DESIGN AND ANALYSIS OF

CONNECTING ROD USING FINITE

ELEMENT ANALYSIS
 ABSTRACT

In this project we are going to do static, modal analysis and of a

Connecting rod. Different materials are used for the making connecting
rods like Alloy steel , Titanium alloy, Aluminium alloy, cast iron alloy. We
take spheroidal graphite iron or nodular graphite iron material for
analysis in ASYS Workbench. Connecting rod is one of the most vital part
of an I.C. engine and used to transfer the reciprocating motion of piston
into the rotatory motion of crankshaft. It is heavily stressed during the
operation subjected to compressive stress due to the gas pressure and
tensile stress due to the Inertia force. The actual dimensions of the
connecting rod are considered and the model of the connecting rod is
designed in solid works and ANSYS is used for static and modal analysis
for finding von misses stresses, frequencies for three materials and
compared to choose the best material suitable for connecting rod.

C10 PROJECT BATCH

M.KRISHNAVAMSI(22985A0318)
V.SRISAI(22985A0331)
T.CHAITANYA(22985A0318)
B.HEMANTH(22985A0334)
G.SATYA SAI MANIKIRAN(22985A0342)
S.TEJA(22985A0374)
Project Guide:
 1

CHAPTER 1

INTRODUCTION
1.1 CONNECTING ROD

A Connecting rod is the part which connects the piston and the crank shaft. It
is the link between both parts. Small end part of the rod is connected to piston with the
help of the pin and the big end part of the rod is connected to the crank shaft. The
purpose of the Connecting rod is to provide fluid movement between piston and crank.

Fig 1.1: Connecting rod

Now a days the need of connecting rod is used in every type of automotive engines.
Like Diesel Engine, Straight or inline Engines, V-Type Engines, Boxer or flat engines.
These are type of automotive engine and all the engines cannot be used without the
use of Connecting rod.

Connecting rod is the backbone of the engine

A Connecting rod is the link between the reciprocating piston and rotating crank shaft.
Small end of the connecting rod is connected to the piston by means of gudgeon pin.
The big end of the connecting rod is connected to the crankshaft. The function of the
connecting rod is to convert the reciprocating motion of the piston into the rotary
motion of the crankshaft. The connecting rods are usually forged out of the open hearth
steel or sometimes even nickel steel or vanadium steel. For low to medium capacity
high speed engines, these are often made of duraluminium or other aluminum alloys.
However, with the progress of technology, the connecting rods these days are also cast
from malleable or spheroid graphite cast iron. In general, forged connecting rods are
compact and light weight which is an advantage from inertia view point, whereas cast
 2

connecting rods are comparatively cheaper, but on account of lesser strength their use
limited to small and medium size petrol engines.

It has mainly three parts namely- a pin end, a shank region and a crank end. Pin end is
connected to the piston assembly and crank end is connected to crankshaft. A
combination of axial and bending stresses act on the rod in operation. The axial
stresses are product due to cylinder gas pressure and the inertia force arising on
account of reciprocating motion. Whereas bending stresses are caused due to the
centrifugal effects. To provide the maximum rigidity with minimum weight, the cross
section of the connecting rod is made as and I – section end of the rod is a solid eye or
a split eye this end holding the piston pin. The big end works on the crank pin and is
always split. In some connecting rods, a hole is drilled between two ends for carrying
lubricating oil from the big end to the small end for lubrication of piston and the piston
pin.

1.2 TYPES OF CONNECTING ROD

There are many types of connecting rod with different I section and H section. But
there are basically two types of connecting rod.

1.2(a) Connecting rod with nut and bolt - The connecting rod with cap at the larger
end is joined by means of bolt and nut. This type of connecting rod is most widely
used in multi cylinder engines. For example: trucks, tractor etc.

Fig 1.2: Connecting rod with nut and bolt

 3

1.2(b) Connecting rod without nut and bolt - This type of connecting rod consist of
single parts itself. And mostly used in single cylinder engine. For example: bikes,
scooter etc.

Fig 1.3 connecting rod without nut and bolt

1.2(c) I-beam connecting rod:

I-beam connecting rods owe their name to their resemblance to a capital 'I'
when you cut them apart. Connecting rods with an I-beam are the most common typeof
connecting rods and thus the ones most often used in serial production. They are cheap
to manufacture and generally withstand more than they would actually need to in
standard engines. Standard I-beam connecting rods are often heavier than those with
an H-beam. These are very lightweight and often sustain up to 1,000 hp, which is
mainly due to the fact that they are milled out of solid, high-strength steel.

1.2(d) Connecting rod with H-beam:

The cross-section of connecting rods with an H-beam resembles a capital 'H',

which is where they get their name from. They are designed for engines that run with
a lot of hp at low speeds, usually charged engines with a turbocharger or compressor.
These are optimal to withstand the pressure from compression. One example of this is
our H-beam connecting rod for the 2.5L TFSI (Turbo fuel stratified injection) like in
the Audi RS3.
 4

1.2(e) X-beam, cross beam:

Connecting rods with an X-beam are the latest achievement from connecting
rod manufacturers. They are like a sort of hybrid between I-beam and H-beam and
combine the best properties of their predecessors. These connecting rods have a large
cross-section, thereby distributing the tension across the entire connecting rod.
Because of their high rigidity and crack resistance as well as minimal weight, they are
basically made for racing.

1.3 FAILURES IN CONNECTING ROD:

The connecting rod connects the pistons to the crankshaft. It converts the linear
motion of the pistons to the rotary motion of the crankshaft. On every stroke, the
connecting rod is stretched and compressed. This pressure, plus other factors, can
cause the connecting rod to break. The broken rod can go through the engine block
completely, ruining the engine--a condition known as "throwing a rod."

1.3(a) Fatigue:

Fatigue is the main cause of broken connecting rods--especially in older

engines. The constant compression during the power stroke and stretching during the
exhaust stroke, over thousands of times a minute, eventually wears the metal out and
it becomes brittle and finally breaks. If the oil is low or dirty it can speed up. this
process. Running the engine hot can also speed up the process.

1.3(b) Pin Failure:

The pin that connects the connecting rod to the piston (called the piston pin, or
gudgeon pin) gets a lot of wear. If this pin snaps the connecting rod is no longer
connected to the engine. For some engines this results in catastrophic engine failure,
the connecting rod goes through the engine block or the crankshaft is bent, but for
some engines it just causes a dramatic loss of power.

1.3(c) Over Revving:

Over revving is the main cause of connecting rod failures in new and high
performance engines. If the tachometer hits the red, even briefly, then the connection
 5

rods are in danger of breaking. This is because the forces acting on a connecting rod
increase dramatically at high revolutions. It does not matter if the tachometer is going
into the red because the car is travelling at a high speed, is going too fast in a low gear
or is simply going too fast because the accelerator is pressed too far while the car is in
neutral, the stress is simply too high at extremely high RPM's.

1.3(d) Hydrolock:

Hydrolock is a deformation of the connecting rod caused when water gets into
the piston chamber. This usually happens after the car has been driven through deep
water such as a flooded street. If only a little water gets into the cylinder the car makes
a knocking or tapping sound and it can be repaired but if enough water gets in the
cylinder that it takes up all the space available at spark time, the connecting rod will
bend or snap

Fig 1.4: Connecting rod that initially failed through fatigue, the further damaged
from impact with crankshaft
 6

1.4 PROBLEM STATEMENT

The objective of the present work is to design and optimize a connecting rod
based upon its material properties by using different materials (aluminium alloy,
titanium alloy, structural steel). The material of connecting rod will be optimized
depending upon the analysis result output. CAD model of connecting rod will be
modelled in CATIA V5 and then analysed in ANSYS Software. After analysis a
comparison will be made between existing material and alternate material which will
be suggested for the connecting rod in terms of stresses, factor of safety and the desired
output results can be achieved.

1.5 PROBLEM OBJECTIVE

1. Design and Analysis of the connecting rod based on the input parameters and then
modelling of the connecting rod in the CATIA V5 software.

2. FEM tool software ANSYS workbench is given model and material input based on
the parameters obtained.

3. To determine the Von-Misses stresses, Shear stress, Total Deformation and to

optimize in the existing Connecting rod design.

4. To calculate stresses in critical areas and to identify the spots in the connecting rod
where there are more chances of failure.

5. To determine the structural analysis and modal analysis of the connecting rod with
materials.

The main aim of the project is to determine the Von-Misses Stresses, Shear stress, on
which the new material can be compared with the existing material used for
Connecting Rod.
 7

CHAPTER 2

LITERATURE REVIEW

1) Kuldeep B, Arun L.R and Mohammed Faheem In their work connecting

rod is replaced by aluminium based composite material reinforced with silicon
carbide and fly ash. And it also describes the modelling and analysis of
connecting rod. FEA analysis was carried out by considering two materials.
The parameters like von misses stress, von misses strain and displacement
were obtained from ANSYS software. Compared to the former material the
new material found to have less weight and better stiffness. It resulted in
reduction of 43.48% of weight, with 75% reduction in displacement
2) D. Soorya Prabakaran and P. Ramachandran -The objective of their project
is to Evaluation of composite material connecting rod by using Aluminium
boron carbide. The connecting rods are commonly used in the internal
combustion engines and are subjected to millions of varying stress cycles
leading to fatigue failure. While the Composite connecting rods are lighter and
may offer better compressive strength, stiffness and fatigue resistance than
conventional connecting rods and their design still represents a major technical
challenge.
3) Sameer Nasir Momin and R.J. Gawande -This study incorporates FEA
modal analysis and experimental modal analysis of connecting rod. A
parametric model of Connecting rod is modelled using CATIA V5 R19
software and finite element analysis is carried out by using ANSYS Software.
Finite element method is used to determine natural frequencies of a connecting
rod and compare results with FFT analyzer. FFT analysis is done by hanging
the connecting rod at small end and experimental results were compared with
FEM.
4) Kumbha Sambaiah , Dr. A Rama Rao and Dr. M Mahesh they studied
about the optimization for connecting rod of internal combustion engine by
using two different materials like forged steel and C-70 connecting rods. For
fulfilling that need here we have selected typical forged steel or ultra-high
strength steel. This steel has strength level above 900MPa and this steel
generally have carbon content ranging from 0.01-0.45%. As strength increases,
 8

critical length/size of defect decreases. Once the critical length of the defect is
reached during processing or application, the material fails catastrophically
without any prior warning. Ultra high strength steels are classified according
to their composition microstructure. The steel C-70 has been introduced from
Europe as crack able forging steel.
5) ASHISH KUMAR and Er. SHUBHAM PARMAR The main aim of this
study is to analyze and optimize the Connecting Rod of Mahindra Pijo. This
research demonstrates the performance of a connecting rod basically depend
on its size optimization and material selection. The dimensions of the existing
connecting rod are measured with the help of a vernier caliper and micrometer.
The model of the connecting rod is designed in SOLIDWORKS with the
measured dimensions and the material of the existing connecting rod is SAE
8620 Finite Element Analysis (FEA) is used for the static structural and steady-
state thermal analysis of the connecting rod by considering the parameters such
as equivalent stress, von misses strain, maximum principal elastic strain, safety
factor and heat flux.
6) Adnan Ali Haider and Akash Kumar In this work, design and structural
analysis of connecting was performed. This work addresses the computation
of strength and deformation characteristics of a connecting rod. Finite element
method is used to analyse the connecting rod’s stress and deformation using
ANSYS Software. For this case, a fatigue and structural analysis will be
performed. The axial compressive load is greater than the axial tensile load.
Therefore, the design is only analyzed for the axial compressive loads. This
analysis shows the importance of the solution of the connecting rod
deformation in view of the changes in materials at the most important variants
of the stress. This variant is frequently overlooked and primary importance is
analyzed with the strength. Factor of Safety and the design of connecting rod
is checked and analyzed.
7) DR.B.K.Roy They have discussed about Various designs of connecting rod
have been analyzed in this report and finally an optimal design has been
selected for Finite Element Analysis. Using ANSYS-12.0 Workbench and
CATIA V5R19,Various results are found out and compared with the existing
results. It has been found out that the study presented here has came up with
 17

3.3 FINAL DIMENSIONS

Table 3.1 Parameters of Connecting Rod

Parameters Size (mm)

Thickness of the connecting rod 4.07

(t)
Width of the section (B = 4t) 16.28

Height of the section (H = 5t) 20.35

Height at the big end (H1) 22.35

Height at the small end (H2) 18.31

Inner diameter of the small end 17.94

Outer diameter of the small end 31.94

Inner diameter of the big end 23.88

Outer diameter of the big end 47.72

 24

4.2 STEP BY STEP DESIGN OF A CONNECTING ROD

STEP 1

Drawing small end and big end of connecting rod and rod

Fig 4.3: Catia v5 dimensions in 2D sketch

Fig 4.4: Extruding of small end, big end, shank and pocket in shank
 25

Fig 4.5: 3D structure of connecting rod