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Int. J. Mech. Eng. & Rob. Res. 2014 Vignesh Shanbhag et al., 2014

MODELING AND SQUEAL ANALYSIS OF BRAKEDISC ROTOR USING ANSYS

Vignesh Shanbhag1*, Vikram Singh1, Rathod Abhik1 and Baskar P1

*Corresponding Author: Vignesh Shanbhag,vigneshsha@gmail.com

In automobile in order to stop the vehicle motion frictional resistance is applied by means ofdevice called brake. In recent years Engineers have been able to eliminate most of the noisegenerated in the vehicle. However to eliminate friction induced squeal in vehicle brakes ischallenging task for automotive engineers. In automobiles Disc brake and wheel are attachedtogether. When brakes are applied to the disc it slows down or stops the rotation of wheel. Thismotion is caused due to friction between disc and the wheel. Due to this large heat is generatedand brakes become too hot which leads to ceasing of work since no much of the heat is allowedto dissipate. This kind of failure is called as brake fade. In order to improve heat dissipation in ourexperiment ventilated disc rotor is used to determine Disc squeal. Modeling of the disc is beendone on Solid works and Modal analysis is done on ANSYS 13.0. Ventilated brake disc squeal isdetermined for cast iron and Carbon-Carbon composites. Comparison is made among thesethree materials and material which generates least squeal is determined and recommended.Maximum squeal was obtained at mode 6 for both the materials and the frequency squealobtained was less then High frequency squeal (8 KHz to 16 KHz) squeal.

Keywords: Brake disc, Squeal, Natural frequency, Modal analysis

INTRODUCTIONDisc brake slows down or stops the vehiclemotion due to the occurrence of friction causedby pushing wheel brake pads against brakedisc with set of calipers. Brake disc is madeof cast iron, Aluminium alloys or carbon-carbonmatrix composites. To stop or slow down therotation of the brake wheel brake pads are

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Int. J. Mech. Eng. & Rob. Res. 2014

1 School of Mechanical and Building Sciences, VIT University, Vellore 632014, India.

mounted on brake calipers and is forcedagainst both sides of the disc. Due to frictioncaused between wheel and attached discwheel it makes the wheel to slow or stop. Herebrake converts kinetic energy of the movingmember to the heat and if the brake becomestoo hot its efficiency gets reduced. Thisphenomenon is called as brake fade. These

Research Paper

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brakes fade leads to squeal. Brake squeal isfriction inducing vibration (Ahmed Abdel-Naser et al., 2012). A rotating brake disccauses instabilities within the brake assemblyleading to vibration amplitudes causing brakesqueal. This has become a serious problemin vehicles. Reducing disc brake squeal hasbecome an important challenging task forresearchers and engineers. They have beenprogress in reducing brake squeal in recentyears. However brake squeal occurs too often,therefore its problem needs to be understoodand solved. Noise induced by brakes andvibrations caused has become a serious issuefor automotive industry due to inconveniencecaused to the customer. This noise is referredas squeal. Squeal is noise whose frequencyis 1000 Hz or higher that causes high andinconvenient sound pressure levels. GenerallyNoise are categorized into:

• Low-frequency noise whose range is 100Hz to 1,000 Hz.

• Low-frequency squeals whose range is1,000 Hz to 7,000 Hz.

• High-frequency squeals whose range is8,000 Hz to 16,000 Hz (Mike Hebbe, 2012).

During high frequency squeal, frictioninduced oscillations are developed in brakedisc which is known as brake squeal. This highfrequency range affects sensitivity of humanear squeal mainly depends on pad, rotor, brakeassembly material and geometry. Brakesqueal also depends on the bulk properties ofcontact surface as well as surface properties.

Brake squeal noise caused during brakingcan be reduced by focusing on modificationssuch as caliper stiffness, mounting bracketsand rotor geometry. Most of the brake pad

manufacturing companies are currently doingtrial and error method to address brake noiseproblem. Suppliers had to depend onexperimental testing to determine squeal andsolve problems. This method is not only costlybut also time consuming method (Mike Hebbe,2012). Therefore approach of addressing theissue is not good. Now a day’s finite elementmethod has been widely used for analyzingvariety of problems in structural, thermalproblems of brake system. In order to reducesqueal a pre stressed complex modal analysisis applied to the brake disc to look intoimportance of friction effects which causesinstability. This modal solution approach isbased on non-linear contact analysis. This waydesigns that causes irritating break squeal canbe identified in early development stages. Inour experiment we have preferred ventilateddisc brake since it consists of set of vanesbetween the two discs which helps in artificialcooling by pumping air through the disc.

Figure 1: Disc Used in Automobile

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PROBLEM DESCRIPTIONWhen vehicle is slowed down or stopped byusing brake it generates various kinds ofnoises. One of them is squeal. This brakesqueal is due to instability due to friction forces,leading to vibrations. To predict this instabilitywe can perform modal analysis of prestressedstructure (Ibrahim Ahmed et al., 2012). Whileperforming modal analysis following points areassumed:

1. Damping is ignored in a modal analysis.

2. Any applied loads are ignored.

3. Pre stressed modal analysis requiresperforming a static structural analysis first.In the modal analysis you can use the InitialCondition object to point to the StaticStructural analysis to include pre stresseffects.

OBJECTIVE• To model ventilated disc brake in solid

works.

• To carry out modal analysis of the ventilateddisc with brake fads.

• To determine natural frequency caused dueto sustained friction-induced oscillations.

• To compare results of cast iron, stainlesssteel, aluminium alloy and determine whichmaterial is superior to be used in brake disc.

MODELING AND MODALANALYSIS OF DISC BRAKESYSTEMVentilated brake disc rotor was designed onsolid works. Ventilated disc was preferred inour experiment for proper heat dissipation andreducing surface temperature (Chengal Reddy

et al., 2013). The saved drawing file from solidworks was later imported to ANSYS 13Workbench using Para solid extension.ANSYS software was preferred since it canhandle any complex geometry shape for anymaterial under different boundary conditionsand loading conditions. In order to reducesqueal, best method of analyzing brake discis by complex Eigen value analysis. Thistechnique is available in ANSYS 13 and canbe used to determine stability of brake disc.The real and imaginary part of complex Eigenvalues is responsible for level of instability ofbrake disc assembly. Once importedfrictionless support was given to brake discand fixed support was given to brake pad.Later meshing was performed and solutionwas obtained.

RESULTSFrom the above table we can see that Castiron has low squeal compared to C-CComposite materials. Minimum squeal wasobtained at mode 1, i.e., 1190.4 Hz for castiron and 1479.8 Hz for C-C composite materialand Maximum squeal was obtained at mode6, i.e., 5426.3 Hz for cast iron and 6754.0 Hzfor C-C composite material. Both Cast ironand C-C composite material squeal is within

Properties Cast Iron C-C Composite

Density 7.2 g/cm3 2.1 g/cm3

Co-efficient ofthermalexpansion 1.1*10-5 C-1 1.5*10-6 C-1

Thermalconductivity 53.3 w/m-K 100-150 w/m-K

Specific heat 0.46 Kj/Kg K 1.42 Kj/Kg K

Tensile strength 152 to 430 Mpa 66 Mpa

Table 1: Property Table

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the low squeal frequency range. Better resultof the squeal may be because of ventilatedbrake disc. From result we can see that asmechanical properties such as densitydecreases, squeal increases slightly. ThoughC-C composite material has more squeal thencast iron its squeal is within the low squealfrequency range. Considering bettermechanical properties C-C Compositematerial compared to cast iron we can

Figure 2: Ventilated Disc

Figure 3: Cost Iron

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Figure 3 (Cont.)

Figure 4: C-C Composite

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Figure 4 (Cont.)

conclude that C-C composite material is mostsuitable material for brake disc.

CONCLUSIONFrom Modal analysis of Ventilated brake discperformed on ANSYS 13.0 we can see:

1. Cast iron has low squeal compared to C-CComposite materials.

2. Minimum squeal was obtained at mode 1,i.e., 1190.4 Hz for cast iron and 1479.8 Hzfor C-C composite material.

3. Maximum squeal was obtained at mode 6,i.e., 5426.3 Hz for cast iron and 6754.0 Hzfor C-C composite material.

4. Both Cast iron and C-C composite materialsqueal is within the low squeal frequencyrange.

5. With reference to the above squeal resultsVentilated type disc brake is best type ofbrake disc design.

6. Since squeal frequency for both materialsis within low frequency range, consideringthe factor of mechanical properties such asdensity and co-efficient of thermalexpansion we can conclude that C-Ccomposite material is best material to beused in Brake disc.

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REFERENCES1. Ahmed Abdel-Naser, Ibrahim Ahmed,

Essam Allam, Sabry Allam and ShawkiAbouelseoud (2012), “Squeal Analysis ofVentilated Disc Brake Using Ansys”,International Journal of Energy andEnvironment, Vol. 3, No. 5, pp. 809-832.

2. Chengal Reddy V, Gunasekhar Reddy Mand Harinath Gowd G (2013), “Modelingand Analysis of FSAE Car Disc BrakeUsing FEM”, International Journal of

Emerging Technology and AdvancedEngineering, Vol. 3, No. 9.

3. Ibrahim Ahmed, Essam Allam, MohamedKhalil and Shawki Abouel-Seoud (2012),“Automotive Drum Brake Squeal AnalysisUsing Complex Eigenvalue Methods”,International Journal of ModernEngineering Research, Vol. 2, No. 1,pp. 179-199.

4. Mike Hebbes (2012), “Breakthrough inBrake Squeal Prediction Helps toEliminate Noise Problems Early inDesign”, ANSYS, Inc., USA.