A disc brake is a type of brake that uses the calipers to squeeze pairs of pads against a disc or a rotor to create friction ppt.ppt

A disc brake is a type of brake that uses the calipers to squeeze pairs of pads against a disc or a rotor[1] to create friction.[2] There are two basic types of brake pad friction mechanisms: abrasive friction and adherent friction. [3] This action slows the rotation of a shaft, such as a vehicle axle, either to reduce its rotational speed or to hold it stationary. The energy of motion is converted into heat, which must be dispersed.

1. Student
Mr. Ghulanavar Rohit D.
J. J. MagdumCollege Of Engineering,
Jaysingpur.
A
Seminar -II Presentation
on
Analysis of disc brake squeal
Guide
Prof. M. V. Kharade
FY M E in Machine Design
2013-14

2. Contents
•Introduction
•Brake noise categories
•Components of disc brake
•Brake noise generation mechanisms
•FEM in brake noise analysis
•Effects of Operational parameters
•Methods to eliminate brake squeal
•Case Study
•Conclusion
•References

3. Introduction
•Brake squeal refers to the high-frequency sound emissions
from a brake that are generated during the braking phase.
•Brake squeal has been one of the most difficult concerns
associated with vehicle brake systems. It causes customer
dissatisfaction and increases warranty costs.
•Hence it is necessary to develop methods to predict noise
occurrence during the design of a brake system.

5. Brake noise categories
Low-frequency noise -:
Caused by friction material excitation at the rotor and lining
interface.
Low-frequency squeal -:
Caused by frictional excitation coupled with ‘‘modal locking’’
of brake corner components.
High-frequency squeal -:
Produced by friction induced excitation imparted by coupled
resonances (closed spaced modes) of the rotor itself as
well as other brake components.

6. Components of disc brake

7. •The rotor (or disc) is rigidly mounted on the axle
hub and rotates with the automobile’s wheel.
•The pair of brake pad assemblies, which consist of
friction material, backing plates and other
components, are pressed against the disc in order
to generate a frictional torque to slow the disc
rotation.
•When a driver depresses the brake pedal, it effects
an increase in hydraulic pressure in the pistons
housed inside the caliper.

8. Brake noise generation mechanisms
Disc brake squeal occurs when a system experiences
vibrations with a very large mechanical amplitude.
Stick–slip mechanism -:
•Avariablefrictioncoefficientwithrespecttosliding
velocity
betweenpadsandrotor,providestheenergysourcefor
thebrakesqueal.
•Squealnoisewasfoundtobemorelikelywhenthe
decreasingrelationshipbetweenthefrictioncoefficient
andtheslidingvelocitybecomepronounced.

9. Geometric instability -:
•High levels of vibration result from geometric instabilities of
the brake system assembly.
•The variable friction forces are caused by variable normal
forces.
•Even if the coefficient of friction is constant, variable
friction forces are still possible.

10. Analysis of brake squeal noise
(a)A transient solution of the dynamic equations of motion,
(b) Evaluation of the Routhcriterion, and
(c) An eigenvalue analysis of the system
Based on the usefulness of the information, complex
eigenvalues are used as a measure of the system stability.

11. The equation of motion for a vibrating system is
For friction induced vibration, it is assumed that the forcing
function F is mainly contributed to by the variable friction force at
the pad–rotor interface
by combining Eqs. (1) and (2) and by moving the friction term to
the left-hand side`

12. Method to evaluate the contact stiffness
between rotor and pads
Stress–strain relationship method:-
The contact stiffness kc of the spring is related to the normal force
applied to the mass m and to the spring length variation, dL, by the
following equation:

13. So, The contact stiffness becomes a function of the Young’s
modulus of the elastic material (friction material), the contact area
between the pad and rigid surface (rotor) and the length L.

14. FEM in brake noise analysis
•The finite element method has become an indispensable
tool for modeling disc brake systems and providing new
insights into the problem of brake squeal.
•This method provides straightforward means for
generating finite dimensional approximations to the
governing equations of motion for the components of the
brake system.
•It has the capability of generating high-resolution finite
dimensional models of form for a solid continuum.
•The finite element method allows for accurate
representation of complex geometries and
boundary/loading conditions.

15. Finite element model of the
disc brake system.

16. Operational parameters
Co-efficient of friction :-
•High coefficient of the friction between the rotor and pads
generates high sound pressure levels during brake
operation.
•High values for this parameter lead to high levels of
dynamic instability.
•An increase in the friction coefficient leads to an increase in
the unstable frequency.

17. Braking Pressure
•The effect of braking
pressure is introduced
through the variation of
contact stiffness between
the rotor and pads.
•Increase in braking
pressure leads to high
values for contact
stiffness.

18. Wear
•The effects of wear leads
to changes in the
dimensions of the brake
pad also leads to several
changes in the pad friction
material.
•The occurrence of metal
plateaus, hot spots and
thermoelastic instability
are directly related to wear.

19. Methods to eliminate brake squeal
•Use of an anti-squeal product, such as disc brake quiet
between the backing plates and calipers.
•Application of a grease, which can be an anti-seize
compound, to the piston-backing plate contact areas.
•Use of vibration shims between the backing pads and
calipers. These shims often consist of constrained layer
dampers.
•Chamfering and/or slotting of the pads of friction material.
•Sanding the surfaces of brake rotors.
•Lubrication of the pins that connect the caliper to its
mounting bracket.

20. The application of
brake noise insulators
is evaluated for each
brake system, since
the effects of
additional damping
are the opposite to
those of changes in
stiffness.
Brake Noise Insulator

21. Case Study
Hat-disc brake
system.

22. •The dynamic instability of a gyroscopic non-conservative
brake system is numerically predicted with respect to
system parameters.
•The squeal propensity for rotation speed depends on the
vibration modes participating in squeal modes.
•The negative slope of friction coefficient takes an important
role in generating squeal.

23. FINDING
•Disc squeal is believed to be caused mainly by
friction-induced dynamic instability.
•With an increase in the friction coefficient, there is
an accompanying increase in the instability of the
system.
•Wear is an operational condition that must be
considered in numerical models, since it has a
strong effect on the stability characteristics.
•Increase in braking pressure leads to high values of
contact stiffness.

24. References
•Ma´rio Tricheˆs Ju´nior, Samir N.Y. Gerges *, Roberto Jordan”Analysis of brake
squeal noise using the finite element method: A parametric study”Mechanical
Engineering Department, Acoustics and Vibration Laboratories, University Campus,
Trindade, CEP 88040-900, Floriano´polis, SC, Brazil.
•JaeyoungKang ”Squeal analysis of gyroscopic disc brake system based on finite
element method ”Division of
MechanicalandAutomotiveEngineering,CollegeofEngineering,KongjuNationalUniver
sity,Cheonan-Si,RepublicofKorea.
•N.M. Kinkaid, O.M. O’Reilly, P. Papadopoulos,” Automotive discbrake squeal”
Department of Mechanical Engineering, University of California, Berkeley, CA
94720-1740, USA
•Yi Dai a, Teik C. Lim b,*”Suppression of brake squeal noise applying finite element
brake”Department of Mechanical, Industrial and Nuclear Engineering, 598 Rhodes
Hall, P.O. Box 210072, Cincinnati, OH 45221, USA.

25. Thank You and Discussions