elements. It has good mechanical properties and exhibits good weldability. It

is one of the most common alloys of aluminum for general purpose use.

It is commonly available in pre-tempered grades such as, 6061-O (solutionized), 6061-T6

(solutionized and artificially aged), 6061-T651 (solutionized, stress-relieved stretched and

artificially aged).

Al MMC’s

Metal Matrix Composite (MMC): A composite material in which one constituent is a metal

or alloy forming at least one percolating network. The other constituent is embedded in this

metal matrix and usually serves as reinforcement.

These generally have low density and high strength. They are used in high performance

motor vehicles in wheel rotors, shafts, axles, engine components etc. The only limiting factor

is manufacturing ease and cost.

Al-SiC MMC is a particle reinforced MMC, with Al as matrix and SiC as fibre. The yield

strength is 338 MPa.

Al-C is a Continuous fibre reinforced MMC, with Al as matrix and Carbon as fibre. The yield

strength is 620 MPa.

7

CHAPTER : III

Design Of Component

The design of hub depends upon the space given to it, which is decided according to the other

suspension components like shock position, arm length, suspension geometry, brakes position

etc. As given in the literature survey, based on the suspension geometry, the space available

was obtained.

3.0 Conventional Design

The Conventional design of a front wheel hub consists of a circular disc with bolt-holes,

called baseplate . Extruded from this is a hollow stepped section, which houses the bearings.

Another disc is extruded upon this which acts as the brake disc and is usually made from a

different material than the hub.

8

3.1 Initial CAD design

Based on the suspension packaging, steering linkages,suspension arms (wishbone system),

available space and adherence to track length limit,accessibility of brake disc-calliper

assembly, the hub dimensions were fixed to be the following

Fig 5. HUB side view

The disc with dia. 132 mm is the baseplate, to be mounted on the rim. The 26mm long

section is the bearing housing. The 84 mm dia disc is the brake disc mount. As can be seen in

the next figure, the base plate has bolt-holes according to the pitch circle diameter of the rim.

9

Fig 6. HUB front view

10

CHAPTER : IV

Stress Analysis

The hub is being acted by forces in and about all 3 axes. The major forces encountered are

the centrifugal force during a bump, the impact force during a full speed jump, the torsional

load due to acceleration. All the conditions are considered here, a model is made and von-

mises failure theory is applied to find out induced stresses.

4.0 Mathematical Model

Assuming the hub to be a cantilever beam

fig 8. Equivalent Cantilever system for a Hub

section I, moment of inertia(mm4) L, length(mm)

1 2204400

8.5

2 355300

26

3 17052800

6

Table 1 : Moment of Inertia of equivalent sections of the Hub

11

l1 l2 l3

4.0.1 Tensile Stress

Assuming a bump height of 15cm and length 20 cm.

Fig. 7 vehicle hitting a bump

Assuming the speed of vehicle : 45 km/hr i.e 11.11 m/s

Assuming the radius of suspension travel = .67

Centrifugal force on the wheel = 30000 N

This force is acting perpendicular to the face of the baseplate.

The stress developed by eqn 2.1 is = 4 MPa

This is the axial load on the hub, σx = 4Mpa

4.0.2 Bending Stress

Using method of superposition, static deflection due to weight at front wheel, and assuming

material to be steel

dtotal = d1 + d2 + d3

dtotal = 1.5 x 10-4

mm

12

15

20

assuming an impact load condition,from Mechanics of Materials(JAMES M. GERE TMH)

pg 674

If an impact loading is equalised to a weight W falling from a height H,then, deflection due to

impact loading in terms of height of fall and static deflection for same weight is,

dmax = dst + ( dst2 + 2Hdst)

1/2

IMPACT ENERGY : assuming the vehicle at max speed falling from height of 3 feet

And assuming half the energy to be absorbed by the suspension system, then the impact

energy on the hub-rotor assembly is = 12511 J

The equivalent height of fall for the front wheel is 9.11 m

Applying the deflection eqn above,

We get dmax = 1.2 mm

Strain = 4.4 x 10-4

From eqn 2.2,

Induced stress, σy = 88 Mpa for steel with deflection = 1.2 mm

Similarly for Aluminium, σy =86 MPa with deflection of 2mm.

4.0.3 Torsional Load

Maximum torsion is observed at maximum acceleration of the vehicle

We know

Power =Torque x ang. Velocity

P=Tw

T= P/ w

T= Pr/v

KE = 0.5mv2

13

Power = d/dt(KE)

= mav

T= mavr/v

T= mar

amax for the vehicle was calculated to be 10 m/s2, that is at a max torque from the engine and

gearbox

therefore, T= 187 N-m

applying torque eqn.

θ =Tl/GJ

θmax = θ1 + θ2 + θ3

θmax = 8.3 x 10-5

rad

shear strain = 1.9 x 10-4

induced shear stress, τ =16 Mpa

4.0.4 Von-Mises Stress

σx= 4 MPa

σy = 88 MPa

τxy = 16 Mpa

applyin eqn 2.5

σ1 = 91 Mpa

σ2 = -2 MPa

after applying eqn 2.6

σvon mises= 92 MPa

14

The presence of holes, steps and fillets lead to stress concentration. The stress concentration

factor for such notches individually are known.

In our case there is a combination of shear and bending stresses, with a combinations of holes

and fillets. Hence, incorporation of theoretical stress concentration factors would lead to

approximate and possible wrong conclusions.

Hence it was decided to find out the stress concentration factor from Finite Element

Analysis(FEA) of the component.

15

4.1 Finite Element Modelling

Finite element analysis was done in order to find the actual stresses that are experienced by

the component under different loading.

ANSYS 11.0 was used for the finite element analysis. The component was modelled in the

ANSYS 11.0 modelling environment, with the same dimensions as the real one.

Selection Of Element

Element selected for the analysis is a 3D beam element.A 3D beam element has 3 DOF per

node (x,y and z direction). It has both strain and bending capabilities. Hence this element was

chosen.

In ANSYS 11.0 it comes as “Beam element 3D 44”

Meshing

Meshing of the entire component was done within the ANSYS 11.0 environment. Tetrahedral

free meshing was done, as the component had smooth curves, and cylindrical

topology.Hexahedral would not produce a smooth topology.

The meshing was automatically refined at the points where there was discontinuity in the

form of step, hole etc.

The total no of nodes were 41619

Constraints

The bigger baseplate is bolted on to the wheel rim and his hence constrained in 3 DOF.

Loads

Loads are applied on the other base plate. The load was calculated as shown above in the

calculations section. All the loads were applied on to the model and analysis was done.

16

4.1.1 Analysis Of Initial Design

Fig.9, 10 : Analysis of Steel

17

Fig 11.Analysis For Aluminum

Fig. 12 : Analysis For Al-Sic Mmc

18

Fig 13 : Analysis For Al-C , Mmc

19

4.1.2 Observations and design changes suggested

In all the above cases, the stress does not exceed 220 MPa,the highest stress coming at the

point where the hub is bolted on the wheel.The contour plot very starkly shows that the area

between the holes for bolts, are areas of negligible near zero stress. Hence for material

reduction (that is weight reduction) such areas can be removed.

After optimising the design and removing material at unwanted locations, this is how it

looked like.

Fig 14 : Opimized hub design

After removal, again analysis was carried out for the same.

20

4.1.3 Analysis Of New Design

Fig 15 : Modified Steel Hub Analysis

Fig 16 : Modified Aluminium Hub Analysis

21

Fig 17 : Modified Al-Sic Mmc Analysis

As can be easily noted , the stress induced in the new design is more than the previous

design. Yet it is within the Factor of safety, with a max stress value of 250 MPa. One can

easily notice in the increase in the area/elements of increased stress. Previously lesser overall

area was under stress. Also note the increased stress in the bearing mount region.

Hence finally, the new design with reduced material was decided to be used. This was a result

of OPTIMIZATION THROUGH SIMULATION.

22

CHAPTER V : MATERIAL SELECTION

The final material selection was based on various factors like strength, elasticity, hardness

required, cost, machinability, weight etc.

The comparison table in the next sheet was made according to the data collected from data

books about the 5 materials considered for the component.

As can be seen, steel has excellent performance in all spheres except its weight.Since this

Hub is for high performance, weight is of concern. But C45 steel has an excellent fracture

toughness. Hence it can be used for mass production commercial vehicles for whom cost and

safety is of primary concern.

Aluminium 6061 –T6 has excellent properties, except that it is easily deformed. Yet it

maintains all the FOS values.It is remarkably light-weight, cheap, easily available and easily

machined. It seems to be the best candidate for High Performance race/recreational ATV

vehicles.Its easy deformation does not render it safe for commercial applications.

Al 2011 T6 also offers similar performance, except that its costlier than Al 6061-T6.

The Al-C MMC has excellent properties, but is in fact too strong for our application. The cost

and manufacturing involved are too high for this purpose.

The Al-SiC MMC too has great properties. But is similar to that of Al 6061 T6. And for the

cost that would incur for this purpose is impractical.

Hence the final material selected is Al 6061 T6.

23

CHAPTER : VI

Conclusion

Thus , the design and stress analysis of the front wheel hub was carried out in a systematic

manner. After performaing FEA, stress concentrations were found out. Accordingly,

dimensions and material has been selected, based on weighted method.

6.0 Final Specifications

Dimensions:

Fig 18. New, Optimized Hub Isometric View Fig. 19 New, Optimized Hub Side view

25

Fig 20 : New, Optimized Hub Front View

26

6.1 Observations

The following points were observed in the design process

1. Static loads have very less induced stress on the component

2. Major stress is from impact load, hence material should have high impact strength

3. The induced stress for both aluminium and steel is almost the same

4. The deflection in aluminium is more than steel, but well within the elastic limit

5. Selection of element is very important to get accurate results

6. Element is a beam element, because the analysis is approximated to a cantilever

beam

7. FEA shows that stress concentration due to holes, steps etc are around 2.4-2.8, due to

presence of multiple holes and multiple steps

8. Material reduction was done in areas where the stress was negligible

9. After material reduction , maximum stress increased by 15-20 %

10. After material reduction stress concentration and stress area also increased.

11. MMC , though are high performance material, are very costly to be put use in such

applications. Work needs to be done by researchers in order to reduce cost of MMC’s.

This could greatly improve performance of various machine components

12. Machinabilty is an important factor when planning for scaled production of parts.

27

6.2 Scope for Future Work

The engineering world today is moving towards automation in all spheres. One such field is

design automation. This project has a structured approach to solving the design problem. The

approach above can be made into an algorithm for automated design of this component for

similar sized/type vehicles. This reduces design cycle time. Literature work is already

underway, and the authors are hopeful to achieve a novel algorithm for standard machine

elements for automated design.

28

References

The following books and papers, relating to design and analysis of wheel hubs were studied

Design of machine elements, V.B.Bhandari TMH

Strength of materials by James M. Gere

Design Data PSG

Automotive Vehicle Technology, Hanz-Heisler

BOSCH AUTOMOTIVE HANDBOOK

Design criteria and Durability approval of Wheel hubs, Gerhard Fischer and

Vatroslav V. Grubisic,SAE tech. paper series-

Design of Formula SAE suspension, Badih A. Jawad and Jason Baumann, SAE tech.

paper series

Material Science and Engineering, William D. Callister, Wiley Publications

ASME Materials Handbook, ASME

29