The objective of this final year project is to study the mechanical performances of a Eddy Current Braking system using the finite element method (FEM).
Finite element (FE) models of the braking system was created using Creo and simulated using ANSYS which is based on the finite element method (FEM). The Braking system was simulated under three different loading conditions: one magnetostatic tests and two stress analysis which are (1) Principle Stress and (2) Von-Mises Stress analysis is done using the commercially available software ANSYS. Particular attention was given to the Magnetostatic simulation for the Electromagnet where a potential problem may arise due to its design.
Three-dimensional modeling and meshing using the simulation program ANSYS were successfully implemented in this project, allowing for greater flexibility and accuracy in the results achieved.
LIST OF TABLES
Table No. Table Description Page No
Table 2.1 DETAIL OF PATENTS 14
Table 2.2 DETAIL OF RESEARCH PAPERS 16
Table 3.1 DETAIL OF PARTS USED IN THE MODELING 20
Table 4.1 GANTT CHART 30
LIST OF FIGURES
Figure No Figure Description Page No
Fig 1 ELECTRO MAGNETIC BRAKE 17
Fig 2 ACTUAL BRAKE SYSTEM 18
Fig 3 ACTUAL BRAKE SYSTEM 19
Fig 4 ASSEMBLED 3D MODEL 20
Fig 5 ASSEMBLED 3D MODEL 20
Fig 6 MESHED MODEL OF ELECTROMAGNET 23
Fig 7 MESHED MODEL OF SHAFT 23
Fig 8 VON-MISES STRESS CONCENTRATION OF SHAFT 25
Fig 9 MAX. PRINCIPAL STRESS CONCENTRATION OF SHAFT 25
Fig 10 MAGNETOSTATIC SIMULATION OF ELECTROMAGNET 27
Fig 11 MAGNETOSTATIC SIMULATION OF ELECTROMAGNET 27
Fig 12 GANTT CHART 30
LIST OF SYMBOLS
a deceleration, m/s2
c Specific heat capacity of brake-disks, kJ/kg.k
f maximum torsional force, N
F braking force, N
G gravity, m/s2
M maximum vehicle weight, kg
r disk effective radius, mm
R tire half radius, mm
W motorcycle force, N
?? friction coefficient, dimensionless
??1,2,3 principal stresses, N/mm2
??nom nominal stress, N/mm2
??uc ultimate compressive strength, N/mm2
??ut ultimate tensile strength, N/mm2
??v Von Mises Stress, N/mm2
??y Yield Stress, N/mm2
TABLE OF CONTENTS
Acknowledgement 3
Abstract 4
List of Tables 5
List of Figures 6
List of Symbols 7
Table of Contents 8
Chapter: 1 Introduction to Project 9
1.1 Eddy current 9
1.2 Conventional brakes 9
1.3 Eddy Current Brake 10
1.4 Designing and Modeling of ECB 11
1.5 Analysis of ECB 11
1.5.1 History of Ansys Inc. 12
1.5.2 Products of Ansys Workbench 12
Chapter: 2 Literature Review 14
2.1 Patents 14
2.2 Research Papers 14
Chapter: 3 Design and Modeling 17
3.1 Reverse Engineering 17
3.2 Creo Modeling 19
Chapter: 4 Simulation by ANSYS 21
4.1 Simulation Procedure 22
4.1.1 Techniques of 3D Meshing 22
4.1.2 Stress Analysis Method 23
4.1.3 Static Test-Torsional strength simulation 24
4.1.4 Static Test-Magnetostatic Simulation 26
Chapter: 5 Conclusion 28
References 29
Gantt Chart 30
CHAPTER – 1
Introduction
1.1 EDDY CURRENT
Eddy currents are electric currents induced within conductors by a changing magnetic field in the conductor. These circulating eddies of current have inductance and thus induce magnetic fields. These fields can cause repulsive, attractive, propulsion, drag and heating effects. The stronger the applied magnetic field, the greater the electrical conductivity of the conductor, and the faster the field changes, the greater the currents that are developed and the greater the fields produced.
The term eddy current comes from analogous currents seen in water when dragging an oar breadthwise: localized areas of turbulence known as eddies give rise to persistent vortices. Somewhat analogously, eddy currents can take time to build up and can persist for very short times in conductors due to their inductance.
Eddy currents in conductors of non-zero resistivity generate heat as well as electromagnetic forces. The heat can be used for induction heating. The electromagnetic forces can be used for levitation, creating movement, or to give a strong braking effect. Eddy currents can also have undesirable effects, for instance power loss in transformers. In this application, they are minimized with thin plates, by lamination of conductors or other details of conductor shape.
1.2 CONVENTIONAL BRAKES
Normally the friction brakes are used in the automobiles.A friction brake is a type of automotive brake that slows or stops a vehicle by converting kinetic energy into heat energy, via friction. The heat energy is then dissipated into the atmosphere. In most systems, the brake acts on the vehicle’s roadwheel hubs, but some vehicles use brakes which act on the axles or transmission. Friction brakes may be of either drum or disc type.
1.2.1 Drum brake
A drum brake is a vehicle brake in which the friction is caused by a set of brake shoes that press against the inner surface of a rotating drum. The drum is connected to the rotating roadwheel hub.
1.2.2 Disc brake
The disc brake is a device for slowing or stopping the rotation of a road wheel. A brake disc (or rotor in U.S. English), usually made of cast iron or ceramic, is connected to the wheel or the axle. To stop the wheel, friction material in the form of brake pads is forced mechanically, hydraulically, pneumatically or electromagnetically against both sides of the disc. Friction causes the disc and attached wheel to slow or stop
1.3 EDDY CURRENT BRAKE
An eddy current brake, like a conventional friction brake, is responsible for slowing an object, such as a train or a roller coaster. However, unlike electro-mechanical brakes, which apply mechanical pressure on two separate objects, eddy current brakes slow an object by creating eddy currentsthrough electromagnetic induction which create resistance, and in turn either heat or electricity.
1.3.1 Circular eddy current brake
Electromagnetic brakes are similar to electrical motors; non-ferromagneticmetal discs (rotors) are connected to a rotating coil, and a magnetic fieldbetween the rotor and the coil creates a resistance used to generate electricity or heat. When electromagnets are used, control of the braking action is made possible by varying the strength of the magnetic field. A braking force is possible when electric current is passed through the electromagnets. The movement of the metal through the magnetic field of the electromagnets creates eddy currents in the discs. These eddy currents generate an opposing magnetic field (Lenz’s law), which then resists the rotation of the discs, providing braking force. The net result is to convert the motion of the rotors to heat in the rotors.
1.3.2 Linear eddy current brake
The principle of the linear eddy current brake has been described by the French physicist Foucault, hence in French the eddy current brake is called the "frein ?? courants de Foucault".
The linear eddy current brake consists of a magnetic yoke with electrical coils positioned along the rail, which are being magnetized alternating as south and north magnetic poles. This magnet does not touch the rail, as with the magnetic brake, but is held at a constant small distance from the rail (approximately 7 mm).
When the magnet is moved along the rail, it generates a non-stationary magnetic field in the head of the rail, which then generates electrical tension (Faraday’s induction law), and causes eddy currents. These disturb the magnetic field in such a way that the magnetic force is diverted to the opposite of the direction of the movement, thus creating a horizontal force component, which works against the movement of the magnet.
1.4 DESIGNING AND MODELING OF EDDY CURRENT BRAKING SYSTEM
In our project we first did the reverse engineering in order to get started with our design. While designing we carried out many time consuming measurements using various measuring tools like vernier calliper, gauges, measurement tapes and many more.
After measuring all the dimensions of the braking system, we started to prepare our designs using trial and error method. We took a great care whether our design is feasible or not and keeping that in mind we prepared our design.
After making the design of our braking system our next step was to transform it into a 3D model using CAD. And to do this we first needed to learn a drafting and modeling software which uses CAD method to make a 3D model. And we learned software named PTC CREO 2.0 which helped us to convert our 2D design into a 3D working model. In the later part of our project report a detailed description of the software and our work is presented.
1.5ANALYSIS OF THE EDDY CURRENT BRAKING SYSTEM
In this project, the electromagnetic behavior and performance of the above mentioned braking system under certain loading conditions will be studied. This shall be done by simulating the loading conditions the braking system is predicted to undergo andanalyzing the results. The primary focus of this project is to simulate the performances of the system using ANSYS.
In this study, the braking systems for a eddy current brake will be modeled, tested and then analysed. As the braking power of the system is more important during hard braking and stops, the electromagnetism of system would be studied for braking purpose.
The analysis and comparison study will be done through modeling and simulation using the respective software; Creo and ANSYS. After building a finite element (FE) model of the above mentioned system in Creo, the models would be simulated using ANSYS. The system will be simulated under three different loading conditions: two stress tests and one magnetostatic. The two stress simulations are principle stress simulation and vonmises simulation. For magnetostatic analysis, electromagnetic simulation will be performed.
In order to obtain accurate and reliable results for the simulations, the meshing of the electromagnet must be properly carried out. In ANSYS, simulation tests can be either carried out in two or three dimensions. In this project, three-dimensional simulation techniques shall be studied and used to carry out the various tests in attempt to achieve more accurate results. Various simulation methods, such as techniques to input load conditions and stress profiles will also be studied and improved. These will enable a more accurate simulation of the real conditions that the braking system actually experience.
1.5.1 History of Ansys Inc.
The company was founded in 1970. by Dr. John A. Swanson as Swanson Analysis Systems, Inc. SASI. Its primary purpose was to develop and market finite element analysis software for structural physics that could simulate static (stationary), dynamic (moving) and thermal (heat transfer) problems. SASI developed its business in parallel with the growth in computer technology and engineering needs. The company grew by 10 percent to 20 percent each year, and in 1994 it was sold to TA Associates. The new owners took SASI’s leading software, called ANSYS??, as their flagship product and designated ANSYS, Inc. as the new company name
1.5.2 Products of Ansys Workbench
‘ Systems & Multiphysics
‘ ANSYS Fluent
‘ ANSYS HFSS
‘ ANSYS Maxwell
‘ ANSYS Mechanical
‘ ANSYS Multiphysics
‘ Fluid Dynamics
‘ ANSYS Fluent
‘ ANSYS CFX
‘ ANSYS CFD-Flo
‘ ANSYS CFD Professional
‘ FLUENT for CATIA V5
‘ ANSYS CFD-Post
‘ Structural Analysis
‘ ANSYS Multiphysics
‘ ANSYS Mechanical
‘ ANSYS Structural
‘ ANSYS Professional
‘ ANSYS DesignSpace
‘ Application Customization Toolkit (ACT)
‘ ANSYS Rigid Body Dynamics
‘ Electronics
‘ RF & Microwave
‘ ANSYS DesignerRF
‘ ANSYS HFSS
‘ AnsoftLinks for MCAD
‘ Signal Integrity
‘ ANSYS HFSS
These are some important products of Ansys Workbench which are used most extensively.
CHAPTER – 2
Literature Review
2.1 Patent Survey
Sr No. Title Author Objective Conclusion
1 Eddy current brake for motor vehicles Andreas Seiwald
In order to install an eddy current brake in the universal joint shaft of a motor vehicle, use is made of support members which can be fixed to the longerons of the chassis and each of which can be associated with a mounting plate on the housing. Each support member has mounting apertures arranged according to a first geometrical configuration, and a number of threaded bores, different from that of the mounting apertures, are arranged according to a second geometrical configuration in each mounting plate. In this way a set of mounting orifices can be made to coincide, as desired, with a correspondingly configured set of threaded bores, thus making it possible to obtain different mounting positions depending on the height and angle of inclination of the shaft. In the embodiment shown the supporting bracket is provided with the mounting hole and the mounting plate with a large number of threaded holes
It would also be the inverse division conceivable in which a greater number of mounting holes are provided in the support bracket when the mounting plate, such as according to the prior art has only four threaded holes, so that especially for such eddy-current brake built-in different vehicle types with one and the same support console is enabled.
2 EDDY CUURENT BRAKE SYSTEM
Grima Gete Desta, Kevin Jerome Pavlov,
Zhesheng Li.
An eddy current brake or retarder device for bringing a vehicle to rest is
disclosed. The device includes a stator mounted to a frame of the vehicle, a plurality of poles disposed along a perimeter of the stator, a plurality of coils each wound about about each of the plurality of poles, wherein an adjacent pair of poles form an electromagnet when the coil is energized, and rotor in communication with a transmission axle of the vehicle and located concentric with the stator. A relative rotation of the rotor with respect to the stator produces eddy currents between the poles of the stator and an outer surface of the rotor, causing the rotor to come to a rest.
In an aspect of the present invention, an eddy current brake or retarder device for bringing a vehicle to rest is provided. The device includes a stator, a plurality of poles, a plurality of coils, and rotor. The rotor is in communication with a transmission axle of the vehicle and located concentric with the stator, and wherein in a relative rotation of the rotor with respect to the stator produces eddy currents between the poles of the stator and an outer surface of the rotor, causing the rotor to come to a rest.
Table 2.1
2.2 Reserch papers survey
Srno Title Author Objective Conclusion
1 The Research on Test-Bed Test System of Automobile Eddy Current Retarder
Yunda HU, china
Test-bed test system of automobile eddy current retarder is studied. After introduction to sensors needed and detection principles, the process of signal collection and treatment by single chip is put forward. Besides, precision
compensation and standardization of sensor is conducted, all constituent parts and function are introduced, including forward computer interface. Simple analysis and discussion is conducted on analogue principle of two operation stations of retarder. In the end, the design idea of test software is put forward and flow chart of the design is provided. The design idea put forward is to analyze in two paths digital and analog signals. Digital signal is sent to 8032 single chip directly for counting treatment and then to IPC (Industrial Personal Computer) for analysis. And analog signal after A/D transformation and a serial of signal conditioning is sent to IPC for analysis. The sophistication of test system is lowed and efficiency of data analysis is improved.
2 Modeling analysis of the electromagnetic braking action
on rotating solid cylinders OrianoBottauscio a, Mario Chiampi b, Alessandra Manzin The electromagnetic diffusion and the electromechanical phenomena arising in a solid cylinder rotating inside a magnetic field are here analyzed. The study is developed through a time stepping Finite Element voltage-driven formulation,
employing the sliding mesh technique for handling the cylinder motion. The influence on the dynamic behavior and energy dissipation of the material electric and magnetic properties, the geometrical parameters and the supply conditions is investigated considering a model problem. In this work a coupled electromagneto-mechanical formulation has been developed and applied to the analysis of a solid cylinder rotating in a magnetic field. Despite the model simplicity, all the physical phenomena governing the device behavior have been taken into account. The results of the analysis, developed under different supply conditions, have put in evidence the fundamental role of the material properties on the braking action, and consequently the importance of an exhaustive modeling of eddy currents and magnetic saturation phenomena.
3 COMPARISON STUDY OF TWO DISK BRAKE SYSTEMS USED IN MOTORCYCLES
ZHENG HAN, Singapore The objective of this final year project was to study and compare the mechanical performances of a conventional brake-disk system and a newly designed Perimetral brake-disk system using the finite element method (FEM). In this final year project, three-dimensional modeling and meshing using the simulation program ANSYS were successfully implemented. The two-dimensional technique previously used by Sunstar has been successfully modified and improved to using three-dimensional techniques for modeling and simulation. This has allowed for greater flexibility and accuracy in the results achieved.
Table 2.2
CHAPTER – 3
Design and Modeling
3.1 REVERSE ENGINEERING OF ECB
‘ Reverse engineering is the process of discovering the technological principles of a device, object, or system through analysis of its structure, function, and operation. It often involves disassembling something (a mechanical device, electronic component, computer program, or biological, chemical, or organic matter) and analyzing its components and workings in detail – for either purposes of maintenance or to support creation of a new device or program that does the same thing, without using or simply duplicating (without understanding) the original.
‘ Reverse engineering has its origins in the analysis of hardware for commercial or military advantage. The purpose is to deduce design decisions from end products with little or no additional knowledge about the procedures involved in the original production. The same techniques are subsequently being researched for application to legacy software systems, not for industrial or defence ends, but rather to replace incorrect, incomplete, or otherwise unavailable documentation.
Fig 1
‘ As computer-aided design (CAD) has become more popular, reverse engineering has become a viable method to create a 3D virtual model of an existing physical part for use in 3D CAD, CAM,CAE or other software. The reverse-engineering process involves measuring an object and then reconstructing it as a 3D model. The physical object can be measured using 3D scanning technologies like CMMs, laser scanners, structured light digitizers, or Industrial CT Scanning (computed tomography). The measured data alone, usually represented as a point cloud, lacks topological information and is therefore often processed and modeled into a more usable format such as a triangular-faced mesh, a set of NURBS surfaces, or a CAD model.
‘ Reverse engineering is also used by businesses to bring existing physical geometry into digital product development environments, to make a digital 3D record of their own products, or to assess competitors’ products. It is used to analyze, for instance, how a product works, what it does, and what components it consists of, estimate costs, and identify potential patent infringement, etc.
‘ Using reverse engineering method we formed the base of our project in which we are going to model the design of the retarder which is used in most of the Heavy vehicles, passenger vehicles, magnetic trains etc.
‘ We went to one of the service station of Bus and we carried out the reverse engineering of the eddy current braking system normally known as ‘Retarder’ and measured the dimensions of the various parts or components such as Disk, Electromagnets etc.
‘ We used different measuring instruments like vernier calliper, measure tape, scale, micrometer etc and noted the dimensions of all the components of the referred eddy current braking system.
‘ Following are some data we took during reverse engineering of the eddy current braking system:
Fig 2
Fig 3
These are pictures of eddy current braking system
‘ The above mentioned mechanism in the pictures is the reference of our design data of our project.
‘ We prepared our design based on the data we got from reverse engineering and created 3D model of this system by using CAD software known as CREO Parametric 2.0.
3.2 CreoModelling
Before any simulations or tests can be carried out, it is important to first draw an accurate model of the system which is to be analysed which in this case is the Eddy Current Braking system. The Eddy Current Braking system is supposed to be able to replace the conventional brake systems to operate efficiently in the heavy vehicles. The most suitable design was chosen and modeled using the commercially available software Creo. After that this model will be simulated in theanalysis software which is commonly named as ANSYS. The virtually modeled system is as shown in the figure.
Fig 4 Fig 5
This model consist of the following things :-
PARTS QUANTITY
1. MAIN SHAFT 1
2. BEARING 2
3. HOLLOW CYLINDER 1
4. DISK CONTAINING ELECTROMAGNETS 2
5. ELECTROMAGNETS 16
6. ROTATING DISK 2
7. KEY 1
8. COVER 1
Table 3.1
CHAPTER – 4
Simulation by ANSYS
After modeling the braking system in Creo, the models are then exported to ANSYS in the form of IGES files. In ANSYS, the models are allocated their material properties and then meshed. The material used for electromagnet and the shaft are chosen or are selected from the predefined materials in the library of the software. Thereafter by applying appropriate loading conditions, simulations are carried out using ANSYS to study the performance of the different designs under the actual working conditions.
For any simulation to take place first we have to assign the boundary conditions to the system which is to be simulated. Without boundary conditions we would not be able to create a atmosphere of real situations which are going to be occurring on the system when used in practical applications.
For eddy current braking system, it is only necessary to carry out the simulation of the electromagnet of the system. The shaft and disc of the system can be excluded as they are rarely prone to failure. But as they also are subjected to the various stress. For these reasons, failure often occurs to the shaft. Thus, by simulating electromagnet and shaft, it allows the model to be less complicated and the reduction of computation time.
There are three important simulations carried out to investigate the performance of the system under working conditions. They are magnetostatic test, principle stress and vonmises stress simulation. It is important to note that as much of the final design and specifications of the braking system are not yet finalized, some assumptions have had to be made about the design in order to carry out the tests.
The first test was done to know whether our system would be able to perform efficiently in real situations and the remaining two tests are performed to check whether the propeller shaft which is subjected to torsional moment which acts on it while the application of brake is capable to withstand these stresses without failure or not.
4.1 Simulation Procedures
4.1.1 Techniques of 3D Meshing
Meshing can be done manually or automatically. For manual mesh, the analyst manually defines the nodes and elements. For automatic meshing, there is free and mapped meshing. A free mesh has no restrictions in terms of element shapes, and has no specified pattern applied to it. It usually works with triangle elements for 2D or tetrahedral elements for 3D. Compared to a free mesh, a mapped mesh is restricted in terms of the element shape it contains and the pattern of the mesh. For 3D meshing, a mapped volume mesh contains only hexahedron elements. Mapped meshing is normally done for symmetrical and uniformly shaped bodies; it may be too restrictive for complex geometry but usually produces good mesh quality (well-shaped elements) when they work.
Computational simulation techniques require solving the complex differential or partial differential equations that govern these phenomena. There are many types of methods being used to solve these complex partial differential equations. In this project, the simulation software, ANSYS, uses the finite element method (FEM) to solve these equations. Other common, numerical methods are boundary element methods, finite difference methods, finite volume methods, and spectral methods. In these methods, the spatial domain where the partial differential governing equations are defined is often discretized into meshes. In recent years, element-free or meshfree methods have emerged as a developed class of numerical methods.
The main technique used in this project’s simulation is mapped meshing. This is because the model of the braking system symmetrical; hence by using mapped meshing, well-shaped elements can be obtained. Volume sweep meshing is then used to map the entire model. Using volume sweeping, an existing unmeshed volume is filled with elements by sweeping the mesh from a bounding area (also referred to as the "source area") throughout the volume. Since the source area mesh (done by meshing the area) consists of quadrilateral elements, the volume is filled with hexahedral elements. The swept mesh is fully associated with the volume. Unlike other methods for extruding a meshed area into a meshed volume, volume sweeping is intended for use in existing unmeshed volumes. Thus it is particularly useful in these situations:
‘ Importing a solid model that was created in another program and meshing it in ANSYS, which is precisely the case in this project as the model is created in Creo and subsequently exported to ANSYS.
‘ If the source area is unmeshed prior to volume sweeping, ANSYS meshes it automatically when the volume sweeper is invoked. The other extrusion methods require the area to be meshed manually before invoking them.
In 3D meshing, the two general types of solid elements to be used are tetrahedron shaped elements and hexahedron shaped elements. In this project, the majority of the meshing will be carried out using hexahedron shaped elements as it has a better aspect ratio, better accuracy and is easier to control in terms of size as compared to tetrahedron shaped elements. The eight-node hexahedral element is linear (p = 1), with a linear strain variation displacement mode [8]. Tetrahedral elements are also linear, but can have more discretization errors because they have a constant strain. Meshes comprised of hexahedrons are also easier to visualize than meshes comprised of tetrahedrons. In addition, the reaction of hexahedral elements to the application of body loads corresponds to loads under real world conditions more precisely.
The meshing of the electromagnet and the shaft is as shown is the figure below.
Fig 6 Fig 7
‘ In the above fig. meshing of electromagnet and shaft is done using automatic method so that mapped meshing is done.
‘ The no. of nodes and elements in Electromagnet are: 7562 and 3182.
‘ The no. of nodes and elements in Shaft are: 1108 and 210.
4.1.2 Stress Analysis Methods
Failure analysis in ECB systems can be divided into two parts ductile failure and brittle failure both in case of ECB acts on the shaft. It is useful to adopt the view point that facture and yielding are separate events and that either one may occur first depending on the combination of material or stress states involve.
Ductile failure would predict the yielding or deformation of the shaft. For ductile failure, the Von Mises Stress (Octahedral Shear Stress Yield) criterion is used. Finite element analysis results are typically presented as Von Mises stresses. It is calculated by combining stresses in two or three dimensions, with the result compared to the tensile strength of the material loaded in one dimension. Stress is in general a symmetric 3??3 matrix. Von Mises stress reduces this to a single number (a scalar) for the purposes of calculating yield criteria.
The Von Mises Stress in three dimensions is given by,
where ??1, ??2, ??3 are the principal stresses.
It should be noted that both Tresca (Maximum Shear Stress Yield) Criterion and Von Mises Criterion are widely used in metals. The maximum difference between them is 15% which is relatively small compared to safety factors commonly used and to various uncertainties usually involved in mechanical design. Thus, the choice between the two is not a matter of major importance. Von Mises Criterion is used here as it is readily available in the software used. If more conservatism is desired, Tresca Criterion could be chosen.
To predict cracking and locate weak points that may lead to crack formation, the Maximum Principle Stress Criterion is used. The Maximum Principle Stress Criterion states that failure occurs in a multiaxial state of stress when either a principal tensile stress reaches the uniaxial tensile strength ??ut or a principal compressive stress reaches the uniaxial compressive strength ??uc. Since ??uc is usually considerably greater than ??ut, ??ut is used. For a more conservative analysis in this project, the yield stress is used as a comparison instead of ultimate tensile strength.
where ??1, ??2, ??3 are the principal stresses [9].
Both Von Mises and Maximum principle Stress Criterion are used in this project as a relative gauge to predict the performances of the brake-disk in ductile and brittle failure respectively.
4.1.3 Static Test – Torsional Strength Simulation
(a) Purpose of Test
In this simulation, a torsional force is exerted on the shaft, simulating the torsional force that a braking system experiences during hard braking. This is similar to actual braking conditions, when the rider comes to an emergency stop while travelling at high speed. It is important to ensure that the shaft of the system is able to withstand the high torsional stress generated due to the electromagnets producing the braking effect on the propeller shaft. In this test, it is important to check for any distortions, where there might be stress concentrations during braking.
(b) Assumptions
1) The maximum torque is concentrated on the shaft where the braking system is mounted.
2) The maximum weight of the heavy vehicle is the same for the eddy current braking system and the conventional braking system: which is equal to the total weight of the heavy vehicle, the rider and luggage.
3) Maximum friction coefficient between the wheels and the ground is assumed to be 0.8.
A torsional force is simulated on the surface of the shaft. The nodes within a rectangular shape on the surface of the shaft are chosen, simulating the dimensions of a shaft. In this way, the torsional force is simulated to be applied from braking system onto the shaft. This value of torsional force is calculated based on the maximum deceleration that the vehicle will experience during hard braking.
The figure shows the stress concentration on the shaft.
Fig 8 Fig 9
In Fig 8 the result of Equivalent (Von-Mises) stress acting on the shaft while braking while in Fig 9 the result of Maximum principal stress acting on the shaft is shown.
The Max. Equivalent stress is 5.5×105 N/mm2 which is under permissible limits and the Max. value of Maximum principal stress is 5.52×105 N/mm2 which is also within permissible limits. So both these simulations we find that the shaft will not fail when brakes are applied.
4.1.4 Static Test – Magnetostatic Simulation
(a) Purpose of Test
In this simulation, the magnetic effect produced by the electromagnet to stop the vehicle in motion is simulated. The magnetostatic effect on the braking system is the effect produced by the electromagnet on the rotating disc which is keyed to the shaft. This is similar to actual braking conditions, when the rider comes to an emergency stop while travelling. It is important to ensure that the magnetic effect produced by the electromagnetis enough to retard and stop the vehicle at the will of the driver.
In this simulation we have used air as the medium for the generation of electromagnetism by applying current and voltage to the source conductor.
(b) Assumptions
1) The speed of the heavy vehicle is assumed to be 30km/hr.
2) The mass of the heavy vehicle is assumed to be 9 ton.
3) The effect of the magnetism produced by the electromagnet is assumed to be concentrated on the electromagnetic disc.
4) The energy supplied from the battery to the electromagnet is 2 Ampere.
5) Number of turns on the coil of the electromagnet is assumed to be 2000.
6) The coil is made up of the copper, the shaft is made of the cast iron and so as the core of the electromagnet.
The electromagnetic force is simulated on the surface of the electromagnetic disc. After the simulation the optimization technique is used for the selection of the material. The value of electromagnetic force is calculated based on the maximum deceleration that the vehicle will experience during hard braking.The figure shows the magnetostatic analysis of the electromagnet.
Fig 10 Fig 11
In Fig 10 the resultant directional force produced by the electromagnet is shown while in Fig 11 total force produced by the electromagnet is shown.
There are three axis in which the electromagnetic force is produced by the electromagnet when voltage and current is applied to the Source Conductor. Also the electromagnetic force is calculated using a cylindrical enclosure of Air medium.
Out of all the three directions we need to have the directional force in z-axis which is our resultant force responsible for the braking action of the vehicle. This directional force is responsible for producing the braking force required to retard the vehicle.
CHAPTER – 5
Conclusion
In the current work, three-dimensional (3D) modeling and electromagnetic analysis is carried out using the PTC Creo 2.0 and ANSYS 14.5 Inc.respectively. This allowed for greater flexibility and accuracy in the results achieved. The performances of an Eddy Current Braking system under three different simulation environments were studied. Under torsional strength simulation, the system performs better with its maximum values of First Principal Stress and Von Mises Stress being significantly lower than those in the conventional brake-disk. This can be attributed to the lower torsional force experienced by the system.
Under electro magneto static simulation, the system designed produces the required amount of power to stop the vehicle which is approx. 2.5KN for 1 electromagnet. As there are 16 electromagnets so based on the result obtained from 1 electromagnet one can conclude that current model is able to stop and retard the vehicle at the wheel of the driver.
Refrences
1. Yevtushenko, A. and Ivanyk, E., ‘Determination of Heat and Thermal Distortion in Braking Systems,’ Wear 185, Elsevier, 1995, pp. 159-165.
2. Roth, G., ‘Analysis in Action: The Value of Early Analysis,’ SAS IP, Inc., USA, 1999.
3. ANSYS Modelling and Meshing Guide, ANSYS Release 5.6, SAS IP, Inc., 4th edition, 1999, Chapter 7.
4. Zienkiewiez, O. C., and Taylor, R. L., ‘The Finite Element Method,’ Butterworth Heinemann, 5th edition, 2000, pp. 1-27.
5. Valvano, T. and Lee, K., ‘An Analytical Method to Predict Thermal Distortion of a Brake Rotor,’ Society of Automotive Engineers, Inc, 2000.
6. Liu, G.R., ‘Mesh Free Methods, Moving Beyond the Finite Element Method,’ CRC Press, 2002, pp. 1-25.
7. Tan, H.N., ‘2-D Heat Transfer Analysis Using Meshfree Methods,’ Department of Mechanical Engineering, NUS, 2002/2003, pp. 1-7.
8. Liu, G.R. and Quek, S.S., ‘The Finite Element Method: A Practical Course,’ Butterworth Heinemann, 2003, pp. 199-232, 246-280.
9. Kurowski, P. M., ‘Finite Element Analysis for Design Engineers,’ SAE International, Warrendale, 2004, pp. 1-147.