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Coupled Field Finite Element Analysis of Car Disc Brake Rotors

Dept. of Mechanical Engineering SDMCET, Dharwad 1

TABLE OF CONTENTS

Chapters Page No.

ACKNOWLEDGEMENT

ABSTRACT

CHAPTER 1: INTRODUCTION 06

1.1 Fundamentals of Braking System

1.1.1 Principle of braking. 07

1.1.2 Coefficient of friction 08

1.2 Braking systems.

1.2.1 Brake types in cars.

1.2.1.1 Drum Brake. 08

1.2.1.2 Disc Brake. 08

1.2.1.3 Antilock Braking System (ABS) 08

1.2.2 Air brakes. 09

1.2.3 Exhaust brakes. 09

1.2.4 Electric brakes. 09

1.2.5 Parking brakes. 10

1.3 Braking system components.

1.3.1 Brake pedal. 10

1.3.2 Brake lines. 10



1.3.3 Brakes fluid. 10

1.3.4 Master cylinder. 11

1.3.5 Divided systems. 11

1.3.6 Tandem master cylinder. 12

1.3.7 Power booster or brake unit. 12

1.3.8 Hydraulic brake booster. 12

1.3.9 Electrohydraulic braking (EHB). 12

1.4 Disc brake systems.

1.4.1 Disc brake operation. 13

1.4.2 The rotor. 15

1.4.2.1 Brake fade 16

1.4.2.2 Rotor Metallurgy 16

1.4.2.3 Rotor Surface finish 17

1.4.3 Disc brake pads. 17

1.4.4 Disc brake calipers. 18

CHAPTER 2: LITERATURE REVIEW 19

CHAPTER 3: MATERIAL PROPERTIES OF DISC BRAKE

ROTORS 25

3.1 Materials used 25



3.2 Cast Iron 25

3.3 Specifications of car and Material Properties of Gray cast iron

3.3.1 Solid disc brake rotor

3.3.1.1 The specifications of car 26

3.3.1.2 The materials properties 26

3.3.2 Ventilated disc brake rotor

3.3.2.1 The specifications of car 27

3.3.2.2 The materials properties 27

CHAPTER 4: THEORY AND CALCULATIONS

4.1 Assumptions. 29

4.2 Stopping distance. 29

4.3 Weight transfer. 30

4.4 Braking efficiency. 31

4.5 Kinetic energy and Heat flux.

4.5.1 Approaches 32

4.5.2 Macroscopic model approach 32

4.6 Calculations

4.6.1 Calculations for heat flux application time 33

4.6.2 Calculations for kinetic energy heat flux time

4.6.2.1 Solid disc brake rotor 33



4.6.2.2 Ventilated disc brake rotor 35

CHAPTER 5: GEOMETRIC MODELING

5.1 Pro e Wildfire 4. 37

5.2 Module 2 - Part Modeling. 37

5.3 Module 5 - Drawing. 38

5.4 Modeled and drafted components. 38

CHAPTER 6: FINITE ELEMENT MODELING 41

6.1 Meshed components 42

6.2 SOLID90 43

6.2.1 SOLID90 Element Description 43

6.2.2 SOLID90 Input Data 44

6.2.3 SOLID90 Input Summary 44

6.2.4 SOLID90 Output Data 45

6.2.5 SOLID90 Assumptions and Restrictions 45

CHAPTER 7: FINITE ELEMENT ANALYSIS

7.1 Introduction. 47

7.2 Steps in FEA.

7.2.1 General Steps. 47

7.2.2 Steps in ANSYS. 47



7.3 Coupled field analysis. 48

7.3.1 Thermal Structural Analysis 49

7.3.2 Thermal and Structural Boundary Conditions 49

7.4 Modal analysis. 50

7.5 Procedure adopted for thermal analysis

of disc brake rotors. 50

7.6 Procedure adopted for structural analysis


7.7 Procedure adopted for modal analysis


CHAPTER 8: RESULTS

8.1 Inputs and results of ANSYS 11 52

8.2 Plots of Results

8.2.1 Solid disc brake rotor 53

8.2.2 Ventilated disc brake rotor 61

CHAPTER 9: CONCLUSION 69

CHAPTER 10: FUTURE SCOPE 70

REFERENCES



CHAPTER 1

INTRODUCTION

At the end of the 19th century the development of a brake system for the newly

invented automobile vehicles was needed. From that moment on, brake system which

makes use of several components (the brake disc among them), was developed. It was

after the beginning of the Second World War, in 1938, that the brake system

technological advance got great impulse due to the aeronautics industry necessity. Around

1886, in Germany, Gotlieb Daimler and Carl Benz would change the history of the world

forever, because they created, independently, the first prototypes of internal combustion

automobiles. This invention gave rise to the development of several automobile

components, and among them was the brake system. In the United States, in 1890,

according to Hughes, the American Elmer Ambrose Sperry invented a brake similar to the

present disc brake. An automotive brake disc brake rotor is a device for slowing or

stopping the motion of a wheel while it runs at a certain speed. In this project work the

complete study of brake systems used in cars is studied and the actual dimensions of the

solid and ventilated disc brake rotors of TATA indica cars are taken which are used to 3D

modeling of rotors in Pro e Wildfire 4. The model is then converted to iges format and

imported to Altair Hypermesh 7 for meshing. After meshing it is imported to ANSYS 11

with element for meshing defining as SOLID 90. Here coupled field finite element

analysis and modal analysis is carried using general purpose finite element analysis. Then

the results are compared for both solid and ventilated disc brake rotors and alternate

materials are also suggested.

The goals of our project are as follows:

i. Complete study of braking system in car.

ii. Conceptualization of working of the disc rotor.

iii. To carry out coupled-field analysis i.e., thermal to static structural analysis which

gives thermal stresses and their corresponding displacements in the disc brake

rotor due to the application of temperature.



iv. To predict natural frequencies and associated mode shapes by considering density

of the disc material.

v. Comparison of solid and ventilated rotor based on the above results.

vi. Suggesting the suitable material for disc brake rotor and checking whether the

design is safe or not based on the above results.

1.1 Fundamentals of Braking system

1.1.1 Principle of braking:

A basic braking system of a car has:

Brake pedal.

Master cylinder to provide hydraulic pressure.

Brake lines and hoses to connect the master cylinder to the brake assemblies.

Fluid to transmit force from the master cylinder to the wheel cylinders of the

brake assemblies, and

Brake assemblies drum or disc that stop the wheels.

The driver pushes the brake pedal; it applies mechanical force to the piston in the

master cylinder. The piston applies hydraulic pressure to the fluid in the cylinder, the

lines transfer the pressure which is undiminished in all directions within the brake lines

to the wheel cylinders, and the wheel cylinders at the wheel assemblies apply the brakes.

Force is transmitted through the fluid. For cylinders of the same size, the force

transmitted from one is the same value as the force applied to the other. By using

cylinders of different sizes, forces can be increased or reduced. In an actual braking

system, the master cylinder is smaller than the wheel cylinders, so the force at all of the

wheel cylinders is increased. When brakes are applied to a moving vehicle, they absorb

the vehicles kinetic energy. Friction between the braking surfaces converts this energy

into heat. In drum brakes, the wheel cylinders force brake linings against the inside of the

brake drum. In disc brakes, pads are forced against a brake disc. In both systems, heat

spreads into other parts and the atmosphere, so brake linings and drums, pads and discs

must withstand high temperatures and high pressures.

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