2. Numerical and Experimental Investigation of Squeal Noise Generated In A Disc Brake
System and Reduction of It
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1. INTRODUCTION
Disc brake squeal is one the major problem in automotive sector as it created
discomfort to the customer which ultimately incurs warranty costs. Under operating
condition disc brake system creates a high pitched noise which irritates customer. The
reason for instability is mainly due to friction induced vibrations. The individual
modes of components of the disc brake system tend to couple together due to friction
generated in the disc brake system. Squeal is noise generally occurs above 1 kHz of
frequency. Low-frequency squeal is defined as noise which occurs between 1 and 7
kHz, usually below the first rotor-in-plane mode. High frequency squeal which is
above 7 kHz of frequency occurs usually at rotor-out-plane. This brake noise, with
frequencies ranging from1 to 12 kHz is quite annoying since levels of 110 dB may be
reached. The schematic diagram of disc brake working is shown in fig.1.
Figure 1 working of disc brake system [2]
Kinkaid et. al. [2] presented a wide review on disc brake squeal. The review
included the theory right from the inception of the problem. Coupling of mode was
the major factor affecting the squealing of brakes. It was also mentioned that squeal
greatly occurred when the natural frequencies of components were close to each
other. Many models based on certain theories were further discussed which includes
decrease in coefficient of friction μk with increase in velocity vs, sprag slip effect,
decrease in coefficient of friction μk with increase in velocity vs combined with sprag
slip effect, self excited vibration with constant μk, splitting doublet modes and
hammering. Gottfried Spelsberg-Korspeter [3] related the symmetric nature of the
rotor which results in squealing of brake. He suggested that by breaking the symmetry
of the rotor the assembly could be stabilized. Francesco Massi et. al. [4] in his study
presented integration of two different numerical procedures to identify the mechanism
bringing to squeal instability and to analyze its dynamics. The purpose of this study is
to compare the two models so that the linear one can be used to predict the squeal
onset conditions, and the nonlinear one to investigate the squeal characteristics by
studying the evolution of the contact dynamics in the time domain. Antti Papinniemi
et. al. [1] presented literature review on disc brake squeal. The addition of the friction
coupling forces at the friction interface results in the stiffness matrix for the system
containing asymmetric off-diagonal coupling terms. This coupling is considered to be
the root cause of the brake squeal.
3. N.N. Kadu and Mr. N. Vivekanandan
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2. MODEL VALIDATION
To validate the disc brake system the disc brake was modeled in numerical software
to carry out modal analysis. The natural frequency so obtained was validated with the
experimental modal analysis. On assembly level the brake pressure was kept at 0.5
MPa and the rotor was mounted on the four bolts. The comparative results of
numerical and experimental modal analysis can be seen in table no. 01. The error so
obtained is well within 20 percent. The first natural frequencies of numerical
simulation and experimental analysis is shown in table no. 01.
Table 1 Numerical and Experimental comparison
Numerical Frequency Experimental
Frequency
Frequency
.
Disc
rotor 1492.2 Hz
1324 Hz
Brake
Pad
2647.4 Hz 2176 Hz
Assem
bly
1551.3 Hz 1500 Hz
3. COMPLEX MODAL ANALYSIS
The disc brake so modeled was then analyzed for instability levels after validation. In
complex modal analysis a nonlinear solver is used to solve the static solution. A brake
pressure of 0.5 MPa is applied and rotor was given a cylindrical support and was free
to move in circumferential direction. Pad outer surface was restricted in x and y
direction and was set free in z direction. The contacts so obtained in static structural
are then fed to modal analysis. To incorporate the instability angular velocity of 8.33
rps is applied. The results obtained show that the instability occurs at frequency of
6712 Hz. The positive real part of 16.04 suggests that the system is unstable. To study
the reason of instability, modes shapes and frequency of the individual components
were studied. It was seen that brake rotor and brake pad had a frequency near to that
of unstable frequency obtained. It was observed that 5th
diametrical mode of the rotor
4. Numerical and Experimental Investigation of Squeal Noise Generated In A Disc Brake
System and Reduction of It
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had a frequency of 6575.3 Hz and 2nd
twisting mode of brake pad at frequency of
6140.7 Hz coalesce together and the system starts to resonate with high amplitudes
resulting in squeal noise.
Figure 2 Coupling modes of disc rotor and brake pad
To validate the unstable frequency a squeal test was performed. The set-up can be
seen in fig.03. The results of this squeal tests shows a good conformance with the
numerical results. Five such test were taken the results of which can be seen in table
02. The maximum noise of 94.80 dB was obtained at frequency of 6310 Hz. All the
other frequency lies in the range of 5000 Hz to 7000 hz which is ± 20% of 6712 Hz.
Figure 3 Squeal test set-up
Table 2 Results of squeal tests.
Sr. No. Squealing frequency (Hz) Sound pressure level
(dB)
1 6310 94.80
2 5012 91.348
3 5394 92.486
4 5012 89.874
5 5197 92.112
5. N.N. Kadu and Mr. N. Vivekanandan
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4. MODIFICATIONS TO REDUCE SQUEAL
Ten different configurations were studied in order to reduce the squeal noise in the
disc brake system. All the ten medication were studied and numerically analyzed for
the instability. The results of these ten configurations are shown in table 03. From
these configuration second and the tenth configuration shows no instabilities. From
these two, second configuration was discarded as it results in weakening of disc brake
rotor which could result in hazardous accidents. The final modification select was the
tenth configuration.
Table 3 Ten Different modification studied.
Sr. no. Configuration Configuration details
1.
Disc Rotor with two holes of 4mm.
Instability of 14.032 at frequency
of 3342 Hz.
2.
Disc Rotor with three holes of
4mm.
No Instabilities.
3.
isc with three hole at an an le of
.
Instability of 13.129 at frequency
of 4393.5 Hz.
4.
Brake pad with 4mm slot at the
center.
Instability of 12.789 at frequency
of 8666.5 Hz.
6. Numerical and Experimental Investigation of Squeal Noise Generated In A Disc Brake
System and Reduction of It
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5.
ra e pad with two slot at
.
Instability of 24.46 at frequency of
6377.3 Hz.
6.
Combination of 3rd
and 5th
configuration. isc with three hole at an an le of
and brake pad with two 4mm
slot.
Instability of 15.366 at frequency
of 636 Hz.
7.
Combination of the 3rd
and 4th
configuration.
isc with three holes at an an le of
and brake pad with 4mm slot at
the center.
Instability of 5.139 at frequency of
9356.2 Hz.
8.
Brake pad with 8mm slot at the
center.
Instability of 6.3419 at frequency
of 8620.3 Hz.
9.
isc with three hole at an an le of
and brake pad with 5mm slot at
the center.
Instability of 7.5711 at frequency
of 9353.8 Hz.
10.
Brake Pad with 10 mm center slot.
No instabilities.
The selected tenth configuration was checked experimentally. The results of these
are shown in table no.04. It can be observed that the unstable frequency of the range
5000 Hz to 7000 Hz is totally eliminated. Also it can be seen that the noise level so
7. N.N. Kadu and Mr. N. Vivekanandan
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obtained for different frequency is well within the 80 dB. Beyond 80 dB value sound
is considered to be noise. So the results obtained shows that pad modification did
resulted in elimination of noise.
Table 4 Squeal Test for modified disc brake system.
Reading Number Frequency (Hz)
Sound pressure level of
squeal (dB)
1 3182 74.01
2 1585 66.99
3 1585 70.07
4 1585 69.51
5 1585 72.67
4. CONCLUSION
The present work discuss about instabilities generated in a disc brake of an
automotive. The main source of instability was found to be coupling of modes of rotor
and the brake pad. The system tends to be unstable when the modes get coupled
resulting in generation of squeal noise. The experimental and numerical solutions
have a good conformance. The study so performed shows that the structural
modification in both rotor and brake pad can be done so as to remove squeal noise.
But the most significant solution can be brake pad modification. A slot of 10 mm was
sufficient to reduce the squeal noise upto 0.8 coefficient of friction value. Above 0.8
of friction value the disc starts to squeal again.
5. ACKNOWLEDGEMENT
The authors gratefully acknowledge the support of Pimpri Chinchwad College of
Engineering for providing the necessary resources to complete this study.
REFERENCES
[1] Antti Papinniemi, Joseph C.S. Lai, Jiye Zhao,Lyndon Loader, Brake squeal: a
literature review, Applied Acoustics 63 (2002) 391–400.
[2] N.M. Kin aid, O.M. O’Reilly, P. Papadopoulos, Auto otive disc bra e squeal,
Journal of Sound and Vibration 267 (2003) 105–166.
[3] Gottfried Spelsberg-Korspeter, Eigenvalue optimization against brake squeal:
Symmetry, mathematical background and experiments, Journal of Sound and
Vibration 331 (2012) 4259–4268.
[4] Francesco Massi, Laurent Baillet, Oliviero Giannini, Aldo Sestieri, Brake squeal:
Linear and nonlinear numerical approaches, Mechanical Systems and Signal
Processing 21 (2007) 2374–2393
[5] Mario Triches Junior, Samir N.Y. Gerges, Roberto Jordan, Analysis of brake
squeal noise using the finite element method: A parametric study, Applied
Acoustics 69 (2008) 147–162.
[6] Santhosh Sivan. K, Chandrasekar Sundaram, Arangarajan. A and Dr. Senthil
Kumar. P, Speed Dependent Dual Caliper Action in Disc Brake. International
Journal of Mechanical Engineering and Technology, 5(10), 2014, pp. 106 – 114.
![Numerical and Experimental Investigation of Squeal Noise Generated In A Disc Brake
System and Reduction of It
http://www.iaeme.com/IJMET/index.asp 11 editor@iaeme.com
1. INTRODUCTION
Disc brake squeal is one the major problem in automotive sector as it created
discomfort to the customer which ultimately incurs warranty costs. Under operating
condition disc brake system creates a high pitched noise which irritates customer. The
reason for instability is mainly due to friction induced vibrations. The individual
modes of components of the disc brake system tend to couple together due to friction
generated in the disc brake system. Squeal is noise generally occurs above 1 kHz of
frequency. Low-frequency squeal is defined as noise which occurs between 1 and 7
kHz, usually below the first rotor-in-plane mode. High frequency squeal which is
above 7 kHz of frequency occurs usually at rotor-out-plane. This brake noise, with
frequencies ranging from1 to 12 kHz is quite annoying since levels of 110 dB may be
reached. The schematic diagram of disc brake working is shown in fig.1.
Figure 1 working of disc brake system [2]
Kinkaid et. al. [2] presented a wide review on disc brake squeal. The review
included the theory right from the inception of the problem. Coupling of mode was
the major factor affecting the squealing of brakes. It was also mentioned that squeal
greatly occurred when the natural frequencies of components were close to each
other. Many models based on certain theories were further discussed which includes
decrease in coefficient of friction μk with increase in velocity vs, sprag slip effect,
decrease in coefficient of friction μk with increase in velocity vs combined with sprag
slip effect, self excited vibration with constant μk, splitting doublet modes and
hammering. Gottfried Spelsberg-Korspeter [3] related the symmetric nature of the
rotor which results in squealing of brake. He suggested that by breaking the symmetry
of the rotor the assembly could be stabilized. Francesco Massi et. al. [4] in his study
presented integration of two different numerical procedures to identify the mechanism
bringing to squeal instability and to analyze its dynamics. The purpose of this study is
to compare the two models so that the linear one can be used to predict the squeal
onset conditions, and the nonlinear one to investigate the squeal characteristics by
studying the evolution of the contact dynamics in the time domain. Antti Papinniemi
et. al. [1] presented literature review on disc brake squeal. The addition of the friction
coupling forces at the friction interface results in the stiffness matrix for the system
containing asymmetric off-diagonal coupling terms. This coupling is considered to be
the root cause of the brake squeal.](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)