Disc brake Design And Analysis

 Brake Disc Design and analysis is a project through which we have aimed to achieve an understanding and learning of development of a product straight 

from its conception to manufacturing, encompassing all the stages such as Initial 

Calculations, Designing, Material Selection and Manufacturing considerations.

Targets of the Project

Try to simulate the various physical and thermal loads on the brake disc.

To study various calculations and contributing factors on selection of a brake disc

To research further on all the included topics and suggest improvements in the design and materials used

To study the kinds of loads and stresses of a brake under use.

To study materials generally used for manufacturing of brake discs in the industry.

To estimate ways to better research the variation of results found during analysis and actual use.

Brake Calculations

What we want to achieve through the Brake Calculation ?

To find the effective disc diameter

To understand the load on the disc to help select a suitable material

To find the dynamic load transfer on the front and the rear axle

To find the pressure exerted on the brake disc and also the torque on the wheel centre

FBD for Brake Calculation

Excel Sheet of Brake Calculation

Result of Brake Calculation

From the calculations, Pressure on Disc part between pads found is 5.63 x 106 N/m2                                        The surface temperature in a single stop was found to be 463K, and by estimating for multiple stops, it reaches up to 600Kelvin

Brake Torque on the front disc was found through calculations to be 485 N.m

Ideal Properties for Brake DiscProperties Justification for Required Property

HardnessBrake disc is generally expected to have high hardness for slower wear rates. The hardness generally required is about 32-38 HRC

Temper SofteningAs in braking applications the temperature reached are often as high as 400 degrees temper softening might lead to warping and deformation of disc under the physical loads.

StrengthThe strength of the material should be high ( 450 MPa ) to withstand the loads and this is measured in terms of its yield/compressive strength

Fatigue StrengthAs it is a component that is supposed to work for a long time of application depending on the use, its expected to work without failure for large number of cycles. This is measured in terms of creep strength.

Carbon CeramicTYPES PROPERTIES PROBLEMS IMPROVEMENT

C/C-SiC is a Carbon fiber phase added to

a Silicon Carbide matrix.

• Increased strength with lower density.

•Ability to withstand high temperatures without failure.

•Low Coefficient of Thermal Expansion.

•Can withstand surface Temperatures of 1000C with minimal wear.

• Inefficient and much weaker if used

in cold condition.

• Cracking on occur on the surface.

• Low demand for high performance

brakes.

• Expensive

• Make the material with a higher

ceramic content in order to achieve higher surface temperature.

• Use of more thermally

conductive fibre in the ceramic matrix

in order to have high performance.

Aluminum Matrix CompositesTYPES PROPERTIES PROBLEMS IMPROVEMENT

Aluminum Matrix Composite

( AMC )MMC Rotor

• Light weight ( 60% weight reduction as compared to Cast Iron ).

• Better heat conductivity.

* Ability to distribute wear uniformly over the surface.

• Lower coefficient of friction and wear rates than classical

steel discs.

• Highly costly as well as difficult to

manufacture.

• Reduce brake noise and wear

• Improves unsprung mass which leads to

better vehicle acceleration and maneuverability.

TYPES PROPERTIES PROBLEMS IMPROVEMENT

C/C-SiC is a Carbon fiber phase added to

a Silicon Carbide matrix.

• Increased strength with lower density.

•Ability to withstand high temperatures without failure.

•Low Coefficient of Thermal Expansion.

•Can withstand surface Temperatures of 1000C with minimal wear.

• Inefficient and much weaker if used

in cold condition.

• Cracking on occur on the surface.

• Low demand for high performance

brakes.

• Expensive

• Make the material with a higher

ceramic content in order to achieve higher surface temperature.

• Use of more thermally

conductive fibre in the ceramic matrix

in order to have high performance.

Stainless Steel

As on braking all the kinetic energy is converted into heat energy- which is generated at the brake pad-disc interface we will distribute this as heat power supplied at the disc pad interface(only at the part of disc in contact with pads)

We’ll determine kinetic energy by assuming a given speed, lets say 25m/s to be brought to a complete stop given by 0.5*mass*velocity^2.. The max coefficient of friction would provide us with deceleration hence the stopping time, so we’d know how the power is distributed over time.

We’d analyze the disk under this heat power provided as a flux only for the while the brakes are applied, and convection throughout the rest of the disk surface so it is simultaneously also cooling reflecting a real scenario. Initial temperature is assumed to be same as the surroundings, the convection coefficient used is an estimate and we’ll look to calculate a closer value through CFD simulation

Thermal Analysis of Brake Disc

Thermal Boundary Conditions :Temperature Allows for the definition of a temperature on a certain entity or body

Convection applies a convection boundary condition to the selected faces. The convection coefficient and ambient temperature are specified and the heat lost due to convection is calculated automatically.

Heat Flux Applies some amount of heat into a face per unit area.

• Heat Flux Applies some amount of heat into a face per unit area.

Heat Power Applies some amount of heat to a vertex, edge, face or component. Radiation Allows surface-to-surface or surface-to-ambient radiation. In our model, we will apply convection to all faces because all of the faces will be exposed to the air. In addition, we will apply a heat power to the faces that the brake pads touch.

Screenshot of the Analysis :

Comparison with proven Standardhttp://www.wsdot.wa.gov/research/reports/fullreports/434.1.pdf

 

This validates that the temperature calculated in our case is much lower due to lesser weight and therefore less kinetic energy, and heat is rejected better.We have simulated a maximum of 300 Celsius, compared to 500 tested in research by SAE

Thermocouple Sensors:

We have searched for multiple thermal sensors we can use to validate our thermal analysis practically. The sensor can be attached on a bike or a car and can give accurate readings. The chaleenge is to select a sensor which gives not only accurate values, but gives result in the correct format, has good frequency response, and is also cheap. These were our main options-

We finally chose the TC Direct rubbing type thermocouple for our application, because-1) The motec sensor was very expensive and it had a wider range of operable

temperatures which we did not require.2) The texense sensor was a infrared sensor which detects temperature through

radiation and is found to be less accurate in testing.

Our personal TC Direct Thermocouple sensor

Further Study :We’ll aim at optimizing weight and convection rates through iterations of simulations using different designs adding ribs or holes, varying them in number and diameter to reach an optimum solution for the selected test vehicle.

We had stumbled upon some research on using a closer to real value of convection through a CFD simulation of air around the brake disc. I’m personally in contact with totalsim.co.uk. It would lead to a closer value of the convection coefficient that would result in a more accurate result.

We have gone through a number of research papers on the Ideal brake disc materials, its something we might look into. We have scouted for various active temperature sensing and data logging units, I’d attached a few pdf’s of some products along by motec and texense

Thank You

Presented By :

Ananya Bharadwaj Ashwani Saini Chanchal Krishna 2k12/AE/10 2k12/AE/18 2k12/AE/26