Modelling and analysis of rotor braking system

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The main purpose of this project is Optimization of Automotive Brake Disc and analysis the unsteady state thermal behaviour of the dry contact between the brake disc and pads during the braking phase.

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Nội dung Text: Modelling and analysis of rotor braking system

International Journal of Mechanical Engineering and Technology (IJMET) Volume 10, Issue 03, March 2019, pp. 1217-1226. Article ID: IJMET_10_03_124 Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=3 ISSN Print: 0976-6340 and ISSN Online: 0976-6359 © IAEME Publication Scopus Indexed MODELLING AND ANALYSIS OF ROTOR BRAKING SYSTEM K Srinivasa Rao Assistant Professor, Department of Mechanical Engineering, Velagapudi Rama Krishna Siddhartha Engineering College, Vijayawada-520007, A.P. India U V Narayana Rao Assistant Professor, Department of Civil Engineering Velagapudi Rama Krishna Siddhartha Engineering College, Vijayawada-520007, A.P. India G Sridhar Babu and M Rajesh Assistant Professor, Department of Mechanical Engineering, Velagapudi Rama Krishna Siddhartha Engineering College, Vijayawada-520007, A.P. India ABSTRACT A brake is a mechanical device which simulated frictional safety is connected to moving machine part, to stop the movement of a machine. At present performing this function, the brakes take in either kinetic energy of the moving part or the potential energy surrendered by items being brought down by lifts and so forth. The energy absorbed by the brakes is scattered as heat. Disc brake is a recognizable automobile application where they are utilized broadly for car and bike wheels. The disc is sandwiched between two pads activated by cylinders backed in a calipers mounted on the stud shaft. At the point when the brake lever is pressed using pressurized hydraulic pressurized fluid is constrained into the chambers pushing the contradicting cylinders and brake pads into frictional contact with the disc. The frictional heat produced amid braking application can result in various negative impacts on the brake assembly, for example, brake blur, untimely wear, thermal splits and disc thickness variation (DTV). The main purpose of this project is Optimization of Automotive Brake Disc and analysis the unsteady state thermal behaviour of the dry contact between the brake disc and pads during the braking phase. The thermal-structural analysis to determine the deformation and the Von Misses stresses established in the disc. The objective of the project is the design, analysis and optimization of disc brake using Ansys. The brake disc is designed by a 3Dmodelling software CATIA V5R20 and we analyse structural and thermal conditions on disc brake using ANSYS 15. Keywords: Brake, Cylinder Thermal Stresses, wear resistance. http://www.iaeme.com/IJMET/index.asp 1217 editor@iaeme.com
K Srinivasa Rao, U V Narayana Rao and G Sridhar Babu and M Rajesh Cite this Article: K Srinivasa Rao, U V Narayana Rao and G Sridhar Babu and M Rajesh, Modelling and Analysis of Rotor Braking System, International Journal of Mechanical Engineering and Technology, 10(3), 2019, pp. 1217-1226. http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=10&IType=3 1. INTRODUCTION 1.1. BRAKE A brake is a contact mechanical device for changing over the momentum or kinetic energy of the moving vehicle into heat by method for rubbing. It is obliged to stop or ease off the vehicle in the briefest conceivable separation when needed to do so. Braking of a vehicle relies on the static function that demonstration in the middle of tires and street surface. Brakes take a shot at the following standard to stop the vehicle: "The kinetic energy because of movement of the vehicle is scattered as heat energy because of contact between moving parts (wheel or wheel drum) and stationary parts of the vehicle (brake shoes)". The heat energy so produced because of use of the brakes is dispersed into the air. Brakes work most successfully when they are connected in a way so the wheels don't bolt totally, yet keep on moving without slipping on the surface of the street. The whole time, the brakes take in either kinetic energy of the moving part or the potential energy surrendered by articles being brought down by lifts, and so on. The energy absorbed by the brakes is scattered as heat. This heat is dispersed into the encompassing air to stop the vehicle, so the slowing mechanism ought to have the following prerequisites: 1. The brakes are solid enough to stop the vehicle inside a base Distance. 2. The driver ought to have fitting control over the vehicle amid braking, not to slip. 3. The brakes must have great against blur aspects. 4. The brakes ought to have great against wear properties 1.2. MECHANICAL BRAKES The mechanical brakes, according to the direction of acting force, may be divided into the following two groups, a) Radial brakes b) Axial brakes 1.2.1. RADIAL BRAKES In these brakes, the force acting on the brake drum is in radial direction. The radial brakes may be sub-divided into external brakes and internal brakes. According to the shape of the friction element, these brakes may be block or shoe brakes and band brakes. E.g. block brakes and band brakes. http://www.iaeme.com/IJMET/index.asp 1218 editor@iaeme.com
Modelling and Analysis of Rotor Braking System 1.2.2. AXIAL BRAKES In these brakes, the force acting on the brake drum is in axial direction. The axial brakes may be disc brakes and cone brakes. The analysis of these brakes is similar to clutches. E.g. Disc brakes, Cone brakes. 1.3. WORKING OF DISC BRAKES Disc brakes are responsible for stopping your vehicle. They consist of three main parts: brake pads, a caliper, and a rotor. Brake pads are located on each side of the rotor and are actually pushed against the rotor to stop the wheel and thereby stop your vehicle. The pads create the necessary friction to stop the vehicle. The caliper is a device located over the top of the rotor and contains both brake pads. There are two types of calipers: floating calipers and fixed calipers. A floating caliper can compress itself and contains only one piston. When the brakes are applied, brake fluid will force the piston into the brake pad, which will press against the rotor. Then, the other side of the caliper will press the other brake pad against the rotor to stop the wheel and vehicle. A fixed caliper doesn’t move; so, it contains two pistons located on each side of the rotor. Now a days the disc brakes are of different types according to their geometry and size. The shape and size varies from industry to industry, but mostly they are classified into two types solid disc and ventilated discs. In solid discs the heat dissipation is lower than ventilated disc. For two wheeler vehicles the solid discs are avoided due to their low heat dissipation, so we use ventilated discs. Coming to the heavy vehicles, at first solid disc brakes are used later some modification are done , so that a fin like structures are provided for in the middle for the disc for air flow to dissipate the heat Figure 1.5 Solid and Ventilated Discs 2. DESIGINING The models all are of solid modeling type, the first four models dimensions are as follows, here outer radius is 240mm is same for all the discs. The thickness we had taken is 5mm the inner radius changes form disc to disc , because for the material optimization we consider different changes. 2.1. Model 1 This is one of the existed model , we can observed this model in some bikes. As we know that ventilated rotor disc are used for the better heat dissipation. In this model the holes are provide for that reason, so that air passes through out the surface of the disc and the temperature is reduced. http://www.iaeme.com/IJMET/index.asp 1219 editor@iaeme.com
K Srinivasa Rao, U V Narayana Rao and G Sridhar Babu and M Rajesh 2.2. Model 2 In this model curved slots are provided for better cooling of the disc rotor ,so that we can reduce the stress developed in the rotor. So the durability of the disc can be increased ,it is the exact idea behind this model design. To optimize the material internal shape is modified as shown in the above fig 2.3. Model 3 It is modified form the model 2 , the reason behind this is discussed in the next chapter 2.4. Model 4 This model is designed base on the analytical results obtained for previous models we had designed. The inner radius is 140mm, this design is so what similar to the latest trending designs of disc rotors of disc brakes which are available in the market. All the model which we are draw in the catia are related to the two wheeler vehicles. 2.5. Model 5 This model is related to the four wheeler vehicles. In this we also design the existinig models of the heavy vehicles disc brakes; here we try to compare the models which were in the used in the present vehicles like cars. In this project we try to investigate the best model among them. Coming to the design the outer radius is 320 it is common for all the models. Dimensions 320 x 32 mm , Height 77mm, Wear limit 30mm thick for ventilated discs, 20mm for solid disc 3. DESIGN OF VENTILATED DISC The ventilated type disc rotors the difference in the models are model 5 has hole which are proved for air flow provided in it like ventilated disc .The first step in analysis is modeling, that part is completed. The model which was generated in catia can't open in ansys workbench, so we have convert that model files into .igs format. Design of Model 1 Design of Model 2 Design of Model 3 Design of Model 4 Design of Model 5 Design of Ventilated Disc 4. MESHING Meshing is one of the major part which should be observed in the analysis, In computational solutions of partial differential equations, meshing is a discrete representation of the geometry that is involved in the problem. Essentially, it partitions space into elements (or cells or zones) http://www.iaeme.com/IJMET/index.asp 1220 editor@iaeme.com
Modelling and Analysis of Rotor Braking System over which the equations can be approximated. Zone boundaries can be free to create computationally best shaped zones, or they can be fixed to represent internal or external boundaries within a model. Three-dimensional meshes created for finite element analysis need to consists of of tetrahedral, pyramids, prisms or hexahedra The procedure for generating a mesh of nodes and elements consists of three main steps: 1 Set the element attributes .2 Set mesh controls (optional, ANSYS offers a large number of mesh controls, which you can choose from to suit your needs). 3. Generate the mesh. As we can see for the above figure ,in that meshing the major part of elements are the pyramidal shaped elements, it is five nodal pyramidal element. Similarly other models are meshed in the same way, so can observe nearly same kind of mesh in them. After giving all the attributes to the models they are solved by taking the required terms which are to be calculated. By clicking the solve option in the ansys workbench, so we can derive the solution or results from the models 5. RESULTS AND DISCUSSIONS The main aim is to develop a new design by comparing the results of an existing model to the model which we have designed, so all the models are tested for same conditions. The results which are obtained are discussed in this chapter. Here two types of analysis are done on first four models which were designed, they are structural and thermal. Let first discussed about the structural, in structural we find the vonmises stress and the deformation 6. STRUCTURAL ANALYSIS In order to apply the conditions of pressure and temperature on the rotor surface we made a extrusion equal to the thickness of the rotor on its surface and slice the extrusion. The surface which is extruded is exposed to the loads. The loads that we make use here are Pressure of 0.1Mpa and a thermal condition of 120 degrees on that extruded part. A rotational velocity of the disc is taken to be 50 radians/sec. By applying the given conditions the following results are obtained. 6.1. Model: 1 Figure Equivalent stress : Figure Total deformation Above analysis results are the existing model results, results obtained for the load we have applied for the model are ; equivalent stress , deformation. Here the maximum stress are seen at the ventilated holes because of the stress concentration factor it exists at the holes. Maximum deformation is the area around where the braking force is applied this is due to the compression http://www.iaeme.com/IJMET/index.asp 1221 editor@iaeme.com
K Srinivasa Rao, U V Narayana Rao and G Sridhar Babu and M Rajesh Table Results of Model 1 Minimum Maximum Deformation - mm 0 0.095 Stress -Mpa 2.62 345.45 6.2. Model:2 Figure Equivalent stress Figure Total deformation Table Results of Model 2 Minimum Maximum Deformation - mm 0 0.071 Stress(von-mises) Mpa 0.026 185.26 6.3. Model:3 Because of the second model is failed we go for some geometric modification, as previously discussed that due cantilever effect the model is failed so we provided some support at the end of the slot which were on the disc by adding material. And the results for this In this model as we observed that the maximum stress obtained is equal to the stress in the first model and the minimum stress reduced compare to the existed model i.e first model .As in the second model failure occurs due to the deformation, in this model there is a slight deformation. Due increase in stress and slight deformation this model is also considered as failed. Table Results of Model 3 Minimum Maximum Deformation -mm 0 0.031 Stress(von-mises)- Mpa 0.057 346.56 http://www.iaeme.com/IJMET/index.asp 1222 editor@iaeme.com
Modelling and Analysis of Rotor Braking System 6.4. Model:4 Figure Equivalent Stress Figure Total deformation The models 2,3 are failed so that we rethink a new design , this idea is by seeing some of latest designed available in the market. This is also analyse under same conditions as of previous models. The results are as follows Table Results of Model 4 Minimum Maximum Deformation - mm 0 0.033 Stress(von-mises)- Mpa 0.102 308.45 The results which are obtained for this model has 10% reduction in the maximum stress than first model, the minimum stress are also reduced as well. Coming to the deformation models 2,3 are failed due to deformation but in this model the deformation is very low and negligible. It is good model and passed the analysis. The maximum stress is seen in the holes where the braking force is applied, the actual stress or average stress is about. Results of all the models are tabulated as follows and compared: Table Comparison of Stress Model Material Min.Stress (Mpa) Max.stress(Mpa) Avg. Stress (Mpa) Model 1 Gray cast iron 2.46 345.45 173.955 Model 2 Gray cast iron 0.024 185.26 92.642 Model 3 Gray cast iron 0.05 346.56 173.305 Model 4 Gray cast iron 0.102 308.45 154.27 Table Comparison of deformation Model Material Min.Deformation Max.Deformation Status Negligible Model 1 Gray cast iron 0 0.095mm deformation Model 2 Gray cast iron 0 0.031mm Deformed Model 3 Gray cast iron 0 0.071mm Deformed Model 4 Gray cast iron 0 0.033mm Not deformed 7. THERMAL ANALYSIS The analysis which was performed is transient thermal analysis, in this analysis we find out the heat flux and temperature distribution in the rotor. Temperature are developed in the rotors are due to the friction between the brake pads and the disc when the brake is applied .Heat flux or thermal flux is the rate of heat energy transfer through a given surface, per unit time. As the heat flux value is high heat transfer will increases http://www.iaeme.com/IJMET/index.asp 1223 editor@iaeme.com
K Srinivasa Rao, U V Narayana Rao and G Sridhar Babu and M Rajesh 7.1. Model:1 Figure Temperature distribution Figure Heat flux 7.2. Model 2 Figure Temperature distribution Figure Heat flux 7.3. Model: 3 Figure Temperature Distribution 7.4. Model: 4 Figure Temperature Distribution http://www.iaeme.com/IJMET/index.asp 1224 editor@iaeme.com
Modelling and Analysis of Rotor Braking System 7.5. Model: 5 Figure Equivalent Stress Figure Total deformation 7.6. Model:6 Figure Equivalent Stress Figure Total deformation 7.7. Model:7 Figure Equivalent Stress Figure Total deformation 8. CONCLUSION Conclusion is the crucial part of a project or any work. By analysing the results we come to the conclusion that the model 4 is much optimised and the stress, deformation, heat flux, temperature distribution produced are less compared to the existed model i.e model 1. So we can say that this model is best among the all others in all aspects we were considered. We came to this conclusion by comparing the values of existed model which was analysis under the same conditions where the other models are analysed .In this work we conducted structural and thermal analysis. On the base of the value obtained in the analysis, we conclude that model 4 is the optimized model, had a better strength too. Coming to other models that are use for four wheeler vehicles, here we try to find out the which one is the best among the three existing models which we taken for analysis. In this we done the structural analysis on the models, by considering the stress, deformation and temperature gradient we concluded that model 7 is better than the others. Even though the model 6 having less stress and deformation value it has low cooling capacity, as the temperature decreases the thermal stress also decreases. Model 7 has better ventilated system than model 6, so we chosen model 7 is better than other models REFRENCES [1] Design of Machine Elements By V. B. Bhandar, Third Edition, Mcgraw Hill Education, [493]. pp. 75–78. http://www.iaeme.com/IJMET/index.asp 1225 editor@iaeme.com
K Srinivasa Rao, U V Narayana Rao and G Sridhar Babu and M Rajesh [2] Swapnil R. Abhang, D.P.Bhaskar, ‘‘Design and Analysis of Disc Brake, IJETT – Volume 8 Number 4- Feb 2014,[165] [3] Manjunath T V, Dr Suresh P M, ‘‘Structural and Thermal Analysis of Rotor Disc of Disc Brake’’ IJIRSET, ISSN: 2319-8753Vol. 2, Issue 12, December 2013. [4] Kenneth Domond ‘‘Brake Rotor Design and Comparison using Finite Element Analysis: An Investigation in Topology Optimization’’,2010 [5] J.Slavic, M.D. Bryant and M. Boltezar (2007), "A new approach to roughness-induced vibrations on a slider.", J. Sound and Vibration, Vol. 306, Issues 3–5, 9 October 2007,pp. 732–750. [6] Thoms, E. (1988), "Disc brakes for heavy vehicles", IMechE, pp. 133–137. [7] Stringham, W. et al. (1993), "Brake roughness – disc brake torque variation", disc distortion and vehicle response, SAE Technical Paper Series, no. [8] Jacobsson, H. (1997), "Wheel suspension related disc brake judder", ASME, no. DETC97/VIB-4165, pp. 1–10 [9] Jacobson, H. (1996), "High speed disc brake judder – the influence of passing through critical speed", In EuroMech – 2nd European Nonlinear Oscillations Conference, Prague, no. 2, pp. 75–78. http://www.iaeme.com/IJMET/index.asp 1226 editor@iaeme.com