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ICTAMDMES'20 IOP Publishing
IOP Conf. Series: Materials Science and Engineering 923 (2020) 012001 doi:10.1088/1757-899X/923/1/012001

Design and analysis of connecting rod using composite

materials (AL7075, AL6061, AL7075+SiC, AL6061+SiC)

Mohanakrishnan R1, Iniyan K2, Sabarish Kumar P3, Arun Vasantha Geethan K4
1,2,3,4
Department of Mechanical Engineering, St. Joseph’s Institute of Technology,
Chennai ,Tamilnadu, India.

E-mail:rmkrishnan98@gmail.com,iniyan19@gmail.com,pskgps@gmail.com

Abstract. Connecting rod is a vital part of an internal combustion engine which forms a link
between piston and the crankshaft. Due to huge amount of forces acting on the piston owing to
high engine load and rpm, cyclic compressive and tensile forces act on the connecting rod and
results in fatigue and failure. So, to in order avoid this, the existing connecting rod is to be
replaced by composite materials. Because these materials have good mechanical properties
such as wear resistance, hardness and high tensile strength. A 3D model of connecting rod is
modeled using Solidworks and FEA analysis is carried out by ANSYS 18.2. In this paper
analysis is performed on the connecting rod using AL7075, AL6061, AL7075+10%SiC and
AL6061+10%SiC to find out the best material for construction of connecting rod.
Keywords: Connecting rod; ANSYS; AL7075; AL6061; AL7075+SiC; AL6061+SiC

1. Introduction

India is one of the world’s largest automobile manufacturers. Two wheelers account for around 80%
of the vehicle sales. The important part of an automobile is the internal combustion engine. It consists
of piston, connecting rod, crankshaft, and crank. The connecting rod forms a link between piston and
crankshaft, the function of connecting rod is to transmit force acting on the piston to the crankshaft.
The connecting rod is a slider and crank mechanism which converts the reciprocating motion of the
piston into the rotational motion of the crankshaft. Connecting rod has two ends, one is pin end and the
other is crank end. Pin end is attached with piston by gudgeon pin and crank end is attached to the
crank pin by a crankshaft.
So, it is essential to rectify the problems for the better utilization of the engine and better life and
performance of the engine. Usually the connecting rods are made up of forged steel, cast iron. The
main disadvantage of using these materials is that they have higher density, which leads to produce to
heavier engine components and motorcycle. So, a less dense material should be used for the
manufacture of the connecting rod in order to reduce weight and inertia forces. In this case,
Aluminium is chosen for the manufacture of the connecting rod due to low density.
Aluminium and its alloy possess low density, high thermal conductivity and high resistance to
corrosion. These materials have low melting point and high ductility. The mechanical properties can
be improved by alloying and cold working. The major alloying elements are zinc, magnesium, silicon,
copper etc. Recent attention has been given to the alloys of aluminium and other low-density materials
as engineering materials for applications in aerospace, automobile and defense etc.

Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution
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ICTAMDMES'20 IOP Publishing
IOP Conf. Series: Materials Science and Engineering 923 (2020) 012001 doi:10.1088/1757-899X/923/1/012001

Aluminum is added with composite materials to make metal matrix composites. These materials
improve the mechanical properties of the connecting rod. The most commonly used composite
material is Silicon Carbide
Silicon carbide (10%SiC), which is also known as carborundum, is semiconductor containing
silicon and carbon. It exists in nature as the extremely rare mineral moissanite. Synthetic 10%SiC
powder has been mass-produced since 1893 for use as an abrasive material
Grains of silicon carbide can be bonded together by the process called sintering to form very
hard ceramics that are widely used in applications requiring high endurance such as car brakes, car
clutches and ceramic plates in bulletproof vests, cutting tools, grinding materials.

2. Problem specification

The aim of the paper is to design, analyze and determine the mechanical properties, feasibility of the
connecting rod made of Al6061, Al7075, Al6061+10%SiC and Al7075+10%SiC. 3D model of the
connecting rod was made using Solidworks 2016. Model was imported into ANSYS 18.2 for analysis.
Model was analyzed to find the stress, strain, and the deformation.

Figure 1: 3D model of connecting rod

3. Design of connecting rod

A connecting rod is an engine component which is subjected to alternating direct compressive and
tensile forces. Due to fact that the compressive forces are predominant over the tensile forces, the
cross section of the connecting rod is designed as a strut and the Rankine Gordon formula is employed
to find the dimensions of the cross section. A connecting rod subjected to an axial load may buckle
in x-axis as neutral axis within the plane of motion of the rod, or y-axis may be a neutral axis.
For buckling analysis, the connecting rod is assumed to be fixed at both ends. The connecting
rod is to be designed to be strong in both the axes.
According to Rankin formulae,
About x-axis,

= = [ ∴ 𝑓𝑜𝑟 𝑏𝑜𝑡ℎ 𝑒𝑛𝑑𝑠 ℎ𝑖𝑛𝑔𝑒𝑑 𝐿 = 𝑙]

[ ] [ ]

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ICTAMDMES'20 IOP Publishing
IOP Conf. Series: Materials Science and Engineering 923 (2020) 012001 doi:10.1088/1757-899X/923/1/012001

About y-axis,

= = [∴ 𝑓𝑜𝑟 𝑏𝑜𝑡ℎ 𝑒𝑛𝑑𝑠 𝑓𝑖𝑥𝑒𝑑 𝐿 = 𝑙/2]

[ ] [ ]

Figure 2: Buckling on applying load

The loads must be equal in order to resist buckling in the both axes.
= = [or]
[ ] [ ]

[ ] =[ ]
4 [or]

If I xx > 4*Iyy, then buckling will occur about the Y-axis and if I xx < 4*Iyy, then buckling occurs
about the X-axis. But practically Ixx is kept slightly lesser than 4 Iyy. A value between 3 and 3.5 is
taken for it. In practice the connecting rod is only designed to withstand buckling about x axis, since
the buckling about y axis is lesser than x axis by 4 times.
Cross sectional area= 2[4t2] + 3t2=11𝑡
Moment of inertia about the X-axis =2[4t2] + 3t2=11𝑡
Moment of inertia about x-axis,

Moment of inertia about y-axis,

𝑡 + * 3𝑡 = 𝑡
= 3.2
The value of Ixx/Iyy is found out to be between 3 and 3.5. Hence the chosen proportions are
appropriate

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ICTAMDMES'20 IOP Publishing
IOP Conf. Series: Materials Science and Engineering 923 (2020) 012001 doi:10.1088/1757-899X/923/1/012001

4. Pressure calculation of 100cc engine

Table 1: Specifications of 100cc Engine

Displacement 100cc
Bore 50mm
Stroke 49.5mm
Length of rod 99mm
Max power 5500w @ 8000rpm
Max torque 8Nm
Compression 9:1
ratio
Density of petrol 737.23 kg/m3

4.1 Calculation of gas pressure:

PV=MRT (Ideal Gas equation)
Where,
P- Pressure
V- Volume in
R- Gas constant in J 𝑜𝑙
T- Temperature in K
M- Mass in kg
M = Ƿ*V = 737.23 * 9.7* = 0.071kg
Where,
Ƿ = Density of petrol
V = volume of the cylinder
R= / = (8.314/114.28) = 72.786
= Gas constant
= molecular weight of petrol
P = MRT/V = (0.071*72.786*300)/9.72*
= 15.95MPa.

4.2 Calculation of Force due to pressure:

= P*A
Where,
P- Gas pressure in MPa
A-Area in
= 15.95 * (Л/4) *
= 3.13KN

4.3 Calculation of Inertia force:

= mr ( /n)
Where,
- Inertia force
- Angular velocity
w = 2ЛN/60 = 837.76
= 0.2488*1.25*24.75
= 5232.6N

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ICTAMDMES'20 IOP Publishing
IOP Conf. Series: Materials Science and Engineering 923 (2020) 012001 doi:10.1088/1757-899X/923/1/012001

5. Design calculations of existing connecting rod

[ ]
Where,
* FOS = 156509.375N
L = length of connecting rod =125mm
d=bore diameter = 50mm
A=area of cross section = 11𝑡
σc = 572MPa

On substituting these values, we get

t = 5mm, B=20mm, H=25mm

Thickness at crank end =1.5*H = 31.25 mm

Thickness at piston end = 0.75*H = 18.75 mm

Figure 3: Cross section of the shaft section of the connecting rod

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ICTAMDMES'20 IOP Publishing
IOP Conf. Series: Materials Science and Engineering 923 (2020) 012001 doi:10.1088/1757-899X/923/1/012001

6. Results and discussion

6.1 Stress

Figure 4: AL6061 under load showing stress

Figure 5: AL7075 under load showing stress

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ICTAMDMES'20 IOP Publishing
IOP Conf. Series: Materials Science and Engineering 923 (2020) 012001 doi:10.1088/1757-899X/923/1/012001

Figure 6: AL6061+10%SiC under load showing stress

Figure 7: AL7075+10%SiC under load showing stress

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ICTAMDMES'20 IOP Publishing
IOP Conf. Series: Materials Science and Engineering 923 (2020) 012001 doi:10.1088/1757-899X/923/1/012001

Stress
176
174
172
170
168
166
Stress
164
162
160
158
156
AL6061 AL7075 AL6061+SiC AL7075+SiC

Figure 8: Comparison of stress acting on materials

6.2 Elastic Strain

Figure 9: AL6061 under load showing elastic strain

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ICTAMDMES'20 IOP Publishing
IOP Conf. Series: Materials Science and Engineering 923 (2020) 012001 doi:10.1088/1757-899X/923/1/012001

Figure 10: AL7075 under load showing elastic strain

Figure 11: AL6061+10%SiC under load showing elastic strain

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ICTAMDMES'20 IOP Publishing
IOP Conf. Series: Materials Science and Engineering 923 (2020) 012001 doi:10.1088/1757-899X/923/1/012001

Figure 12: AL7075+10%SiC under load showing elastic strain

Elastic Strain
0.003

0.0025

0.002

0.0015
Elastic Strain

0.001

0.0005

0
AL6061 AL7075 AL6061+SiC AL7075+SiC

Figure 13: Comparison of elastic strain acting on materials

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ICTAMDMES'20 IOP Publishing
IOP Conf. Series: Materials Science and Engineering 923 (2020) 012001 doi:10.1088/1757-899X/923/1/012001

6.3 Deformation

Figure 14: AL6061 under load showing deformation

Figure 15: AL7075 under load showing deformation

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ICTAMDMES'20 IOP Publishing
IOP Conf. Series: Materials Science and Engineering 923 (2020) 012001 doi:10.1088/1757-899X/923/1/012001

Figure 16: AL6061+10%SiC under load showing deformation

Figure 17: AL7075+10%SiC under load showing deformation

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ICTAMDMES'20 IOP Publishing
IOP Conf. Series: Materials Science and Engineering 923 (2020) 012001 doi:10.1088/1757-899X/923/1/012001

Deformation
0.14

0.12

0.1

0.08

0.06
Deformation
0.04

0.02

0
AL6061 AL7075 AL6061+SiC AL7075+SiC

Figure 18: Comparison of deformation acting on materials

Table 2: Overall values of mechanical properties

Materials Stress Strain Deformation
(MPa) (mm)
AL6061 174.95 0.0025 0.1219
AL7075 174.95 0.0024 0.1183
AL6061+10%SiC 168.69 0.00164 0.0796
AL7075+10%SiC 162.45 0.0025 0.1224

7. Material cost calculation

Volume of connecting rod = 8.844294*

Table 3: Mass of materials

MATERIAL MASS
(kg)
AL6061 0.2387

AL7075 0.2485
AL6061+10%SiC 0.2441
AL7075+10%SiC 0.2512

Mass of AL6061 rod = Ƿ*V = 2700*8.844294*

= 0.2387kg

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ICTAMDMES'20 IOP Publishing
IOP Conf. Series: Materials Science and Engineering 923 (2020) 012001 doi:10.1088/1757-899X/923/1/012001

Mass of AL7075 rod = Ƿ*V = 2810*8.844294*

= 0.2485kg
Mass of AL6061+SiC rod = Ƿ*V = 2760* 8.844294*
= 0.2441kg
Mass of AL7075+SiC rod = Ƿ*V = 2840* 8.844294*
= 0.2512kg
AL6061 = ₹ 215/ Kilogram
AL7075 = ₹600/ Kilogram
Silicon Carbide Powder = ₹85/ Kilogram
10%SiC alloy so 90% aluminium and 10%SiC is
Cost of 1 kg of 7075-SiC will be = 600*0.9 + 85*0.1
= ₹548.5
Cost of 1kg of 6061-SiC will be =215*0.9+85*0.1
= ₹202
(The above values are taken from www.indiamart.com)
Cost of connecting rod is
AL6061 = 0.2387*215 = ₹51.32
AL7075 = 0.2485*600 = ₹149.1
AL6061+10%SiC = 0.2441*202 = ₹49.3
AL7075+10%SiC = 0.2512*548.5 = ₹137.78

Cost
160
140
120
100
80
Cost
60
40
20
0
AL6061 AL7075 AL6061+SiC AL7075+SiC

Figure 19: Material cost comparison

8. Conclusion

On comparing the various result data from the FEA analysis method, we find
 The elastic strain on AL7075 alloy is lesser than AL6061 Alloy by 4% and the total
deformation of Al 7075 is lesser than AL6061 Alloy by 3%.
 When comparing the stress of AL7075+10%SiC alloy with AL7075 alloy we find that the
stress reduction about 7% and increase in elastic strain by 4% and deformation by 3.5%.
 When comparing AL7075+10%SiC alloy with AL 6061+10%SiC alloy we see that
AL7075+10%SiC has a lower stress by 3.7% but higher elastic strain and deformation of
3.5%.

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ICTAMDMES'20 IOP Publishing
IOP Conf. Series: Materials Science and Engineering 923 (2020) 012001 doi:10.1088/1757-899X/923/1/012001

We choose AL6061+10%SiC as the alternate material because it is able to withstand the applied load
without much deformation or strain and also the fact that AL6061+10%SiC is also lighter in weight
compared with AL7075+10%SiC and is also relatively cheap market price.

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