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VSRD International Journal of Electrical, Electronics &
Communication Engineering, Vol. III Issue XII December 2013 / 407
e-ISSN : 2231-3346, p-ISSN : 2319-2232 VSRD International Journals
: www.vsrdjournals.com
RESEARCH ARTICLE
OPTIMIZATION OF CONNECTING ROD BY USING NON-LINEAR STATIC FINITE
ELEMENT ANALYSIS
1Ajit Kumar Senapati* and 2Gopal Krushna Mohanta 1Associate
Professor, 2Assistant Professor, 1,2Department of Mechanical
Engineering
Gandhi Institute of Engineering &Technology, Gunupur,
Odisha, INDIA. *Corresponding Author : [email protected]
ABSTRACT This paper deals with nonlinear static analysis and
optimization of forged steel connecting rod. Optimization is
important as less time is required to produce the connecting rod
which is stronger, lighter with minimum cost. In this article
connecting rod material is replaced by Aluminium reinforced with
Boron carbide for motorbike. A 2D drawing is drafted from the
calculations. A parametric model of connecting rod is modeled using
HYPERMESH 4.0 software. Analysis is carried out by using RADIOSYS
software. Finite element analysis of connecting rod is done by
considering two materials, viz. Aluminium Reinforced with Boron
Carbide and Aluminium 360. The best combination of parameters like
Von misses stress and strain, Deformation, Factor of safety and
weight reduction for two wheeler connecting rod were done in
RADIOSYS software. The design and weight of the connecting rod
influence the engine performance. Specifications of connecting rod
have been evaluated to calculate the loads acting on it. Structural
analysis is carried out on piston end and crank end of connecting
rod then further study was conducted to explore weight reduction
opportunities for a production of connecting rod. The component is
to be optimized for weight subject to constraint of allowable
stress and factor of safety. The percentage weight reduction
obtained was 7.35% by optimization. Connecting rod, Static
analysis, Carbon steel.
Keywords : FEA; Static; Aluminium; Aluminium reinforced with
Boron carbide; Aluminium 360; Connecting Rod; Optimization;
etc.
1. INTRODUCTION Automobile components are in great demand these
days because of increased use of automobiles. The increased demand
is due to improved performance and reduced cost of these
components. R&D and Test engineers should develop critical
components in shortest possible time to minimize launch time for
new products. This necessitates understanding of new technologies
and quick absorption in the development of newer products.
Connecting rod is highly dynamically loaded component used for
power transmission in combustion engines. It is considered as key
component in terms of structural durability and efficiency. It acts
as an intermediate link between the piston and crankshaft of I.C
engine. Its basic function is to transmit thrust from piston to
crankshaft. Connecting rods are subjected to forces generated by
mass and fuel combustion. These two forces results in axial and
bending stresses.
Bending stresses appear due to eccentricities, crankshaft, case
wall deformation, and rotational mass force. Therefore, a
connecting rod must be capable of transmitting axial tension, axial
compression, and bending stresses caused by the thrust and pull on
the piston and by centrifugal force. FEA has evolved powerful tool
supporting engineers in various fields of product development and
research with continuous increasing computational capabilities.
Webster et al. [1] was first to carry out three dimensional FEA of
high speed diesel engine connecting rod. X. Hou et al. [2] carried
out sensitivity analysis and optimization based on the combination
in design of the connecting rod of LJ276M electronic gasoline
engine. T.H. Lee et al. [3], proposed meta model based shape
optimization of
connecting rod considering fatigue life. Meta model based design
optimization of connecting rod can reduce the actual cost of
computer simulations compared with that of classical design
optimization. P. Charkha et al. [4], carried out analysis and
optimization of forged steel connecting rod. The structural
improvement of diesel engine connecting rod was carried by Z. Bin
et al.[5], showed that the exposed destructive position is the
transition location of small end and connecting rod shank at
maximum compression condition. Z. Bin et al [6],. presented the
design connecting rod of internal combustion engine using the
topology optimization with objectives to develop structural
modeling, FEA and the optimization of the connecting rod. M.S.
Shaari et al. [7], investigated that with fully reverse loading,
one can estimate longevity of a connecting rod and also find the
critical points from where there is possibility of crack growth
initiation in the connecting rod of universal tractor (U650). M.
Omid et al [8], introduced a method of the connecting rod
structural. The thermal deformation and mechanical deformation will
cause connecting rod cracks, tortuosity, etc. Therefore, it is
essential to analyze the stress field, temperature field, heat
transfer, thermal load and mechanical load coupling of connecting
rod in order to lower the heat load and improve the thermal stress
distribution and improve its working reliability during the
connecting rod designed. Analysis method of the finite element
provides a powerful calculation tool, which is better than test
method and theory analysis method and has become an important means
for internal combustion engine performance study.
Connecting rods are widely used variety of engine. The function
of connecting rod is to transmit the thrust of the
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Ajit Kumar Senapati and Gopal Krushna Mohanta VSRDIJEECE, Vol.
III (XII) December 2013 / 408
piston to the crank shaft, and as the result the reciprocating
motion of the piston is translated into rotational motion of the
crank shaft. It consist of a pin end. A shank section, and crank an
end .Pin end and crank end pin holes are machined to permit
accurate fitting of bearings. One end of the connecting rod is
connected to the piston by the piston pin. Connecting rods are
subjected to forces generated by mass and fuel combustion .Theses
two forces results in axial load and bending stresses. A connecting
rod must be capable of transmitting axial tension, axial
compression, and bending stress caused by the thrust and full of
the piston and by centrifugal force. Finite element (FEM) Model is
a modern way for fatigue analysis and estimation of the component
.The influential component factors are able to change such as
material .cross section conditions etc.
In modern automotive internal combustion engine, the connecting
rods are most usually made of steel for production engine. But can
be made of aluminium or titanium for high performance of engines of
cast iron for application such as motor scooters. They are not
rigidly fixed at either end , so that the angle between the
connecting rod and piston can change as the rod moves up and down
and rotates around the crank shaft .The big end connects to the
bearings journal on the throw connecting rod is under tremendous
stress from the reciprocating load represented by the piston
,actually stretching and being compressed with every rotation, and
the load increases to the third power with increasing engine speed
.Connecting rod for automotive applications are typically
manufactured by forging from either wrought steel or powder metal.
Schematic diagram for connecting rod as shown in figure 1.
2. SPECIFICATION OF THE PROBLEM The objective of the present
work is to design and analysis of connecting rod made of Aluminum
Reinforced with Boron carbide. Steel and aluminum materials are
used to design the connecting rod. In this project the material
(carbon steel) of connecting rod replaced with Aluminum Reinforced
with Boron carbide. Connecting rod was phase variable sinusoidal
voltage waveforms by modulating the on and off times of the power
switches. In industrial drive applications, the PWM inverter
operates as a three-phase variable-frequency, variable-voltage
source with fundamental frequency varying from zero to three times
the motor nominal frequency. In some control schemes where a
three-phase, variable-frequency current source is required, current
control loops are added to force the motor currents to follow an
input reference (usually sinusoidal) created in Pro-E. Model is
imported in ANSYS 12.0 for analysis. After analysis a comparison is
made between existing steel and aluminum connecting rod viz.,
Aluminum Reinforced with Boron carbide in terms of weight, factor
of safety, stiffness, deformation and stress.
3. EXISTING METHODS A. Steps in Modeling of Connecting Rod :
Optimized
Connecting Rod has been modeled with the help of PRO/E Wildfire
4.0 software. The Orthographic and Solid Model of optimized
connecting rod is shown in figures below :
Fig.1: Drawing of Connecting Rod (Optimized)
Fig.2: CAD Model of Connecting Rod in HYPERMESH
The following is the list of steps that are used to create the
required model: a. Choose the reference plane. b. Set the dimension
in mm. c. Go to sketcher and sketch circular entities. d. Then
extrude these entities for making the both ends of connecting rod.
e. Again reference plane is selected for shank of connecting rod.
f. Entities is made that should be tangential to both ends. g.
Extrude the entities symmetrically. h. Plane is selected for making
entities of groove. i. Groove is made on the shank and mirrored
for
creating groove on both side. j. Datum plane is selected for
creating small holes
on piston end k. Then holes are made on the periphery of
piston
end.
B. Specification of Existing Connecting Rod : Table 1 shows the
specifications of the connecting rod for carbon steel (Suzuki GS).
The typical chemical composition of the material is 0.61%C, 0.095%
Al, 0.82%Mn, 0.00097%Br, 0.145% C, 7.8Co, 75.56Fe and 3.25 Mo.
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Table 1 : Specifications of Connecting Rod S.L Parameters Value
1 Bore Stroke (mm) 5758.6
2 Length of connecting rod 112 mm
3 Thickness of connecting rod For C.S = 3.2mm For AL
360 = 4.1 mm
4 Width of connecting rod For C.S = 12.8mm For AL
360 = 16.4 mm
5 Height of connecting rod
For C.S H1 =12mm H2 =17.6mm
For C.S H1 =12mm H2 =17.6mm
C. Structural Analysis of Connecting Rod : Dimensions of Width
and height of the connecting rod is For C.S = 12.8mm and For AL 360
= 16.4 mm. A 3-D model of connecting is used for analysis in ANSYS
12.0. The loading conditions are assumed to be static. Analysis
done with pressure load applied at the piston end and restrained at
the crank end or other load applied at the crank end and restrained
at the piston end. The element chosen is SOLID 187; it was used
with the tetrahedral option, making it a 10-node element with 3
degrees of freedom at each node. The finite element analysis is
carried out on carbon steel connecting rod as well as on three
different materials of carbon steel, aluminium boron carbide and
aluminium 360. From the analysis the equivalent stress (Von-mises
stress), strain, displacements were determined and are shown in
figure 3-14. Table 2 shows the comparative of factor of safety for
three different materials.
Fig. 3: Loads and Boundary Conditions
Carbon Steel:
Fig. 4: Von Misses Strain of Carbon Steel
Fig. 5: Von Misses Stress for Carbon Steel
Fig. 6: Displacement of Carbon Steel
Aluminium 360
Fig. 7: Von Misses Strain of Aluminium 360
Fig. 8: Von Misses Stress of Aluminium 360
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III (XII) December 2013 / 410
Fig. 9: Displacement of Aluminium 360
Aluminium Boran Carbide:
Fig. 10: Von Misses Strain of Aluminium Boron Carbide
Fig. 11: Von Misses Stress Aluminium Boron Carbide
Fig. 12: Displacement Aluminium Boron Carbide
Results :
Table 2 : Comparison of Factor of Safety
Material Properties
Carbon Steel
Aluminium 360
Aluminium Boron
Carbide Yield
strength 415 172 300
Tensile Strength (Mpa)
540 317 485
Theoretical Factor of
Safety (Mpa)
6 6 6
Allow Stress ( Mpa ) 69.17 28.47 50
Ansys Result (Mpa) 49 43.295 43.295
Working Factor of
Safety (N)
8.47 4 6.95
Result For Weight of Connecting Rod : Density of Carbon steel =
7.87e-6 Kg/mm3 Volume of connecting rod = 92419.78mm3 Weight of
connecting rod = Density Volume
=7.87e-692419.78 = 0.727 kg = 7.131 N
1. Density of Al 360 =2.685e-6 kg/mm3 Volume of connecting rod
=180935.21 mm3 Weight of connecting rod =Density Volume
= 0.48581 kg = 4.765 N Percentage of reduction in weight = W of
Carbon steel-W of Al 360 / W of Carbon steel
=0.727-0.48581/0.727 =0.3317
Aluminium boron carbide = W of Carbon steel-W of Aluminium boron
carbide/W of Carbon steel
=0.727-0.48581/0.727 =0.3317
Result for Stiffness of Connecting Rod: Carbon steel Weight of
connecting rod =0.727Kg
Deformation =0.00941mm Stiffness =Weight/Deformation
=0.727/0.0094 =77.34 kg/mm
Aluminium360 Weight of connecting rod =0.48581Kg
Deformation =0.0033166mm Stiffness =Weight/Deformation
=0.48581/0.00331 =146.77 kg/mm
Aluminium Boron Carbide Weight of connecting rod =0.48581Kg
Deformation =0.012219mm
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Stiffness = Weight/Deformation = 0.48581/0.012219 = 39.7585
kg/m
Result for Percentage of Increase in Stiffness: Aluminium 360
=77.34-146.77/77.34
= -0.8977 Aluminium boron carbide
= 77.34-39.7585/77.34 = 0.4855
Result for Percentage of Stress Reduction : Aluminium 360
=49.625-43.925/49.625
= 0.1035 Aluminium boron carbide
=49-43.925/49 = 0.1035
4. GRAPHS
Fig. 15: Von-Misses Stress for Three Materials
Fig. 16: Von-Misses Strain for Three Materials
Fig. 17: Displacement for Three Materials
Fig. 18: Working Factor of Safety for Three Materials
Discussion: By checking and comparing the results of materials
in above tables and finalizing the results are shown in below. For
considering the parameters, the working factor of safety is nearer
to theoretical factor of safety in aluminium boron carbide.
Percentage of reduction in weight is same in Aluminium 360 and
aluminium boron carbide. Percentage of increase in stiffness in
aluminium boron carbide is more. Percentage of reducing in stress
ALUMINIUM BORON CARBIDE and ALUMNUM is same than CARBON STEEL.
Optimization: Objective of the optimization task was to minimize
the mass of the connecting rod under the effect of a load range
comprising the two extreme loads, the peak compressive gas load,
such that the maximum, minimum, and the equivalent stress amplitude
are within the limits of the allowable stresses.
a) Optimization Statement: Objective Function: Minimize Mass
Subject to Constraints
[1] Maximum Vonmises Stress < Allowable Stress
[2] Factor of safety > 1.3 [3] Manufacturing Constraints
b) Optimized Model : After carrying out static structural
analysis the stresses in each loading conditions were studied and
then area where excess material can be removed were decided so that
maximum Vonmises stress does not exceed allowable and factor of
safety is kept above 1.3. As shown in Fig.3 Following four regions
showed scope for material removal. 1. Head Region of Pin End was
reduced by 1.5 mm
then fillet of1.5mm was given to its sharp edges. 2. Shank of
connecting rod was reduced from 3mm
to 1.5mm. 3. Oil hole was given fillet of 1.2mm. 4. Head Region
of Crank End was reduced by 2.2
mm and fillet of 2mm was given to its sharp edges.
Optimized geometry was modified in Design modeler of ANSYS
Workbench.
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Ajit Kumar Senapati and Gopal Krushna Mohanta VSRDIJEECE, Vol.
III (XII) December 2013 / 412
Fig. 13: Optimized Model of Connecting Rod
Results : Maximum Vonmises stresses and deformation was found
out using static structural analysis in ANSYS workbench. Fig: 4
shows stress distribution for compressive loading at crank end. In
this case max stress occurred at oil hole due stress concentration.
Max stress occurred in the transition area between crank end and
shank region as shown in Fig: 5 for compressive loading at pin end.
Stress distribution for Tensile loading at pin end is shown in Fig:
6. below shown is mass and factor of safety for both original as
well as optimized model.
Fig. 14 : Stress Distribution for Compressive Loading at Crank
End
Original Model: Mass =670.24 gm Factor of Safety = 1.31
Optimized Model: Mass = 620.98 gm Factor of safety is 1.30
Following Table 3 gives the comparison between equivalent stress
and deformation at different loading conditions for original model
as well as optimized model.
Table 3 : Maximum Vonmises Stresses and Deformation of Original
and Optimized Connecting
Rod
Model Original Optimi
zed Original
Optimized
Types of
loading
Applied
pressure
Max Von misses Stress (Mpa)
Deformation X 10-4 (m)
Tensile Loading
Crank end 363.5 370 2.851 3.62
Pin end
284.88 282.59 1.731 1.96
Compressive
Loading
Crank end
334.17 300.42 1.9 7.79
Pin end 94.78 114.54 0.854 0.975
Fig. 14: Stress Distribution for Compressive Loading at Pin
End
% Weight Reduction = (Original mass-Optimized mass)/(Original
mass) X 100 = (670.24-620.98)/670.24 X 100 = 7.35 %
Discussion : The peak stresses mostly occurred in the
transition
area between pin end, crank end and shank region. The value of
stress at the middle of shank region is well below allowable
limit.
Also forces at pin end are lower in comparison to the forces in
crank end so strength of pin end should ideally be lower in
comparison to the strength of crank region.
In tensile loading with pressure applied at the crank end and
pin end restrained maximum value of vonmisses stress was observed
for both original as well as optimized model compared to other
loading conditions this is critical loading condition usedfor
optimization study.
Stress concentration was occurring at the oil hole in tensile
and compressive loading conditions pressure applied at crank which
concluded that fillet is given to the oil hole for reduction of
stress concentration. Fillet of 1.2 mm was given to oil hole.
Factor of safety was greater than 1.3 in both tensile as well as
compressive loading cases for both original as well as optimized
model.
Percentage weight reduction was about 7.35% which will save
material directly to reduce the manufacturing cost with increased
engine efficiency. Fig. 6. Stress Distribution for Tensile loading
at Pin end.
5. CONCLUSION Finite Element analysis of the connecting rod of a
Hero Honda Splendor has been done using FEA tool
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Ajit Kumar Senapati and Gopal Krushna Mohanta VSRDIJEECE, Vol.
III (XII) December 2013 / 413
ANSYSWorkbench. From the results obtained from FE analysis, many
discussions have been made. The results obtained are well in
agreement with the similar available existing results. The model
presented here, is well safe and under permissible limit of
stresses. Conclusion is based on the current work that the
design parameter of connecting rod with modification gives
sufficient improvement in the existing results.
The weight of the connecting rod is also reduced by 0.477g.
Thereby, reduces the inertia force.
Fatigue strength is the most important driving factor for the
design of connecting rod and it is found that the fatigue results
are in good agreement with the existing result.
The stress is found maximum at the piston end so the material is
increased in the stressed portion to reduce stress.
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