Any contribution to this research made by others, with whom I have worked at NIT Rourkela or elsewhere, is expressly acknowledged in the thesis. I am fully aware that in case of any non-compliance detected in future, the Senate of NIT Rourkela may withdraw the degree awarded to me through the present thesis. Many thanks to Auto Tech Labs for their great explainer videos on disc brake operation.
And finally to his family, especially his mother for all the mental support and encouragement throughout the project and also during his student years at NIT Rourkela. In the previous research works, finite element analysis of the disc brake was carried out mostly on ICEM-CFD CFX, structural analysis with structural boundary conditions and thermal analysis with thermal boundary conditions. Simulations were performed using coupled-field thermostructural 3D analysis in the transient structural module of ANSYS 15.0 workbench.
In this research work, we have tried to analyze the temperature heat generation along with simultaneous cooling in the transient structural module. These simulation results find one hot tire temperature profile in the center of the disc brake rotor where the brake pad is in contact with the rotor, which shows the maximum temperature generated on the disc surface.
1 Introduction
Disc Brake
- Background
- Brake system function
- Types of brake
- Brake components
- Principle behind disc brake system
- Disc brake working
- Heat dissipation from disc brake
- Problems with disc brakes
Brakes are classified according to the method of attachment of fixed brake bands or brake shoes to rotating brake drums as internal expansion or external contraction. They are also classified as mechanical, hydraulic or electric depending on whether the braking force is transferred from the pedal or hand lever to the brake shoes using a mechanical linkage or electrically controlled or hydraulic pressure or a combination of hydraulics and air or hydraulics and electricity, depending on which method braking is required. Brake components are mainly composed of five to six parts, some of them are as follows. a) Master cylinder assembly b) Brake caliper assembly c) Wheel hub assembly d) Disc brake rotor.
Brake rotor is one of the most crucial parts of a vehicle braking system which is attached to the wheel using a wheel hub. When you apply the brakes, high pressure hydraulic fluid is received from the master cylinder by the caliper. Whenever we push the inner brake pad against the rotor, the caliper frame pushes because of the fluid.
Heat is dissipated from the disc brake by three basic cooling phenomena, as given below. a) 60% of the total energy is dissipated due to convection, b) 34% remains there as stored thermal energy. So it is one of the most important tasks to control the excessive temperature in the brake system.
Objectives
Motivation
2 Literature Review
They proposed a model that is considered as a tool to aid in the interpretation and dimensioning of the tribological and thermal behavior of the friction media. Their result shows that the fraction of heat flux due to friction evacuated by the disk (more than 0.9) is higher than the fraction of heat flux evacuated by the pin. This phenomenon is directly proportional to its convection coefficient and the disk speed [13].
As part of the contact science model, convective cooling and weight variation (time dependent) on the free surfaces of the brake pad were used. An FE examination of the heat exchange (transient) issue for a circle/cushion framework was performed using the Nastran/MSC Patran software package. The use of new materials was simulated, the purpose of which is to ensure greater stability and improve the braking efficiency of the vehicle.
This research has been carried out using ANSYS 11 to analyze the variation of deformation and stresses across the disc brake and the temperature distribution. The transient thermoelastic analysis of the brake discs under repeated braking conditions was performed and the results were compared with those of the cast iron disc [17]. Von Mises stress, the aggregate deformations, and the temperature of the disc rotor and contact pressure increases in the pads, as the thermal stress is separated from the mechanical stress, which causes wear and crack propagation of the disc rotor and pads.
The creator finds that aggregate deformations and Von Mises stress of disc brake and brake contact pressure increase when both mechanical and thermal perspectives are combined [18-19]. They break down the thermo-elastic procedure that occurs in disc brakes, heat conduction and elastic conditions were addressed along with contact issues. Computational results were presented for the temperature and heat flux acquisition at each friction surface between the pads and the brake rotor.
Thermal resistance between the disc and pad prevents the disc from absorbing the heat generated at the contact plate surface, causing brake fluid to evaporate. He investigated the effect of brake rotor ventilation on the thermal conduction of the disc brake. The analysis shows that spiral ventilation plays an important role in cooling the rotor during the braking phase [25].
3 Finite Element Analysis
- Introduction
- Building the model
- Obtaining the solution
- Mathematical model of the problem
- FE formulation for heat conduction
- Basic analysis types
- Thermal analysis
- Structural analysis
- Analysis planning
For the analysis, the initial stage of the thermal field in the disk volume is the thermal conduction state in the coordinate (cylindrical) frame (r, ϴ, z) and placed in the disk axis and z defines the disk thickness. Thus, the distribution of the flow of heat will be uniformly distributed in the outward direction, which means that neither flow of heat nor temperature will vary in ϴ direction. The goal of this area of the thesis is to build an approximate time-stepping strategy for axisymmetric control conditions that change with time.
If this is to happen, the accompanying start and the boundary conditions are taken into account [15]. To obtain the matrix form of equation (3.2) the use of standard Galerkin's technique was there. To find out the solution of the simple differential equations (3.18) the integration method (direct) can be used.
Based on the assumption, the temperature {𝑇}𝑡 and {𝑇}𝑡+∆𝑡 at time t and 𝑡 + ∆𝑡, respectively, the relationship of both variables is given below. 3.18 we obtain the implicit algebraic equation as follows. A stationary (not changing with time) thermal simulation determines the temperature assignment and other thermal quantities under the load conditions that will not change over time. A stable load condition is a condition where the effects of heat storage changing over time can be overlooked.
Transient (change with time) thermal analysis of the transfer of temperature and other heat quantities under conditions that change over time.
4 Modelling and Analysis
Assumptions
Problem definition
- First Task- Geometry modelling
- Thermal analysis (steady-state and transient) using structural steel
- Basics of coupled-field analysis
- Element types used in Coupled-Field
But we still do not know how to perform analysis when the disc rotates and heat is generated due to the braking phenomenon. Our fifth task was to perform thermal-structure coupled analysis to generate steady temperature profile along with both convection and conduction cooling.
COUPLED-FIELD
SOLID226 Geometry
Fourth Task- Thermal-Structural Coupled-Field Analysis
Disc Rotor Brake Pad
5 Result and Discussion
If we consider only the convection cooling phenomenon, the results will be as in the above result. But conduction phenomenon is not considered in the analysis; therefore temperature profile generated due to friction is so smooth and with sharp edges. Both the last analyzes are almost the same, but still show different results, and this is because of the boundary conditions.
6 References
