Special Issue - 2016 International Journal of Engineering Research & Technology (IJERT)

ISSN: 2278-0181
IC-QUEST - 2016 Conference Proceedings

Mechanical Property Which Affect the

Performance of Disk Brake Material
Prof. R. K. Pohane Dr. S. C. Kongare Prof. S. P. Daf
PhD Scholar, HOD (Mechanical Engineering.) Asst. Prof. (Mechanical Engineering.)
P.B.C.O.E A. S. Polytechnic P.B.C.O.E
Nagpur, Maharashtra, India Wardha, Maharashtra, India Nagpur, Maharashtra, India

Abstract: Safety aspect in automotive engineering has partly to reduce cost and partly to alter the brake pad
been considered as a number one priority in development of properties, for example, to reduce noise and improve
new vehicle. Brakes convert friction to heat, but if the brakes thermal properties. They can be made of barium sulfate and
get too hot, they will cease to work because they cannot
dissipate enough heat. Ventilated disc brake is the state of the mica. Frictional additives, such as graphite, metal sulfides,
art technology in automobile brake system. This paper and metal oxides/silicates, are used to control the friction
reviews work of previous investigators on transient thermal and wear. Brake pads are grouped into three categories:
analysis on the vented disk rotor and rotor designs to evaluate non-asbestos organic (NAO), semi-metallic, and low
and compare their performance. The brake system metallic. According to Sanders et al. [2].Rajendra Pohane &
technological advance got great impulse due to the automobile R.G.Choudhari[1] presented paper on Design and Finite
industry necessity. Historically, the first material used to
make brake discs was the gray cast iron, which is a material
Element Analysis of Disc Brake (2010) The objective of
that fits the requirements it is intended for, such as: good this research is to study disc brake system, to simulate disc
thermal conductivity, good corrosion strength, low noise, low brake assembly and to prepare the FEM model for
weight, long durability, steady friction, low wear rate, and a
good price/benefit ratio. This research study that the affect
mechanical and physical property of which affect the
performance of disk brake material.

Keywords: Ventilated disc brake, Heat Transfer coefficient,

Heat flux. Brake discs, fatigue.
I. INTRODUCTION
Modern passenger cars have disc brakes on the front
wheels, and there is a growing trend to have them on the
rear wheels as well. The main purpose of a disc brake is to
FIG 01: DISK BRAKE
slow down a vehicle by transforming kinetic energy into
frictional heat. A rotor (brake disc) is firmly fitted to and
rotates with the wheel. Two brake pads (linings) are contact analysis A three dimensional finite element
positioned inside a caliper mounted on the knuckle. The model of the brake pad and the disc was developed to
knuckle is mounted on the chassis. When the driver hits the calculate steady state, and transient state analysis. The
brakes, the brake cylinder pressure increases and the piston comparison was made between the solid and ventilated disc
pushes the pads into contact with the rotor. The friction keeping the same material properties and constraints and
force between the brake pads and rotor exerts braking using general purpose finite element analysis. It shows that
torque on the rotor, which is connected to the wheel, and the how general purpose finite element analysis software can be
subsequent friction between the tire and the road makes the used to analyze the stresses at disc to pad interface. A wear
car slow down. This thesis examines a disc brake for the simulation routine has also been adopted. It is found that the
right front wheel of a typical passenger car. This disc brake total heat flux and thermal error is less in solid plate than in
assembly consists of a ventilated rotor, a sliding caliper with the perforated (ventilated) plate. The steady state thermal &
a single piston, and two brake pads. Most rotors used in Transient Thermal Analysis are carried out on the two types
passenger cars are made of gray cast iron. The brake pads of disc brake i.e. perforated (ventilated) plate and Solid
can be made of many different material combinations, but plate. The input conditions, boundary conditions & other
are essentially constructed of four components: a binder, analysis settings are same for both types of brakes.
reinforcing fibers, fillers, and frictional additives. TING-LONG HO Et al. (1974), Investigated on the effect
The main task of the binder, which is made of polymer- of frictional heating on brake material
based resin, is to hold the components of the brake pad (Aircraft)[3].Masahiro Kubota et al. (2000), presented paper
together. The main task of the reinforcing fibers, which can on development of a lightweight brake disc rotor: a design
be made of metal, glass, carbon, and ceramic fibers, is to approach for achieving an optimum thermal, vibration and
give mechanical strength to the brake pad. Fillers are used weight balance[4]. This paper presents a parametric study

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Special Issue - 2016 International Journal of Engineering Research & Technology (IJERT)
ISSN: 2278-0181
IC-QUEST - 2016 Conference Proceedings

that was conducted on the basis of an analysis of airflow of disc considered for studies one without wear and one
through the ventilation holes as well as a thermal stress with 7mm wear on both sides. Maximum speed is 250
analysis and a vibration analysis during braking. Based on km/hr and the ambient and initial disc and surrounding
the relationships obtained between rotor weight, shape and temperature is 50 C Temperatures and stress in discs under
each performance requirement, a method is presented for different loads is very high. Although they are fulfilling the
designing a lightweight disc rotor. Computational fluid buyer’s requirements for safety, this investigation not
dynamics analysis approach is used to visualize the actual considered shearing forces, residual stress and the cyclic
process. Short and gourd shaped fins arrangement had been loads during brake discs lifespan. The results need to be
used and the results verified that ant squeal performance compared with experimental results. Talati and Jalalifar
was improved, and also a substantial weight reduction was (2009), presented a paper on Analysis of heat conduction in
achieved compared with the baseline rotor shape without a disk brake system[8]. Zaid, et al. (2009) presented a paper
causing cooling performance and heat resistance to on an investigation of disc brake rotor by Finite element
deteriorate. Choi and Lee, (2004) presented a paper on analysis. In this paper, the author has conducted a study on
Finite element analysis of transient thermo elastic behaviors ventilated disc brake rotor of normal passenger vehicle with
in disk brakes [5]. A transient analysis for thermo elastic full load of capacity[9]. The study is more likely concern of
contact problem of disk brakes with frictional heat heat and temperature distribution on disc brake rotor. In this
generation is performed using the finite element method. To study, finite element analysis approached has been
analyze the thermo elastic phenomenon occurring in disk conducted in order to identify the temperature distributions
brakes, the coupled heat conduction and elastic equations and behaviors of disc brake rotor in transient response.
(cylindrical coordinates) are solved with contact problem. Modeling is done in CATIA & ABAQUS/CAE has been
Material used is carbon composite and wear is assumed used as finite elements software to perform the thermal
negligible. The numerical simulation for the thermo elastic analysis on transient response. Material used is Grey cast
behavior of disk brake is obtained in the repeated brake iron, with maximum permissible temperature 550 C. For
condition. The computational results are presented for the load analysis 10 cycles of breaking and 10 cycles without
distributions of pressure and temperature on each friction breaking (idle) operation is considered total of 350 seconds.
surface between the contacting bodies. It is observed that Result provided during 1st, 5th and during 10th cycle. Thus,
the orthotropic disc brakes can provide better brake this sure study provide better understanding on the thermal
performance than the isotropic one because of uniform and characteristic of disc brake rotor and assist the automotive
mild pressure distribution. JIANG LAN et al. (2011), industry in developing optimum and effective disc brake
presented paper on thermal analysis for brake disk of rotor. Piotr Grzes & Adam Adamowicz (2011), presented
Sci/6061 Al. Alloy co-continuous composite for CRH3 paper on analysis of disc brake temperature distribution
during emergency braking considering air flow cooling [6]. during single braking under non-axisymmetric load [11].
The thermal and stress analyses of SiCn/Al brake disk First step of the analysis based on the previously developed
during emergency braking at a speed of 300 km/h model where the intensity of heat flux was assumed to be
considering airflow cooling were investigated using finite uniformly distributed on the friction surface of disc during
element and computational fluid dynamics methods. All braking process, and the heat is transferred exclusively in
three modes of heat transfer were analyzed. The highest axial direction, whereas during the second, the three-
temperature after emergency braking was 461 °C and 359 dimensional rotor is subjected to the non-asymmetric
°C without and with considering airflow cooling, thermal load to simulate realistic thermal behavior of the
respectively. The equivalent stress could reach 269 MPa brake action. Operation conditions, thermo-physical
and 164 MPa without and with considering airflow cooling, properties of materials and dimensions of the brake system
respectively. The airflow through and around the brake disk were adopted from the real representation of the braking
was analyzed using the Solidwork2012 simulation software process of the passenger vehicle. Arbitrarily selected four
package. The results suggested that the higher convection values of the velocities at the moment of brake engagement
coefficients achieved with airflow cooling will not only were applied to the models so as to investigate theirs
reduce the maximum temperature in the braking but also influence on the obtained solutions of the temperature
reduce the thermal gradients, since heat will be removed evolutions on the contact surface of the disc volume
faster from hotter parts of the disk. Oder G. et al. (2009), referring to two separated finite element analysis. Two- and
worked on thermal and stress analysis of brake discs in three-dimensional FE modeling techniques is used
railway vehicles [7]. Performed analysis deals with two considering FEA approach. Finite element analysis and Fast
cases of braking; the first case considers braking to a Fourier transform been used to reduce computational time.
standstill; the second case considers braking on a hill and Radiation heat transfer had been neglected and wear on the
maintaining a constant speed. In both cases the main contact surface is negligible. We can conclude that the large
boundary condition is the heat flux on the braking surfaces amount of heat generated at the pad/disc interface during
and the holding force of the brake calipers. In addition the emergency braking indisputably evokes non-uniform
centrifugal load is considered. Finite element method temperature distributions in the domain of the rotor,
approach is been used, 3D model has been modeled for whereas the pad element is constantly heated during mutual
analysis. Brake disc material is rounded graphite; two types sliding.

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Special Issue - 2016 International Journal of Engineering Research & Technology (IJERT)
ISSN: 2278-0181
IC-QUEST - 2016 Conference Proceedings

II. PHYSICAL AND MECHANICAL PROPERTIES 5. Linear dependence was expected, because increasing C or
I. Diffusivity CE amounts is the fastest way of improving gray cast iron
Cast irons are indicated to produce brake discs because graphitization. There was a 25% increase of diffusivity in
besides the low costs of the production, they have excellent brake discs with a increase of 0.40% of EC (Yamada &
thermal conductivity, which eases the dissipation of the heat Kurikuma, 1998). Hecht et al. (1999) also noticed that in
generated by the friction of the pads during a stop, and the gray cast irons, diffusivity is reduced with the increase of
capacity of damping vibrations, which are prime the temperature until 500ºC. Above this temperature, the
characteristics of this kind of component. One of the ways difference noticed in diffusivity of alloys with similar
to improve the heat transfer ability is to increase its thermal values in 500ºC is reduced. These data suggest that high
diffusivity. It describes the heat diffusivity during the diffusivity and thermal benefits can be reached by
transient process, and is also a fundamental parameter to the controlling the casting process of brake discs in gray cast
brake design. Thermal diffusivity may be used to calculate iron with longer graphite flakes.
the heat conductivity, which is an inherent measure of how
well the material transmits heat. Brake discs with improved II. Abrasion strength
thermal conductivity present increase in thermal fatigue The diffusivity value on ferrite phase is higher than the
strength (Jimbo et al. 1990), making it possible to increase one presented by the pearlitic microstructure. Thus, it could
its service life, that is, if the gray cast iron characteristic of be concluded that best iron alloy to brake discs production
conducting heat can be increased without sacrificing other would be a gray iron presenting longer graphite flakes on a
objective criteria, the disc performance can be improved. ferritic matrix. This is not true because the matrix type
The main factors that influence the heat transfer in cast influences diffusivity just a little (Fitzgeorge & Pope, 1959;
irons are distribution, size and morphology of the graphite Omerod, 1978) and the disc must present good mechanical
phase, because graphite flakes have much higher heat strength, especially regarding abrasion. This is why most
conductivity than the matrices. The cast iron heat brake discs used in passenger cars are produced with cast
conductivity is proportional to the ratio between its surface irons whose microstructure presents graphite flakes on
area and its respective volume. Thus, cast irons with pearlitic matrix. Pearlite, consisting of intercalated lamellae
nodular graphite are worse conductors than the vermicular of ferrite phase and cementite phase (Fe3C), results in a
ones, which in turn are worse than the ones with graphite matrix with higher mechanical strength (Omerod, 1978). To
flakes. In 1983, Okamoto et al. (1983) reported that the cast avoid producing the components from gray cast iron alloys
iron thermal conductivity is proportional to the graphite with identical chemical composition and different
flakes shape (or the graphite nodules). In 1990, Jimbo et al. mechanical properties, it is necessary that the solidification
(1990) described the benefits of using cast iron with high rate is the same, so that the microstructure is not modified.
thermal conductivity in brake discs. However, the change in As a consequence, molding, fusion and casting parameters
friction characteristics such as the friction coefficient value have to be strictly controlled at every new production. If the
and the amount of particles generated by friction, analyzed chemical composition is modified by means of adding alloy
as a gray iron microstructure function, has not been much elements, the mechanical properties
discussed in literature. Little attention has been given to the
correlation between the relative quantity of phases in gray Table No 02 : HARDNESS EFFECT
iron and the performance under friction. In 1999, Hecht et Harding Effect of alloying element.
al. (1999) observed that gray cast iron Element Hardening Effect
C,N
TABLE 01: CHEMICAL COMPOSITION OF ALLOY
Chemical composition of grey cast iron base alloy P
Si
Metallic Alloy
Element Ti
A B C D
3.20- 3.20- 3.60- 3.70- Al
%C
3.60 3.60 3.80 3.90
Cu
1.90- 1.90- 1.80- 1.75-
%Si Mn
2.40 2.40 2.20 1.95
0.60- 0.60- 0.60- 0.50- Mo
%Mn
0.90 0.90 0.80 0.80
Max Max Max Max V
%P
0.20 0.10 0.10 0.10 Ni
Max- Max Max Max
%S Cr
0.12 0.10 0.12 0.13
0.25- 0.10- Max
%Cr -
0.40 0.25 0.20 will be changed. In other words, to modify mechanical
0.40- 0.30- Max properties, two factors are really important: cooling speed
%Mo -
0.50 0.60 0.10
0.30- Max
and chemical composition. Despite being possible to
%Cu - - produce good quality cast irons without adding alloy
0.45 0.40
Thermal diffusivity is influenced by a subtle change in elements, just controlling the carbon, silicon and manganese
chemical composition and presented a linear relation contents and the production technique, it is usual to add
between thermal diffusivity and equivalent carbon (or alloy elements to obtain not only higher strengths with
higher equivalent carbon, but also because microstructures
maximum length of graphite flakes), as observed in Figure
are less susceptible to thickness variation of the parts.

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Special Issue - 2016 International Journal of Engineering Research & Technology (IJERT)
ISSN: 2278-0181
IC-QUEST - 2016 Conference Proceedings

Practically all alloy elements tend to increase the tensile and to determine which one of them is more appropriate to
toughness strength, and the most efficient to gray cast iron braking because, with trucks and passenger cars
are manganese, vanadium, molybdenum, chrome and performance improvement, there is a growing increase of
copper. Manganese promotes the pearlitic microstructure the demand for brake discs technological improvement.
formation, increasing mechanical strength and toughness; Because it is, perhaps, the most important piece of the disc
vanadium is a strong pearlite former and graphite refiner; brake system, the brake disc is submitted to three types of
molybdenum increases mechanical strength to heat, creep fatigue: thermal, where the component is only submitted to
and corrosion, Cr increases corrosion and abrasion strength abrupt temperature variations with no load; isothermal,
and Cu is a strong pearlite stabilizer. where the temperature is stable and the load, variable; and
thermo mechanical (in or out-of-phase), where temperature
III. Hardness: and load are changeable. The most important, for
representing better the conditions the disc is submitted to
The hardening effect produced by alloy elements in solid during the braking process, is the out-of-phase thermo
solution in ferrite can be seen schematically in Table (Milan mechanical fatigue, where the maximum load is applied
et al., 2004). Notice that despite all elements increase the when the temperature is the lowest possible and vice-versa.
alloy strength, the ones that form interstitial solid solution The discs exposed to high thermal stresses require materials
have a stronger effect than the substitution ones. Besides the that offer better strength to thermal fatigue. In these cases,
direct way, by forming a solid solution and second-phase gray cast irons with nickel, chrome and molybdenum have
precipitates, alloy elements can indirectly act upon the been used (Yamabe et al., 2002), as the ones used by
increase in strength through grain refining, dessulfuring or General Motors, for example, which posses 12% nickel,
globalizing sulfides, stabilizing carbides, degasifying and more chrome and molybdenum(Sakamoto et al., 1993).
also increasing the material harden ability. Rhee et al. However, the disadvantage of these alloys is, without a
(1972) pointed that a change in the disc chemical doubt, the high cost.Yamabe et al. (2002) studied the
composition affected very strongly both mechanical possibility of producing truck discs with a cheaper cast iron
properties and the lining/disc wear rates. Libsch & Rhee alloy with high thermal fatigue strength. They used
(1979) related the effects of variation in chemical prototypes of different alloys with variable quantities of
composition upon the disc. They showed that small changes elements and some of them had cerium inoculated. They
on alloy elements level changed the lining and disc wear verified the connection between the material thermal fatigue
level. Anderson (1992) stated that thin graphite flakes strength, its physical and mechanical properties, and its
reduce lining and disc wear. Zhang et al. (1993) studied cast corresponding microstructure. They noticed that the higher
iron triblological properties in terms of phosphorus graphite quantity is distributed on a matrix with refined
concentration and graphite morphology and observed that grains, the lower the crack propagation rate is, and that the
cast iron with phosphorus and compact (or vermicular) number of graphite flakes increases with nickel addition and
graphite morphology presented high friction coefficient and some cerium inoculation. They also observed that the
low mass loss due to wear. Cho et al. (2003) investigated thermal fatigue limit is not severely affected by the number
gray cast iron features regarding phase quantities, graphite of cycles before the beginning of the crack, but after it.
and ferrite, and the micro constituent pearlite, controlling From this survey, a low cost brake discs alloy was
the microstructure by the carbon quantity variation developed, equivalent to the one used nowadays.
(equivalent carbon) and cooling speed. They noticed the Conclusion It is noticed that, historically, despite all the
free ferrite quantity and the pearlite quantity in the gray iron evolution that took place during the 20th century, brake
disc do not affect the friction coefficient. Additionally, they discs of automobile vehicles are still produced with the
observed a friction coefficient increase with a higher centennial and very cheap gray cast iron, which still offers
graphite area perceptual. the best price/benefit ratio, even after receiving some alloy
IV. Fatigue elements addition. From the technological point of view,
It is known that the brake disc form and physical along the time a great number of experiments were
properties can affect the braking performance and cause accomplished, especially after 1938, with the beginning of
problems such as vibration, material loss during the stop the Second World War. However, as experimental projects
and noise (Metzler, 1990; Rhee, 1972). This happens like the ones described above are really expensive and
because gray cast iron physical properties, such as thermal slowly executed, nowadays the advance of the development
conductivity, vibration weakening, thermal expansion of materials and brake discs project has been almost
coefficient and the specific heat, change according to the exclusively based on modeling in terms of low cost and
phases present in gray cast iron (Chapman & Mannion, speed. In modeling, one tries to predict the component
1982). In the last decades, great attention has been given to behavior (life), through finite elements, simulating several
improve brake discs performance concerning its behavior parameters under thermal, isothermal, and especially thermo
when there is friction with the brake pads. This great effort mechanical fatigue, which is the one that represents best the
led to materials development, such as: non-ferrous copper real braking. Although this type of analysis presents
alloys, aluminum matrix composites and, nowadays, carbon meaningful results, there is the need of experimental works
composites (Wycliffe, 1993; Rhee, 1970). However, gray to validate them, i.e., it is necessary to study the component
cast iron is still very used in automobile disc brakes under real rather than only virtual conditions.
because, as mentioned earlier, besides having good physical III. CONCLUSION
and mechanical properties, it is cheap and easily produced.
Nevertheless, a more detailed characterization of these The material which is used for disk brake having
alloys is necessary, especially concerning the wear strength required intended property such as: good thermal

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 Special Issue - 2016 International Journal of Engineering Research & Technology (IJERT)
ISSN: 2278-0181
IC-QUEST - 2016 Conference Proceedings

conductivity, good corrosion strength, low noise, low linings: the effect of rotor microstructure. Tribology International,
weight, long durability, steady friction, low wear rate, and a v. 36, p. 537-545, 2003.
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