International Journal of Engineering Trends and Technology (IJETT) – Volume 25 Number 3- July 2015
A Coupled Thermal- StressFinite Element Analysis of Single
Braking Effect on Motorcycle Rear Hub Brake
Achebe Chinonso Hubert1Nnamdi Benedict Anosike1and AbdulrahmanJibrilla Adamu2
1
DepartmentMechanical Eng.Dept.NnamdiAzikiwe University Akwa, Anambra State Nigeria
2
M. Eng. Student Mechanical Eng. Dept. NnamdiAzikiwe University Akwa, Anambra State, Nigeria
ABSTRACT
A coupled thermal-stress analysis was carried out on
CY80 motorcycle rear brake hub 3D axis-symmetry model
in ANSYS 14.0® to evaluate the thermal stresses due to
single braking for 4 seconds. The Cambridge
Engineering Material Selector (CES Edupack® 2011)
was used to select materials with lightweight, good
stiffness, high yield strength and thermal conductivity for
the analysis. The material properties obtained from
Cambridge Engineering Material Selector were added
into the ANSYS 14.0 material property library. The
results from the Matlab program written showed a
maximum operating temperature of 1190C and a brake
drag force of 2160N. The 3D model developed in creoelements was imported into ANSYS 14.0 and the results
of Matlab (1190C and 2160N) were used for the finite
element analysis (FEA). Results obtained from FEA gave
a maximum value of 56.2MPa for the von misses which
was lower than the ultimate tensile strength of Cast iron
(BS Grade 200) and Aluminumalloy (LM 12-M) with
values of 200MPa and 171MPa respectively.
The
maximum deformation was obtained as1.395x10-4m.The
results obtained from the FEA indicated that the material
considered is unlikely to fail during hard braking of
4seconds.
Key words: Axisymmetry, Material Selection, Finite
Element Analysis, Thermal Stress,
I.
Introduction
The motorcycle drum brake consists of two major
components, the drum and the brake shoe. The drum brake
is made of cast aluminum alloy and friction part of the
drum in contact with the lining is made of cylindrical steel;
this is to achieve light weight as it is an important factor in
designing rotating components.The brake helps to slow
down or stop a moving motorcycle. Friction brake requires
transforming large amount of kinetic energy into heat over
very short time periods and in the process they create high
ISSN: 2231-5381
temperature and substantial thermal stresses. So all parts of
the brake especially the rotor and the friction material,
must resist the temperature and stresses arising from
combined thermal and mechanical loadings. The friction
surface of a drum brake is inside the drum and thus the
frictional heat has to transfer through the drum material to
the outside surface before it can be dissipated by
convection or radiation [1].
Computer Aided Design and Analysis is currently being
used as the tool for analyzing mechanical systems as it
serves as the necessary shift from the conventional
approach and the introduction of Computer Aided Material
Selection to this field increasingly makes Engineering
analysis simpler, more effective and less costly [2].
Kang and Cho [3] investigated thermal deformation and
stress analysis of disk brakes by finite element method for
ventilated disk and solid disk. By comparing the result of
maximum temperature in the braking process, the
ventilated disk showed a lower temperature than the solid
disk. The effect of temperature increase and decrease,
depending on the vent area generated in the flange part of
the disk.Analysis of design parameter effects on vibration
modes of a motorcycle drum brake and brake shoe using
the finite element method were also carried out [4]. They
reported that the drum brake had 42 mode shapes in the
frequency range of 100 Hz to 12 kHz. Most of the mode
shapes occurred in pair (repeated root). The brake shoe was
found to have 10 mode shapes in the frequency range
analyzed.
Madenci and Guvenstated the use of axisymmetry in
analyzing rotating parts [5]. The use of symmetry analysis
reduces model size, CPU time required for solution while
delivering the same level of accuracy in the result. The
physical system under consideration exhibitssymmetry in
geometry, material properties, and loading, then it is
computationally advantageous to model only a
representative portion. If the symmetry observations are to
be included in the model generation, the physical system
must exhibit symmetry in all of the following:
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International Journal of Engineering Trends and Technology (IJETT) – Volume 25 Number 3- July 2015
• Geometry
• Material properties
• Loading
• Degree of freedom constraints
A single application of the vehicle’s brakes from vehicle
maximum road speed to zero at high deceleration
represents a single very severe braking duty cycle,
dissipating maximum kinetic energy. Although this type of
brake usage can be relatively rare it is essential that the
vehicle can perform such braking safely.
These were adequately taken care of in this work
A single application of the vehicle’s brakes from vehicle
maximum road speed to zero at high deceleration
represents a single very severe braking duty cycle,
dissipating maximum kinetic energy was considered.
Although this type of brake usage can be relatively rare it is
essential that the vehicle can perform such braking safely
[1].
There are so many research works on disc brake. Thermal
and structural analysis of disc brake for different cut
patterns was carried out by [6] using Pro-E and ANSYS
workbench to analyze the effect of design on cooling
performance using computational fluid dynamics (CFD).
They reported that elliptical type of cut pattern has better
heat transfer than the circular type of cut pattern but the
structural analysis showed that elliptical type cut pattern is
weaker to withstand braking forces when compared to
circular type of cut pattern.
The energy associated with a moving road vehicle of mass
M (kg) travelling at a speed of v (m/s) is the ‘translational
kinetic energy K.E (J), and this is absorbed as kinetic
energy and dissipated it in the form of heat.
Where:
Translational kinetic energy=K.E=1/2mv2 (1)
Braking power defines the rate of frictional energy
transformation and is needed to calculate heat flux input for
brake thermal analysis. The power developed by a brake at
any instant during a brake application is given as [7]:
(2)
And the heat flux on the hub is given as
(3)
Where;
This work considered motorcycle drum brake because it
has not received much attention like the disc brake in finite
element analysis. It also leveraged on Cambridge
Engineering material Selector EduPack to select a light
weight, stiff, good ultimate tensile strength and good
thermal conductivity for the coupled thermal stress analysis
in ANSYS 14.0.
II.
Coupled Thermal Analysis due to Single
Braking
The three types of braking conditions that can be defined
for brake thermal performance analysis in road vehicles
are:
1.
2.
3.
Single application of the vehicle’s brakes; often termed
‘stops’ (to rest) or ‘snubs’ (from an initial road speed
to a final road speed).
Repeated application of the vehicle’s brakes; often
associated with fade tests.
Continuous application of the vehicle’s brakes often
called drag braking; usually associated with
maintenance of a constant speed on a long downhill
gradient.
Surfacearea(A)=2πrh(4)
An important defining parameter of a friction brake rotor
material is its maximum operation temperature (MOT),
which should be higher than the maximum anticipated
surface temperature under the most severe duty condition
[1].
Figure 1: HubDimens
Single stop temperature rise Tmax is the temperature rise
due to single braking condition and it is given as [8]:
(5)
t = stoppage time (sec)
density (kg/m3)
K= thermal conductivity (w/moC )
C= specific heat (j/Kg oC)
The moments about the fulcrum of an internal expanding
brake [9] are
(6)
(7)
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International Journal of Engineering Trends and Technology (IJETT) – Volume 25 Number 3- July 2015
And the actuating force is calculated from
The actuating force
(8)
Let
The radial force generated on the pad of friction material is:
Level 3 data base was used asa preliminary search for
brake materials using custom material. The first stage
Figure2 is chart of yield strength versus thermal
conductivity. Materials with large values of tensile strength
and thermal conductivity, suggest metals and alloys as one
possibility Figure 2.
(9)
(10)
Therefore, the frictional drag force generated is:
(11)
III.
Methodology
Figure 2: The bubble chart of tensile strength against thermal conductivity
Figure 1 shows the dimensions of the hub and Table 1
shows the parameters used in writing a MATLAB program
to calculate single stop temperature rise due to single
braking condition and braking torque on the hub. The
advantage of using MATLAB programming is that any
changes in the input could be made very easily and solution
quickly obtained.
The search was further narrowed using the property limit.
The desired upper limit for constrained attributes was
entered 400oC in the properties limit dialog box. The search
engine rejects all materials with attributes that lie outside
the limits as also shown in Figure 2.
The final selection was made using price versus density
bubble chart shown in Figure 3.
Figure 1: Hub dimensions
Table 1: Parameters for Calculation
Parameter
Value
Unit
Mass
255
Kg
Velocity
70
Km/h
Time
4
Sec
Brake drum Diameter
0.015
m
A.
Figure 3: The bubble chart of maximum service temperature against Price
All materials that did not pass the screening are shown in
grey color. From Figure 3 cast iron (BS Grade 200) and
aluminum cast (LM 12)were chosen. The material
properties of the two materials obtained from CES
EduPack software is shown in Table 2
Material selection
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International Journal of Engineering Trends and Technology (IJETT) – Volume 25 Number 3- July 2015
Table 2: Material Properties of the materials
S/
N
Material property
Cast iron
Aluminum
BS Grade 200
Cast
elements with 38248 nodes and 20742 elements
(tetrahedrons). Figure 5 shows the meshed model, the
meshing was refined in the contact zone (hub-pad). This is
important because in this zone the temperature varies
significantly.
LM 12-M
1.
Density
7050 kg / m3
2900 kg / m3
2.
Thermal conductivity
46 W / m oC
127 W / m oC
3.
Ultimate
200MPa
171MPa
Tensile
strength
4
Specific Heat
460 J / kg oC
944 J / kg oC
4.
Linear Expansivity
1.1x10-5
2.2 x10-5
5.
Young’s Modulus (E)
103.0GPa
71GPa
6.
Poisson’s ratio
0.26
0.32
Figure 5: Mesh Model of the hub
Boundary Conditions and Thermal Loadsused for the
analysis include:
Braking system works by turning kinetic energy into
thermal energy through friction. A Transient thermal
analysis was performed to determine the temperature
caused by the thermal load. The materials properties of the
two materials were used in ANSYS. Modeling and analysis
using any Finite Element Analysis (FEA) geometry
requires large amounts of time and massive amounts of
computing power [5]. In order to shorten the time and
decrease the computing efforts, a simplified model was
developed taking advantage of ANSYS Design modeler
(DM) symmetry. The model was then created in Creoelement using the coordinate measuring machine andwas
imported into ANSYS and further developed in ANSYS
Design modeler environment to axis-symmetry model as
shown belowin Figure 4.
The temperature on the hub due to contact discpad sides was calculated as 119oC.
Convective heat transfer coefficient h taken as
5.0 W/ m2 k
The ambient temperature assumed to be 25oC
A coupling analysis for heat and structure was conducted to
obtain the thermal deformation and thermal stress due to
friction of the hub as a result of the pressure exerted on the
pad in braking condition. The result of the transient state
thermal analysis was used as input into setup of the static
structural analysis.Boundary conditions for Static
Structural analysis were frictional drag force of 2,610N,
and cylindrical constraint at the center of the hub.
Figure 6 shows the boundary condition for static structural
analysis. Stress, strain and displacement were solved.
Aluminum
Cast iron
Figure 4: Axis-symmetry Model of the Brake Hub
Meshing is the process in which geometry is spatially
discretized into elements and nodes. The elements used for
the meshing of the hub are tetrahedral three-dimensional
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Figure 6: Static Structural Analysis Boundary conditions
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IV.
4.0 Result and Discussion
The maximum temperature of 119oC and the
frictional drag force of 2,610N obtained from Matlab
program were used in the coupled thermal-static
structural analysis. Figure 7 shows the temperature
distribution on the hub. The red color indicates
maximum point; green indicates average while blue is
minimum temperature. The maximum temperature for
the thermal analysis was 126oC and it occurs at
surface of the cast iron material which was in contact
with the friction lining.
Figure 10: Von Misses vs. time
The equivalent Von misses strain as shown in figure 10 has
a minimum value of 6.32x10-7m/m and maximum of
6.24x10 -4m/m which is around the inner circumference of
the hub.
Figure 7:Temperature distributions on the hub
Figure 8 shows the Equivalent Von-Misses stress
distribution for the coupled–thermal stress analysis with a
maximum value of 56.20MPa and minimum of 1.02KPa.
The maximum value recorded during the simulation is
important as it shows point of highest stress concentration.
From the simulation, the maximum stress occurs on the
frictional surface around the outer surface of the hub as
shown in Figure 8. The results of the finite element
analysis have shown that for the materials under study, the
maximum Von misses stress of 56.20MPa obtained which
is lower than the corresponding permitted ultimate tensile
stress values of the cast iron 200MPa. Figure 9 shows
graph of Von misses stress vs. time
Figure 10: Von Misses strain distribution on the hub
The total deformation is shown in Figure 11 with
maximum 1.39x10-4m. The deformation is maximum along
the hub without web. The graph of total deformation versus
time in Figure 12 shows that deformation increases with
braking time; this shows that deformation is proportional to
braking time for the considered time.
Figure 11: Total deformation distribution
Figure 8: Von Misses stress distribution on the brake hub
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International Journal of Engineering Trends and Technology (IJETT) – Volume 25 Number 3- July 2015
Figure 12: Total deformation distribution vs time
5.0 Conclusion
The use of finite element analysis in product design
validation has been explored in this research work.
Computer Aided Analysis was employed to determine the
Structural integrity and thermal effects using Finite
Element method on motorcycle rear hub. The result of the
analysis using ANSYS software showed that the materials
considered were appropriate since the maximum von
Misses stress is below the ultimate tensile strength of the
materials.
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