Automotive Brake Disc Design To Suppress High Frequency .
International Journal of Engineering Research & Technology (IJERT)ISSN: 2278-0181Vol. 3 Issue 1, January - 2014Automotive Brake Disc Design to Suppress High Frequency Brake Squeal NoiseProf. V KumarProf. S. V. ChaitanyaProf Mechanical Engineering,AISSMS College of Engineering ,PuneAssist. Prof. Mechanical Engineering,AISSMS College of Engineering ,PuneMr. Sandip B. PhadkePG Scholar, Mechanical EngineeringAISSMS College of Engineering ,PuneAbstractIntroductionFigure 1 : High frequency brake squeal hypothesisExperimental case studiesAbove hypothesis is true for one of the developmentproject and hence to further confirm the same threedifferent case studies are done as below:Case study 1 : Structural modifications like slot, holeare done on existing brake discCase study 2 : Structural modifications like slot,chamfer, cut-out on brake pad changes in shimCase study 3 : Change in vane pattern (existing disc isof 37 straight vanes whereas new disc is of 31 straightvanes)IJERTOf the various countermeasures used to address discbrake squeal noise, noise shims have proven to be veryeffective in addressing medium to high frequencysqueal related to rotor bending vibration. However, forsqueal noise at low frequency and squeal related torotor in-plane vibration, noise shims are less effective.Recently, there is more and more evidence showingthat many field claims of brake squeal noises arerelated to the brake rotor’s in-plane vibration modes.So it becomes necessary to review brake design forsuppression of high frequency brake squeal noise.Disc brake noise generation during braking is one ofthe most important issues faced by automotivemanufacturers worldwide. Despite brake noise is not asafety issue and has little impact on brakingperformance, it gives customers the impression ofunderlying quality problems of the vehicle. In addition,the customers view that the noise emitted from thebrake system is indicator of malfunctioning conditionand consequently lose confidence on the quality of thevehicles.Existing plain brake discBrake noise complaints forms a major warranty costs tovehicle and brake manufactures. Also it affects thebrand image of the brake manufacturer. Considering allabove it has become prime objective to minimize brakenoise during vehicle design and development phase. Toachieve this, understanding the root causes for brakenoises observed during development phase is essentialand countermeasure need to defined based on suchdeeper understanding of brake noise phenomenon.HypothesisThe high frequency brake squeal propensitysignificantly increases if there is modal couplingbetween brake disc in-plane and out of plane modes.IJERTV3IS10108www.ijert.orgFigure 2: Brake squeal noise with existing brake discIn existing brake disc there is modal coupling betweenin-plane and out of plane modes at 6.5kHz. And insqueal noise test also the major frequency observed is6.5kHz. So the hypothesis is true for this case.165
International Journal of Engineering Research & Technology (IJERT)ISSN: 2278-0181Vol. 3 Issue 1, January - 2014Case study 1:Case study 3:Figure 3: Brake squeal noise with structural modificationsin existing brake discCase study 2:With 31 straight vane disc there is decoupling of inplane and out of plane modes of brake disc. Howeverthere is modal coupling at 7.35kHz but the amplitudesare comparatively lower . Squeal noise test results alsoshown that 6.5kHz frequency is eliminated which waspresent in all earlier modifications but there isoccurrence of new high frequency i.e. 7.35kHz.IJERTAny of structural modification (rectangular slot / holes /inclined slot) in brake disc could not decouple in-planeand out of plane modes at 6.5kHz. And during squealnoise tests with these brake discs show prominentoccurrence of 6.5kHz.Figure 5: Brake squeal noise with 37 and 31 straight vanediscsBased on case studies brake disc modal couplinghypothesis is confirmed. And to reduce such highfrequency brake squeal noise modifications in brakedisc could be an effective as well as stable solution.Brake disc modifications:Figure 4: Brake squeal noise with structuralmodifications in brake pad different shims tested withexisting brake discWith existing brake disc (37 straight vanes) differentpad modifications (like slot, chamfer, cut-out as shownin figure 4) and different types of shims brake squealnoise is evaluated and in all these cases there is acommon squeal frequency which is 6.5kHz.IJERTV3IS10108www.ijert.orgIf there is a modal coupling between in-plane and outof plane bending modes for an existing brake disc, inorder to shift modes following are two options:1.2.Change stiffness by doingmodifications in brake geometryChange material propertiesstructuralTo do such modifications we need to understand thebrake geometry, materials used for brake disc and otherfunctional requirements of brake disc.166
International Journal of Engineering Research & Technology (IJERT)ISSN: 2278-0181Vol. 3 Issue 1, January - 20141.Brake geometry :Good cooling or heat dissipation performanceFigure 6 : Brake disc geometryIJERTa) The rubbing surface section is a one-piece castingwith cooling fins(vanes) between the braking surfaces(cheeks) to enable air to circulate between the brakingsurfaces and make the rubbing surfaces less sensitive toheat build-up and more resistant to fade.b) The top hat section is mounted to the vehicle wheelhub and is shaped like a hat in order to protect thewheel bearings from the high temperatures inducedduring braking action at the rotor-pad interface.c) The section that connects cheeks and top hat sectionis known as the neck.Brake disc material:Figure 7 : Brake disc coolingFollowing are materials used for automotive brake disc:2.a) Gray Cast Ironb) Aluminium metal matrix composites (Al-MMCs)c) Carbon reinforced ceramic matrix composites(CMCs)Thermo-mechanical distortion resistance (conningresistance)Brake disc functional requirements:If we are able to decouple in-plane and out of planemodes of brake disc by doing a modification, then it isequally important to verify that this change is meetingrest all functional requirements of brake disc.Following are the functional requirements of brakedisc:IJERTV3IS10108www.ijert.orgFigure 8 : Brake disc conning3.4.Optimum strength to weight ratio and cost(material selection)Cracking resistance167
International Journal of Engineering Research & Technology (IJERT)ISSN: 2278-0181Vol. 3 Issue 1, January - 2014Figure 11: Co-relation between FEA and experimentaltest resultsFigure 9 : Brake disc crackingMode shape :Degassing, glazing and debris controlIJERT5.Figure 10: Brake disc glazing6.7.Lower brake pad wearProtect wheel bearings from heat generated duringbraking actionUse of FEA modal analysis for modifyingbrake disc design:With the help of FEA modal analysis it is possible tomodify brake disc design in order to shift modes.In the following example with the help of Abacussoftware modal analysis is done for 37 straight vanedisc and comparison is made between experimentalmodal test data and FEA modal data. Also mode shapesare evaluated as below:Conclusion :1.Brake squeal propensity is higher at the frequencywhere there is modal coupling between in-plane andout of plane modes of brake disc.2.Influence of in-plane mode is higher than out of planemode and hence it is very difficult to completelyeliminate this high frequency squeal noise bymodifications in brake pad and shim.3.With changes in brake disc structure especially thevane pattern it is possible to split the modal coupling ata particular frequency. But there is a possibility thatmodal coupling at one frequency is eliminated but itappears at other frequency.4.Considering the complexity of problem, it isadvisable to have at least two different disc designs (forexample, disc1 with 37 vanes and disc2 with 31 vanes)at the start of project so that if with disc1, it is notpossible to suppress high frequency, then there is scopeto go for disc2.IJERTV3IS10108www.ijert.org168
International Journal of Engineering Research & Technology (IJERT)ISSN: 2278-0181Vol. 3 Issue 1, January - 2014Future workThe way forward would be to completely ELIMINATEhigh frequency brake squeal with modifications inbrake disc using FEA modal analysis.Also considering complexity of brake squealphenomenon we need to validate this hypothesis onmore number of brakes and arrive at guideline for brakedisc design to counter high frequency brake squealnoise.ReferencesIJERT[1] SAE Paper 2002-01-0922 “Modal Coupling and ItsEffect on Brake Squeal” Research and VehicleTechnology, Ford Motor Co.[2] “Investigation of the Effects on BrakingPerformance of Different Brake Rotor Designs” Paper by Mirza GrebovicIJERTV3IS10108www.ijert.org169
frequency brake squeal noise modifications in brake disc could be an effective as well as stable solution. Brake disc modifications: If there is a modal coupling between in-plane and out-of plane bending modes for an existing brake disc, in order to shift modes following are two options: 1. Change stiffness by doing structural
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C. Modeling ANSYS workbench The finite element method is analyzed on ANSYS Workbench 17.2. The project schematic on workbench. The geometrical model of Al-MMC brake disc- Kevlar brake pad, Al-MMC brake disc-aluminum alloy brake pad and Al-MMC brake disc-ceramic brake pad were simulated by ANSYS
(2) Install the front disc brake anti-squeal shim to each front disc brake pad. NOTICE Figure 3. 1 Front Disc Brake Anti-squeal Shim 3. Road test the vehicle to confirm proper brake pad installation. NOTICE When applying disc brake grease, use the grease enclosed with a front disc brake pad kit or supplied
on disc brakes The problem: Brake pad fails to disengage and rubs against the disc. This can cause the brake system to overheat. Causes: Brake pad seized Brake piston stuck in calliper Driving with depressed brake pedal, e.g. when going downhill Possible consequences: Reduced brake
frequently. Hydraulic disc brakes are comparatively more efficient than drum brake. Disc brake consist of a master cylinder with a reservoir in which hydraulic Fluid is kept, then the brake lines which will connect the master cylinder to the various brake calipers, brake caliper is the most important part of the whole disc brake system
squeal, best method of analyzing brake disc is by complex Eigen value analysis. This technique is available in ANSYS 13 and can be used to determine stability of brake disc. The real and imaginary part of complex Eigen values is responsible for level of instability of brake disc assembly. Once imported frictionless support was given to brake disc
for the calculation of the unstable frequencies of a car disc brake and the analysis procedure. The stationary components of the disc brake are modeled using finite elements and the disc as a thin plate. This approach facilitates the modelling of the disc brake squeal as a moving load problem.
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