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J. Technological Advances and Scientific Res./ eISSN- 2454-1788, pISSN- 2395-5600/ Vol. 2/ Issue 01/ Jan-Mar. 2016 4

DESIGN AND ANALYSIS OF SIX CYLINDER FOUR STROKE ENGINE CRANK SHAFT

P. Preetham1, S. Srinivasa Prasad2

1Post Graduate Student, Department of Mechanical Engineering, Nova College of Engineering and Technology. 2Professor, Department of Mechanical Engineering, Nova College of Engineering and Technology.

ABSTRACT

The main objective of this study to analyze the average von-misses stress and principle shear stress over the crankshaft

using ANSYS Workbench software, the model creation can be created by well-known 3D modelling software SolidWorks.[1]

ANSYS will be used as a tool for analysis and optimization of crankshaft. The crankshaft conducting static analysis of the

crankshaft and dynamic analysis using modal analysis to find total deformation and frequency of the crankshaft. While

converting the reciprocating motion into rotary motion by the crankshaft, it is subjected to various stresses and vibrations. The

study to be carried out to check the load carrying capacity of the crankshaft. Static and dynamic analysis is conducted on the

structural steel crankshaft, Inconel x750 crankshaft of six cylinder four stroke engine.

KEYWORDS

Solid Works, ANSYS Workbench, FEM.

HOW TO CITE THIS ARTICLE: Preetham P, Prasad SS. Design and analysis of six cylinder four stroke engine crank shaft.

J. Technological Advances and Scientific Res. 2016;2(1):14-26, DOI: 10.14260/jtasr/2016/3

INTRODUCTION

The crankshaft plays a vital role in all Internal Combustion

Engine. It is a large component, which converts the

reciprocating displacement of the piston to a rotary motion

with a four link mechanism. It has complex shape of geometry.

The crankshaft experiences a cyclic load, due to the cyclic load

fatigue failure occur over a period. The fatigue analysis has to

be considered in the design stage itself. The design and

development of crankshaft has always been an important task

for the production industry in order to reduce the

manufacturing cost of the product minimum weight possible

and proper fatigue strength and other functional

requirements. These improvements result in lighter and

smaller engines with better fuel efficiency and higher power

output. This study was conducted on a single cylinder four

stroke cycle engine. Two different crankshafts from similar

engines were studied in this research. The finite element

analysis was performed in four static steps for each crankshaft.

Stresses from these analyses were used for superposition with

regards to dynamic load applied to the crankshaft. Further

analysis was performed on the forged steel crankshaft in order

to optimize the weight and manufacturing cost.

The crankshaft, sometimes casually abbreviated to crank

is the part of an engine which translates reciprocating linear

piston motion into rotation. To convert the reciprocating

motion into rotation, the crankshaft has “Crank throws” or

“Crankpins,” additional bearing surfaces whose axis is offset

from that of the crank, to which the "Big ends" of the

connecting rods from each cylinder attach. It typically

connects to a flywheel to reduce the pulsation characteristic of

the four-stroke cycle and sometimes atorsional or vibrational

Financial or Other, Competing Interest: None. Submission 22-01-2016, Peer Review 25-01-2016, Acceptance 28-01-2016, Published 02-02-2016. Corresponding Author: P. Preetham, D. No. 13-245, Chandamama Peta, Nandigama-521185. E-mail: [email protected] DOI:10.14260/jtasr/2016/3

damper at the opposite end to reduce the torsion vibrations

often caused along the length of the crankshaft by the cylinders

farthest from the output end acting on the torsional elasticity

of the metal.

1.1 Objective of the project

The automobile industry is showing increased interest in the

replacement of crankshaft with Inconel x750 crankshaft due to

high strength to weight ratio. Therefore; this project aims at

comparative study of design parameters of a traditional

crankshaft assembly by performing dynamic analysis using

ANSYS Workbench software the maximum bending stress and

corresponding payload have to be determined by considering

the factor of safety. Determining and assessing the behaviour

of the different parametric combinations of the crankshaft,

their natural frequencies are compared with the excitation

frequencies at different speeds of the crankshaft.

II OVERVIEW OF CRANKSHAFT

2.1 Crankshaft definition

A crankshaft is used to convert reciprocating motion of the

piston into rotary motion or vice versa. The crankshaft consists

of the shaft parts which revolve in the main bearings, the crank

pins to which the big ends of the connecting rod are connected,

the crank arms or webs which connect the crankpins and the

shaft parts. The crankshaft depending upon the position of

crank, may be divided into the following two types. The

crankshaft is the principal member of the crank train or crank

assembly, which latter converts the reciprocating motion of the

pistons into rotary motion. It is subjected to both torsional and

bending stresses and in modern high-speed, multi-cylinder

engines these stresses may be greatly increased by resonance,

which not only renders the engine noisy, but also may fracture

the shaft. In addition, the crankshaft has both supporting

bearings (Or main bearings) and crankpin bearings and all of

its bearing surfaces must be sufficiently large so that the unit

bearing load cannot become excessive even under the most

unfavourable conditions.

At high speeds the bearing loads are due in large part to

dynamic forces-inertia and centrifugal. Fortunately, loads on

main bearings due to centrifugal force can be reduced and even


J. Technological Advances and Scientific Res./ eISSN- 2454-1788, pISSN- 2395-5600/ Vol. 2/ Issue 01/ Jan-Mar. 2016 Page 15

completely eliminated by the provision of suitable

counterweights. All dynamic forces increase as the square of

the speed of rotation. (i.e. FDynamic↑⇒Speed2 ↑).

2.2 Classification of crankshaft

Types of crankshaft

A crankshaft is composed of the crankpins, crank arms, crank

journals and driving ends. As a rule crankshafts are forged in a

single piece, but occasionally they are built up. Built-up

crankshafts are used in small single- and double-cylinder

motorcycle engines. The enclosed flywheels of these engines

take the place of the crank arms, the crankpin and crank

journals being bolted to the flywheels, which latter are cast

with solid webs. The built-up construction also has advantages

when it is desired to support the crankshaft in three or more

ball bearings, as with a one-piece shaft all intermediate

bearings would have to be stripped over the crank arms and

therefore would have to be made extraordinarily large. A

crankpin together with the two crank arms on opposite sides

of it is frequently referred to as a “Throw.” In some crankshafts,

there is only a single throw between a pair of main journals or

supporting bearings.

2.2.1 Based on the position of the crank pin

Overhung crankshaft or side crankshaft

Centre crankshaft

Fig. 2.2.1: Overhung crankshaft or side crankshaft

Fig. 2.2.2: Center crankshaft

2.3 Major parts of crankshaft

The major parts of crankshaft are shown in the below figure.

These figure illustrates the assembly of the crankshaft and

elucidates each and every part of the crankshaft, which is

assembled as in the figure. Every part assembled as in the

figure is elaborated and explained below.

Fig. 2.3: Crankshaft parts

Counter weight

Flywheel mounting flange

Oil hole

Main bearing journal

Main journals

2.3.1 Crank-Throw

This is the distance from the main journal centers to the big-

end-journal centers. It is the amount the cranked arms are

offset from the center of rotation of the crankshaft shown in

Fig 3.3. A small crank-throw reduces both the crankshaft

turning effort and the distance the piston moves between the

dead centers. A large crank-throw increases both the leverage

applied to the crankshaft and stroke of the piston.

2.3.2 Crank-Webs

These are the cranked arms of the shaft, which provide the

throws of the crankshaft. They support the big-end crankpin.

They must have adequate thickness and width to withstand

both the twisting and the bending effort, created within these

webs. But their excessive mass causes inertial effect, which

tends to wind and unwind the shaft during operation.

2.3.3 Main bearing Journal

Main-journal is the parallel cylindrical portions of the

crankshaft, supported rigidly by the plain bearings mounted in

the crankcase. The journals diameter must be proper to

provide torsion strength. The diameter and width of the

journal should have sufficient projected area to avoid

overloading of the plain bearing.

2.3.4 Connecting-Rod Big End (Crankpin) Journals

These journals have cylindrical smooth surfaces for the

connecting-rod big-end bearings to rub against.

Fig. 2.3.4: Model of crankshaft



2.4 Function of crankshafts in IC engines

The crankshaft, connecting rod and piston constitute a four bar

slider crank mechanism, which converts the sliding motion of

the piston (Slider in the mechanism) to a rotary motion. Since

the rotation output is more practical and applicable for input

to other devices, the concept design of an engine is that the

output would be rotation. In addition the linear displacement

of an engine is not smooth, as the displacement is caused by

the combustion of gas in the combustion chamber. Therefore,

the displacement has sudden shocks and using this input for

another device may cause damage to it. The concept of using

crankshaft is to change these sudden displacements to a

smooth rotary output, which is the input to many devices such

as generators, pumps and compressors.

Crankshaft must be strong enough to take the downward

force of the power stroke without excessive bending, so the

reliability and life of the internal combustion engine depend on

the strength of the crankshaft largely. The crank pin is like a

built in beam with a distributed load along its length that

varies with crank positions. Each web is like a cantilever beam

subjected to bending and twisting. 1. Bending moment which

causes tensile and compressive stresses. 2. Twisting moment

causes shear stress. There are many sources of failure in the

engine one of the most common crankshaft failure is fatigue at

the fillet areas due to the bending load causes by the

combustion.

The moment of combustion the load from the piston is

transmitted to the crankpin, causing a large bending moment

on the entire geometry of the crankshaft. At the root of the fillet

areas stress concentrations exist and these high stress range

locations are the points where cyclic loads could cause fatigue

crank initiation leading to fracture.

2.5 Working of crankshaft in general

Power from the burnt gases in the combustion chamber is

delivered to the crankshaft through the piston pin and

connecting rod. The crankshaft changes reciprocating motion

of the piston in cylinder to the rotary motion of the flywheel.

Conversion of motion is executed by use of the offset in the

crankshaft. Each offset part of the crankshaft has a bearing

surface known as a crank pin to which the connecting rod is

attached. Crank-through is the offset from the crankshaft

centre line. The stroke of the piston is controlled by the throw

of the crankshaft. The combustion force is transferred to the

crank-throw after the crankshaft has moved past top dead

centre to produce turning effort or torque, which rotates the

crankshaft. Thus all the engine power is delivered through the

crankshaft. The cam-shaft is rotated by the crankshaft through

gears using chain driven or belt driven sprockets. The cam-

shaft drive is timed for opening of the valves in relation to the

piston position. The crankshaft rotates in main bearings, which

are split in half for assembly around the crankshaft main

bearing journals.

Both the crankshaft and camshaft must be capable of

withstanding the intermittent variable loads impressed on

them. During transfer of torque to the output shaft, the force

deflects the crankshaft. This deflection occurs due to bending

and twisting of the crankshaft. Crankshaft deflections are

directly related to engine roughness. When deflections of the

crankshaft occur at same vibrational or resonant frequency as

another engine part, the parts vibrate together. These

vibrations may reach the audible level producing a ―thumping

sound. The part may fail if this type of vibration is allowed to

continue. Harmful resonant frequencies of the crankshaft are

damped using a torsional vibration damper. Torsional stiffness

is one of the most important crankshaft design requirements.

This can be achieved by using material with the correct

physical properties and by minimizing stress concentration.

The crankshaft is located in the crankcase and is

supported by main bearings. Figure 3.62 represents schematic

view of a typical crankshaft. The angle of the crankshaft throws

in relation to each other is selected to provide a smooth power

output. V-8 engines use 90-degree and 6 cylinder engines use

120-degree crank throws. The engine firing order is

determined from the angles selected. A crankshaft for a four

cylinder engine is referred to a five bearing shaft. This means

that the shaft has five main bearings, one on each side of every

big end, which makes the crankshaft very stiff and supports it

well. As a result the engine is normally very smooth and long

lasting.

Because of the additional internal webs required to

support the main bearings, the crank case itself is very stiff.

The disadvantages of this type of bearing arrangement are that

it is more expensive and engine may have to be slightly longer

to accommodate the extra main bearings. Counter weights are

used to balance static and dynamic forces that occur during

engine operation. Main and rod bearing journal overlap

increases crankshaft strength because more of the load is

carried through the overlap area rather than through the fillet

and crankshaft web. Since the stress concentration takes place

at oil holes drilled through the crankshaft journals, these are

usually located where the crankshaft loads and stresses are

minimal. Lightening holes in the crank throws do not reduce

their strength if the hole size is less than half of the bearing

journal diameter, rather these holes often increase crankshaft

strength by relieving some of the crankshaft’s natural stress.

Automatic transmission pressure and clutch release forces

tend to push the crankshaft towards the front of the engine.

III MODELLING ON CRANKSHAFT

The software used for Modelling of crankshaft SOLID WORKS

and software it is developed by Dassault Syste mes. This is

CAD/CAM/CAE software, but we are using this for only 3-D

part modelling (CAD). This CAD includes. [2]

3.1 Steps involved in design of crankshaft

1. Open solid works software.

2. Open new part drawing.

3. Go to sketch command, select front plane.

4. Draw the profile using circle and fillet as per the

dimensions.

5. Exit the sketch and enter into feature manager and select

boss-extrude.

6. Extrude the object as per the dimension.

7. Again come to sketch manager and select plane1 and

draw a circle.

8. Exit sketch and extrude the selected sketch up to the

given dimension.

9. Draw a circle in the same plane and extrude it.

10. Repeat the same procedure by selecting up to 8 planes.

11. Revolve the required entities using sketch command.

12. Fillet all the sharp edges in the model.

13. Save the drawing in .x_t format.



Fig. 3.1: In this figure shows that designing of crank web

from sketch tool bar

Fig. 3.2: In this figure draw a circle on web and use the

same command to extrude

Fig. 3.3: In this figure again draw the same web from sketch

tool bar and extrude by using boss extrude command

Fig. 3.4: In this figure copy the crank web already

drawn on planes

Fig. 3.5: In this figure follow the same to get six

cylinder positions

Fig. 3.6: In this figure use the command fillet to get smooth

surface on sharp edges



Fig. 3.7: This figure shows the top view of completed design of crankshaft.[3]

IV BASICS OF FINITE ELEMENT ANALYSIS

4.1 Introduction to F.E.A

The name finite element is of recent origin, through the

concept has been used for centuries. The basic philosophy is to

replace the actual problem into a simpler model, which will

closely approximate the solution of the problem at hand. A

continuum is divided into a much; two adjacent regions placed

side by side will have a common edge. It is assumed that the

elements are connected at nodal points and it is only there that

the continuity requirements are to be satisfied. Once the

discrimination is made, the analysis follows a rather set

procedure. The stiffness matrix of the individual element is

formulated. The forces are distributed in the real structure are

transformed to actually distribute in the real structure are

transformed to act at the nodal lines. Assembly of individual

elements is carried out to obtain stiffness matrix of the whole

structure. In the finite element analysis, therefore the

continuum is divided into a finite number of elements, having

finite dimensions and reducing the continuum from infinite

degree of freedom to finite degrees of unknowns. The problem

to be solved by the finite element method is done in two stages:

1. The element formulation.

2. The system formulation.

The first stage involves the derivation of the element

stiffness matrix. The next stage is the formulation of stiffness

and load of the entire structure.

Static analysis

Static analysis calculates the effects of steady loading

conditions on a structure while ignoring inertia and damping

effects, such as those caused by time – varying loads.[4]

Static analysis is used to determine the displacements,

stress, stains and forces in structures or components caused by

loads that do not induce significant inertia and damping

effects. Steady loading and response conditions are assumed,

that is the loads and structures response are assumed to vary

slowly with respect to time.[5]

The kinds of loading that can be applied in a static

analysis include externally applied forces and pressure.

Steady–state inertial forces (Such as gravity or rotational

velocity) Temperatures (For thermal strain).

Modal analysis

In many engineering applications, the natural frequencies of

vibration are of interest. This is probably the most common

type of dynamic analysis and is referred to as ‘Eigenvalue

analysis.’ In addition to the frequencies, the mode shapes of

vibration which arise at the natural frequencies are also of

interest. These are the undamped free vibration response of

the structure caused by an initial disturbance from the static

equilibrium position. This solution derives from the general

equation by zeroing the damping and applied force terms.

Thereafter, it is assumed that each node is subjected to

sinusoidal functions of the peak amplitude for that node.[6]

If we deal with an FE (Finite element) structure for which

there is more than one d.o.f., R is the load which contains the

moments as well as forces, K is the stiffness matrix, C is the

damping matrix and M is the mass matrix.

KD+CD+MD=R

D is the nodal velocity; D is nodal acceleration and D

amplitude (global) d.o.f. With no damping C=0. Vibration is

free if loads are either zero or constant. Vibration motion

consist of displacements that very sinusoidally with time

relative to the mean configuration Dm created by constant

loads Rc.

D = Dm + DSinωt Dm is the vector of nodal displacements

in vibration and w is the natural frequency in radians per

second.

Where Dm = K-1Rc hence Dm = K-1Rc

Substituting all this information and C = 0 we obtain

[K - ω2 M]D = 0

As the governing equation of undamped free vibrations,

mathematically it is called Eigenvalue problem. A natural

frequency may also be called as resonant frequency and ωi2 is

various called Eigenvalue, latent root or characteristic number.

A mode may also be called an Eigenvector, mode shape, normal

mode or principal mode the smallest non-zero ωi is called the

fundamental natural frequency of vibration.



Whereas the Eigenvalue, λ, is equal to the total number of

degrees of freedom in the model, each Eigenvalue or frequency

has a corresponding eigenvector or mode shape. Since each of

the Eigenvectors cannot be null vectors, the mode shapes are

also of interest to the engineer. These are normalized to the

maximum displacement of the structure. The Theoretical

solution implies that the structure will vibrate in any mode

shape indefinitely. However, since there is always some

damping present in any structure, the vibrations eventually

decay.

V DYNAMIC ANALYSIS OF CRANKSHAFT

5.1 Steps involved in ANSYS Workbench 14.5

1. Start menu-programs-ANSYS-ANSYS workbench.

2. Select finite element model in left menu bar and drag it

into the screen page.

3. Then import the model by using add input mesh.

4. After importing update the project.

5. Select static structural and drag into the screen.

6. Update the model and click setup.

7. Open the window and click static structural and insert

boundary conditions, pressure on the required areas.

8. Click solution and insert the solution parameters like

deformation, stress, strain, etc.

9. After inserting solve the model with given input

conditions.

10. To change the material go to geometry, select the model

and import new material.

11. Repeat the same procedure for different materials.

12. Save the file in .igs format.

Import the IGS format file to ANSYS workbench 14.5 and

mesh the crankshaft

Fig. 5.1: Imported the IGS format of crankshaft to ANSYS

workbench

Fig. 5.2: Meshing of model carried out in ANSYS 14.5

Mesh the Crankshaft

Mesh Statics:

Type of Element: Tetrahedrons

Number of Nodes: 753229

Number of Elements: 686492

5.2 STATIC STRUCTURAL ANALYSIS

A static structural analysis determines the displacements,

stresses, strains and forces in structures or components

caused by loads that do not induce significant inertia and

damping effects.[7] Steady loading and response conditions are

assumed, that is the loads and the structure’s response are

assumed to vary slowly with respect to time. The types of

loading that can be applied in a static analysis include

externally applied forces and pressures, steady-state inertial

forces (Such as gravity or rotational velocity), imposed

(Nonzero) displacements, temperatures (For thermal strain).

5.2.1 Applying material-1 for crankshaft

PROPERTY VALUE YOUNGS MODULUS(E) 2X105MPA SHEAR MODULUS(G) 0.769X105MPA POISSON’S RATIO(µ) 0.3

DENSITY(ρ) 7850kg/m3 Table 5.2.1: Material I details

Define boundary condition for analysis

Boundary conditions play an important role in Finite Element

Analysis. Here, we have taken fixed supports on ends and

which acts as bearings.

Fig. 5.2.1.1: Fix the ends with roller support bearing as

shown in the figure

Fig. 5.2.1.2: The pressure 3.5 MPa is applied on the top of

the crankpin surface then apply pressure on the crankpin

as shown in the figure



Run the analysis and Get Results

Fig. 5.2.1.3: Total deformation(mm)

Fig. 5.2.1.4: Crankshaft von Mises stress (MPa).[8]

Fig. 5.2.1.5: Crankshaft shear stress (MPa)

5.2.2 Applying material-2 for crankshaft

PROPERTY VALUE YOUNGS MODULUS(E) 213.7KN/mm2 SHEAR MODULUS(G) 218.0KN/mm2 POISSON’S RATIO(µ) 0.29

DENSITY(ρ) 8.28X1000kg/m3 Table 5.2.2: Material II details

Fig. 5.2.2.1: Total deformation (mm)

Fig. 5.2.2.2: Crankshaft von Mises stress (MPa)

Fig. 5.2.2.3: Crankshaft shear stress (MPa)

MATERIAL TOTAL

DEFORMATION (mm)

EQUIVALENT STRESS (MPa)

SHEAR STRESS (MPa)

STRUCTURAL STEEL

0.0084988 4.2822 0.84067

INCONEL X750

0.0077197 4.2409 0.84445

Table 5.2.3: Results of structural analysis of two materials

5.3 MODAL ANALYSIS

In order to determine fundamental mode shapes and

corresponding natural frequencies, Modal Analysis of the

modified design of crankshaft is to be done.[9] Modal analysis



is a technique to study the dynamic characteristics of a

structure under vibrational excitation. Natural frequencies,

mode shapes and mode vectors of a structure can be

determined using modal analysis. Modal analysis allows the

design to avoid resonant vibrations or to vibrate at a specified

frequency and gives engineers an idea of how the design will

respond to different types of dynamic loads.

5.3.1 Material I details

Material type:- Structural steel

Poisson ratio:- 0.3

Young’s modulus:- 2x105 MPa

Fig. 5.3.1.1: First mode of vibration

Fig. 5.3.1.2: Second mode of vibration

Fig. 5.3.1.3: Third mode of vibration

Fig. 5.3.1.4: Fourth mode of vibration

Fig. 5.3.1.5: Fifth mode of vibration

Fig. 5.3.1.6: Sixth mode of vibration

Fig. 5.3.1.7: Seventh mode of vibration



Fig. 5.3.1.8: Eighth mode of vibration

Fig. 5.3.1.9: Ninth mode of vibration

Fig. 5.3.1.10: Tenth mode of vibration

5.3.2 Material II details

Material type:- Inconel X750

Poisson ratio:- 0.29

Young’s modulus:- 213.7KN/mm2

Fig. 5.3.2.1: First mode of vibration

Fig. 5.3.2.2: Second mode of vibration

Fig. 5.3.2.3: Third mode of vibration

Fig. 5.3.2.4: Fourth mode of vibration



Fig. 5.3.2.5: Fifth mode of vibration

Fig. 5.3.2.6: Six mode of vibration

Fig. 5.3.2.7: Seventh mode of vibration

Fig. 5.3.2.8: Eighth mode of vibration

Fig. 5.3.2.9: Ninth mode of vibration

Fig. 5.3.2.10: Tenth mode of vibration

5.3.3 RESULTS OF MODAL ANALYSIS

VI RESULTS AND CONCLUSION

MODES 1 2 3 4 5 6 7 8 9 10

STRUCTURAL STEEL 1.753 1.753 1.766 1.655 2.114 2.977 2.2866 2.3458 3.1889 3.1793

INCONEL X750 1.707 1.707 1.72 1.611 1.611 2.891 2.276 3.10 3.06 3.38

Table 5.3.3: Results Modal Analysis

6.1 INTRODUCTION

From the two material specifications, the crankshaft is

performed dynamic analysis to find the maximum safe stress

and the corresponding pressure. And also modal analysis is

performed for various parametric combinations to find the

natural frequencies and mode shapes to find the behaviour of

the crankshaft. And these natural frequencies are compared

with the excitation frequencies.



6.2 STATIC STRUCTURAL ANALYSIS

Static structural analysis is performed to crankshaft total

deformation, von Mises stress, shear stress by using ANSYS

workbench 14.5 software and the results are compared

between two different materials at a pressure 3.5 MPa.

6.2.1 Static analysis performed on steel material.[10]

Material properties 1:

Material type:- Structural steel

Poisson ratio:- 0.3

Young’s modulus:- 2x105 MPa

Material II details:

Material type:- Inconel X750

Poisson ratio:- 0.29

Young’s modulus:- 213.7KN/mm2

MATERIAL TOTAL

DEFORMATION (mm)

EQUIVALENT STRESS (MPa)

SHEAR STRESS (MPa)

STRUCTURAL STEEL

0.0084988 4.2822 0.84067

INCONEL X750

0.0077197 4.2409 0.84445

Table 6.2.1: Results of structural analysis

6.3 MODAL ANALYSIS

In order to determine fundamental mode shapes and

corresponding natural frequencies, Modal Analysis of the

modified design of crankshaft is to be done. Modal analysis is a

technique to study the dynamic characteristics of a structure

under vibrational excitation. Natural frequencies, mode shapes

and mode vectors of a structure can be determined using

modal analysis. Modal analysis allows the design to avoid

resonant vibrations or to vibrate at a specified frequency and

gives engineers an idea of how the design will respond to

different types of dynamic loads.

MODES 1 2 3 4 5 6 7 8 9 10 STRUCTURAL STEEL 1.753 1.753 1.766 1.655 2.114 2.977 2.2866 2.3458 3.1889 3.1793

INCONEL X750 1.707 1.707 1.72 1.611 1.611 2.891 2.276 3.10 3.06 3.38 Table 6.3.1: Results of modal analysis

Modal analysis is performed on two materials of crankshaft; the above table shows ten modes of natural frequencies.

Line graph shows the difference of modes between two materials

Fig. 6.3.2: Shows comparison of two different materials

CONCLUSION

From the above results, Inconel X750 is subjected to less

deformation compared to remaining two materials.

The crankshaft design is also safe since the von Mises

stresses are within the limits.

From the obtained results structural steel has less

frequency compared to other two materials.

Mode shapes and modal frequencies are determined for

all the mode numbers using modal analysis.

The maximum deformation appears at the center of

crankpin neck surface.

The maximum stress appears at the fillets between the

crankshaft journal and crank cheeks and near the central

point journal.

From the results it is concluded that the crankshaft

design is safe since the von mises stresses are within the

limits.

The maximum deformation was located at the link

between main bearing journal and crankpin and crank

cheeks.

The resonance vibration of system can be avoided

effectively by appropriate structure design.



LITERATURE REVIEW

1. Rinkle Garg and Sunil Baghl.[1] have been analyzed

crankshaft model and crank throw were created by Pro/E

Software and then imported to ANSYS software. The result

shows that the improvement in the strength of the

crankshaft as the maximum limits of stress, total

deformation and the strain is reduced. The weight of the

crankshaft is reduced, thereby reduces the inertia force. As

the weight of the crankshaft is decreased this will decrease

the cost of the crankshaft and increase the IC engine

performance.

2. C.M. Balamurugan et al.[2] has been studied the Computer

aided Modelling and Optimization of crankshaft and

compare the fatigue performance of two competing

manufacturing technologies for automotive crankshafts,

namely forged steel and ductile cast iron. The three

dimensional model of crankshaft were created by solid

edge software and then imported to ANSYS software. The

optimisation process included geometry changes

compatible with the current engine, fillet rolling and

results in increased fatigue strength and reduced cost of

the crankshaft without changing connecting rod and

engine block.

3. Gu Yingkui, Zhou Zhibo.[3] have been discussed a three-

dimensional model of a diesel engine crankshaft were

established by using PRO/E software and analytical ANSYS

Software tool, it shows that the high stress region mainly

concentrates in the knuckles of the crank arm and the main

journal and the crank arm and connecting rod journal,

which is the area most easily broken.

4. Abhishek Choubey and Jamin Brahmbhatt.[4] have been

analyzed crankshaft model and 3-dimensional model of the

crankshaft were created by Solid Works Software and

imported to ANSYS software. The crankshaft maximum

deformation appears at the centre of crankpin neck

surface. The maximum stress appears at the fillets between

the crankshaft journals and crank cheeks and near the

central point journal. The edge of main journal is high

stress area.

5. R.J. Deshbhratar and Y.R. Suple.[5] have been analyzed 4-

cylinder crankshaft and model of the crankshaft were

created by Pro/E Software and then imported to ANSYS

software. The maximum deformation appears at the centre

of crankshaft surface. The maximum stress appears at the

fillets between the crankshaft journal and crank cheeks

and near the central point. The edge of main journal is high

stress area. The crankshaft deformation was mainly

bending deformation under the lower frequency and the

maximum deformation was located at the link between

main bearing journal and crankpin and crank cheeks. So

this area prone to appear the bending fatigue crack.

6. Solanki et al.[6] presented literature review on crankshaft

design and optimization. The materials, manufacturing

process, failure analysis, design consideration, etc. were

reviewed. The design of the crankshaft considers the

dynamic loading and the optimization can lead to a shaft

diameter satisfying the requirements of the automobile

specifications with cost and size effectiveness. They

concluded that crack grows faster on the free surface, while

the central part of the crack front becomes straighter.

Fatigue is the dominant mechanism of failure of the

crankshaft. Residual imbalances along the length of the

crankshafts are crucial to performance.

7. Meng et al.[7] discussed the stress analysis and modal

analysis of a 4 cylinder crankshaft. FEM software ANSYS

was used to analyze the vibration modal and distortion and

stress status of crank throw. The relationship between

frequency and the vibration modal was explained by the

modal analysis of crankshaft. This provides a valuable

theoretical foundation for the optimization and

improvement of engine design. Maximum deformation

appears at the center of the crankpin neck surface. The

maximum stress appears at the fillet between the

crankshaft journal and crank cheeks and near the central

point journal. The crankshaft deformation was mainly

bending deformation was mainly bending deformation

under the lower frequency. Maximum deformation was

located at the link between main bearing journal and

crankpin and crank cheeks. So the area prone to appear the

bending fatigue crack.

8. Guangming and Zhengfeng.[8] performed study on

torsional stiffness of engine crankshaft. Modified Ker

Wilson formula and Carter formula were employed to

calculate torsional stiffness of engine crank throw in the

case of different thickness and width of both sides of crank

throw. Furthermore, the finite element modals of crank

and free part of crankshaft linked to torsional dynamic

models were developed. Then the intrinsic torsional

vibration frequency of crank and free part of crankshaft are

carried out by finite element method. According to

mechanics of materials and empirical formula, a

theoretical calculation formula of crank torsional stiffness

is proposed in the conditions of the thickness and width on

both sides of crank throw are different. By calculation and

comparative analysis of a real crankshaft example to verify

the finite element analysis method and finite element

model is feasible.

9. Xiaoping et al.[9] sets the automatic solving model, which

integrates the parameters geometric module, finite

element analysis module, numerical calculation module.

This model was based on the multidisciplinary

collaborative design optimization platform, combining the

finite element analysis, variable structure parameters of

the design and the design of experiment. Then the sample

matrix is setup by Latin hypercube sampling method. The

sensitivity analysis, the main effect analysis and the

interaction analysis of the key structural parameters on

crankshaft fatigue strength were accomplished. Results

show that the crankshaft fillet radius has the greatest

influence on the crankshaft strength and the crank radius

has less influence on the crankshaft strength.

10. Ling et al.[10] conducted fatigue life prediction modeling

and residue life assessment based on Statistics of Historical

Working State (SHWS) at crankshaft using Fatigue Damage

Accumulation (FDA) theory. Dynamic response of typical

operation performance is analyzed with software ANSYS of

finite element analysis and high stress zone was found.

Then via rain flow cycle counting for stress time obtained

together with SHOP, fatigue load spectra of key parts are

compiled. Finally, FDA model is built up with nominal

stress method and residue life based on SHWS is predicted

for crankshafts of diesel engine. It was found that main

shaft journal of crankshaft near the power output side and



connected rod journal have relatively high stress and FDA

of the same time is relatively larger.

11. Bin et al.[11] investigated the vibration model of 480 diesel

crankshaft and the stress analysis of crankpin. Three

dimensional models of 480 diesel engine crankshaft and

crankpin were created through Pro E software. Finite

element analysis software ANSYS was used to analyze the

vibration model and the distortion and the stress status of

the crankpin. This explains the relationship between the

frequency and the vibration model. Stress analysis of

crankpin provides the maximum deformation and

maximum stress point. The crankshaft deformation was

mainly bending deformation under lower frequency. The

maximum deformation was located at the link between

main bearing journal and crankpin and crank cheeks. So

the bending crack was prone to appear at this area. The

maximum deformation appears the bottom of crank cheek.

The maximum stress appears at the transition radius of

crank cheek and connecting rod journal.

12. Gongzhi et al.[12] carried out dynamic strength analysis of

crankshaft for marine diesel engine. The finite element

models of crankshaft, bearing, piston and connecting rod

was created in ANSYS and simplified by substructure

technique. The result files of reduced models were

introduced into EXCITE software to create multi-body

dynamics calculation of crankshaft in one working cycle.

Compared with single crankshaft strength analysis, non-

linear multi-body dynamics method is closer to the actual

boundary conditions of the crankshaft load. Combining

AVL-EXCITE multi-body dynamics and ANSYS finite

element method analyzed the dynamic characteristics of

marine crankshaft. This shows that under normal

operating conditions, the maximum stress of crankshaft

occurs on journal fillet.

REFERENCES

1. Rincle Garg, Sunil Baghla. Finite element analysis and

optimization of crankshaft. International Journal of

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2. Balamurugan CM, Krishnaraj R, Sakhivel M, et al. Computer

aided modelling and optimization of crankshaft.

International Journal of Scientific and Engineering

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crankshaft based on PRO/E and ANSYS. Third

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International Journal of Advanced Engineering Reaserch

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6645.

7. Farzin H. Montazersadgh, Ali Fatemi. Stress analysis and

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AISI, August 2007.

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crankshaft crank using a geometrically restricted finite

element model. SAE technical paper no. 2002-01-2183,

Society of automotive engineers, warrendale, PA, USA.

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crankshaft sections under bending with consideration of

residual stresses. International Journal of Fatigue

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