international journal of pure and applied mathematics...
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DESIGN AND ANALYSIS OF COMPOSITE HELICAL SPRING FOR TWO WHEELER SHOCK
ABSORBER
P.Dhanapal1, K.R. Mathevanan2, M. Rahul Krishnan3, R.Thennarasan3
1Professor,
Department of Mechanical Engineering
Karpagam College of Engineering, Coimbatore - 641 032, Tamilnadu, INDIA 2Assistant Professor,
Department of Mechanical Engineering,
Karpagam College of Engineering, Coimbatore - 641 032, Tamilnadu, INDIA 3Mechanical Student,
Department of Mechanical Engineering,
Karpagam College of Engineering, Coimbatore - 641 032, Tamilnadu, INDIA
Abstract: The automobile industry has shown
increased interest in the replacement of ferrous metals
using composite materials due to high strength to
weight ratio. The present study describes design and
comparative analysis using standard empherical
formula and ANSYS of steel spring with the glass and
carbon fibre epoxy materials. Carbon fibre has
maximum deflection. A maximum of 5% deviation
occurs in the carbon epoxy spring while comparing the
theoretical and experimental values and the other two
materials are low. Hence the usage of this analysis
software has an error of 5% only. Glass fibre epoxy
shows the maximum spring rate. The ultimate yield
stress of the carbon fiber epoxy is 216 % and 32%
compared with the steel.
AMS Subject Classification: 74E30
Keywords: Analysis, Design, Conventional materials,
Composite material, Stresses.
1. Introduction
Suspension systems have been applied to vehicles,
from the horse-drawn cart with flexible leaf springs, to
the modern automobile with complex control
algorithms. The suspension of a road vehicle is usually
designed with two objectives; to isolate the vehicle
body from road irregularities and to maintain the wheel
control with the roadway. Leaf spring, coil spring and
their combination are used as suspension systems in
automobiles.
Pro-Engineer is a parametric, feature-based
modeling architecture incorporated into a single
database philosophy with advanced rule-based design
capabilities. This data is then documented in a standard
2D production drawing or the 3D drawing standard
ASME Y14.41-2003. ANSYS is standard FEA tool
used to solve problems in various disciplines like civil
and electrical engineering, as well as the physics and
chemistry. ANSYS provides a cost-effective way to
explore the performance of products. The multifaceted
nature of ANSYS also provides a means to ensure that
users are able to see the effect of a design on the whole
behavior of the product, be it electromagnetic, thermal,
mechanical etc.
Generic steps to solving any problem in ANSYS
are Define the solution domain, Create the physical
model, Fix boundary conditions and add the physical
properties. Solve the problem and present the results. In
numerical methods, the main difference is an extra step
called mesh generation. This is the step that divides the
complex model into small elements that become
solvable in an otherwise too complex situation. Below
describes the processes in terminology slightly more
attune to the software.
Multi leaf spring is designed by finite element
approach using CAE tools (i.e CATIA, ANSYS) and
analysed the stress-deflection. When the leaf spring is
fully loaded, a variation of 0.632 % in deflection is
observed between the experimental and FEA result (1).
The oscillatory behavior of stresses is also responsible
for causing rotational movement of springs in slots,
observed in experimental analysis. The failure locations
matched with considerable amount of failures occurred
in experiment (2). Numerical results have been
compared with theoretical results and found to be in
good agreement three different composite helical
springs. Compared to steel spring, the composite helical
spring has been found to have lesser stress. Weight of
spring has been reduced and has been shown that
changing percentage of fiber, especially at
Carbon/Epoxy composite, does not affect spring weight
(3). Composite mono leaf spring reduces the weight by
International Journal of Pure and Applied MathematicsVolume 118 No. 11 2018, 549-555ISSN: 1311-8080 (printed version); ISSN: 1314-3395 (on-line version)url: http://www.ijpam.eudoi: 10.12732/ijpam.v118i11.70Special Issue ijpam.eu
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85% for E-Glass/Epoxy, 91% for Graphite/Epoxy, 90%
for Carbon/Epoxy over conventional leaf spring (4).
Composite leaf springs of varying width and
thickness and constant cross section has been analyzed
in ANSYS software and observed that Boron
Aluminum is the best suitable material for replacing the
steel in manufacturing of mono leaf spring (5). The
weight of the composite spring was much lesser, this
can be justified by the amount of fuel saved and the
stiffness of springs. An optimum design of composite
springs is required to balance the weight and stiffness;
hence the application of composite springs is limited to
light commercial vehicles. In this study, advanced
composite materials are chosen as spring materials, the
dimensions of the springs are chosen as per the springs
available in the market. Their behavior is analyzed
using ANSYS software.
2. Materials and Methods
The suspension system of Yamaha RX100 is chosen for
the analysis. Figure 1 shows the assembled view of
solid modeling of the actual spring components. The
shock absorber is dismantled, sizes of individual
components are measured and reverse engineering is
applied to get this model.
Figure 1. Assembled View
A modal analysis is typically used to determine
the vibration characteristics (natural frequencies and
mode shapes) of a structure while it is being designed.
It can also serve as a starting point for detailed dynamic
analysis, such as a harmonic response or full transient
dynamic analysis. A reduced solver utilizing
automatically or manually selected master degrees of
freedom to drastically reduce the problem size and
solution time.
The actual spring contains 18 numbers of active
coils with 57 mm coil outer diameter, 220 mm length,
10.52 mm pitch and 7mm circular section wire.
Materials library of the necessary object being modeled
are defined. This includes thermal and mechanical
properties. The mesh type is defined. The last task is to
apply the constraints, such as physical loadings or
boundary conditions. The software provides a platform
for different type of loads like static, dynamic, shock
load etc. Obtain solution. After the solution has been
obtained, there are many ways to present the results
such as tables, graphs, and contour plots. The
theoretical values of stiffness, deflection and the
stresses are calculated with standard formulae and
standard design data book and compared with the
experimental value to conform the correctness.
Carbon-fiber reinforced thermoplastic (CFRP)
were commonly used in structural engineering
applications, in sports equipment such as racing
bicycles, in aerospace engineering for micro Air
vehicles and also used in high-end automobile racing.
2.1 Analysis Procedure
The following procedure is carried out in order to
analyze the springs differing in the material in ANSYS
workbench. First convert the spring model file which is
designed using Pro-E into IGES format. Select
geometry mode and change the input mode to ‘mm’.
Go to file→ import external geometry file and browse
for the IGES file (Figure 2a). Then generate the spring.
Discretization is the first and major step in the
successful analytical evaluation of any component in
FEM. This process of discretizing the solid part into
finite number of elements is called Meshing in ANSYS.
Select new mesh and change the reference center as
fine and select generate mesh. Fine’ should be selected
to get the nearest approximate results. The meshed
object should be moved to the simulation mode for
proceeding the analysis. Select convert to simulation
option, the window changes to simulation mode. Select
new analysis → static structural Apply fixed end and
give the load on the whole geometry of the spring, the
material properties are defined.
Figure 2a. spring solid model
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Figure 2b. Meshed view
Choose static structural → solution and choose
insert → deformation → total in order solve the
analysis for total deformation due to applied load.
Choose equivalent elastic strain and equivalent stress
(von- mises) for solving. Select new analysis → modal.
Analysis settings → options, enter value for maximum
modes to find, say 6. Add total deformation for 6
modes and for each consecutive total deformation,
under Definition, set the Mode value to corresponding
to respective mode number. Solve the modal analysis
by right clicking Modal Analysis in the left pane.
3. Results and Discussions
In this analysis circular cross-section is considered. The
load acting on the entire rear suspension system is 1000
N. The rear suspension system comprises of a pair of
shock absorbers. Hence the load on one suspension in
the rear is half of the entire load which is 500 N. This
load is applied on the spring in static structural analysis
for which the deflection, Von-Mises stress is studied.
The behavior of the spring due to its self-weight is also
studied under modal analysis.
3.1 Steel Spring
Under Geometry, choose material → import and
continue the above given procedure. Figure 3a shows
the maximum deflection of the steel spring as 21.154
mm for the static condition. Figure 3b shows that the
equivalent von-mises stress is 392.570 MPa. In figure
3c the equivalent von-mises strain is obtained as 0.0018
and the final deflection of the spring in modal analysis
is 36.11mm from figure 3d.
Figure (3a). Total Deflection
Figure (3b). Von-Mises stress
Figure (3c). Von-Mises strain
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Figure (3d). Total Deflection (Modal)
3.2 Carbon Epoxy
Figure (4a). Total Deflection
Figure (4b). Von-Mises stress
Figure (4c). Von-Mises strain
Figure (4d).Total Deflection (Modal)
Carbon epoxy spring material analysis, under
geometry, choose Material → Import, if the material is
predefined just choose the material after verifying the
properties and continue the procedure. The maximum
deflection of the Carbon Epoxy spring (Figure 4a) is
22.264 mm for the static condition but for the steel
spring as 21.154 mm. Figure 4b shows that the
equivalent von-mises stress as 392.80 MPa whereas for
steel spring is 392.570 MPa. The Equivalent von-mises
strain is obtained as 0.0020 in figure 4c but for steel
spring it is 0.0018. The final deflection of the spring in
modal analysis is 45.826 mm but for the steel spring is
36.11 mm.
3.3 Comparison Charts
The ANSYS software results show varieties of output
values for different spring materials. Some of the
performances are described in table 2. Bar charts are
drawn to compare and discuss the important parameters
like deflection, spring rate and von-mises stress.
International Journal of Pure and Applied Mathematics Special Issue
552
Table 2. Comparison table for results
Material Steel Carbon Epoxy
Modal
Results
Deflection
(mm)
Frequenc
y (Hz)
Deflection
(mm)
Freque
ncy
(Hz)
Mode 1 27.973 8.492e-4
41.469 2.435 e-3
Mode 2 27.973 1.727e-3
41.469 2.875e
-
3
Mode 3 27.973 3.718e-3
41.469 6.22 e-3
Mode 4 35.42 13.961 45.51 17.86
Mode 5 35.37 14.942 45.46 17.97
Strain 1.88 e-3 2.10123 e-3
Densit
y (x10-
6
kg/mm3)
7.8 1.6
Figure 5. Deflection
The theoretical and experimental deflection is
expressed in figure 5, carbon fiber has maximum
deflection. Comparing the theoretical and experimental
values, a maximum of 5% error occurs in the carbon
epoxy spring and the other two materials are low.
Hence the usage of this analysis software has an error
of 5% only. The spring rate is compared in figure 6.
Glass fiber epoxy shows the maximum spring rate. The
higher stiffness and spring rate is the glass epoxy
springs because this fiber has high stiffness compared
to the carbon fiber of same size.
Von-mises and ultimate Yield Stress in the
springs are shown in figure 7, where the von-mises
stress is uniform in all the springs. The ultimate yield
stress of the carbon fiber epoxy is 216 % and 32 %
compared with the steel and glass fiber epoxy. Ultimate
yield stress of carbon is more compared to the glass
fiber gives higher this higher yield stress.
Figure 6. Spring Rate
Figure 7. Stress
4. Conclusion
The analysis has a maximum of only 5% variation with
the theoretical calculations. The analysis describes that
the use of glass fiber epoxy as a substitute for steel
spring would results in reduced yield stresses and
strain, also reduction in deflection for variation in
frequencies. Also it is found that the weight of the
spring is reduced, and the factor of safety of the
composites is found to be high. The glass fiber epoxy is
an alternate for the shock absorber coil springs.
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553
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