A Report

Entitled
ANALYSIS OF CONNECTING ROD
USING DIFFERENT MATERIALS
By
Shahid khan
(19MD805)

Submitted to: Dr. Ketul Brahmbhatt

BVM Engineering College,
Vallabh Vidhyanagar
RESEARCH METHODOLOGY AND
EXPERIMENTAL TECHNIQUE
 INDEX
1. Abstract…………………………………
(3)
2. Introduction……………………………..
(4)
3. Connecting rod material………………...
(6)
a) Aluminum……………………………………………………...(6)
b) Forged steel…………………………………………………….(6)
c) Titanium.……………………………………………………….(7)

4. Literature review………………………..
(7)
5. Connecting rod design…………………
(11)
6. Analysis and optimization……………...
(19)
a) Modeling of connecting rod…………………………………..(19)
b) Fatigue analysis……………………………………………….(21)
7. Nomenclature…………………………..
(23)
8. Conclusion……………………………..
(24)
9. References …………………………….
(25)
 Abstract
Of
ANALYSIS OF CONNECTING ROD
USING DIFFERENT MATERIALS
Shahid khan(19MD805)
BVM Engineering College
July 2020

Selection of connecting rod for good performance of

automotive engine is very difficult. The objective of the activity
is to select the appropriate materials for a connecting rod(CR)
where the constraints and factors are to make the product as
light and cheap as possible and yet strong enough to carry the
maximum load without failure in high cycle fatigue. The
fracture toughness also needs to be above a certain minimum
value. A further advance requirement is that the connecting rod
should not be buckled during operation. These constraints and
factors are used to select an appropriate cross section and
material for the construction of connecting rod. The material
used in the connecting rod should be prefer wisely because
during the manufacturing process it has to undergo various
processes in production and suitable heat treatment processes,
which is very important for strength and stiffness as well. Based
on which the High Strength Carbon Fiber reinforced composites
connecting rod will be compared with connecting rod made up
of Forged Steel and Aluminum Alloy. The component was
optimized for weight and cost which is subject to fatigue life and
space constraints and manufacturability. Obtained the maximum
weight reduction in a connecting rod without changing the main
physical parameters. Optimization for weight reduction and for
design correction of the connecting rod. Analyses are carried out
in CREO PARAMETRIC and ANSYS software.

1. INTRODUCTION
The automobile engine connecting rod is a high volume
production, crucial part. It enlink reciprocating piston to the
rotating crankshaft, transmitting the propensity of the piston to
the crankshaft. Every vehicle that contains an internal
combustion engine(IC Engine) requires at least one connecting
rod(CR) depending upon the number of cylinders in the engine.
Material, such as forged steel, aluminum alloys, titanium, and
cast iron are used in the production of CR. The Small end of the
connecting rod(CR) is connected to the piston end using a
gudgeon pin by press fit and the big end is connected to the
crank shaft using fasteners. During operation thrust force which
is exerted on the piston by the combustion of the fuel, this force
is to be transmitted to the crankshaft by the connecting rod, due
to this force the connecting rod undergoes large amount of
stress. Stresses on the connecting rod(CR) are always high due
to the combustion chamber pressure, inertia forces, which
induces high stresses temperature and that can be lead to the
catastrophic failure
 Fig1. Nomenclature of connecting rod

Failure of a connecting rod, usually called "throwing a rod" is

one of the most common causes for catastrophic engine failure
in cars. However, failure of the connecting rod is not common
since the big automobile companies try to keep a very high
factor of safety of 2 or 3 or above than that. To provide warranty
of the components, automobile companies should have the
robust design and manufacturability. By having all this
constraints in consideration, a number of engines fail or cease
because of failure of the connecting rod assembly, which leaves
the companies to consider that the connecting rod as a very high
risk component. While designing and optimizing the connecting
rod, Venugopal Vegi suggested that measures have to be taken
to reduce the stresses in the connecting rod. Methods, like
grinding the edges to give smooth surface and radius to prevent
crack initiation shot peening method, are used which induces
compressive surface stress to balance the weight of the
connecting rod and piston assembly to reduce the bending stress
due to centrifugal action.
 2. CONNECTING ROD MATERIALS

Forged steel: Forged steel is an alloy of iron and carbon and

that is compressed under large pressure to make a robust
substance. It has been used for thousands of years to create all
types of materials. Modern forged steel is made by specialized
machines or hydraulic hammers. There are many things which
must include when understanding the benefits of forged steel.
It is currently eco boost mustang material which is used mostly
in aerospace application.this material is used to handle high
stress. In figure 2 shows Forged steel (FS) - A cosmetic trend
has started by using Aluminum alloy as a CR member mainly to
reduce the weight of the component, however due to innovation
in machine design, engineers have moved back to the steel.
Neelen of late model Engines explains, The weight below the
gudgeon pin is not a big of a concern as the weight above it. He
also said that this is one of the biggest reasons for moving back
from Aluminum alloys.

Fig2. Forged steel

Aluminum: Aluminum 7075 material is used as Connecting

rod(CR) to reduce the weight of the component and it gives
cushion effect between the piston head and crank shaft at higher
rpm. This connecting rods are generally manufactured using
CNC machines, which has high fatigue life and robust. It used in
Aircraft fittings, gears, and shafts, meter shafts and gears,
missile parts, regulating valve component, worm gears, keys,
aircraft, aerospace and defense applications; bike frames etc.

Fig3. Aluminum 7075 CR

Titanium: For their incredible properties, the high strength

titanium alloys have developed using our original chemical
composition series are widely adopted for automotive vehicles,
especially for motorcycles, in connecting rods, engine valves,
and other components in the automobile.
 3. LITERATURE REVIEW

In thesis by the Pravardhan S. Shenoy and Ali Fatemi,

Optimization and analysis was performed to reduce weight as
well as manufacturing cost of a forged steel connecting rod
subjected to cyclic load comprising the peak compressive gas
load and the peak dynamic tensile load at 5710 rev/min,
corresponding to 360 degree crank angle.
According to the Ramesh B T, Vinayaka Koppad , Hemantha
Raju, Aluminum7075 weights three times less than Forged
Steel; this material CR is mainly used in aerospace application.
Forged Steel has very high stress handling capacity without
yielding
In the paper done by AbhinavGautam, K PriyaAjit , static
stress analysis of connecting rod of SS 304 used in Cummins
NTA 885 BC engine is conducted, It is observed that the area
close to root of the smaller end is very prone to failure, may be
due to higher crushing load due to gudgeon pin assembly. As the
stress value is max in this area and stresses are cyclic in nature
so chances of fatigue failure are always higher close to this
region.
In the paper done by Kuldeep B, Arun L.R, Mohammed
Faheem, it is concluded and validate that Weight can be
reduced by changing the material of the current AL360
connecting rod to hybrid ALFASiC composites. The new
optimised connecting rod is comparatively much robust than the
former.
According to the Yogesh N Dupare, He also said that axial
stress is due to combustion chamber pressure and inertia forces
and bending stress is due to centrifugal action of the connecting
rod when connected to the crank shaft. He also said that 50-90%
of the failure of the connecting rod are due to fatigue failure,
thus it is important to consider fatigue failure in the connecting
rod design and great care must be included by the Computer
aided Engineering team in a company to perform analysis on
fatigue.
Ford Eco Boost mustng uses forged steel as a CR. There is
always been a thug of war in automobile industry to choose the
type of connecting rod material. In this research forged steel and
aluminum 7075 material is used as a connecting rod material.
CAE analysis is carried out to pick the better material. Computer
aided Engineering team in a company performs analysis on all
the real world problems using various software by applying real
world constraints to get solutions. Every company is equipped
with a CAE team which is perform a detailed analysis on the
connecting rod in every automobile companies by applying
combustion chamber constraints like pressure, inertia forces.
This team done with a real time results after the analysis is
carried out. If the CAE team approves the design then the actual
production of the part run. The connecting rod selected in this
analysis is under investigation to validate the stresses and
fatigue life of the component. If the connecting rod fails the
design requirement, a new design proposal is given where ever
necessary.
Adolf said that Connecting rod of composite material formed
from reinforcement fiber bound in the form of an endless loop
with constant cross-sectional area(A) and varying cross-
sectional shape, and said that endless loop of reinforcement
fibers enclosed by the jacket of aluminum, said connecting rod
comprising a connecting rod eye, a connecting rod shank and an
arc curved part of a connecting rod head in the form of a double
loop of reinforcement fibers which has cutouts in the vicinity of
the connecting rod head, and where in said arc curved part is
adapted to match a corresponding arc curved part and form a
circle with both curved parts forming the circle enlink by
expansion bolts
Webster (1983) performed three dimensional finite element
analysis(FEA) of a high-speed diesel engine connecting rod. For
this analysis they used the maximum compressive load which
was measured experimentally, and the maximum tensile load
which is essentially the inertia load of the piston assembly mass.
The load distributions on the piston pin end and crank end were
determined experimentally. They modeled the connecting rod
cap separately and also modeled the bolt pretension using beam
elements and multi point constraint equations.
Pai (1996) presented an approach to optimize the shape of
connecting rod subjected to a load cycle consisting of the inertia
load deducted from gas load as one extreme and peak inertia
load exerted by the piston assembly mass as the other extreme,
with fatigue life constraint. Fatigue life defined as the sum of the
crack initiation and crack growth lives; it was obtained using
fracture mechanics principles. The approach used FEA Routine
to first calculate the displacements and stresses in the rod; these
were used in a separate routine to calculate the total life. The
stresses and the life were used in an optimization routine to
evaluate the objective function and factor. The new search
direction was determined using finite difference approximation
with design sensitivity analysis. The author was able to reduce
the weight by 30%, when compared with the original
component.
Serag (1989) developed approximate mathematical formula to
define connecting rod weight and cost as objective functions and
also the constraints. The optimization was achieved using a
Geometric Programming technique. Constraints were imposed
on the compression stress, the bearing pressure at the crank and
the piston pin ends. Fatigue was not addressed. The cost
function was expressed in some exponential form with the
geometric parameters.

4. CONNECTING ROD DESIGN

Being one of the critical intermediate part in an internal

combustion engines design, the CR must be able to withstand
loads and transmit a major deal of power. It’s no longer surprise
that a failure in a connecting rod can be one of the most costly
and damaging failures in engine. But it is important to
understand the dynamic condition.
The different forces which acting on the connecting rod are
discussed below:
1. Forces on the piston because of gas pressure and inertia of the
reciprocating parts.
2. Force because of inertia of the connecting or inertia bending
forces.
3. Force because of friction of the piston rings and of the piston.
4. Forces because of friction of the piston pin and crank pin
bearing.

Fig4. Forces acting on the connecting rod

Forces on the piston because of gas pressure,

---------- (a)
Inertia force of the reciprocating part,

------ (1)
Total force acting on the piston or piston pin
Fp = Force due to gas pressure ± inertia force = FL ± FI
The negative sign is indicate the piston moves from TDC to
BDC and positive sign indicate piston moves from BDC to
TDC. When weight of the reciprocating parts (WR = m.R.g) is
consider, then
FP = FL ± FI ± WR--------- (2)
The force FP gives increasing to a force FC in the CR and the
thrust FN on the sides of the cylinder walls from fig.4 we see
that force in the connecting rod at any instant is,

------- (3)
The force in the CR would be max when the crank and the
connecting rod are perpendicular to each other (i.e. θ = 90°). But
at this position, the pressure of gas would be decreased
considerably. Thus, for all practical concern, the force in the
connecting rod FC is taken equal to the maximum force on the
piston due to pressure of gas FI, neglecting piston inertia effects.

Forces because of the inertia of the connecting rod,

The inertia forces would be opposite to the direction of
acceleration forces. The inertia forces can be resolved into two
components, one is parallel to the connecting rod and the other
is perpendicular to the rod. The parallel components add up to
the force acting on the connecting rod (CR) and produces thrust
on the pins. The perpendicular components produces bending
action and the stresses induced in the connecting rod is called
bending stress(BM).

Fig. 5 Bending stresses

Variation of the inertia force on the connecting rod is linear and
is like a simply supported beam of variable loading as shown in
fig.2.Assuming that the connecting rod is of uniform cross-
section and has mass m1 kg per unit length, therefore,
1. Inertia forces per unit length at the crank pin=m1*w2 r
2. Inertia forces per unit length at piston pin=0
3. Inertia force due to small element of length dx at distance x
from piston pin p, dFI=m1*w2 *r*x/l*dx
4. Resultant inertia force

Since it has been assumed that 1/3rd mass of the connecting rod
is concentrated at piston pin P and 2/3rd at the crank pin,
therefore, the reaction at these two ends will be in the same
proportion i.e.,
RP=FI/3 and RC=2FI/3

In designing a CR, the following dimensions are required to be

determined.
• Dimensions of cross-section of the CR
• Dimensions of crankpin at big end and the piston pin at the
small end
• Size of bolts for securing the big end cap, and
•Thickness of the big end cap the procedure adopted in
determining the above mention dimensions are discussed below:
Dimension and cross-section of the CR is a machine
components which is subjected to alternating direct compressive
and tensile forces. Since the compressive forces are much higher
than the tensile forces, therefore the cross-section of the CR is
designed as the Rankine’s formula is used.
A CR, as shown fig.5 subjected to an axial load (W) may buckle
with X-axis as neutral axis or Y-axis as neutral axis. The
connecting rod is considered like both ends hinged for buckling
about X-axis and both ends fixed for buckling about Y-axis. A
connecting rod should be equally strong in buckling about the
axes.
Ixx and Iyy = Moment of inertia of the section about X-axis and
Y-axis respectively,
Kxx and Kyy = Radius of gyration of the section about X-axis
and Y-axis respectively
According to the rankine’s formula,

Where L = Equivalent length of the CR, and

a = Constant
= 1/75k, for MS
 = 1/9k for wrought iron
= 1/1.6k, CI

Fig6. Dimensions Of The CR

Thikness of the flange = t

Width of the section B = 4t
Depth of section H = 5t
Cross-sectional area A = 2(4t*t) + 3t*t = 11t*t
MOI of section about x-axis,

MOI of section about y-axis,

Since the value of Ixx/Iyy lies amidst 3 to 3.5, therefore, I-
section chose is quite satisfactory. After deciding the
proportions for I-sections of the connecting rod, its dimensions
are determined by considering the buckling of the rod about X-
axiS and applying Rankine’s formula and that is buckling load,

The buckling load may calculated by the following relations,

i.e., WB = Max force of gas X FOS. The factor of safety taken
as 5 to 6.
Note that the,
1. The I-section of the CR is used because of its lightness and to
keep the inertia forces as low as possible especially in case of
high speed engine. It can also withstand high gas pressure.
2. Sometimes a connecting rod have rectangular section. For
slow speed engines circular cross-sections may be used.
3. Since CR is manufactured by forging, therefore the sharp
corners of I-section are rounded off as shown fig 6 above. For
easy removal of section from dies. [1, 2, 3, 4]

6. ANALYSIS AND OPTIMIZATION

a) Modeling of connecting rod:

The modeling of connecting rod made up of forged still
was done in the creo parametric 3.0 after that load analysis,
stress analysis and total deflection done through the Ansys
workbench 13.0.
 Fig7. Drawing Of The CR

Fig8. Loading Condition At The Boundary

Fig9. Normal Stress

 Fig10. Total Deformation

b) Fatigue analysis:
When the connecting rod is applied cyclic loads like
pressure and inertia force, the material start to become
weaken, this is known as the fatigue. When the material is
subjected to repeatable cyclic loading, there will be
progressive and localized structural damage. The stress
developed will be always less than the yield stress and
ultimate stress, however due to repeated loading; the
material will fail from generations of crack to brittle
material like failure. This type of failure generation is very
hard to identify since the connecting rod is not visible to
naked eyes and it is inside the engine cylinder. This type of
failure is called throwing a rod as dicussed in the
introduction and the whole engine ceases. According to the
survey, 90% of the connecting rod failure is due to the
fatigue. Fatigue analysis is carried out to see if the CR
fulfills infinite life requirement, also if the CR fails, further
analysis is carried out to find value of the stress for which
the life of the CR increases to infinite and giving FOS of
value is 2.
 1. Minimum life of the CR is 500 cycles only.
2. CR is at high risk of failure as the minimum life of the
component is 500 cycles only.
3. It is the responsibility of the design engineer to redesign
the CR to give fatigue life of 10E6 cycles.

Figure11. Stress Versus Time Graph (S-N Graph)

Stress vr cycles to failure graph is plot. Sm, endurance limit,

and corrected endurance limit is add in the graph and Stress
value below 309 MPa gives the material infinite life.
The above stress value gives the CR infinite life and FOS of 2
and infinite fatigue life. This satisfies the design guide
requirement.
In real life situation, the material have lot of manufacturing
defects so the corrected endurance limit has to be found out by
finding out what are the possible errors that can be found.
Shigleys says, Mechanical engineering design hand book is very
unrealistic to consider the specimen to have an endurance limit
same as the one calculated for lab work. These constrains vary
in real life compared to lab specimen. Varies factors which
affects are like heat treatment, corrosion, surface tension, stress
concentration, Size, shape, life, stress, speed, fatigue, galling

7. NOMENCLATURE
 8. CONCLUSION

This overview research report studies the possibilities of weight

reduction in forged steel CR. For weight reduction process,
static strength was considered as a structural factor. First, the
connecting rod was 3D CAD modeled. After that load analysis
was performed using ANSYS software. From the results of the
study we will get the results as below:

It was analyzed that connecting rod is designed at its maximum

engine speed and maximum gas pressure (P).

As per the data getting from the finite element analysis (FEA),
there is a large clearance of material removal from big end area,
small end area and area connecting to the small end of the
connecting rod(CR).

It was also conclude that the connecting rod of titanium material

has higher mechanical properties and better machinability and
lower ductility and mainly has less weight compared to the steel
 9.REFRENCES
1. Pravardhan S. Shenoy A Thesis “Dynamic Load Analysis
and Optimization of Connecting Rod”.

2. Dr ramesh B T “Analysis and Optimization of Connecting

Rod With Different Materials”.

3. Vinayak Chumbre, Vinayak Kallannavar, Anilkumar

Shirahatti, Ratan Patil, Shirish M. Kerur “Design and
Comparative Analysis of Connecting Rod using Finite
Element Analysis”.

4. Dr. B S N Murthy, K. Adarsh Kumar, Mohammed Abdul

Shafeeq , S. Sai Sundara Praveen “Design and Analysis of
Connecting Rod for Weight and Stress Reduction”.

5. G. Naga Malleshwara Rao “Design Optimization and

Analysis of a Connecting Rod using ANSYS”.

6. Prateek Joshi, Mohammad UmairZaki “FEM Analysis of

Connecting Rod of different materials using ANSYS”.

7. Mr.Ruchir Shrivastava “ Finite Element Analysis Of

Connecting Rod For Two Wheeler And Optimization Of
Suitable Material Under Static Load Condition”

8. Ram Bansal “Dynamic Simulation Of A Connecting Rod

Made Of Aluminium Alloy Using Finite Element Analysis
 Approach” IOSR Journal Of Mechanical And Civil
Engineering (IOSR-JMCE)

9. Kuldeep B, Arun L.R, Mohammed Faheem “Analysis And

Optimization Of Connecting Rod Using
Composites”,ISSN: 2319-8753 International Journal Of
Innovative Research In Science, Engineering And
Technology.

10. Pravardhan S. Shenoy And Ali Fatemi ”Connecting

Rod Optimization For Weight And Cost Reduction”SAE
Technical Paper 2005-01-0987, 2005.

11. GVSS Sharma and P SrinivasaRao “Process Capability

Improvement Of An Engine Connecting Rod Machining
Process”Journal of Industrial Engineering International
2013.