Optimization_of_braking_system_of_a_go-k.pdf

Optimization of Braking System of a Go-Kart BY ANNE.NAVEEN BABU 10031793 Contact: [email protected] A thesis submitted in partial fulfilment of the requirements of Staffordshire University for the degree of Master of Science in Automotive Engineering SUBMITED TO PROFESSOR PETER WARDLE

Faculty of Computing, Engineering & Technology Staffordshire University March 2013

Abstract The mobility feature of all automobiles is controlled by means of braking system, which helps the driver to reduce the speed or stop completely depending on the requirements and situation. A braking system is liable to work efficiently and effectively without causing any Mechanical, Thermal, Vibrational and Fatigue failures while in application. These kinds of failures are predetermined using available theories and experiments and prevented while designing the components to suit for their application. A commercially used Go-Kart car has been designed with a basic mechanical cable –operated disc brake system, which is been effectively used in the racing circuits without causing any mechanical failures. But racing cars are needed to be designed for performance, in which mass reduction for the overall body is one of the important criteria without affecting the efficiency. While balancing mass and efficiency, the mechanically operated braking system can be optimized considering only the mechanical failures. To start with, the existing braking system is reverse engineered using 3D scanner to obtain virtually scaled data and modelled by modifying it to acceptable CAD geometry assembly. Then assembly file is divided into different component files to make it suitable for FEA using computational method. After a careful literature survey, the forces affecting and the supports providing the stability to maintain equilibrium of the braking system is determined using acceptable theory and law. Using, FEA approach, the estimated worst condition mechanical failures possible in the braking system with existing materials is predicted. Then, the properties and details of existing materials are replaced with other materials with reduced mass and same or higher strength in each component is collected from a Material database package. Using the same FEA method, the results of possibility of failures are predicted. The worst condition mechanical failures can be obtained only if it is tested in uphill, downhill and level road conditions. The predicted results are then compared in spread sheet graphically and discussed further.

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Acknowledgement I am grateful to my supervisor, Professor PETER WARDLE who has not only guided me but also supported throughout the project. Under his guidance I was able to learn the structural integrity and application. It is a pleasure to thank the Staffordshire University, library, E-source; software installed in the other libraries which made my learning more flexible and was able to complete my project on time. I would also thank lab assistant Mr.ABBAS who has helped me in doing the experiment and providing the tools and equipment required. I would like to offer my thanks and regards to my parents. They always supported me and encouraged me for completion of my project.

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Table of Contents Abstract ................................................................................................................................................... 1 Acknowledgement ................................................................................................................................... 2 List of figures ......................................................................................................................................... 6 List of tables ............................................................................................................................................ 7 1

2

Introduction ..................................................................................................................................... 1 1.1

Back ground ............................................................................................................................ 1

1.2

Automotive Braking System ................................................................................................... 1

1.2.1

Mechanism ...................................................................................................................... 1

1.2.2

Drum Brakes.................................................................................................................... 1

Literature Review ............................................................................................................................ 4 2.1

Go Kart .................................................................................................................................... 4

2.2

Disc Brakes ............................................................................................................................. 4

2.2.1

Parts of Braking system ................................................................................................... 5

2.2.2

Operation and mechanism ............................................................................................... 5

2.2.3

Advantages of Disc brakes .............................................................................................. 6

2.2.4

Disadvantages of Disc Brakes ......................................................................................... 6

2.2.5

Braking System Design/Testing Checkpoints ................................................................. 7

2.2.6

Design Solution Selection process .................................................................................. 7

2.3

3

2.3.1

Component under Analysis ............................................................................................. 8

2.3.2

Types of forces ................................................................................................................ 9

2.3.3

Engine Specifications .................................................................................................... 10

2.3.4

Gradient calculation ...................................................................................................... 10

CAD Modelling Using Creo parametric from Scanned data ......................................................... 12 3.1

4

5

Boundary Conditions............................................................................................................... 8

Konica Minolta Vivid 910 Non-Contact 3D Digitizer .......................................................... 12

3.1.1

Application .................................................................................................................... 12

3.1.2

Procedure ....................................................................................................................... 12

3.2

Creo Parametric (CAD modelling Package) ......................................................................... 13

3.3

ANSYS Design Modeller ...................................................................................................... 14

Significance about CES edu pack.................................................................................................. 15 4.1

Selection of Materials using CES Edupack ........................................................................... 15

4.2

Translation design process .................................................................................................... 16

4.3

Frame ..................................................................................................................................... 16

FEA Analysis of the Brake Calliper assembly .............................................................................. 17 5.1

Preliminary analysis over brake plate from brake lever using existing design ..................... 17 iii | P a g e

5.1.1

Material specification .................................................................................................... 18

5.1.2

Boundary conditions for brake lever analysis ............................................................... 18

5.1.3

Results ........................................................................................................................... 19

5.2

5.2.1

Material specification .................................................................................................... 21

5.2.2

Boundary conditions...................................................................................................... 21

5.2.3

Results ........................................................................................................................... 22

5.3

6

Preliminary analysis over brake calliper from brake plate and pad ...................................... 21

Analysis of brake callipers with respect to previous analysis ............................................... 24

5.3.1

Material specification .................................................................................................... 24

5.3.2

Boundary conditions...................................................................................................... 24

5.3.3

Mesh refinement ............................................................................................................ 25

5.3.4

Results ........................................................................................................................... 26

Analysis along the gradients.......................................................................................................... 30 6.1

Downhill calculation with existing specification .................................................................. 30

6.1.1 6.2

Uphill with existing specification.......................................................................................... 36

6.2.1 7

8

Results in Uphill movement .......................................................................................... 37

Material Selection using CES Edupack......................................................................................... 40 7.1

Selection of material for brake lever ..................................................................................... 40

7.2

Selection of material for Brake calliper................................................................................. 41

7.3

Selection of material for brake plate ..................................................................................... 42

7.4

Selection of Material for Brake pad ...................................................................................... 43

FEA Analysis of the Brake Calliper post Material Selection (Phase 2) ........................................ 46 8.1

9

Results for Brake lever analysis along the downhill ..................................................... 31

Results of after post material selection .................................................................................. 46

8.1.1

Safety factor of brake lever – Post material selection ................................................... 46

8.1.2

Deformation and stress of brake lever- Post material selection .................................... 46

8.1.3

Safety factor of Brake plate and brake pad- Post material selection ............................. 47

8.1.4

Total deformation and equivalent stress for brake pad and plate .................................. 47

8.1.5

Safety factor in brake calliper........................................................................................ 48

8.1.6

Deformation on brake calliper ....................................................................................... 48

8.1.7

Stresses on the brake calliper – Post material selection ................................................ 49

Comparison of Existing and optimized results .............................................................................. 50 9.1

Mass comparison ................................................................................................................... 50

9.2

Price Comparison .................................................................................................................. 50

9.3

Safety factor comparison ....................................................................................................... 51

9.4

Equivalent stress comparison ................................................................................................ 52 iv | P a g e

9.5 10

Total deformation Comparison.............................................................................................. 54 Discussion ................................................................................................................................. 56

10.1

Discussion based on Individual Components ........................................................................ 56

10.2

Discussions based on Overall assembly ................................................................................ 56

11

Conclusion ................................................................................................................................. 58 11.1

Recommendations ................................................................................................................. 58

Bibliography .......................................................................................................................................... 60 12

Appendix ................................................................................................................................... 62

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List of figures Figure 1-1 –Methodology flow chart ...................................................................................................... 2 Figure 2-1- A Go kart car: (Central Polytechnic College Thiruvananthapuram, 2012) .......................... 4 Figure 2-2 – Disc brake rotor and calliper assembly ............................................................................... 5 Figure 2-3 – Operation and Mechanism (Baja Motorsport, 2012) .......................................................... 6 Figure 2-4 – Sliced view of Disc braking system.................................................................................... 7 Figure 2-5 – Parts of Brake assembly (Baja Motorsport, 2012) .............................................................. 8 Figure 2-6 – Brake calliper under analysis .............................................................................................. 8 Figure 2-7 – Go kart using the brake calliper to be analysed (Source: (Redwood Engineering (UK) Ltd., 2010)) .............................................................................................................................................. 9 Figure 2-8 – Forces acting on a moving car (BBC, 2013) .................................................................... 10 Figure 3-1- Scanned file using Minolta Scanner ................................................................................... 12 Figure 3-2-CAD geometry exploded view after modelling .................................................................. 13 Figure 3-3 – Brake Calliper assembled with brake disc model ............................................................. 14 Figure 4-1- Overview of CES- Edupack (Source: (EduPack, 2013)).................................................... 15 Figure 4-2- Selection Filter used in CES............................................................................................... 16 Figure 4-3- Screening tool for material selection (EduPack, 2013) ...................................................... 16 Figure 5-1 – Fulcrum mechanism of brake lever (Source: (The Engineering Toolbox, 2013)) ............ 18 Figure 5-2 – Boundary conditions for brake lever ................................................................................ 19 Figure 5-3 – Force reaction at fixed support and cylindrical joint ........................................................ 20 Figure 5-4 – Safety factor of brake lever............................................................................................... 21 Figure 5-5 – Boundary conditions for brake pad and calliper ............................................................... 22 Figure 5-6- Force reaction for brake pad and calliper ........................................................................... 22 Figure 5-7 - Force reaction for lever and brake pad .............................................................................. 22 Figure 5-8– Safety factor for brake plate and brake pad ....................................................................... 23 Figure 5-9– Directional deformation for brake plate ............................................................................ 23 Figure 5-10– Equivalent stress for brake plate ...................................................................................... 24 Figure 5-11– Boundary conditions for brake callipers .......................................................................... 25 Figure 5-12– Meshing for brake callipers ............................................................................................. 26 Figure 5-13 - Safety factor for brake calliper ........................................................................................ 27 Figure 5-14– Directional deformation along rotation of brake disc ...................................................... 27 Figure 5-15– Directional deformation along lateral side of brake disc ................................................. 28 Figure 5-16– Directional deformation along downward of brake calliper ............................................ 28 Figure 5-17– Stress concentration on brake calliper ............................................................................. 29 Figure 6-1 –Along the downhill gradient .............................................................................................. 30 Figure 6-2– Safety factor on brake lever during downhill movement .................................................. 32 Figure 6-3– Joint force on brake lever during Downhill movement ..................................................... 32 Figure 6-4– Force reaction on brake lever during Downhill movement ............................................... 33 Figure 6-5– Force reaction on brake pad from calliper during Downhill movement ............................ 33 Figure 6-6– Force reaction on brake plate from lever pin during Downhill movement........................ 34 Figure 6-7– Safety factor on brake plate during Downhill movement .................................................. 34 Figure 6-8– Safety factor on calliper during Downhill movement ....................................................... 35 Figure 6-9–Deformations along downward of brake calliper ............................................................... 35 Figure 6-10–Stresses along downward of brake calliper ...................................................................... 36 Figure 6-11–Uphill gradient .................................................................................................................. 37 Figure 6-12 – Safety factor for brake lever in uphill ............................................................................. 38 Figure 6-13 – Safety factor on brake pad and brake plate on uphill ..................................................... 38 vi | P a g e

Figure 6-14 – Stresses on Brake calliper ............................................................................................... 39 Figure 6-15 – Safety factor of brake calliper......................................................................................... 39 Figure 7-1- Material selection for lever ................................................................................................ 41 Figure 7-2–Material selection for brake Calliper .................................................................................. 42 Figure 7-3–Material selection for Brake plate....................................................................................... 43 Figure 7-4- Pad yield strength ............................................................................................................... 44 Figure 7-5–Pad material with maximum service temperature............................................................... 45 Figure 8-1 – Safety factor for brake lever - Post material selection ...................................................... 46 Figure 8-2 – Directional deformation and equivalent stress – Post material selection ......................... 47 Figure 8-3 – Safety factor for Brake pad and brake plate – Post material selection ............................. 47 Figure 8-4 – Total deformation and equivalent stress in brake pad and plate – Post material selection ............................................................................................................................................................... 48 Figure 8-5 –Safety factor in brake calliper - Post material Selection .................................................... 48 Figure 8-6- Deformations in brake calliper – Post material selection ................................................... 49 Figure 8-7-Stresses on brake calliper – Post material selection ............................................................ 49 Figure 9-1 – Mass comparison for individual parts before and after optimization ............................... 50 Figure 9-2 –Price comparison for individual parts before and after optimization ................................ 51 Figure 9-3 – Safety factor comparison for individual parts in level ground ......................................... 51 Figure 9-4 - Safety factor comparison for individual parts in uphill motion......................................... 52 Figure 9-5 – Safety factor comparison for individual parts in downhill motion ................................... 52 Figure 9-6 –Equivalent stress comparison for individual parts for Level ground ................................. 53 Figure 9-7 – Equivalent stress comparison for individual parts for Uphill motion ............................... 53 Figure 9-8 - Equivalent stress comparison for individual parts for Downhill motion........................... 54 Figure 9-9 – Deformation on level ground after optimization .............................................................. 54 Figure 9-10 – Deformation on uphill motion after optimization ........................................................... 55 Figure 9-11 – Deformation on downhill motion after optimization ...................................................... 55

List of tables Table 5-1 – Level ground calculation values ........................................................................................ 17 Table 6-1 –Downhill movement calculation values .............................................................................. 30 Table 6-2 –Uphill calculation values..................................................................................................... 37 Table 7-1 – Comparison of materials for brake lever............................................................................ 40 Table 7-2- Comparison of material for Brake calliper .......................................................................... 41 Table 7-3 – Comparison of material for brake plate ............................................................................. 42 Table 7-4 – Comparison of material for Brake pad ............................................................................... 43 Table 11-1 – change of material for whole assembly............................................................................ 58 Table 11-2 –Change of materials with Selected parts (Long studs and Assembly bolts) ..................... 58

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1 Introduction 1.1 Back ground In the present scenario, the automotive sector is growing vigorously with its competitors by presenting automobiles endowed with its best performance, safety, efficiency, durability and reliability. On one hand, Passengers cars serve for travelling from one place to another for personal as well as official use. On another hand racing cars are manufactured for entertainment and business from leading brands which serves as a prestigious product while competing on the racing circuits. In such cases these racing cars are much concentrated on performance than luxury and style. Each and every part is designed based on their contribution in enhancing the performance and racing standards. With respect to the racing car standards and conditions, this particular project deals with the “Optimisation of braking system in a Go-kart car”. The braking system is an essential for a racing car to provide deceleration at the corners and stop of the vehicle. As a most active component, this particular system of an automotive suffers a major wear and tear due to enormous heat dissipated during friction next to tyre. But more than wear and tear, the braking efficiency plays the first preference in case of a Go-kart racing car. Also the cost is not at the top preference in this case, since car is to be manufactured in a lower quantity for a prestigious event. Unlike the passenger cars and other racing cars, the go kart cars usually have less body weight literally almost equal to the weight of the driver. Out of whole body, 75% of weight is provided by the engine which equally weighs to a two wheeler engine.

1.2 Automotive Braking System The objective of the braking system is to decelerate the automobile and stopping it with respect to specific distance and time. And this distance and time depends on the foot force applied by the driver. According to law of conservation of energy, brakes are the device which converts rotational energy of the wheel to heat energy by producing a physical contact. 1.2.1 Mechanism The force exerted by the driver on the brake pedal, which is transferred to the power booster for amplification which is operated by Pascal’s law where the small force is converted to 10 times larger force with the help of hydraulic mechanism. The piston pushes the brake fluid inside the master cylinder which triggers the piston which transmits the higher force generated by the piston of larger surface area to apply brakes by the action brake calliper towards the rotor disc or drum by means of frictional contact. 1.2.2 Drum Brakes Drum brakes comprises a rotating drum mounted along the wheel and the brake calliper exerts a force which gets transmitted to the inside surface of the brake drum. In short, the direction of force is radially outward to the rotor drum. So the action of brake callipers stops the rotation of drum which ultimately slows down the rotation of wheel. As soon as the foot pedal triggers the pressure inside the cylinder, the brake pads present on the leading and trailing edge of the brake calliper generate a contact with the brake drum to slow down the rotation of the disc. And also retractions are provided in the foot pedal as well as callipers to bring back the braking condition to its initial state from the final state depending on the driver’s intention.

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1.2.2.1 Advantages of drum brakes:  Parts are available and easily manufactured  Less expensive comparatively 1.2.2.2 Disadvantages of drum brakes:  This needs routine maintenance  Drum brakes heats up and expands the drum wearing out the lining material  Braking efficiency is lowered in wet conditions

Figure 1-1 –Methodology flow chart

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Hypothesis: Optimizing the materials in different parts of Go-Kart brake calliper using theoretical input and FEA output to predict the effective change.

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2 Literature Review 2.1 Go Kart Go Kart is a 4-wheeled car with small sized engine purposely used in United States in earlier1950s. Art Ingels was the first one to develop the concept of Karting. He built the first concept car in California in year 1956. From there it became famous all over America and Europe. The Go Kart car does not have any suspension system and differentials. And they are geometrically designed to fit the racing tracks. They are used for entertainment and for hobbies by non-professional drivers. They are known to be cheapest form of race vehicles which even can be used by the children starting from age 8. It is also a safest way of introducing race drivers to racing career. Drivers can prepare themselves for high speed control, reflex development and high response decision making skills. These cars are also used for analysis to bring out efficiency in order to withstand the commercial motor racing firms. It consists of basic parts like chassis, Engine, Steering, transmission, tyres, brake and an electric starter. As we are concerned about the braking system, these go karts in earlier models had single rear drum brakes. And the brake was capable of stopping the car running at 40 mph.

Figure 2-1- A Go kart car: (Central Polytechnic College Thiruvananthapuram, 2012)

2.2 Disc Brakes A Disc brake is a braking system used in wheels which slows down the rotation of wheel by friction generated on the rotor disc by push brake pads with the help of calliper sets. These brakes are usually made of cast iron, but in recent cases they are made of composite materials such as reinforced carbon-carbon and other ceramic matrix composites. Disc brake system was found in America around 1970s. Earlier they were used in few cars and a decade after it was used in almost all modern card and light weight trucks in front as well as in all four wheels. (Gilles, 2004)

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Figure 2-2 – Disc brake rotor and calliper assembly

2.2.1 Parts of Braking system  Brake pedal – Controlled by driver  Brake booster – Enhances braking effectively  Master Cylinder – Pascal’s law to multiply the force by means of hydraulics  Calliper and Disc – Contacting parts to serve the purpose of driver(Either stopping or slowing down)  Brake lines – Connection to transfer the hydraulic power to the brake callipers  Brake fluid – Hydraulic agent to transfer power from Master piston to brake piston  Connecting rod – Metallic part to deliver drivers response from brake pedal to piston of master cylinder. 2.2.2 Operation and mechanism Disc brake consists of a rotor (disc) and a set of calliper which is similar to bicycle brake as shown in Figure 2-2 O-ring made of rubber with square cut seals the disc brake that applies piston to its bore. While comparing with drum brake system, the disc brake system does not require spring element to return the brake to its original position after brake release, Instead the O-ring distorts while braking and when released, the seal returns it to its original position by pulling the piston back and allowing the linings to release the rotor. The linings, pad, glides which is located on the surface of the rotor disc are designed in such a way to wipe off contaminants. (Gilles, 2004) Brake pedal to Brake calliper- As soon as the driver applies foot effort on the brake pedal, the force generated transfer to the piston present in the master cylinder as shown in the Figure 2-3. Then the piston from the master cylinder applies pressure to the brake fluid present in the cylinder by passing through the brake lines. And then it transfers it to each and every brake callipers to stop the wheels. Brake Calliper to wheels – When the brake calliper mechanism receives the hydraulic fluid in the cylinder, it forces the piston in brake calliper to push the brake pad towards the rotor disc. By this way the motion of the wheels will be arrested by the brake pads. Here the kinetic energy of 5|Page

the wheels is transferred in the form of heat energy to the brake power depending on the torque generated by the wheels. Higher the torque, higher the heat energy generated to the pads as well as to atmosphere. In order to withstand high temperature and stresses induced while braking, the material for the brake pad, brake lines and rotor disc should be chosen carefully.

Figure 2-3 – Operation and Mechanism (Baja Motorsport, 2012)

2.2.3 Advantages of Disc brakes  When the linings on the rotor disc get wear, the piston slides forward to the bore to selfadjust with the slack though it consumes more fluid from the reservoir.  They also have a mechanism of parking brake that will automatically adjust the piston to thread forward to manage the clearance.  They are relatively light in weight, less costly and better heat dissipation.  Less distortion when subjected to brake lining force when compared with drum brake systems  Braking efficiency is more compared to drum brakes, since the contaminants falls of the rotor avoiding wear in brake pads  Disc brakes are good to be used as front brakes, due to the effect it applies on each side of vehicle avoiding pull along one particular direction, where as it is not possible in drum braking which results in unequal lining wear due to uneven size of the drum diameters. (Gilles, 2004) 2.2.4

 



Disadvantages of Disc Brakes

Due to the large size of the rotor disc, it is prone to the amplify noise by resulting vibration. Since harder linings and thin rotor increases the complexity of the problem These brakes are not efficient as drum brakes in the application of parking brake. Disc brakes does not self-energize as drum brakes do since they feel difficult to handle the slick surfaces of the rotor. It is similar in holding a glass between a couple of glass pieces. When in motion the hydraulic system helps in gripping the brake pad to stop the vehicle, whereas in parking position hand or foot effort does not help in effective braking as self-energized drum brakes do.

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Figure 2-4 – Sliced view of Disc braking system

2.2.5 Braking System Design/Testing Checkpoints The design and testing of the braking system should have the following check points before designing.            

Braking Effectiveness Braking efficiency Stopping Distance, lightly and fully laden Response time Partial Brake system failure Brake fluid volume analysis Thermal Analysis Emergency and Park brake Specific Design Measures In-Use factors Component sizing Safety regulations

2.2.6 Design Solution Selection process For designing a braking system, the following rules should be followed while carrying out each and every step          

Considering all the constraints, the best yielding reasonable design should be compromised. The basic requirements and needs should be determined clearly and precisely. Instead of running production changes after implementation, one best simple design will be fine enough. It is not required that the first design will always be the best one. Design Optimization should be followed in a systematic approach. Each and every design concepts should be clearly evaluated with alternate solutions. Variation in concepts should be practiced. To get rid of the production cost, the material cost should be minimized while designing. To be used globally, every design considerations should be standardized Valid Complaints brings out a valid design considerations and inputs.

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 

Accident database should be investigated which are relevant to brake failures. A ranking matrix would help in obtaining the best design on considering cost, safety as well as other influential factors.

Figure 2-5 – Parts of Brake assembly (Baja Motorsport, 2012)

2.3 Boundary Conditions As per the available braking standards of Go kart car, the forces needed for braking is calculated from the vehicle specifications. And the point where the brake caliper is mounted is determined. Though the mounting position plays a major role in providing a better braking efficiency, the mounting position is not considered when the static analysis is performed only on the brake caliper assembly, since the mounting positions and details of the vehicle chassis are unknown. 2.3.1

Component under Analysis

Figure 2-6 – Brake calliper under analysis

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Figure 2-6 – Brake calliper under analysis shows the picture of brake calliper under analysis. This calliper is purposely design to suit the requirements of a Go Kart car as shown in the Figure 2-7 (Redwood Engineering (UK) Ltd., 2010)

Figure 2-7 – Go kart using the brake calliper to be analysed (Source: (Redwood Engineering (UK) Ltd., 2010))

For designing an effective braking system, one has to determine the boundary conditions affecting it. The following are the boundary condition requisites for the concerned Braking System They are     

Types of Forces Speed at which the Brakes are applied The Gradient or the angle of inclination of the Go-kart with respect to the ground level Location of Centre of Gravity Wheel Diameter

2.3.2 Types of forces A vehicle under motion exerts the following forces on the wheels     

The effect of gravity on the car The reactionary forces from the road on to the wheels The Engine speed which pushes the car forward The friction force between the tire-road interface Air Resistance acting on the front of car

Figure 2-8 shows the forces acting on the car and in turn the wheels of the car

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Figure 2-8 – Forces acting on a moving car (BBC, 2013)

Go-karts have very low ground clearance as they are used for racing applications. The purpose of which is to overcome air resistance which in turn gives better aerodynamic performance. 2.3.3 Engine Specifications Engine: Honda Gx160-163 cm3 Brake power = 3.6 Kw Engine Speed = 3600 rpm Dry weight of engine = 15 Kg Top Speed = 40 mph 2.3.4 Gradient calculation The gradient or the angle of inclination of the car with respect to the ground is also important as they influence the braking effort. Based on the gradient there are three sub cases on which the final optimized Braking system is tested. Gross weight of vehicle W = 65 kg Wheel base = Radius of wheel = 0.12 m 2.3.4.1 Assumptions Velocity = Weight distribution – 45% for Front and 55% for the rear Level ground stopping distance s = 10 m Height of Centre of Gravity = 0.015 m 2.3.4.2 CASE1: Gradient=0

(Engineering Inspiration, 2013) has formulated the equations for the Go-Kart running on a flat Track and the gradient is 0 (Level Road) as follows Deceleration

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Total Braking Force

Static Front weight Static Rear weight

(

)

[2] [3] [4]

Dynamic Front Weight

[5]

Dynamic Rear Weight

[6]

Brake Torque Disc Effective Radius

[7] [8]

Deceleration MFD

[9]

Tangential Force

[10]

Normal Force N.F

[11]

2.3.4.3 CASE2: Gradient>0 When the Go-Kart is running on a inclined track where gradient is >1 (Up the Hill) Slope

[12]

Degrees Stopping Distance Velocity

Static Front Weight

[13] [14] [15] [16]

Static Rear Weight

[17]

2.3.4.4 CASE3: Gradient <0 When the Go-Kart is running on a inclined track where gradient is <1 (Down the hill) Stopping Distance Velocity

Static Front Weight

[18] [19] [20]

Static Rear Weight

[21]

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3 CAD Modelling Using Creo parametric from Scanned data The brake calliper under analysis was scanned using Minolta Scanner to obtain the cloud scan data required for the elementary design. Using the cloud data the Brake Calliper was designed in Creo Parametric 2.1

3.1 Konica Minolta Vivid 910 Non-Contact 3D Digitizer Vivid 910 digitizer uses laser-beam light to scan the work piece and creates 3D data image by determining the distance information. The beam creates scan using high precision galvanometric mirror with 640X480 resolutions where each individual points can be measured. Scanning is performed to obtain the 3D virtual image of the physical model and import into the computational design package to use the scaling and then modelling it further for analysis and design improvement. 3.1.1 Application Konica Minolta digitizer is used in quite a number of applications  Examination and verification of component in casting and injection moulding  For obtaining data for FEA in analysing automotive components and for its verification results  For evaluating accessories which does not have previous CAD data  Interference check and mock ups for mechanical components by creating design data  Other research process involved in requirement of 3D modelling of solid parts.  Data creation in CAE department.  Integrated with rapid prototyping which are in need of different scaling and sizing.

Figure 3-1- Scanned file using Minolta Scanner

3.1.2 Procedure The Konica Minolta digitizer apparatus consists of a 1. 2. 3. 4.

3D scanning laser beam integrated camera with distance locator, Turn table A computer peripheral with device integrating software Calibration chart 12 | P a g e

5. Lens box containing different lenses based on the distance, position and location of physical model The physical model is mounted on the turn table and coated with powder used for flaw detector, since the reflection surface and black objects does not help in providing acceptable 3D image data. The software is initiated for setting up the scanner in a proper position before taking final images. After setting up the scanner in a position facing the turn table with the physical part, the 3D images are obtained for each rotation and displayed on the software package. The user has to organize the image and register the images together by gathering the common points lying between them and form as a single 3D image. This 3D image should be exported in the form of STL (Stereo lithography) file as shown in Figure 3-1. This file can be further exported to CAD package for surface modelling. (Engnet, 1998)

3.2 Creo Parametric (CAD modelling Package) PTC (Parametric Technology Corporation) Creo Parametric tool is advanced version of Pro Engineer Wildfire 5. It is one of the standard software used for 3D CAD modelling and assembling. Creo Parametric facilitates in engineering field to improve design, analysis and manufacturing the mechanical components which needs engineering change. This software allows creating 3 dimensional virtual solid models. The date after CAD modelling can be further taken for analysis by considering real life behaviour under specific operating conditions. If the design is successful, then it is taken to the next stage of manufacturing using CAM. (Shih, 2013)

Figure 3-2-CAD geometry exploded view after modelling

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After obtaining the 3D image in the form of STL file from the Minolta digitizer, the image is imported in CREO parametric and then surface modelled using modelling tools available in it. Starting from creating the datum planes for the whole assembly, then surface modelling each and every part using the editing tools like extrude, constant and variable section sweep, revolve, swept blend, boundary blend, style, project, fill, offset etc., to make separate part file and gathered to form a complete brake calliper assembly as shown in Figure 3-2-CAD geometry exploded view after .

3.3 ANSYS Design Modeller ANSYS Design Modeller is a part of ANSYS Workbench which can be used as CAD editing tool before exporting to the FEA environment. Design Modeller serves as an intermediate tool between standard CAD package and standard FEA package. In design modeller, the FEA Engineer can modify, edit and change the original CAD model to suit or favour the FEA model. In short, FEA model simplification to improve the meshing constraints by avoiding the design complexities can be done in ANSYS Design modeller.

Figure 3-3 – Brake Calliper assembled with brake disc model

For model simplification and analysis enhancement in FEA, the CAD model is edited using the tools such as freeze, unfreeze, slicing, projection, body operation, Boolean and symmetry were used.

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4 Significance about CES edu pack CES EdupackTM is considered to be one of the top teaching resources in the field of Material Engineering, design and processing. Prof .Mike Ashby and few other colleagues from University of Cambridge originated the concept of creating CES edupack with the help of Granta Design group. CES Edupack has established comprehensive resources with organized material library and user friendly options to access the materials available in the world. These data were augmented from various text books, lectures, projects and exercises. A unique recourse was developed as a result supporting materials, Sustainable design methods in the subject areas which includes mechanical engineering, industrial engineering, product design, material science and other relevant subjects. Now it is used along with all years of undergraduate and post graduate studies and even for research and teaching purposes. The material data available here contains almost all the characteristics and properties of the materials needed based on the particular family as shown in Figure 4-1

Figure 4-1- Overview of CES- Edupack (Source: (EduPack, 2013))

4.1 Selection of Materials using CES Edupack The CES package contains 3 different levels of database level1,2 and 3. Level 1 consists of details including Material name, electrical properties, application, thermal properties and mechanical properties with limited amount. Level 2 includes the data from Level 1 and other numerical data, technical details and guidance for design changes. Level 3 includes level 1 and level 2 and full accessibility for CES selection with numerical data for all materials. All the levels are having the options of browsing, searching and selection. By hierarchy method, the browsing can be done to explore the database depending on the material family. The searching method can be performed by specifically mentioning the name of the material needed. And by selection method, the records of a material can be retrieved based on design criteria as shown in Figure 4-2. (EduPack, 2013)

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Figure 4-2- Selection Filter used in CES

4.2 Translation design process Most of the engineering parts take one or more functions such as pressure, heat transfer, load etc. It is necessary to consider the constraints. The part dimensions are fixed and constrained to get applied by boundary conditions without experiencing failures. The ultimate aim of the design engineers is to make the design less cheap and reduce the mass as much as possible. In the translate design process, the engineer provides details about objective, function, and variables. (EduPack, 2013)

4.3 Frame    

Function – The function of Engineer is to reduce the mass and make it as cheap as possible Screening – The materials which are not suitable for the application is removed based on screening process as shown in Figure 4-3. Ranking – The materials are further filtered based on the ranking that displays the list of best materials suitable process. Documentation – Detailed explanation about the material is obtained based on the rankings (EduPack, 2013)

Figure 4-3- Screening tool for material selection (EduPack, 2013)

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5 FEA Analysis of the Brake Calliper assembly In phase 1, the basic analysis is split to number of sub analysis using part files instead of analysing assembly as a whole. There are two main reasons, which serve to split the analysis in categories.  The results are necessary to be plotted for individual parts instead of analysing the assembly as a whole so that forces causing the stresses and displacements can be carefully identified in order to pin point the variations and problems happening in individual carefully which in turn supports in reasonable optimization  Meshing and convergence plays a vital role in FEA, which takes less time and reduced errors in simplified geometry rather than providing varied results in complicated geometry. Moreover the simulations with complicated geometry consume more computer memory and time to provide the output that will not be always available. Considering these reasons, the analysis is divided into three different parts based on a strategy, 1. Brake lever analysis 2. Brake plate and pad analysis 3. Brake Calliper analysis

5.1 Preliminary analysis over brake plate from brake lever using existing design Initially the load is transferred from the foot to the master cylinder with piston and reaches the lever part of brake calliper assembly. To calculate the forces affecting the lever and transferring the forces to the wheels, theoretical formulations are needed to be executed to obtain maximum possible forces affecting the whole assembly. By using equations [1] to [21], various parameters are obtained as shown in Table 5-1. Table 5-1 – Level ground calculation values

Level ground analysis Parameters Speed

Values

Units 40 mph

17.88 m/s

Total vehicle weight

65 Kg

Stopping distance

10 m

Average deceleration

15.98472 m/s^2 1.629431 g

Total braking force

1039.007 N

static frtwt(Ws) Dynamic front weight Rear static weight

29.25 kg 30.72101 kg 35.75 kg

Dynamic rear weight

21.03986 Kg

Brake Torque

124.6808 Nm 6.25 cm

Disc effective radius

0.0625 m 17 | P a g e

Deceleration (MFDD)

2.226607 g 21.84302 m/s^2

Tangential force

1994.893 N

Normal force

9974.465 N

5.1.1 Material specification After finding out the parameters affecting the brake calliper as a whole, it is necessary to find out the matching material for each and every components of the brake calliper assembly. To carry out that, the components are individually tested for Vickers hardness. Using Vickers hardness test, one could probably find the material properties and suitable material matching the existing one. Using experiment and CES Edu pack, it is easy to predict the properties of material and approximately judge the family of material. In this case of lever Cobalt-base-super alloy, multiphase, MP159, cold drawn, aged (solution treated) was found to be the closely matching material for the existing brake lever. Also, Stainless steel, ferrite, AISI 429, wrought, annealed found to be matching with brake plate using Vickers hardness number while comparing with the materials available in CES material library. 5.1.2 Boundary conditions for brake lever analysis The brake lever force acts similar to fulcrum mechanism as shown in Figure 5-1

Figure 5-1 – Fulcrum mechanism of brake lever (Source: (The Engineering Toolbox, 2013))

To start with, after defining the materials in engineering data of ANSYS workbench, and linking the materials to the corresponding parts, the loads and support constraints should be defined reasonably according to the available standards and formulation. According to the Parameters Speed

Values

Units 40 mph

17.88 m/s

Total vehicle weight

65 Kg

Stopping distance

10 m

Average deceleration

15.98472 m/s^2 1.629431 g

Total braking force

1039.007 N 18 | P a g e

static frtwt(Ws) Dynamic front weight Rear static weight

29.25 kg 30.72101 kg 35.75 kg

Dynamic rear weight

21.03986 Kg

Brake Torque

124.6808 Nm 6.25 cm

Disc effective radius Deceleration (MFDD)

0.0625 m 2.226607 g 21.84302 m/s^2

Tangential force

1994.893 N

Normal force

9974.465 N

, the boundary condition is defined by establishing fixed support in the plate model, which is considered to be a rigid body in order to measure only the results obtained from the brake lever. And bearing load is applied to the pin end where the lever is physically connected to the brake master cylinder. Also the other end of the lever is connected to joint load where bearing load will get transmitted to the body of brake calliper as shown in Figure 5-2. Whereas the brake plate considered being a rigid body is fixed on the other side to get the maximum stresses and deformation possible in the brake lever. Another consideration taken in account for creating the normal force on the pin end as per the calculation shown in Table 5-1, the bearing load is provided to the lever at point A to generate the equivalent normal reaction force at point B as shown in Figure 5-2.

Figure 5-2 – Boundary conditions for brake lever

5.1.3 Results After setting the boundary conditions and suitable mesh, model is made to run for simulation in order to get the result of interest. Here the result of interest is mainly focused on transfer of loads from one component to another. Precisely, the output obtained from one component is taken as input for another component. So the force reaction obtained from the fixed position of plate is 19 | P a g e

taken and the joint force obtained in the bearing joint of the lever as shown in the Figure 5-3 and cylindrical support is considered for the next analysis as a boundary condition. 5.1.3.1 Reaction and joint forces on lever

Figure 5-3 – Force reaction at fixed support and cylindrical joint

5.1.3.2 Safety factor of the lever Safety factor plays a major role to decide if the component is strong enough to withstand the loads and supports while in application. In this case the allowable safety factor is assumed to be 2, if it is less than that the component is supposed to be not under design standards of the brake calliper. The safety factor of the brake lever component is shown in Figure 5-4 of brake lever.

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Figure 5-4 – Safety factor of brake lever

5.2 Preliminary analysis over brake calliper from brake plate and pad After finding the reaction forces generated on lever of brake calliper, the input forces affecting the brake plate and brake pad are obtained directly as an input for next simulation. In this case analysis is made over two different components with different material properties bonded together. And one more force acting on the brake pad is also considered. This force is nothing but the tangential force caused by the rotation of brake disc. Apparently both forces are meeting in this particular analysis theoretically. The result of this analysis in turn provides the input for the next analysis with brake calliper separately. And in this case the brake calliper body is acting as a rigid body and does play a role as a supporting element to calculate the reaction force and not as main component. As this result only need to show the effect of plate and pad with existing material and geometry. 5.2.1 Material specification As mentioned before, the brake pad and brake plate does have a different material property which was tested in Vickers hardness test. And the properties of materials were obtained from the CES material library matching the Vickers hardness number. Thus the material for Brake pad is supposed to be Asbestos (amosite) (f), brake plate with Stainless steel, ferrite, AISI 429, wrought, annealed, brake calliper model with Al-70%Sic (p) MMC powder product. 5.2.2 Boundary conditions After specifying the materials and its properties in engineering data, the boundary conditions are linked to the geometry in static structural environment to carry out the simulation. The loads and supports and the reaction forces obtained from the previous analysis are substituted here get the results of interest. In this case, the reaction force of brake lever is transferred to the brake plate and the tangential force calculated theoretically due to the maximum speed of the disc rotation is specified on the brake pad is defined based on theoretical calculation as per the values generated in

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Figure 5-5 – Boundary conditions for brake pad and calliper

5.2.3 Results After establishing the boundary conditions for brake pad and brake plate assembly, the model is made to run with acceptable mesh settings to obtain force reactions, stresses displacement and safety factor. And the point to be noted here is, according to Newton’s third law of motion “Every action has equal and opposite reaction”. That means the input force given to the part generates the same force as a reaction with respect to the geometry irrespective to the material specified. And also as an added advantage of finite element method, the force corresponding to each coordinate axis also determined, 5.2.3.1 Reaction forces for Brake pad and brake plate

Figure 5-6- Force reaction for brake pad and calliper

Thus the output results of brake pad and brake plate assembly is obtained as shown in Figure 5-6 and Figure 5-7 will be taken as input to the brake calliper assembly.

Figure 5-7 - Force reaction for lever and brake pad

5.2.3.2 Safety factor for brake pad and brake plate Now similar to the previous analysis performed in brake lever component, the same conditions are established in brake pad and brake plate. The Figure 5-8 and brake pad shows, factor of safety is weak in the brake plate. Above all, the factor of safety depends on the load applied and the yield strength of the material. So it is clearly evident that the yield strength of the material should be more enough to withstand the design load in order to bring out the safe component while in application.

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Figure 5-8– Safety factor for brake plate and brake pad

5.2.3.3 Directional deformation along tangential direction of brake disc rotation The directional deformation along the force applied in the tangential direction shows the deformation of plate towards the brake calliper. That reveals that whenever brake is applied, this part of the brake plate gets affected more to stresses and strains than the other symmetrical part. Moreover, it is also clear that the part need not be symmetrical since the tangential force is applied in one particular direction where symmetry does not exist as visible in the Figure 5-9.

Figure 5-9– Directional deformation for brake plate

5.2.3.4 Equivalent stress along the tangential direction of brake disc rotation The equivalent stress for the brake plate along the tangential direction as seen in Figure 5-10 shows that the equivalent stress in the region where there is a sudden change in geometry presents the highest value. And of course the brake pad geometry was hidden in this case since, the stress

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value in this region was considerably negligible and if it is added, and then the stresses to be presented for the brake plate will be hidden.

Figure 5-10– Equivalent stress for brake plate

5.3 Analysis of brake callipers with respect to previous analysis The simplification of the model gets completed here considering the remaining calliper geometry with best mesh and appropriate boundary conditions obtained from the previous analysis. As the whole calliper assembly has couple of components which are symmetrical about the tangential direction of the wheel except the brake calliper components, since they differ in the supports attached and the attachment of pair of long studs which gets bonded in only one of the callipers. Other calliper is attached with nuts along the long studs defined by no separation contact. 5.3.1 Material specification As mentioned earlier, the Vickers hardness test is carried out and the corresponding hardness number is plotted to find out the relevant material properties from CES edu pack and it is verified finally by calculating the overall mass of the physical component assembly measured in the weighing machine. The existing material obtained for the components are Al-70%SiC(p) MMC powder product for brake calliper, Stainless steel, ferrite, AISI 429, wrought, annealed for assembly bolt, and Stainless steel, ferrite, AISI 429, wrought, annealed for long stud. 5.3.2 Boundary conditions The boundary conditions are specified according the output obtained from the results of previous two analyses. Yet the forces of bearing load acting on the joint of the lever is transferred to the calliper body on both sides also the tangential forces obtained from the brake pad and plate assembly is transferred to the pad rest present on the calliper. On the other hand the supports are established in one side of one calliper and other calliper is let free. And the inner part of both the calliper part is provided with compression only support by considering the compression caused by the rotating disc. Since the geometry of the disc is eliminated by just applying the compression only support exerted on the brake pad which in turn passes to the brake calliper for model simplification as shown in the

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Figure 5-11– Boundary conditions for brake callipers

5.3.3 Mesh refinement The meshing part of the brake calliper is not simple compared to the previous two analyses, since the geometry arrangement is comparatively complicated. So in order to establish proper mesh in the geometry, slicing of the part is performed in the design modeller and simplified the geometric complexities. After establishing the reasonable changes with sweep able bodies, the refinement was performed to obtain valid and relevant results as shown in Figure 5-12. Moreover there is no chance of performing the validation of results with the experiment.

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Figure 5-12– Meshing for brake callipers

5.3.4 Results In this case, the reaction forces are not necessary, since all the forces are acting to the same component from all the possible directions available. But it is necessary to calculate the deformations and stresses obtained in all the possible directions, since results from each direction decides whether to change the properties of material or modify the geometry of the component. Also shows which part of the calliper getting affected a lot due to the forces acting on it. 5.3.4.1 Safety factor of the brake callipers Minimum safety factor of brake calliper is shown on Figure 5-13 calliper. The affected region suffers the weakness due to the large amount of tangential force generated by the brake plate while braking. So the affected region should be given consideration for a design change by replacing with new material or modifying the geometry providing better safety factor.

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Figure 5-13 - Safety factor for brake calliper

5.3.4.2 Directional deformation along tangential direction The directional deformation along the tangential direction shows the highest deformation due the larger tangential forces applied by the brake pad. Also from the Figure 5-14, it is evident that deformations are caused not only due to the force applied but also due to the position of supports. The region with the lowest deformation indicates the calliper with fixed support and the calliper part with the maximum deflection indicates the freely hanging part without any fixed supports and the deflection resembles close to a cantilever beam.

Figure 5-14– Directional deformation along rotation of brake disc

27 | P a g e

5.3.4.3 Directional deformation along the lateral side of the brake calliper assembly The directional deformation along the lateral side of brake calliper assembly as shown in Figure 5-15 is comparatively lower than the deformations occurring on tangential direction. But these regions show the secondary consideration that getting deformed.

Figure 5-15– Directional deformation along lateral side of brake disc

5.3.4.4 Directional deformation along vertical direction Similar to the deformation along the lateral direction, vertical direction also shows comparatively lower deflection value, the region of deformation occurrence changes and a part of deformation of the calliper is shared by the long studs and assembly bolts.

Figure 5-16– Directional deformation along downward of brake calliper

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5.3.4.5 Equivalent stress of Brake calliper assembly Instead of calculating the normal stresses acting along each direction, equivalent stress is obtained to find out the weakest point of stress concentration which has the possibility of causing the failure in the brake calliper system as shown in Figure 5-17. And clearly it is evident that the weakest safety factor obtained for the brake calliper shown in Figure 5-13 closely matches with the region with the maximum equivalent stress.

Figure 5-17– Stress concentration on brake calliper

The above results are based on the forces acting on the brake calliper while the vehicle is moving on the level road condition. Next step is to carry out the analysis along the gradients based on inclination by certain degree

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6 Analysis along the gradients After checking the results of analysis on the level road, the braking efficiency of the brakes will be tested on upward and downward gradients as shown in Figure 6-1. To start with, the calculations are continued based on the assumptions taken for the level road. And based on slope, the degree of inclination is calculated in terms of degrees and radians. Later on the formulations are plotted on excel sheet similar to the one made to find the effect of brake calliper on level road as shown in Table 6-1

Figure 6-1 –Along the downhill gradient

6.1 Downhill calculation with existing specification The Table 6-1, shows the calculation needed for the further analysis of brake calliper assembly where there is a change of traction and normal force acting on the car. The calculation shows the effect of downhill movement shows a dramatic increase in value of force that has the possibility of increasing the stresses and deformation in the components of brake assembly. Table 6-1 –Downhill movement calculation values

Downhill inclination Parameters Values Units Slope S= 0.324 Radians θ= 0.313327 Radians Degrees θ= 17.95232 Degrees cos Radians θ= 0.951313 cos Degrees θ= 0.623776 Rf= 54.60329 Kg Rr= 10.39671 Kg Stopping distance D= 9.513133 m Velocity v = 17.00948 m Average decelerationaave= 1.5501 g

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MFDD a= Traction force Braking force= Brake torque = Disc effective radius

15.20648 2.118201 196.54 1350.671 162.0805

m/Sec g N N Nm

6.25 cm 0.0625 m

Tangential force 2593.288 N Normal force= 12966.44 N 6.1.1 Results for Brake lever analysis along the downhill When the vehicle moves down the road, it experiences additional force in the forward direction due to the inclined gravity pulling towards the level ground in order to maintain the equilibrium. Obviously the forces acting on the forward direction will be more than observed on level ground. And the overall weight will deliver a major contribution to the front axle of the car. So the reaction forces happening on front axle of the car will be larger than at the rear end. In the case of downward inclination, the tangential forces generated by the rotation of brake disc will be higher compared to the level ground. Also the braking force to stop the vehicle will be comparatively larger to stop the traction force of the car. Based on the Table 6-1 –, the boundary conditions are altered in place where tangential force and normal force is applied. The other boundary conditions are made constant similar to the level road mode. 6.1.1.1 Safety factor for brake lever on downhill The minimum factor of safety is observed to be decreasing compared to the one compared with the one analysed in the level ground. That shows the safety of using the brake calliper gets decreased while the vehicle moves in downhill condition. And for this particular analysis minimum safety factor is considered to be 2. If the individual part has safety factor more than 2, then the component is said to be in safe condition to go on road as shown in Figure 6-2.

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Figure 6-2– Safety factor on brake lever during downhill movement

6.1.1.2 Reaction and joint forces acting on the brake lever As per the expectation, the force reaction along the normal direction and bearing load is obtained as a larger value compared to the previous lever analysis. And the force reactions are transferred similar to way which was carried out in previous analysis as shown in Figure 6-3 and Figure 6-4.

Figure 6-3– Joint force on brake lever during Downhill movement

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Figure 6-4– Force reaction on brake lever during Downhill movement

6.1.1.3 Force reaction for Brake pad and plate assembly Similar to the previous level road analysis, the reaction force output is transferred to brake pad and plate as an input load. And in this analysis the reaction force is generated on the brake calliper assembly due to the tangential force created by the rotor part of the brake assembly. And the reaction force generated by the brake lever is again gets transferred to the calliper by means of bearing load due to the effect of cylindrical joint located between lever and calliper as shown in Figure 6-5 and Figure 6-6.

Figure 6-5– Force reaction on brake pad from calliper during Downhill movement

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Figure 6-6– Force reaction on brake plate from lever pin during Downhill movement

6.1.1.4 Safety factor for brake pad and plate assembly Safety factor for the brake plate gets slightly decreased while moving downhill compared to the level road movement as shown in Figure 6-7.

Figure 6-7– Safety factor on brake plate during Downhill movement

6.1.1.5 Safety factor for brake calliper assembly Minimum Safety factor in case of brake calliper has decreased more due to the effect of increased forces as shown in Figure 6-8. And it seems to be far less than the recommended value 2. So this is the point where the decision has to be made to change the material which suits standards of SAE by altering the necessary mechanical properties of material that can bring out better safety factor.

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Figure 6-8– Safety factor on calliper during Downhill movement

6.1.1.6 Deformations acting on calliper body Observation of ANSYS results over the brake calliper shows that major part of the deformation occurs on the place where the brake plate gets in contact with the brake calliper along the tangential direction as shown in Figure 6-9. Rest of the other directions including side and vertical axis also has effect due to the lateral force acting from the brake lever, but comparatively lower than the direction of traction.

Figure 6-9–Deformations along downward of brake calliper

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6.1.1.7 Stresses acting on calliper body While observing the stresses occurring on the calliper body as shown in Figure 6-10, a major part of the stress concentration predicted to happen in lateral direction of the body. The reason may be due to the combined effect of forces caused due to traction as well as the force generated from brake lever. The stresses in other two directions show comparatively lower stresses. But on the other hand, it should also be noted that the stresses along the vertical direction shows weakness on one of the long studs. Though it is lower than the first one, this particular region has the next probability to show the weakness in next stage of optimization. So care should be taken in order to avoid the both cases of stress concentration in choosing the method of optimization for the future happenings.

Figure 6-10–Stresses along downward of brake calliper

6.2 Uphill with existing specification In the case of uphill movement of the vehicle, the traction force will be opposing the effect of gravitational pull. So considerably due to reduced speed of the go cart car over the upward inclination, the traction force of the car get reduced compared to the traction force happening on level road. Ultimately the braking force exerted on the braking calliper also gets reduced. Also in all the three cases, the static load of the car also depends on the mass distribution due to the centre of mass acting in the car. Based on the mass distribution, location of centre of mass and the traction force, the slope is calculated and finally the tangential force as well as the normal force required to stop the car is determined using the equations and plotted in the Table 6-2.

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Figure 6-11–Uphill gradient Table 6-2 –Uphill calculation values

Upward inclination Parameters

Values Units Slope S= 0.324 Radians θ= 0.313327 Radians Degrees θ= 17.95232 Degrees cos Radians θ= cos Degrees θ= Rf= 26.325 Kg Rr= 38.675 Kg Stopping distance D= 3.082255 m Velocity v = 5.511072 m Average deceleratonaave= 0.502232 g 4.926899 m/Sec MFDD a= 0.686297 g Traction force 196.54 N Braking force= 437.6174 N Brake torque = 52.51409 Nm Disc effective radius 6.25 cm 0.0625 m Tangential force 840.2254 N Normal force=

4201.127 N

6.2.1 Results in Uphill movement As per the same boundary conditions used in the previous analysis, only the tangential force as well as the normal force is changed according to the Table 6-2 –Uphill calculation values and the solved output files are plotted below. 37 | P a g e

6.2.1.1 Safety factor on Brake lever on Uphill condition Compared to the previous analysis with level road and downhill conditions, the minimum safety factor gets increased due to the less application of load and constant yield strength. Since the value is more than the recommended value 2 as shown in Figure 6-12, the brake lever is said to be safer side while in uphill motion.

Figure 6-12 – Safety factor for brake lever in uphill

6.2.1.2 Safety factor on brake pad and plate on uphill condition The Minimum factor of safety for the brake plate and brake pad predicted to be far safe and near to the maximum value of 15. It is clearly evident that the blue region from Figure 6-13 shows the pad and plate are less prone to the effect of forces generated during the uphill motion.

Figure 6-13 – Safety factor on brake pad and brake plate on uphill

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6.2.1.3 Stresses experienced in brake calliper body In calliper body, the stress concentration seems to happen in the same part of the body which was visible in previous level road and downhill analysis. But competitively lower here due the reduced effect of forces on them. Similarly, the stresses are more on the region of long studs along Y axis.

Figure 6-14 – Stresses on Brake calliper

6.2.1.4 Safety factor on brake calliper during uphill The minimum safety factor seems to be less than the recommended amount 2. So compared with other parts of brake assembly, the calliper mount seems to experience large amount of stress and deformation as shown in Figure 6-15. It is obvious that the optimization should be carefully carried out in calliper body as the first preference.

Figure 6-15 – Safety factor of brake calliper

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7 Material Selection using CES Edupack Material selection plays one of the key criteria in designing a component. The material is selected based on the application which can withstand all the effects caused by the environmental conditions. Such materials are decided based on        

General properties Mechanical Properties Thermal properties Electrical properties Optical properties Durability based on flammability, fluids and sunlight Manufacturability Recycling capability

As the project is concerned with weight reduction, strength and health and safety to design the brake calliper, material selection is filtered according to the requirements, so the other important considerations such as thermal properties, durability and recycling capability are neglected.  Health and safety of the material is based on the chemical properties of the material which can be obtained from the typical uses and previous applications as well as available case studies of the material.  Weight reduction is decided based on the density of material, which can be obtained from general properties of a particular material  The strength of the material depends on elastic modulus and yield strength of the material, which can be taken from mechanical properties of the material.

7.1 Selection of material for brake lever The brake lever which serves as component to transfer force from the piston-cylinder mechanism to the brake pad should have better strength with more than recommended factor of safety. The material used to transfer load using fulcrum mechanism should satisfy the boundary conditions without causing any mechanical failure and health and safety issues. Table 7-1 – Comparison of materials for brake lever

Property

Elastic Modulus (Gpa) Yield strength (Mpa) Density (Kg/m^3) Price/part Other

Cobalt-base-super alloy, multiphase, MP159, cold drawn, aged (solution treated) (Existing) 255

Tool steel, molybdenum alloy, AISI M46 (High speed) (New)

1.91E+03 8.40E+03

2.72E+03 7.90E+03 £ 1.56 Nil

£2.95

Nil

231

Using CES Edupack, properties of existing material such as elastic modulus, yield strength, density etc. were found and tabulated as shown in Table 7-1. Then based on the property filtering 40 | P a g e

order from Density as first, Yield strength as second and Elastic modulus as next; material search algorithm were run in CES Edupack to get best match for product. The properties of new material were listed in Table 7-1 in second column. Figure 9-1 shows the cloud graph of the materials which are satisfying the filtering criteria. So, based on the graph of density against yield strength new material was selected for analysis. Later analysis will be carried out by substituting the new material in place of the earlier one to check the capability.

Figure 7-1- Material selection for lever

7.2 Selection of material for Brake calliper The brake calliper acts as a support for the integrated components present in the assembly. The calliper establishes the contact between the chassis and brake assembly components and while in operation, it serves to transfer normal and tangential forces according to the input of the diver and gradient of road. This particular component has the possibility of getting affected to chances of mechanical failures. Table 7-2- Comparison of material for Brake calliper

Property

Elastic Modulus (Gpa) Yield strength (Mpa) Density (Kg/m^3) Price/part Other

Al-70%Sic(p) MMC powder product (Existing)

Beryllium, grade I-250, hot isostatically pressed

Mg-70%B (f), longitudinal (New)

265

315

296

220

575

900

3.01e3 £219

1.86 e3 £283

2.48e3 £41.5

Nil

Carcinogenic

Nil 41 | P a g e

Using CES Edupack, properties of existing material such as elastic modulus, yield strength, density etc. were found and tabulated as shown in Table 7-2. Then based on the property filtering order from Density as first, Yield strength as second and Elastic modulus as next; material search algorithm were run in CES Edupack to get best match for product. The properties of new material were listed in Table 7-2 in second column. Figure 7-2 shows the cloud graph of the materials which are satisfying the filtering criteria. So, based on the graph of density against yield strength new material was selected for analysis. Later analysis will be carried out by substituting the new material in place of the earlier one to check the capability.

Figure 7-2–Material selection for brake Calliper

7.3 Selection of material for brake plate Brake plate acts as a medium to provide stable support for the brake pad by transferring force between lever to brake pad and brake pad to calliper mount. Table 7-3 – Comparison of material for brake plate

Property

Elastic Modulus (Gpa) Yield strength (Mpa) Density (Kg/m^3) Price/part Other

Stainless steel, ferrite, AISI 429, wrought, annealed (Existing)

Al-60%C-M40 (HM-Cfibber), longitudinal (New)

205

250

520

1100

7.85e3 £0.24 Nil

2.3e3 £37.84 Nil

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Using CES Edupack, properties of existing material such as elastic modulus, yield strength, density etc. were found and tabulated as shown in Table 7-3. Then based on the property filtering order from Density as first, Yield strength as second and Elastic modulus as next; material search algorithm were run in CES Edupack to get best match for product. The properties of new material were listed in Table 7-3 in second column. Figure 7-3 shows the cloud graph of the materials which are satisfying the filtering criteria. So, based on the graph of density against yield strength new material was selected for analysis. Later analysis will be carried out by substituting the new material in place of the earlier one to check the capability.

Figure 7-3–Material selection for Brake plate

7.4 Selection of Material for Brake pad Brake pad is the only component in the brake calliper assembly which goes in contact with another body and converts mechanical energy to heat energy causing friction. Unlike other components, this component suffers the maximum shear stress due to friction with another body. As this is an unavoidable function of the pad component, the material should be selected in such a way that it should not undergo wear and tear and also should have better durability and reliability. Table 7-4 – Comparison of material for Brake pad

Property

Elastic Modulus (Gpa) Yield strength (Mpa) Density (Kg/m^3) Price/part Other

Asbestos (amosite) (f) (Existing)

Kevlar 149 aramid fibber (Trial)

Silica (25-35 micron monofilament, f) (Trial)

Asbestos (white)(f) (New)

169

190

72.4

169

2610

3e3

4890

3.35e3

3.5e3 £0.17

1.48e3

2.19e3

£18.3

£2.5

2.6e3 £ 0.13

Carcinogenic

Nil

Glass

Nil 43 | P a g e

Maximum Service Temperature °C

696

300

730

980

Using CES Edupack, properties of existing material such as elastic modulus, yield strength, density etc. were found and tabulated as shown in Table 7-4. Then based on the property filtering order from Density as first, Yield strength as second and Elastic modulus as next; material search algorithm were run in CES Edupack to get best match for product. The properties of new material were listed in Table 7-4 in second column. Figure 7-4- Pad yield strength shows the cloud graph of the materials which are satisfying the filtering criteria. So, based on the graph of density against yield strength new material was selected for analysis. Later analysis will be carried out by substituting the new material in place of the earlier one to check the capability.

Figure 7-4- Pad yield strength

Kevlar 149 aramid fiber selected as the preferable material, but the service temperature seems to be lower than the existing model though there is no particular warning related to health hazards. In that case, Asbestos (white)(f) material does not have the previous records of creating health hazards. It seems to possess comparatively less mass and high strength with higher range of service temperature as shown in the Figure 7-4 and Figure 7-5. The frictional effects can be tested only in thermal analysis that is not covered in this project.

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Figure 7-5–Pad material with maximum service temperature

All the new materials are now tested by running in the ANSYS static structural simulations with the same boundary conditions in different testing methods like level road, downhill and uphill conditions.

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8 FEA Analysis of the Brake Calliper post Material Selection (Phase 2) The post selection of material section is the first step to carry out the optimization of design. Based on previous analysis and results, it is obvious that the worst case scenario was found in downhill motion of the car since the input forces and output stresses as well as deformations were of high range. So instead of testing the new calliper with post material selection in level road and uphill motion, the analysis can be done only with downhill boundary conditions, if the result in downhill condition is positive then it will automatically provide an inference that the results in level road and uphill conditions will also be safe. If negative then the next step for the design optimization can be preceded.

8.1 Results of after post material selection After substituting the new materials in engineering data of ANSYS Workbench, the simulation is made to run with downhill boundary conditions starting from brake lever. 8.1.1 Safety factor of brake lever – Post material selection Figure 8-1 shows the improvement in minimum safety factor after implementing the new material. Also the improvement is more than the recommended factor 2.

Figure 8-1 – Safety factor for brake lever - Post material selection

8.1.2 Deformation and stress of brake lever- Post material selection Figure 8-2 shows the variation in deformation and stress after post material selection. Evidently the same part of the brake lever shows the maximum stress concentration; even the deformation appears similar to the previous downhill analysis. And one point became clear that unless and until the geometry is altered, the stress concentration and deformation happens mostly in the same region.

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Figure 8-2 – Directional deformation and equivalent stress – Post material selection

8.1.3 Safety factor of Brake plate and brake pad- Post material selection Similar to brake lever analysis, the materials are defined for brake pad and brake plate, and the boundary conditions are set with downhill condition. The result shows nil minimum safety factor, that means there are no chance for the component to get failed, and every region is under maximum safety limit as shown in Figure 8-3.

Figure 8-3 – Safety factor for Brake pad and brake plate – Post material selection

8.1.4 Total deformation and equivalent stress for brake pad and plate Figure 8-4 shows the maximum deformation happening on brake plate which may be due to the increase in elasticity of the pad material. The deformation is observed to be maximum on the end opposite to the direction of tangential force and minimum in the same side of the tangential force. The equivalent stress is observed to be happening on the same location where it happened before

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but reduced compared to the previous analysis based on downhill motion. The region of stress concentration can be changed only after geometry optimisation.

Figure 8-4 – Total deformation and equivalent stress in brake pad and plate – Post material selection

8.1.5 Safety factor in brake calliper Figure 8-4 shows the minimum safety factor obtained in the calliper near the region where the brake pad gets rested. The result seems the same as the previous analysis carried out in the previous model with downhill analysis. On the other hand, the factor seems to be above the required factor. And now the calliper is said to be in the safer limit, since the material change has reduce the probability of failure occurrence.

Figure 8-5 –Safety factor in brake calliper - Post material Selection

8.1.6 Deformation on brake calliper Figure 8-6 shows the total deformation as well as the deformations in individual directions. The total deformation happens to occur on the tangential direction on the same place where the pad gets rested but with reduced deformation than the previous existing model. And along the lateral direction, the deformation happens on the top part of the hanging brake calliper but considerably 48 | P a g e

lower. Even in case of vertical direction, the deformation seems to happen in calliper and long stud, but the effect is negligible comparatively. Overall the deformation caused in the tangential direction has the largest amount of variation.

Figure 8-6- Deformations in brake calliper – Post material selection

8.1.7 Stresses on the brake calliper – Post material selection Figure 8-7 shows the overall stresses acting on the brake calliper with higher stress concentration compared with the previous existing downhill results. But this time the effect seems to be more along lateral direction rather than tangential direction. Nevertheless, the stress concentration in tangential direction shows the second highest result comparatively and vertical direction result shows the least deformation among all.

Figure 8-7-Stresses on brake calliper – Post material selection

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9 Comparison of Existing and optimized results 9.1 Mass comparison Figure 9-1 shows the comparison of parts used in the brake calliper assembly between the existing model to the optimized model. Overall almost 35% of mass reduction is done in the existing model using material optimization. Whereas the brake lever contributes 5.95%, Brake pad with 22.61% reduction, Brake plate with 70.69%, Brake Calliper with 17.60%, and minor components such as long studs and assembly bolts contributes 70.7% and 70.7% respectively. And successfully mass of 418.5g got reduced from total weight 1.197 Kg of brake calliper assembly. Mass Comparison 1.2

1

0.8

Mass in (Kg)

0.6

0.4

0.2

0 Existing model mass (Kg) Optimized model mass (Kg)

Assy bolts

Existing model mass (Kg) 0.091644

Long Studs

Optimized model mass (Kg) 0.02685066

0.123308

0.0361284

0.48943804

0.40325792

Plate

0.19995

0.0585856

Pad

0.132006

0.1021488

Lever

0.1611036

0.1515141

Caliper

Figure 9-1 – Mass comparison for individual parts before and after optimization

9.2 Price Comparison Figure 9-2 shows the comparison of prices for the individual parts. In case of price comparison, unsatisfactory results are obtained. Only few parts are available in lower price and others are having higher price value. Overall there is 9% increase in price in order to compromise with mass reduction. Brake lever shows 47% decrease in price, and pad with 22.6% reduction, but brake plate is with almost 100% increased price. Brake calliper with 61.24% reduction, remaining other two parts such as long stud and assembly nuts shows almost 100% increase in price. Finally the price is increased from £110.81 to £121.75 as a whole.

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Price Comparison Assy bolts

140 Long Studs

120

Price in £

100 80

Caliper

60 40 Plate 20 0

Assy bolts

Existing model price (£) 0.11180568

Optimized model price (£) 17.34552636

Long Studs

0.15043576

23.3389464

Caliper

107.1869308

41.53556576

Plate

0.243939

37.8462976

Pad

0.17028774

0.131771952

Lever

2.94819588

1.56059523

Pad

Lever

Figure 9-2 –Price comparison for individual parts before and after optimization

9.3 Safety factor comparison Figure 9-3 shows that the optimized brake calliper set does have a better strength and durability compared with the previous model. In case of brake plate, brake calliper and brake lever there is a dramatic improvement in safety factor, whereas in Brake pad, assembly bolts and long studs, though there is a change, there is not at all a need of changing with respect to safety factor, since they are already in safer limits in case of level road analysis.

Safety factor for level ground

Factor of Safety for Level ground

70 60 50 40 30 20 10 0 Assy bolts Long Studs

Existing model 10

Optimized model 15

5

15

Caliper

0.5195

2.6701

Plate

3.6215

15

Pad

15

15

0.5917

2.7609

Lever

Figure 9-3 – Safety factor comparison for individual parts in level ground

Secondly, Figure 9-4 - Safety factor comparison for individual parts in uphill motion shows every parts are in safe limits after getting optimized, especially the calliper, plate and lever. And other parts such as pad, studs and bolts remains the same since the forces developed in uphill does not affect the components as much as the forces on level ground and downhill motion affects.

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Safety factor for uphill motion

Factor of Safety for Uphill motion

70 60 50 40 30 20 10 0

Existing model 10

Assy bolts Long Studs

Optimized model 10

10

10

Caliper

1.6062

6.3551

Plate

10.304

15

Pad

15

15

3.7725

5.5167

Lever

Figure 9-4 - Safety factor comparison for individual parts in uphill motion

In case of downhill motion as shown in Figure 9-4 with worst case of forces affecting the parts having better progress for brake calliper, brake plate and Brake lever but other components such as assembly bolts and long studs does not have big changes and also not necessary for the change, since they are already within the limits.

Safety factor for downward model

Factor of Safety for Downhill motion

60 50 40 30 20 10 0 Assy bolts Long Studs

Existing model 10

Optimized model 10

10

10

Caliper

0.418

2.0554

Plate

3.3392

15

Pad

10

15

1.5104

2.2087

Lever

Figure 9-5 – Safety factor comparison for individual parts in downhill motion

9.4 Equivalent stress comparison Equivalent stress on the level ground as shown in Figure 9-5 reveals that overall equivalent stress got reduced due to the change in material. But while carefully checking with the long studs, the stress seems to be increasing even after optimizing with a better material.

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Equivalant stress for level ground

Equivalant stress for Level ground

2000 1500 1000 500 0

Assy bolts

Existing model 119.95

Optimized model 38.876

Long Studs

39.918

65.558

Caliper

356.26

337.07

Plate

71.36

55.208

Pad

30.218

2.3379

Lever

1011.6

985.18

Figure 9-6 –Equivalent stress comparison for individual parts for Level ground

From Figure 9-6, it is clear that the stresses decreased in assembly bolts, long studs, brake plate, brake pad and brake lever. But in case of brake calliper, the stress is increased.

Equivalant stress for Uphill motion

Equivalant stress for Uphill motion

800 700 600 500 400 300 200 100 0

Assy bolts

Existing model 45.655

Optimized model 15.735

Long Studs

45.655

15.735

Caliper

136.97

141.62

Plate

30.087

23.221

Pad

3.304

0.95682

Lever

506.29

493.05

Figure 9-7 – Equivalent stress comparison for individual parts for Uphill motion

From Figure 9-7, a drastic change in the opinion compared to the previous comparisons. Since the worst case scenario due to the effect of downhill forces shows that assembly bolts and long studs shows a large effect of stresses. And in case of calliper, though there is increase in stresses, it shows a slight variation. Other components such as brake plate and brake lever got reduced with stresses to a considerable amount.

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Equivalant stress for Downhill motion

Equivalant stress for Downhill motion

2500

2000

1500

1000

500

0 Assy bolts

Existing model 47.054

Optimized model 194.61

Long Studs

47.054

194.61

Caliper

423.48

437.87

Plate

92.789

71.666

Pad

22.281

2.852

Lever

1264.6

1231.5

Figure 9-8 - Equivalent stress comparison for individual parts for Downhill motion

9.5 Total deformation Comparison Figure 9-8 shows the effect of deformation after deformation. Most of the deformation was observed only on two components such as brake lever and brake pad. The reason may be due the increase in elastic property of the components after changing the material. Other components with different material properties does not show any considerable increase in deformation.

Deformation on level ground

Deformation on Level ground

1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0

Existing model 0.0277

Optimized model 0.020827

Long Studs

0.0552

0.047696

Caliper

0.09355

0.080821

Plate

0.0034

0.0014165

Pad

0.0038

0.32331

Lever

0.86481

0.95884

Assy bolts

Figure 9-9 – Deformation on level ground after optimization

Figure 9-9 shows reduced deformation compared to the existing models. But previous two parts like brake lever and brake pad shows slightly more deflection. It seems like the deformation in these parts increases abruptly even with slight increase in forces applied over them.

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Deformation on Uphill motion

Deformation on Uphill motion

0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0

Assy bolts

Existing model 0.017

Optimized model 0.015089

Long Studs

0.022

0.0188

Caliper

0.3929

0.033949

Plate

0.0014557

0.015138

Pad

0.0015951

0.13624

0.43281

0.4798

Lever

Figure 9-10 – Deformation on uphill motion after optimization

Figure 9-10 shows the worst case deformations due to increased force effects. Assembly bolts and long studs do not show any large change in deformation values though the value got decreased. The brake calliper and brake plate shows the better reduction of deformation after optimization. Only the Brake pad and brake lever show the larger deflections compared to other components.

Deformation on Downhill motion

Deformation on Downhill motion

2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0

Assy bolts

Existing model 0.054025

Optimized model 0.04667

Long Studs

0.054025

0.04667

Caliper

0.12156

0.10501

Plate

0.00445

0.0025

Pad

0.004919

0.42

1.081

1.1985

Lever

Figure 9-11 – Deformation on downhill motion after optimization

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10 Discussion In this chapter, discussion will be made on each and every component and assembly as a whole based on the results and comparison discussed earlier with worst case effects of downhill motion. This will decide what the changes to be made for further improvements.

10.1 Discussion based on Individual Components Brake plate– Undergone more than 70% mass reduction, 100 times increase in price, 77% increase in safety factor, 22% reduction in equivalent stress, 43% reduction in total deformation. It got reduced with the mass and stresses but on the other hand increased in price. So this material can be considered for further analysis by compromising the cost. Brake pad – Undergone almost 23% mass reduction and 23% reduction in price, No considerable change in safety factor, 87% reduction in equivalent stress and 98% increase in total deformation. Except higher deformation other properties shows better improvement. This material can also be considered, deformation in case of brake pad becomes more elastic while in application. Long studs–Undergone almost 71% mass reduction, 100% increase in price, 66% increase in safety factor (though it is not required), 75% increase in equivalent stress, and 13% decrease in deformation. Though it has almost 70% reduction in mass, other factors does not show any good improvement. So it is better to use the previous material to stay effectively. Assembly bolts–Undergone 71% mass reduction, 100 % increase in price, 33.3% increase in safety factor (though it is not required), 75% increase in equivalent stress and 25% decrease in deformation. Price and stress got increased compared with other properties. Even in this case, the price of previous material seems better than the one used for optimisation and the reduction in the mass of this material does not show much considerable change. So the previous material can be used in this case without any change. Brake Lever – Undergone 6% mass reduction, 47% decrease in price, 31% increase in safety factor, 2% decrease in equivalent stress, 10% increase in deformation. The properties of brake lever show considerable improvement in mass and price as well as negligible drawback in deformation. This material can be carried out for further analysis. Brake Calliper – 18% reduction in mass, 61% reduction in price, 80% increase in safety factor, 3% increase in equivalent stress, almost 14% decrease in deformation. Overall properties of brake calliper show good results. And the required result is achieved without any drawback. So this material can also be used for further analysis.

10.2 Discussions based on Overall assembly Considering the optimization of overall assembly component, 35% mass reduction, 9% increased price, 37.05% increase in factor of safety, 86% increase in equivalent stress, 14.75% reduced deformation. This can be further improved by substituting some of the new materials along with some of the previous materials used. Materials for Assembly bolts and long studs can be substituted with previous materials, these materials shows more price and stress effects compared to previous material. And 56 | P a g e

though the factor of safety is within the limit, due to higher equivalent stress, the component may have less life time when it undergoes fatigue analysis. Even material for brake lever can be changed, since the deformation after using the second material is large compared to the previous material. Moreover this deformation can cause reduction in braking efficiency. Though, the factor of safety, pricing and stress levels were good in earlier material; it was prone to health and safety hazards and considered to be carcinogenic. Hence, the new material was chosen based along with higher safety factor. Brake pad shows larger deformation compared to the previous pad material, this may lead to more wear & tear of component, affecting with increase in serviceability of brake system.

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11 Conclusion The goal of the project was to understand the operations and basic functions of mechanical braking cycle and simulate the phenomenon using ANSYS Workbench software. The literature by (Engineering Inspiration, 2013) & (Limpert, 2011) gave an insight into the performance and operation of brake system. Weight reduction is an important aspect of design, one of the easiest ways to achieve weight reduction is by selecting materials with higher strength to weight ratio. It is one of the many strategies which is being followed by leading aviation and automotive industries (EduPack, 2013) Various aspects of the project which involves pre and post material selection simulations are compared here, which summarises some of the findings as follows: 

 



Based on Vickers hardness test results, measurements of geometry of brake calliper assembly were acquired. Later the model is virtually modelled in CAD and analysed in FEA tool to reduce the mass and cost. Large deformations were observed in brake lever and brake pad after changing the material. Since the elastic modulus were higher for these cases. Some of the materials, though they are of high cost with less mass, they are considered for the mass optimisation analysis, since a car to be challenged on circuits should possess high performance level with reduced weight as the first preference than the cost. Most of the materials are replaced based on Health and Safety hazards available in CES Material library. For example, Beryllium and Asbestos (Amosite) are the materials having better strength is to mass ratio, but neglected by considering health and safety issues. The materials are chosen considering reduced mass and higher yield strength, and they are selected based on Ashby’s method and resources available in CES library, which passes the test conditions like downhill motion, uphill motion and level road condition tests. Prices are compared only based on materials neglecting processing and manufacturing costs.

Table 11-1 – change of material for whole assembly

Overall Assembly Characteristic Safety Factor Weight(Kg) Price/assembly

Existing material 1.197 110.8115948

Optimization 50% increase 35% reduction 9% increase

11.1 Recommendations Table 11-2 –Change of materials with Selected parts (Long studs and Assembly bolts)

Selected parts in assembly Characteristic

Optimization 2

Safety Factor

-

Weight(Kg) Price/assembly

0.94525461 83.34017353

Changes

Same as first optimization 21% reduction 25% reduction

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

  

From Table 11-1 it is known that although the first optimisation produced appreciable results in terms of safety factor and weight, the resultant price cost turned out to be high. The Table 11-2 shows the second optimisation in which materials of Long studs and assembly bolt were replaced with the original default material of the brake calliper to obtain a 21% reduction in weight and 25% reduction in price while the safety was same. This optimisation if performed is advantageous as there is an overall improvement in the performance when compared to the original conditions. This condition is desired. Experiment analysis for the deflection of parts with constant cross sections should have been carried out in order to validate the results with analytical and FEA Calculations. Shape optimization can be performed accurately in FEA if the design constraints and model details of the previous brake calliper assembly are available from the company. If fatigue analysis were conducted, the material selection would be done with higher accuracy, since repeated load without equal interval would have been applied in lever joint. While the cyclic loads applied on the brake pad causing failures would have also been evaluated. If temperature analysis was conducted, then the material optimisation would have been precise, since brake pad establishing frictional contact with the rotor disc experiences temperature failure. If Random vibrational analysis was conducted along with material selection and shape optimisation, failures due to vibration could be minimised, since the brake pad generates random vibrations along with the assembly when it contacts the brake disc thereby loosing stability due to friction.

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Bibliography Baja Motorsport, 2012. Owners Manual BR150-D, BR150-1, Go-Kart. [Online] Available at: http://buggynuts.com/service%20manuals/Baja%20DN150%20BR150%20Ownersmanual.pdf [Accessed February 2013]. BBC, 2013. What is the connection between forces and motion?. [Online] Available at: http://www.bbc.co.uk/schools/gcsebitesize/science/add_ocr_pre_2011/explaining_motion/forcesa ndmotionrev1.shtml [Accessed February 2013]. Central Polytechnic College Available at: [Accessed February 2013].

Thiruvananthapuram, 2012. Go Karting. [Online] http://www.slideshare.net/kailassreechandran/go-kart-project

D.Gillespie, T., 2011. Fundamentals of Vehicle Dynamics. s.l.:Society of Automotive Engineers,Inc. Dr.I.C.Wright, 1998. Design Methods in Engineering and Product Design. s.l.:The McGraw-Hill Companies. EduPack, C., 2013. Granta Material Inspiration. [Online] Available at: http://www.grantadesign.com/download/pdf/edupack2013/CESEduPack2013Overview.pdf Engineering Inspiration, 2013. Brake Calculations. [Accessed http://www.engineeringinspiration.co.uk/brakecalcs.html March 2013].

[Online]

Engnet, 1998. ENGNET Engineering Network. [Online] Available at: http://www.engnetglobal.com/c/c.aspx/kon009/productdetail/vivid-910-non-contact3d-digitizer [Accessed February 2013]. Gilles, T., 2004. Automotive Chassis: Brakes, Suspension, and Steering. illustrated ed. s.l.:Cengage Learning. Heiserler, H., 1995. Advanced Engine Technology. London: Edward Arnold. Heisler, H., 2007. Advanced Vehicle Technology. 2 ed. s.l.:Butterworth Heinemann. Huang, X. Y., 2002. Large deflection of elastoplastic. Non-linear strain-hardening cantilevers, Volume 216 Part C, pp. 5-12. James M.Gere, B. J., 2009. Mechanics of Materials. 7 ed. s.l.:CENGAGE Learning. Kent.L.Lawrence, 2010. ANSYS Workbench Tutorial: Structural & Thermal Analysis Using the ANSYS Workbench Release 12.1 Environment. s.l.:SDC Publications. Lee, H.-H., 2011. Finite Element Simulations with ANSYS Workbench 13. s.l.:Schroff Development Corporation.

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Limpert, R., 2011. Brake Design and Safety. 3 ed. s.l.:SAE International. M.Kuowski, P., 2004. Finite Element Analysis for Engineers. Warrendale Pa: SAE International Warrendale. Owen, C. E., 2009. Today's Technician: Automotive Brake Systems. s.l.:Cengage Learning. Redwood Engineering Available [Accessed February 2013].

(UK) at:

Ltd.,

2010. Mechanical Brakes. [Online] http://offroadkartplans.com/mechanical-brake

Shih, R., 2013. Parametric Modeling With Creo Parametric 2.0. s.l.:SDC Publications. The Engineering Toolbox, Available at: [Accessed February 2013].

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Toogood, R., 2009. Pro ENGINEER WILDFIRE 5 MECHANICA Tutorial. Edmonton, Alberta: SDC Publications. Ye, J., 2008. Structural and stress analysis: theories, tutorials and examples. 1 ed. Abingdon: Taylor& Francis e-library.

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12 Appendix s

Stopping Distance (m)

WFS

Weight front static load (Kg)

WRS

Weight rear static load (Kg)

W

Overall weight of car (Kg)

C

Distance between Centre of gravity and rear wheels (m)

L

Wheel base (m)

B

Distance between Centre of gravity and front wheels (m)

Mr

Static rear axle load (Kg)

Ψ

Static load distribution

ax

Deceleration(g units)

Mfdyn

Dynamic front axle load (N)

g

Acceleration due to gravity (m/s2)

BF

Braking force

FA

Total possible Braking force (N)

µr

Coefficient of friction between road and tyre

re

Disc effective radius( m)

D

Disc useable outside diameter (m)

d

Disc useable inside diameter (m)

aave

Average deceleration for the whole stop (g units)

v

Test speed (m/sec)

a

Deceleration (MFFD) (g units)

t

Brake on time (sec)

K.E.

Kinetic Energy (joules)

R.E

Rotational Energy (joules)

T.F

Tangential Force (N)

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