Final Seminar

ByMr. Savant Rushikesh Dadasaheb

Exam Seat No.: 1518

GuideDr. Shekhar Y. Gajjal

Head, PG Mechanical Design EngineeringNBN SSoE, Ambegaon (Bk), Pune-41.

Dissertation on

Finite Element Modelling and Analysis of Brake Squeal

1M.E. Mechanical - Design Engineering

Contents

M.E. Mechanical - Design Engineering2

Abstract1. Introduction2. Literature review3. Methodology4. Finite element modelling of disc-pad assembly5. Finite element analysis of disc-pad assembly6. Experimental Validation7. Results and Discussion Conclusion and Future Scope References Publications

Abstract


Automobile brakes generates several kinds of noisesSqueal is prevalent, annoying and can be reduced

by varying parametersBrake squeal occurs in the range of 1-16 kHzANSYS 14.5 has introduced an ability to perform

brake squeal analysisLinear non-prestressed and full nonlinear perturbed

modal analysis is applied to predict squeal frequency

Full nonlinear perturbed modal analysis is performed with increasing the coefficient of friction and the outer diameter of disc

Increasing friction coefficient has no desirable effect while increased outer diameter decreases squeal propensity

1. Introduction


Brake is a device by means of which artificial frictional resistance is applied to moving machine member to stop motion of machine

During this the undesirable noise is produced called as brake squeal

No precise definition of brake squeal has gained complete acceptance

Brake noise is generally related to comfort and refinement rather than to safety or performance

It is high frequency (1 kHz-16kHz) vibration of brake system components during a braking action resulting a noise audible to vehicle occupants and passers-by

Substantial research has been conducted into predicting and eliminating brake squeal

It is still difficult to predict its occurrence due to complexity of the mechanisms that cause brake squeal

Physically, squeal noise occurs when the friction coupling between the rotor and pad creates a dynamic instability

Frequency range of squeal is between 1 and 16 kHzLow frequency squeal : 1 kHz to 5 kHzHigh frequency squeal : 5 kHz and above


Brake squeal generation mechanisms:A] Mode coupling theory: i. Self-excited vibrationii. If two vibration modes are close to each other in

the frequency range may merge if the coefficient of friction increases

iii.When they merge at the same frequency called couple frequency, one of them becomes unstable producing noise called Squeal.

iv.Variable friction forces are sources for brake squeal

f (Hz)M.E. Mechanical - Design Engineering

6 𝜇


B] Stick slip mechanism:i. Motion made up of periods where the bodies

hardly move, and where there are sudden motions is called as Stick-slip motion

ii.Resistance against the beginning of the motion from the state of the rest called stick mode

iii.Resistance against of an existing motion called slip mode

iv.Stick-slip motion can be introduced by the difference between the coefficient of the kinetic and static friction

v.Variable friction coefficient provides the energy source for the brake squeal

Objectives


To determine unstable squealing modes and frequencies of the braking system

Analysis of effect of increased friction coefficient and increased outer diameter of disc on the modes and squealing

Present WorkTo study types and generation mechanisms of brake

squeal.To learn the basics of ANSYS software (Static Structural

and Modal analysis)Modelling the disc-pad assembly by using CATIA V5

software.Develop finite element model of disc-pad combinationDetermine the effect of increase in outer diameter of the

disc on the squeal propensity of the disc-pad assembly.Study the effect of coefficient of friction on the

frequency of brake squealCompare the results of analysis with experimental

results.


2.1 Analysis of brake squeal noise using the finite element method: A parametric study.


Authors: Mario TrichesJu´nior, Samir N.Y. Gerges*, Roberto

Application of complex eigenvalue analysis in a finite element model of a commercial brake system

The effect of friction coefficient, braking pressure, brake temperature and wear on the dynamic stability of the brake system is examined

Changes in material properties and the application of brake noise insulators and their effects discussed

2.2 Complex Eigenvalue Analysis for Reducing Low Frequency Brake Squeal


Authors: Shih-Wei Kung, K. Brent Dunlap and Robert S. Ballinger

Stiffness of the rotor is changed by a reduction in the Young’s modulus of the rotor material

Parametric studies are also performed to find out the effects of friction coefficient and rotor stiffness

Shifting rotor resonance frequencies may decouple the modal interaction and eliminate dynamic instability

2.3 An Investigative Overview of Automotive Disc Brake Noise


Authors: K. Brent Dunlap, Michael A. Riehle and Richard E. Longhouse

Three groups of brake noise are presented:i) Low frequency noise: below 1 kHzii)Low frequency squeal: 1kHz to 5 kHziii)High frequency squeal: above 5 kHz

2.4 Disc-Plate Squeal Investigation Using Finite Element Software: Study and Compare


Ammar A. Yousif Mohammed, Inzarulfaisham Abd Rahim

The plate on disc as a new model is presented to study the instability of the system

Matrix27 as a contact element is used to simulate the behaviour of the system

Maximum degree of instability appeared as a result of changing the contact stiffness effect rather than changing the friction coefficient plate-disc system

2.5 Review-Automotive disc brake squeal


N. M. Kinkaid, O.M. O’Reilly and P. Papadopoulos

Background sections on vibrations, contact between disc and pad, disc brake systems are included

Disc brake systems, Effect of contact, temperature and wear, Experimental studies on brake squeal, Methods to eliminate brake squeal, Central features of some theories for brake squeal, Models of disc brake squeal and analyses are explained

3. Methodology


Procedure for a typical FEA can be divided into three distinct steps:• build the model (Pre-processor)• apply loads and obtain the solution (Solver)• review the results (Post-processor)

4. Finite Element Modelling of Disc-pad Assembly4.1 Solid modelling of disc-pad assembly:Modelled using CATIA V5 R20 softwareInner diameter of disc: 250 mm Outer diameter of disc: 350 mmDisc thickness:10 mm Brake pad thickness: 15 mm


4.2 Material properties and boundary conditions

• Young’s Modulus (N/m2): 2.0 E+11 Pa• Density: 7850 Kg/m3

• Poisson’s Ratio: 0.3

• Inner diameter of the cylinder hub and bolt holes are constrained in all directions

• Small pressure loading is applied on both ends of the pad to establish contact include prestress effects


4.3 FE Mesh generationElements Used For Meshing of Disc-Pad Modeli] SOLID186: Higher order 3-D 20-node solid element


ii] SOLID187: Higher order 3-D, 10-node tetrahedral structural solid


iii] CONTA174: 3-D 8-Node Surface-to-Surface Contact element


iv] TARGE170: Used to represent various 3-D target surfaces for the associated contact elements


4.4 Meshing the disc-pad model: Hexahedral dominant mesh with sweep method Mesh contains 60351 nodes and 11473 elements


5. Finite element analysis of disc-pad assembly

5.1 Modal analysisUsed to determine vibration characteristics (natural

frequencies and mode shapes) of a structure or a machine component while it is being designed

The frequencies obtained from the modal solution have real and imaginary parts due the presence of an unsymmetric stiffness matrix.

The imaginary frequency reflects the damped frequency while real frequency indicates whether the mode is stable or not.


Results of Modal Analysis of Disc-Pad Assembly


5.2. Brake squeal analysisConcerned with the prediction of the natural

frequencies at which brake squeal occurs

Methods:

5.2.1 Linear Non-prestressed Modal Analysis

• Effective when large deflection or stress-stiffening effects are not critical

• Accuracy is less and prestress effect is not included

• Less time consuming, as Newton-Raphson iterations are not required


Solution processi) Perform a linear partial-element modal analysis

with no prestress effect.

ii)Generate the unsymmetric stiffness matrix.

iii)Generate sliding frictional force.

iv)Perform a complex modal analysis using the UNSYM eigensolver for mode extraction.

v)Expand the modes and postprocess the results.


ResultsComplex eigenfrequencies for first 30 modes


Linear non-prestressed modal analysis predicts unstable mode at 6474.25 Hz

Mode shape plots for unstable modes


Mode Shape for Unstable Mode 21

Mode Shape for Unstable Mode 22

5.3 Full Nonlinear Perturbed Modal Analysis

• Most accurate method for modelling the brake squeal problem than linear non-prestressed modal analysis

• Uses nonlinear static solutions to both establish the initial contact and compute the sliding contact

• Includes prestress effects



Solution processi) Perform a nonlinear, large-deflection static analysis.

Use the unsymmetric Newton-Raphson method. Specify the restart control points needed for the linear perturbation analysis

ii)Perform a full second static analysis. Generate sliding contact to form unsymmetric stiffness matrix

iii)After obtaining the second static solution, postprocess the contact results

iv)Restart the previous static solution and perform the first phase of the perturbation analysis

v)Obtain the linear perturbation modal solution using QRDAMP or UNSYM eigensolver

vi)Expand the modes and postprocess the results

5.3.1 Parametric study with increasing the outer diameter of disc

Increasing the outer diameter of disc in the range of 4% upto 120%.

With increasing outer diameter of disc, the dimensions of pad also varied accordingly

1) When outer diameter is increased by 4%








Results


5.3.2 Parametric Study with Increasing Friction Coefficient

Increasing coefficient of friction from 0 to 0.3 in the range of 0.05

Changes in the frequencies and mode shapes are observed

1) Coefficient of friction 0.0












• Results

6. Experimental Validation


6.1 Test setupNVH brake testing machine

• Single-ended inertia dynamometer• Semi-anechoic chamber• Auto spectrum microphone•Accelerometer


SAE J2521 is commonly used to: i) Determine the propensity of a given friction

material and to generate squeal noise on a given brake configuration

ii)Select and evaluate different brake configurations

ii)Development of noise reduction measures using prototype materials or configurations

Brake-in: 30 snubs; 70 km/h; 100 °C Warm Up: 20 stops; 55 km/h; 100 °C Friction characteristic: 6 snubs; 70 km/h; 100 °C Deceleration: 100 stops; 55 km/h; 25 bar; 50-250-

50 °C

6.2 Test Specifications


6.3 Result

of testBoth noise and accelerometer peaks standing out obviously above the immediate frequency buckets, this is considered a true brake noise event during the dynamometer test.At the frequency 6440 Hz, there is distinctive peak i.e. squeal occurs

7. Results and discussionSqueal frequencies obtained for two methods

shows full nonlinear perturbed modal analysis is more accurate.

When FEA and experimental results are compared, error in FEA solution is found to be 0.4674 % (less than 1%)


Linear non-prestressed modal

analysis

Full nonlinear perturbed modal

analysis

6474.25 Hz 6470.24 Hz

Experimental frequency of Brake

Squeal

FEA frequency of Brake Squeal by

ANSYS

6440 Hz 6470.24 Hz

Conclusion1. As the outer diameter of disc is increased, real

eigenfrequency decreases linearly for both modes 21 and 22

2. For Mode 21, imaginary eigenfrequency decreases and for Mode 22, imaginary eigenfrequency increases as the outer diameter of disc is increased.

3. When coefficient of friction is increased from 0 to 0.1, the real eigenfrequency decreases, further increase in coefficient of friction real eigenfrequency increases again for both modes 21 and 22.M.E. Mechanical - Design Engineering44

4. In this analysis, as the variation is minor, friction coefficient has no desirable effect on brake squeal

5. For Mode 21, imaginary eigenfrequency increases and for Mode 22, imaginary eigenfrequency decreases linearly as the friction coefficient increased

6. Finite Element Analysis result error is 0.4674% which is within the acceptable limit of 1%


Future scope

Further brake squeal analysis can be carried out by variations in structural design

Squeal analysis can be performed by varying parameters such as brake pressure, brake temperature, wear etc.

The materials of assembly can be optimized by composite materials


9. References1) Mario Triches Junior, Samir N.Y. Gerges and Roberto Jordan,

“Analysis of brake squeal noise using the finite element method: A parametric study”, Applied Acoustics 69 (2008), 147-162.

2) Shih-Wei Kung, K. Brent Dunlap and Robert S. Ballinger, “Complex eigenvalue analysis for reducing low frequency brake squeal”, SAE Technical Paper 2000-01-0444, 2000.

3) K. Brent Dunlap, Michael A. Riehle and Richard E. Longhouse, “An Investigative overview of automotive disc brake noise”, SAE Technical Paper 1999-01-0142, 1999.

4) Ammar A. Yousif Mohammed, Inzarulfaisham Abd Rahim, “Disc-plate squeal investigation using finite element software: Study and Compare”, International Journal of Scientific and Technology Research, Vol.2, Issue 1, (January 2013), 143-154.

.


5) João Gustavo Pereira da Silva, Érico Romera Fulco, Paulo Emilio Dias Varante, “Numerical and Experimental evaluation of brake squeal”, SAE Technical Paper 2013-36-030, 2013.

6) N. M. Kinkaid, O.M. O’Reilly and P. Papadopoulos, “Review-Automotive disc brake squeal”, Journal of Sound and Vibration, 267 (2003), 105-166.

7) Nouby M. Ghazaly, Sufyan Mohammed and Ali M. Abd-El-Tawwab, “Understanding mode-coupling mechanism of brake squeal using finite element analysis”, International Journal of Engineering Research and Applications, Vol. 2, Issue 1 (Jan-Feb 2012), 241-250,.

8) Dihua Guan, “Brake vibration and noise-A Review and discussion”, Proceedings of 20th International Congress on Acoustics, Australia (August 2010), 23-27. M.E. Mechanical - Design Engineering

48

9) P. Liu, H. Zheng, C. Cai, Y. Y. Wang, C. Lu, K. H. Ang and G. R. Liu, “Analysis of disc brake squeal using the complex eigenvalue method”, Applied acoustics, Vol. 68 (2010), 603-615.

10) A. Akay, O. Giannini, F. Massi and A. Sestieri, “Disc brake squeal characterization through simplified test rigs”, Mechanical systems and signal processing, Vol. 23 (2009), 2590-2607.

11) M. Noubyand and K. Srinivasan, “Parametric studies of disc brake squeal using finite element approach”, Journal Mechanical, No. 29 (Dec. 2009), 52-66.

12) Abd Rahim Abu-Bakar and Huajiang Ouyang, “Recent studies of car disc brake squeal”, New Research on Acoustics (2008), 159-198.

13) N. S. Gokhale, S. S. Deshpande, S. V. Bedekar, A. N. Thite, “Practical finite element analysis”, First Edition, Finite to Infinite (2008), Pune.

14)ANSYS, ANSYS User’s Manual, Version 14.5, ANSYS Inc, 2011.


10. Paper Published1. Rushikesh D. Savant[1], S. Y. Gajjal[2] and V. G. Patil[3],

“Review on Disc Brake Squeal”, International Journal of Engineering Trends and Technology (IJETT), ISSN: 2231-5381, Volume 9-Number 12, March 2014, pp.605-608.

2. R. D. Savant [1], S. Y. Gajjal [2], “Finite Element Modelling and Analysis of Disc-Pad Assembly”, International Conference on Multidisciplinary Research and Practice, Gujarat.

3. A Research paper titled “Finite Element Modelling and Analysis of Brake Squeal” is accepted for:

• International Journal of Research and Scientific Innovation

• International Journal of Latest Technology in Engineering, Management and Applied Science.


Thank you


Documents

Final Seminar