INDIANINSTITUTEOFTECHNOLOGY(BHU),VARANASI

IIT(BHU),VARANASI

INTERNSHIPPROJECTREPORTON

FEASIBLESOLUTIONFORTHEPROBLEMOFSLIPPINGOFCRANKJOURNALFROMTHEGRIP

OFSPLIT-RINGDURINGFATIGUETESTING

WITH

BHARATFORGELTD.

UNDERTHEGUIDANCEOF

MrRAJESHMANE

SUBMITTEDBY

ARPITGUPTA

AND

PIYUSHRAJ

DURING

MAY2013-JUNE2013

Preface

Each and every report is prepared with a purpose. This report is also prepared

focusing on interpreting the relevant information of my summer internship

training. This report aims at providing brief details about an ongoing project in

the company regarding a feasible solution for the problem of slipping of crank

journal from the grip of split-ring during fatigue testing. The project report

focuses on exploring ways to implement the various engineering innovations in

order to combat the problem of slipping of crank during fatigue testing of it.

The prime objective of this project is to study the force distribution in the

present scenario using engineering simulation software like Ansys, which make

use of FEA (Finite Element Analysis) to calculate stress, force and

displacement fields and provide suggestions to redesign the ring for better

performance.

This report has been prepared to provide the answers to all these questions and

also discuss the various upcoming technologies. All the facts and figures

mentioned in this report are non-manipulative, true and unbiased to the best of

my knowledge.

The diagrams and explanatory text in each section provide definitive,

irrefutable knowledge about the fatigue testing of crankshaft. This internship

report will provide few solutions to the problem faced by the company

regarding the slippage of crankshaft during fatigue testing of it.

This report also includes the detailed profile of the Bharat Forge Ltd. as per the

various sources within the company itself.

It is hoped that this book will be able to answer all the questions of the given

context.

Finally, the successful completion of this project is attributed to my mentor Mr.

Rajesh Mane. The internship training in Bharat Forge Ltd. was the great

learning experience both at my academic & professional level.

Looking forward to the replies of my readers, mentors, and my teachers that

has always been a great source of inspiration and motivation for me.

ACKNOWLEDGEMENT

The experience at Bharat Forge Ltd. has certainly been full of learning and

numerous people are to thank for it.

First of all, we would like to thank Mrs. Leena Deshpande for providing us

with this valuable opportunity here at Bharat Forge. We would also like to

thank Ms. Shobha Ronimath and Ms. Sapna Gadh for their guidance during our

induction and after and for helping us with every process.

We extend our gratitude to Mr. Rajesh Mane for giving us this project and for

being our supervisor. His guidance and encouragement has made it possible for

us to complete this project and learn a lot from the experience. A token of our

gratitude also goes to all the people working in CAE/Fatigue testing lab for

their perpetual support in our times of need. Without their help, this project

would not have been possible.

A special thanks to all our co-interns for making this experience enriching and

memorable.

CONTENTS

ABOUT BHARAT FORGE LTD.

BHARAT FORGE IN PUNE (MUNDHWA)

INTERNSHIP MAIN REPORT

Introduction

Problem faced in split ring arrangement

Procedure opted for analysis

Requirement of clamping force

Analysis of actual clamping force

Redesigning of split ring

PERSONAL LEARNINGS AND EXPOSURE

REFERENCES

ABSTRACT The objective of this project is to find a feasible solution for the problem of

slippage of crank journal from the grip of split-ring during fatigue testing. The

split-ring and collar arrangement is used to clamp the crankshaft journal in the

inertia plates for bending fatigue testing. The grip is jarred open by the

vibrations induced by the Electrodynamic shaker. In case of torsion, only one

inertia plate is hung from the support while the other is hung on the crankshaft

itself. This arrangement can be fatal if the grip comes loose and the inertia

plate, being very heavy, falls and hence, split-rings are not used in this test at

present.

In case of bending, no such risk is present but erroneous results may still result

from this and in case of slippage, the operator has to do the assembly again.

Another difficulty is regarding the non-uniform distribution of forces on the

journal by the split-ring. It is observed that the fretting marks on the split-ring

are concentrated only on diametrical ends. Split-rings also pose the problem of

very long lead times as it is very difficult to assemble and disassemble the

specimen using them. Numerous bolts have to be tightened and loosened in

order to change the specimen. Another problem is that the target load cannot be

applied directly in one go. It has to be applied in small steps which take time to

actually start the test.

A new design for the journal clamp is undoubtedly required. The prime

objective of this project is to study the force distribution on the surface of the

journal in the present scenario using engineering simulation software like

Catia, which make use of FEA (Finite Element Analysis) to calculate stress,

force and displacement fields and also provide the amount of surface stress

applied on the journal by the split ring.

The project also contains detail theoretical calculation of the amount of

clamping force required by the journal to prevent the problem of slippage. The

report also provides various modified model with their detail force analysis

using Catia V5 in order to improve the performance of the fatigue testing

fixture. Thus various suggestions for the redesigning of the split ring for better

performance has been made with detail data analysis obtain using simulation

software.

ABOUT BHARAT FORGE

A PREFERRED TECHNOLOGY & ENGINEERING

DRIVEN DEVELOPMENT PARTNER

Bharat Forge is a forging company based in Pune, India. Bharat Forge Ltd.

(BFL) is a subsidiary of the Kalyani group which was founded by Nilkanthrao

Kalyani. Currently the chairman of the company is B.N. Kalyani, son of Dr. N

Kalyani. The company's international operations are carried out by its

subsidiary Carl Dan Peddinghaus GmbH.

Bharat Forge came into existence in year 1961. Forging began in 1967. The

forging was carried out through hammer forging. In 1991, first Forging

Modernization Division (FMD I) was established. It was based on hydraulic

presses which were bought from Muller-Weingarten and was the first robotic

division in India at the time. The second FMD (FMD II) was established in

1997, which was similar to the previous one apart from the capacity of the

presses which was enhanced to produce heavier and quicker output. Similarly,

the 3rd

FMD (FMD III) was established in 2005 and houses the largest press in

Pune plant (16500 MT).

BFL today has the largest repository of metallurgical knowledge in the region

and offers full service supply capability to its geographically dispersed

marquee customers from concept to product design, engineering,

manufacturing, testing and validation.

The world's largest forging company with manufacturing facilities spread

across India, Germany and Sweden, Bharat Forge manufactures a wide range

of high performance, critical & safety components for the automotive & non-

automotive sector. It is India's largest manufacturer and exporter of automotive

components and leading chassis component manufacturer in the world. BFL's

customer base includes virtually every global automotive backed by several

decades of experience in component manufacturing & metallurgy, the company

is now looking beyond automotive and has embarked on an ambitious and

exciting journey to redefine its already existing presence across several critical

business verticals such as oil & gas, power, locomotive & marine, aerospace,

metals & mining, construction and general engineering.

Bharat Forge will use its strong platform of metallurgical knowledge, design &

engineering capability and manufacturing prowess, to create a strong position

for itself in these sectors. Expanding into new horizons will give Bharat

Forge a completely new growth perspective.

Bharat Forge's machining facilities are world-class and comparable to the best

in the industry. Their state-of-the-art machining facility is the largest of its kind

and has a crankshaft machining capacity of 650,000 units per annum. In

addition, the facility also has the capacity to machine 500,000 Front Axle

Beams and 750,000 Steering Knuckles per annum.

Bharat Forge's Machining facilities include Crankshaft Machining, Front Axle

Beam Machining, Steering Knuckle Machining, Oil and Gas Sector Machining.

Bharat forge Ltd annual turnover is around $2.5 billion. The company follows a

derisked model where if any of the sector is down then it is stabilized by the

other sectors of the company.

It has nine manufacturing plants in India, Germany, Sweden, United States,

Scotland, United Kingdom and mainland China. Backed by a full service

supply capability and dual-shore manufacturing model, Bharat Forge provides

end-to-end solutions from product conceptualization to designing and finally

manufacturing, testing and validation.

In Bharat Forge Ltd. products are produced both by

Closed Die Forging process

Open Die Forging process

Generally closed die forging process is used to produce automobile

components like Crankshafts, Connecting Rods, and Axle Beam etc. While

open die forging is used for producing components of various sectors like

Marine, Defence, Aerospace, and Oil & Gas.

In Bharat Forge, Forging began right from the manufacturing of Die till the

production of the finished product as per the customers requirement. Bharat

Forge LTD has joint ventures with companies like ArvinMeritor, Carpenter

Technology Corporation, FAW Corporation etc.

BFL CORE OBJECTIVE

To be committed to listening and responding to the needs of our customers,

associates and business partners and honoring their individual value.

To be committed to an entrepreneurial spirit that fuels the growth of our

companies and increases shareholder value.

BHARAT FORGE LTD. PUNE

(Mundhwa)

Bharat Forge has 4 plants in India, all of which are in Maharashtra region. They

are:

Mundhwa : Its the main plant of BFL and has all types of forgings

techniques available within .

Baramati : This plant is specialized in ring-rolling process mainly

Chakan : In this Mostly machining processes are prevalent

Satara : Largest plant for heavy forging (Open-die forging)

BHARAT FORGE IS ONE OF THE FEW GREEN FORGING

COMPANIES IN THE WORLD, WITH MAJORITY OF ITS

POWER PRODUCED BY RENEWABLE RESOURCES.

Over the years Bharat Forge has created world-class capacities and

capabilities. Our forging facilities consists of fully automated forgings

press lines ranging from 1600T to 16000T. With a global installed

forging capacity of 560,000 TPA, BFL India (Mundhwa Plant) is the

world's largest single location forging facility with an installed capacity

of 300,000 TPA. All forging press lines are highly flexible, which gives

the company the inherent advantage to simultaneously meet different

customer demands and optimize production. This allows Bharat Forge to

meet the growing demands of its customers continuously.

Bharat Forge Ltd (BFL) Mundhwa plant is divided into following major

departments:

Sales/ITD (International Trade Dept.)

Profit Planning Control (PPC)

Material Dept.

Finance

Human Resource (HR)/ IR

Safety

Closed die forging division (CDFD) Engg.

Die Shop

Forge Shop (FMD I/II/III, HFD I/II)

Heat Treatment

Machine Control Division I/II

MTB

Metallurgical Quality Control

Security

Different types of Forging processes are performed in different departments of

the BFL starting from the designing of the component till the quality &

validation of the components. Whole process of production, from procuring

material to delivery of goods, goes schematically through various departments.

These departments are interlinked with one another for efficient production and

faster problem-solving. These departments are as follows:

Closed Die Forging Division Engg:

In order to produce a customers product, it first has to be designed virtually.

This task comes under CDFD Engg. which makes use of many designing and

simulating softwares to estimate, design and optimize a given specimen. The

process starts with estimation of force and energy required for the job by using

Ansys which is determined by the 2-D or 3-D drawings given by the customer.

Then it is sent to the design team which designs the tooling and die required for

the job with the help of AutoCAD. Once the die is designed, it is sent to CAD

department for its 2-D drawings to be generated which is carried out with the

help of softwares like Unigraphics, Catia and ProE. Afterwards, a 3-D

simulation software (Forge or Deform) gives necessary data about the thermal,

defect, stress and energy distribution in the forging. Finally, the drawing and

model are sent to the CAM department which writes the program for the CNC

machines to produce the required die. Finally the drawing is optimized using

various software.

Die Shop

Once the CDFD Engg. has issued the programs for CNC machines, the dies are

manufactured in the die shop. The general process outlook is as follows.

Firstly planning of the die to be manufactured for the given product is made i.e.

the amount of time required for the manufacturing of the die prior to product

manufacturing. . Finally dies are manufactured as per the required

specifications in High Speed Milling Machines (HSM). After this if there is

any wear or irregularities are there in the dies, then it is removed either through

welding (in case of smaller dies) or CNC machines (for bigger dies). Finally

surface finishing of the dies are made through Electron Discharge Machine

(EDM) followed by Benching (i.e. polishing of the die). Then the die is

checked in CMM and LMM machine for any defect present in the die after

final finishing of the die.

Heat Treatment

After press forging, the products are quenched and thus, develop brittleness or

sometimes, a customer has a special demand of heat treatment of the product.

Whatever the case maybe, all the heat treatments are carried out by this

department. Various processes available are annealing, normalizing, hardening,

nitriding (exclusively for dies), carbo-nitriding, iso-annealing and carbon

restoration. Annealing is process by which any residual stress due to thermal or

mechanical loading is relieved by heating. Carbo-nitriding is the process by

which case hardening is achieved for gears and other products. The shop has both batch-type and continuous-type furnaces. Various quenching media are

used which include water, oil, polymer and even air.

Forge Modernization Division I (FMD I)

This department came into existence in 1991. It is a press forge and houses 5

presses namely,

PTS 900 (16500 MT): It is a mechanical press and is the largest in BFL.

PSH 4.560 (4560 MT): It is a screw press and uses a large flywheel for energy transfer.

LKM 400 (4000 MT)

LKM 2.500 (2500 MT)

LMZ 2500 (2500 MT)

The general process of the division is as follows:

First billets are cut into suitable sizes and heated in an oil-fired surface to a temperature of 1280 degrees Celsius.

The heated billets are de-scaled with water jets at high pressure.

Then they are put into dies and pressed till they take the shape completely.

Forge Modernization Division II

This shop also follows the same process of forging as that of the FMD I/III.

Firstly raw material as per the given specification of the product are sorted and

cut in a band saw to the required dimensions. Then similar to FMD I here also

the cut billet is heated in the oil furnace where 72 billets are heated

simultaneously. After this the same procedure as that of FMD I/III is followed

of that of upsetting, trimming and padding. FMD II shop contains screw

presses of different capacity

1. 16000 ton

2. 6000 ton

3. 5000 ton

4. 2500 ton

Forge Modernization Division III

This division of Bharat Forge Ltd. comes under closed die Forge division.

Generally in this division the process used for forging is similar to that of FMD

I/II. This shop contains three screw presses, which are of following capacity

12500 metric ton

8000 metric ton

5500 metric ton

In this division firstly the raw materials in the forms of billets are cut into the

required dimensions as per the customers specifications for the product. Then

after this jobs were heated simultaneously in the oil furnace for a temperature

range of 1230-1300 Celsius. Then we pass the heated job through rolling

machine in order to increase its length and reduces the cross sectional area.

After that job is sent to main press where firstly job is placed in the blocker die

followed by finishing die in order to give the required shape. Then it is sent to

trimming press where the flash produced during the forging is cut out. After

this job is moved to padding press where it is straightened i.e. any bending that

is present in it is removed. Finally finishing is performed using short blasting or

short peening.

Heavy Forge Division I/II

This division comes under open die forging. These two shop is generally used

to produce products of critical shapes , which cannot be produced by the closed

die forging method. The products which are usually produced in this shop are

wind mill shafts, gear blanks, mining manifolds, camshafts etc. HFD I shop

contains a hydraulic press of 1600 Ton capacity (ZDAS). The shop also

contains QKK12T manipulator having carrying capacity of 12 Ton and travel

speed of 20-40 m/min. Similarily HFD II contains hydraulic press of 4000

metric ton as well as manipulator similar to that of HFD I. The shop also contains various types of furnaces like

1. Slow cooling furnace

2. Normalizing furnace

3. Tempering furnace

Forge Shop

This the oldest forging shop in Bharat Forge which uses Manual forging

technique unlike FMD I/II/III which uses automatic forging machines. This

shop contains Hammer Machine that is used for the forging of the job.

Generally it is used to produce heavy or complex shape products, which cannot

be manufactured, by FMD I/II/III shop. This shop can forge the given job both

vertically as well as horizontally unlike FMD in which only vertical forging is

done. Hammer used for forging in this shop is around 25000 pound. Hence it is

not used for mass production but only for the production of the complex

shapes.

Machined Components Division (MCD I)

MCD I is responsible for the grinding and finishing of the crankshafts that

come out of the pressing shops. This shop has 11 lines for crankshaft finishing

and 6 lines for non-crankshaft products (such as FAB assembly, knuckle,

reinforcement brackets and Al forgings). All the output of this shop is for

domestic sales only.The processes carried out on each line are roughly the

same which include milling of crank pin and journal, grinding of pin, journal,

flange and thrust collar, cutting of key-slot, drilling of centre holes and super-

finishing of the pin and journal to an average roughness of 0.07m. Finally it is

checked for the correct dimension using different types of gauges.

Machined Components Division II(MCD II)

This department was set up in 2004 and is fully automated. It has 4 production

lines and produces fully- finished crankshafts exclusively for export. The gantry system is fully automatic which reduces production time and lot

rejection, even with 24 machines per line. The process sequence is similar to

that of MCD I which includes grinding of flange, pin, journal, thrust collar,

super-finishing of pin and journal, cutting of keyways, drilling of end-holes.

The division produces 800 jobs per day. Tac time is 6.88 minutes per job.

Metallurgical Quality Control Division

MQC division is responsible for the control of material quality that is used in

the forging, both for dies and forgings. It houses apparatus for Jominy end-

quench test, Kinematic viscosity test, Universal tensile test machine, Hardness

machine etc. It carries out various tests on materials to find out the different

physical and chemical properties of raw materials which are different grades of

steels. Physical properties are also determined through microstructures which

are seen through high magnification microscopes. Chemical properties are

determined from the composition of the forging material.

Machine Tool Building (MTB)

MTB is a research and development department which caters to the needs of

the other departments. Its main objectives are to procure machinery for BFL,

re-condition grinding and milling, make super-finishing, gear-cutting and

hobbing machines. Another important objective of this division is to procure

old machines and repair them for further usage. A brand-new machine is very

expensive whereas an old machine can be bought and repaired quite cheaply.

These machines are for BFL plants only and are not sold outside the company.

A2 Line

This shop is generally performed the final machining and painting of the

products like crankshafts and front axle. Firstly the parting line grinding of the

job is done through a robotic machine (special purpose machine). Then end

grinding of the job is done followed by straightening and untwisting of the job.

After this job is sent for visual inspection in MPI (Magnetic Particle

Inspection) where job is magnetized and then seen under UV rays in order to

find whether there is any crack is present in work piece or not.

Environment Management Systems

BFL is an ISO-14001 certified company. It has five waste treatment plants

which are Effluent, Coolant, Acid, Graphite and Sewage Treatment Plant.

BFL also has air and noise monitoring to keep the air and noise pollution to a

minimum as they pose a threat to the environment as well.

Finance

This department handles all the checks and balances of the company. It has

some major sections as follows:

Cash and Bank Responsible for small cash payments and bank dealings.

Expense Keeps an account of expenditure incurred on companys behalf like travels, stationary etc.

Salary Processing payrolls and all other employee-related issues.

Payable Accounts for raw materials, machines and job contracts expenditures.

Receivables Accounts for payments made to the company.

Costing It controls job costings, budget and inventory.

Treasury Maintains investments and arranges long-term and short-

term finance.

Fixed Assets It accounts for the fixed assets (land, machines etc.),

their depreciation and other projects.

International Trade Division (ITD)/Sales

The marketing and sale of products to overseas buyers is carried out by the

ITD. BFL exports automotive parts to North and South America, Europe,

China and Japan and non-automotive parts worldwide. There are teams to

coordinate such sales, which are:

Documentation and Logistics team: They handle all the documentation and transport of the products. 99% of the product sold overseas is

shipped through cargo ships.

Sales and Marketing team: This team is responsible for capturing clients and expanding the companys foreign clientele. It markets the

companys products to potential buyers.

The domestic marketing and sale of the product is carried out by the sales

deptt. The procedure of sales deptt. Is similair to that of ITD starting from

product purchase till the dispatch of the of the product to the customer.

Safety

It employs 39 safety engineers and 23 fire engineers which are trained in fire-

fighting and safety measures should the need arise. Each department has an

HSE (Health, Safety and Environment) Representative who is responsible for

the safety regulations to be followed.

For safety regulations to be employed, one needs HIRA (Hazard Identification

and Risk Assessment). BFL employs Croners method for HIRA. Another lever

is the BBS or the Behaviour Based Safety which divides workers behaviours

into two categories Safe and Atrocious. Safe behaviour is what the worker

should exhibit as is expected from him/her as per the guidelines.

Each department is to carry out the following safety drills:

1. Plant safety inspection of one line per section per week.

2. Identification of two hazards per line per section and

implementation of its control.

3. One safety meeting per month.

4. Weekly tool box talk per line per section.

5. Reduction of oil consumption by eliminating oil leakage and

spillage.

6. One department of fire audit per month.

7. Fire Risk Assessment of one line per section per week

8. One equipment audit per month.

9. One safety Kaizen or suggestion per line per section per month.

Security

Bharat forge Ltd is in 86 acres Surrounded with 6 feet high stonewalls and

barbed wire. There are 100 guards in total at Bharat forge working in groups of

30 in 3 shifts. The next step in the security is the access control where each of

the employees are given the smart card and the visitors as well as the contract

workers are given the manual or smart passes. There is DFMA and Security

gate in order to check the access of the individuals coming inside the premises

Internship Main Report

INTRODUCTION

Crankshaft is a large component with a complex geometry in the engine,

which converts the reciprocating displacement of the piston to a rotary motion

with a four link mechanism. The crankshaft is one of the most critically loaded

components as it experiences cyclic loads in the form of bending and torsion

during its service life, fatigue performance and durability of this component has

to be considered in the design process.

Fatigue is a localized damage process of a component produced by cyclic

loading. It is the result of the cumulative process consisting of crack initiation,

propagation, and final fracture of a component. During cyclic loading,

localized plastic deformation may occur at the highest stress site. This plastic

deformation induces permanent damage to the component and a crack

develops. As the component experiences an increasing number of loading

cycles, the length of the crack increases. After a certain number of cycles, the

crack will cause the component to fail. Applied stresses may be axial (tension-

compression), flexural (bending) or torsional (twisting) in nature. In general

there are three possible fluctuating stress-time modes possible. The simplest is

completely reversed constant amplitude where the alternating stress varies from

a maximum tensile stress to a minimum compressive stress of equal magnitude.

The second type, termed repeated constant amplitude, occurs when the maxima

and minima are asymmetrical relative to the zero stress level. Lastly, the stress

level may vary randomly in amplitude and frequency which is merely termed

random cycling.

During fatigue testing, the test specimen is subjected to completely reversed

constant amplitude alternating loads until failure. The loads applied to the

specimen are defined by either a constant stress range (r) or constant stress

amplitude (a). The stress range is defined as the algebraic difference between

the maximum stress (max) and minimum stress (min) in a cycle:

r = (max - min )

The stress amplitude is equal to one-half of the stress range:

a= r/2= (max- min)/2

Typically, for fatigue analysts, it is a convention to consider tensile stresses

positive and compressive stresses negative.

The mean stress ( m) is defined as

m= ( max+ min)/2

The stress ratio is defined as the ratio of minimum stress to maximum stress:

R= max/min

When load ratio R=-1 then tensile & compressive stresses are same. This is the

kind of cyclic loading is given to the test specimen during fatigue testing of

crankshaft.

The setup of the vertical Bending Fatigue testing of crankshaft consists of

Inertia plates, Electrodynamic Shaker and Split ring along with a single throw

of crankshaft which when assembled together are put to completely reversed

constant amplitude cyclic loading with the help of the shaker which works

within the given frequency range as controlled by its controller in order to

provide a constant resonating condition to the test fixture. Resonating condition

to the specimen provide the worst case scenario for fatigue test as maximum

amplitude of vibration is attained during resonance condition to the fixture and

the specimen.

The electrodynamic shaker used for the test is a device that excites the

specimen or structure according to its amplified input signal. Several input

signals are available for modal testing, but the sine sweep and random

frequency vibration profiles are by far the most commonly used signals.

Test specimen is attached directly to the inertia plate. With some types of

shakers, an armature is often attached to the body to be tested by way of piano

wire (pulling force) or stringer (Pushing force). When the signal is transmitted

through the piano wire or the stinger, the specimen responds the same way as

impact testing, by attenuating some and amplifying certain frequencies. These

frequencies are measured as modal frequencies.

There are two methods that are used for the validation criteria of the crankshaft,

which are:

1. Maximum Bending Moment applied 2. Maximum stress at pin fillet

To measure either of the above, calibration is required to find the correct

arrangement for the test. Usually a load cell is placed between the shaker and

the structure to obtain the excitation force at the pin fillet. Then providing the

given bending moment to the test specimen does the calibration of the force

and then using linear interpolation or extrapolation the required force is

obtained and checked for the test failure criteria. Secondly, a strain gauge is

also placed on the pin fillet of the crankshaft in order to measure the micro

strain produce during the fatigue testing. Then the calibration of the strain for

given bending moment applied on the machine is done in order to obtain the

maximum stress on the pin fillet. Then using linear interpolation or

extrapolation the required stress at the fillet is obtained and checked for the

fatigue failure criteria for the given number of cycle which is given to the

specimen as per the customer or the company requirement. If the specimen

passes the failure criteria for the given number of cycles, then another

specimen of the same batch is tested for much harsh conditions by increasing

the bending moment. Shaker is connected to the inertia plate through the

stringer in which the crankshaft is fixed and as the vibration by the shaker to

the inertia plate is provided. Due to vibration the bending moment is produced

in the crankshaft and since vibration is of fluctuating nature an alternating

bending moment is produced which is measured using load cell for a given

number of cycles.

SPLIT-RING ARRANGEMENT

A split ring is a ring with a slit in its circumference to allow for easy elongation

and/or compression as per the external load. This range of deformation allows a

shaft or a journal (with diameter in a particular range) to be clamped in a

circular housing. It is a friction-type of clamping mechanism which eliminates

the use of keyways. It is useful in cases where notches are to be avoided at all

costs. One such example is the fatigue testing of crankshafts where the journal

is to be clamped in the fixture but without any keyways as they may err the

results of the test. Its arrangement is as shown below.

PROBLEMS FACED IN SPLIT RING

ARRANGEMENT

The two of the major problems faced in the mounting of crankshafts and their

testing are:

Non-uniform gripping of the journal by the ring After observing the fretting marks on the surface of the split ring, one

can clearly see that the forces are not distributed uniformly. Rather, they

tend to be concentrated on diametrically opposite ends. The marks can

be seen in the following picture.

Slipping of the journal from the ring during the test This is the major problem of the current split ring arrangement. For

certain crankshafts (KV-12 and KV-16), the crankshaft tends to slip out

of the ring due to improper clamping. It leads to erroneous results and

dangerous circumstances. Further, due to this phenomenon, the torsion

fatigue test does not employ the split rings. Rather, it depends on shrink

fits of the journals in collars which fit into inertia plate. While being

reliable, this method is time consuming as the company has to get it

fitted from other sources which add to the expenditure of the testing

facility.

Due to excessive fretting, the ring sometimes gets stuck in the collar and

during dis-assembly, has led to bolt failures. It can be seen in the

following pictures.

The solution of these problems requires redesigning of the ring so as to

increase the clamping force with minimal effort from the operator.

PROCEDURE OPTED FOR

ANALYSIS

Firstly the amount of force required for the clamping of the journal in

the test fixture is studied and calculated using basic mechanical theory

taking into consideration the different parameters which will affect the

clamping of the journal into the split ring. Having solved the problem of

clamping force required, then we look for the force which is actually

applied by the split ring on the journal in the original test arrangement

using Finite Element Analysis (FEA).

Once the applied clamping force is obtained for the given arrangement

of split ring and journal, we move towards the theoretical aspect of it

and calculate the amount of force experienced by the journal using basic

mathematical technique.

After doing so, we look for the redesigning of the split ring with the sole

objective of increasing the clamping force between the ring and the

journal so that we would be able to get the required amount of force as

calculated earlier. After doing so, we perform the job of redesigning of

the split ring. Different models were prepared and analysed for the

clamping force using FEA and checked with respect to the required

force.

We also find into the pros and cons of different models which we

designed and the one which is presently used in our analysis in order to

combat the problem of slippage between ring and journal.

REQUIREMENT OF CLAMPING

FORCE SIMPLIFIED STATIC ANALYSIS

To find the clamping force required by the fixture, we make the following

assumptions to simplify the mathematics involved and obtain a rough estimate

of the force. The assumptions made are as follows:

The plate remains vertical at all times. The journal is subjected to pure bending and thus, the pivot is at the

centre of the journal.

The journal, although subjected to bending, remains perfectly horizontal.

Friction is uniform around the circumference of the journal. Effect of gravity is neglected.

After applying these assumptions, the free body diagram of the plate is shown

in the figure.

Taking the moments about point A,

D x f = B.M.

D is the diameter of the shaft (or journal)

f is the friction force on journal by the ring

B.M. is the Bending Moment applied

For the given journal (KV-12), the bending moment required was found (via

calibration using load cell) to be 16000 N-m.

This gives the required friction f = (16000) / (0.165) = 96.9 kN

However, one must remember that this is a simplified static solution. The

conditions imposed are dynamic and the assumptions made may not hold true

every time. Thus, a design factor of safety needs to be included to avoid any

complications during the running of test.

STATIC ANALYSIS (CONSIDERING THE BENDING OF JOURNAL)

A little detailed analysis can be made while considering the bending of journal

to obtain a better estimate of the force required. It, however, still includes

assumptions from before but the bending of the journal is considered.

The journal is taken as a cylinder with diameter of 165 mm and the free body

diagram of the plate considering bending of journal is shown in the figure.

To find the angle made by the bent journal with the horizontal axis, we use the

deflection formula for pure bending,

|

E (Youngs Modulus) = 210 GPa (for steel)

I (Area moment of inertia)

L (Length of assumed journal) = 318.77 mm

M (Bending Moment) = 16000 N-m

On solving, one obtains = 0.019

Now we can solve the equations obtained from the free body diagram of the

plate.

On solving for friction, one obtains,

N (req) = Clamping force required

M = Bending moment applied

D = Diameter of the journal

= Coefficient of friction between ring and journal

= Angle made by the bent shaft with the horizontal

FACTOR OF SAFETY

Since the calculations made are for static case, a factor of safety needs to be

included to account for the dynamic load conditions. The factor is chosen as

per the following procedure.

FS(overall) = FS(material) x FS(geometry) x FS(stress) x FS(failure analysis) x

FS(reliability)

FS(material) = 1.1 (Material properties are known from a handbook or

manufacturers values)

FS(geometry) = 1.05 (Tolerances are average)

FS(Stress) = 1.25 (Nature of loads defined in an average manner with,

overloads of 20-50%, and the stress analysis may result in errors less than 50%)

FS(failure analysis) = 1.3 (Failure analysis is not well-developed)

FS(reliability) = 1.1 (Average reliability of about 92%)

Thus, FS (overall) = 1.1 x 1.05 x 1.25 x 1.3 x 1.1 = 2.065

The modified clamping force plot (with FOS = 2) is as follows,

Coefficient of friction

Force (in kN) (With FoS = 2)

0.1 1945.865889

0.2 971.3171267

0.3 647.1864751

0.4 485.2556143

0.5 388.1400838

0.6 323.4142977

0.7 277.190358

0.8 242.5271952

0.9 215.5697967

1 194.0056663

ANALYSIS OF ACTUAL

CLAMPING FORCE

The major problem with this arrangement is that it relies solely on friction

between the journal and the inner surface of the ring. Due to lack of any

positive contact, the journal is susceptible to slippage which has been quite

frequently observed in several tests. To circumvent this problem, one may

intuitively propose the increase of friction coefficient between the journal and

the ring. The following section explores various parameters which affect the

clamping force and can be modified to achieve maximum possible force.

Many other factors, other than friction between the ring and journal, include:

Friction between collar housing and split-ring,

Tapped holes misalignment,

Flexibility of the split-ring and the bolts,

Weight of the split ring,

Taper angle of the split-ring.

We now try to study and analyse each aspect and provide a suggestion to get

the better of the problem of slippage.

Friction between collar and split-ring & Taper of ring

and collar

An analysis of forces between the collar and the ring using elementary methods

of force balance yields the following relation between the radial force exerted

by the collar on the ring and the friction coefficient between the two,

(neglecting any other force or deformation)

[

]

is the taper angle of the ring and collar (1.9 degrees)

F(bolts) is the total axial force applied by the eight bolts screwed into the

assembly. The axial load can be easily found as the tightening torque is known

to be 85 N-m (specified by the wrench). This yields an axial force of 35 kN per

bolt (by the relation T = 0.2*F*d). This relation implies that the radial force

increases if the friction (or the taper angle ) is reduced.

Since a complete mathematical analysis is very complicated in this case, we

use FEA (Finite Element Analysis) to study the effect of friction coefficient

between the collar and ring and between ring and journal. Following is the

variation of clamping force with the two coefficients of friction obtained

through FEA.

(collar and ring) 0.7 (Collar and ring) 0.5

( ring &

journal)

C22

(MPa)

C33

(MPa)

Avg.

(MPa)

Clamping

force(kN)

C22

(MPa)

C33

(MPa)

Avg.

(MPa)

Clamping

force(kN)

0.05 5.537 5.524 5.5305 342.891 7.408 7.375 7.3915 458.273

0.1 5.3 5.274 5.287 327.794 6.791 6.744 6.7675 419.585

0.2 4.969 4.942 4.9555 307.241 6.235 6.19 6.2125 385.175

0.3 4.813 4.793 4.803 297.786 5.878 5.839 5.8585 363.227

0.5 4.48 4.458 4.469 277.078 5.37 5.339 5.3545 331.979

0.7 4.247 4.23 4.2385 262.787 4.957 4.929 4.943 306.466

0.9 4.09 4.074 4.082 253.084 4.61 4.584 4.597 285.014

*C22 and C33 represent normal surface stresses in non-axial directions of the

journal

The variations can be plotted graphically as shown,

0

50

100

150

200

250

300

350

400

450

500

0 0.5 1

0.7

0.5

Thus, we see that clamping force increases on reducing either of the two

friction coefficients. But, as we have seen before, the required clamping force

increases drastically as the friction between the journal and the clamp is

reduced. Hence, the friction coefficient needs to be optimized in order get

minimum requirement and maximum output.

However, the friction coefficient between collar and ring is to be made as low

as possible. Various ways to reduce friction includes:

Introduce lubrication, liquid or solid.

Improve the surface texture of the outer surface of the ring and inner surface of collar.

Thus, it is advised that the outer surface of the ring should be lubricated.

Note: Only outer surface should be lubricated, not the inner surface.

Tapped-holes misalignment

This is probably the major reason for low clamping force on the journal,

however, a rigorous mathematical calculation still eludes us. The tapped holes

in the ring and the collar are aligned when the ring is not tightened. As the ring

travels into the collar, the taper deforms the ring and shortens its diameter. This

tends to misalign the holes and thus, exerts a bending force on the bolts. Thus,

bolts act as cantilever beams under partially-uniform load and bend inwards

and consequently, act as leaf springs which push the ring outside, reducing

the actual force transmitted to the journal clamp. The evidence for this

phenomenon is the worn out threads of the bolts as seen the picture.

This theory is supported by the observation that the bolts used for tightening

the ring have worn-out threads in the region which enters into the split-ring

tapped hole. A rigid mathematical equation to define this phenomenon is

quite cumbersome and thus, an FEA model is proposed to account for this

factor. Possible remedies include; larger tolerance for tapped holes, flexible

material for bolts and, if possible, reduction in the number of bolts.

An analysis for reducing the number of bolts in the original test fixture was

carried out using FEA. The results are as follows,

NOTE: The following data has been evaluated taking coefficient of friction

between collar and ring as 0.7

Assembly with 8 bolts Assembly with 6 bolts

(Ring and

journal)

C22 C33 Avg. Clamping

force (kN)

C22 C33 Avg. Clamping force

(kN)

0.1 5.3 5.274 5.287 327.794 3.827 3.941 3.884 240.808

0.2 4.969 4.942 4.9555 307.241 3.481 3.409 3.445 213.59

0.3 4.813 4.793 4.803 297.786 3.397 3.259 3.328 206.336

0.5 4.48 4.458 4.469 277.078 3.361 3.118 3.2395 200.849

0.7 4.247 4.23 4.2385 262.787 3.358 3.061 3.2095 198.989

0.9 4.09 4.074 4.082 253.084 3.3 2.975 3.1375 194.525

C22 and C33 are normal surface stresses in non-axial directions of the journal

The plotted graph shows the variation between clamping force and friction

between ring and journal for assembly with 6 and 8 bolts. It is quite evident

that the number of bolts cannot be reduced as the clamping force reduces very

sharply with reduction in bolts.

Flexibility of the split rings and bolts

Just like the previous case, the ring also acts as a spring. And thus, it resists

any deformation and exerts a restoring force back on the collar. This force also

consumes a large part of the radial force exerted by the collar. Thus, there is a

need to increase the flexibility of the ring so that it can transmit maximum

force and can deform easily so that better wrapping can be achieved over the

journal.

0

50

100

150

200

250

300

350

0 0.2 0.4 0.6 0.8 1

8 bolts

6 bolts

This problem is very complex to be solved mathematically as it is a case of

uniform load on a curved circular beam. Thus, it also requires an FEA model

and calculation.

Possible remedies are: Adding kerfs or partial slits in the ring and

changing the material to a much flexible one (for instance spring steel).

An FEA analysis was carried out to see the effects of additional partial slits on

the gripping force. Following are the clamping forces for various coefficient of

friction between ring and journal with the friction between collar and ring

being 0.7.

(Between

ring and

journal)

C22

(MPa)

C33

(MPa)

Avg.

(MPa)

Clamping force (kN)

(With kerfs)

Clamping force(kN)

(Without kerf)

0.1 5.42 5.413 5.4165 335.823 327.794

0.2 5.094 5.097 5.0955 315.921 307.241

0.3 4.912 4.895 4.9035 304.017 297.786

0.5 4.617 4.634 4.6255 286.781 277.078

0.7 4.389 4.375 4.382 271.684 262.787

0.9 4.117 4.078 4.0975 254.045 253.084

The comparison can be seen on the following graph.

The difference in the clamping force is not appreciable. But, since, the

evaluation is only theoretical; its actual performance may be different. Thus,

the ring with kerf model may or may not be beneficial.

Weight of the split ring

This factor is not so imposing on its own but definitely has some contribution.

Another elementary analysis reveals that weight, in fact, can affect the radial

force. The relation is as follows,

0

50

100

150

200

250

300

350

400

0 0.2 0.4 0.6 0.8 1

With kerf

Without kerf

[ [

]] {

}

Here, M is the mass of the split-ring and Mc is the half of the weight of the

crankshaft.

From the relation, the weight also reduces the clamping force, even so slightly.

Since, it is not possible to reduce the weight of the specimen, decreasing the

weight of the split ring can thus, increase the clamping force.

Another advantage of reducing the weight is that it will also reduce the

stiffness of the ring.

Friction between split ring and journal

This is perhaps the easiest of the solutions but has very little scope for

improvement. There are many ways to increase friction between the two

surfaces. Apart from friction coefficient, other ideas can also be employed.

Some of the remedies include:

Increase inner surface roughness of the split ring

Change the surface texture of inner surface of the ring. Circumferential machining marks can enhance the gripping efficiency.

A thin rubber or asbestos gasket may be used (if possible) to increase the contact between the surfaces.

A mild adhesive can be used in a similar fashion.

The friction between the journal and ring has two counteracting effects on

the clamping. Increasing the coefficient of friction reduces the required

clamping force but it also reduces the clamping force transmitted by the

split-ring. Thus, the value of coefficient of friction needs to be optimized.

Following is the plot of required clamping force and available force at = 0.7

and 0.5. The optimized value would undoubtedly the point where the two

curves intersect.

For (Collar & Ring) = 0.7, critical value comes out (Ring & Journal) = 0.75

while, for (Collar & Ring) = 0.5, the critical value reduces to (Ring

Journal) = 0.6

Thus, as the friction between the collar and ring is reduced, the critical

friction coefficient required between the journal and ring also falls down.

0

500

1000

1500

2000

2500

0 0.2 0.4 0.6 0.8 1

(Collar & Ring) = 0.7

(Collar & Ring) = 0.5

Required Clamping force

REDESIGNING OF SPLIT RING

Since, we did not achieve any substantial improvement in the clamping force,

we tried to redesign the split ring. We tried to find out other types of clamping

collars available for holding shafts and journals. We then designed rings which

were coherent with present collar bush so that replacement would not be

required.

One of those ideas was of the muff-type collar bush which employs a

circumferential bolt to clamp the shaft. Since, all the axial load of the pre-

tension of bolt would be utilized in clamping, the number of bolts required to

hold the ring in the collar would be reduced. Thus, the flexibility of the ring

can be increased and mounting time can be reduced. Further, the tightening

torque required would also be reduced substantially.

Following is the crude design of the muff-type clamping ring. The outer

surface has the same taper as the collar already in use.

The muff may either have just one tightening bolt or two. A single bolt reduces

the number of bolts but the clamping force obtained is distributed non-

uniformly over the journal. Thus, we designed with two through bolts and the

ring split in two pieces as shown. It promises a much more uniform force

distribution on the journal.

The comparison between the 8-bolt assembly and muff-type assembly is as

follows,

Friction

Coefficient

C22 (MPa) C33(MPa) Avg.(MPa) Clamping force

Double muff (kN)

Clamping Force Split

ring ( = 0.7) (kN)

0.1 5.901 5.64 5.7705 357.771 327.794

0.2 5.534 5.075 5.3045 328.879 307.241

0.3 5.408 5.072 5.24 324.88 297.786

0.5 5.213 4.804 5.0085 310.527 277.078

0.7 4.998 4.542 4.77 295.74 262.787

0.9 4.786 4.283 4.5345 281.139 253.084

A major disadvantage of this design is the aligning of bolt holes while

assembly. While using split rings, any misalignment is taken care of using a

wedge driven in the slit which loosens the ring on the journal. While, the

wedge is stuck, the ring can be rotated to accommodate any misalignment. This

convenience will not be available in muff-type which will be tightened using

bolts and spring action of a solid split ring.

PERSONAL LEARNINGS AND EXPOSURE

With the culmination of the project, following conclusions/ derivations can be

made with regard to what I learnt, the tasks I performed, and my contribution to

the company and the novelty of the idea behind the project.

TASKS PERFORMED

Since the project was about the feasible solution for the problem of slipping

of crank journal from the grip of split-ring during fatigue testing. It was

initially required to get familiar with the brief & basic knowledge of the Finite

Element Analysis. The complete study carried out by me throughout the

internship training includes developing a strong foundation in the area of

redesigning and stress analysis using FEA with the help of Catia software. The

organised & focussed approach begins with the most basic architecture of split

ring along with the collar and the journal.

Moreover, some basic mechanical and software techniques were also

implemented that were significantly used during the course of our training.

These technologies feature the most significant part of my project. It was

therefore, necessary to learn about these technologies in details.

The most interesting and informative task that we had performed was visiting

the full BFL plant, and gain the knowlegde regarding the different

manufacturing technique in a much better way and also gained bulk of

fascinating knowledge about different types of robotic forging machine.

ACHIEVEMENTS AND BENEFITS

Being a part of well-established company like Bharat Forge Ltd. proved to be

a great learning experience for us. The internship has not only helped us to

polish our academic knowledge but has also refined & brushed-up our

communication skills.

Apart from this we gained an adequate and detailed knowledge of the Catia,

Ansys software. These add to our skill set which will definitely help us later on

in our professional lives.

Briefly, the training experience with Bharat Forge Ltd. enabled us to gain an

ultimate professional knowledge. Moreover, we learned how the academic

world differs from the professional. The responsibilities, tasks, colleague

interaction, interaction with the workers are some of our learnings in Bharat

Forge Ltd. worth mentioning.

Not only this, we learned about the strength & importance of working in a

team. Moreover, we understood the various leadership and management

qualities that a professional should have.

The entire internship experience with Bharat Forge Ltd. was like an

opportunity that one should definitely aspire for. Looking forward to work with

company like BFL in future.

REFERENCES

http://www.udco.com/sseries.shtml

Design & Analysis of Crankshaft Bending Test

Mechanical Engineering Design By Joseph Shigley

Mechanical of Material by Beer & Johnston

Practical finite element Analysis By Nitin S Gokhale

http://en.wikipedia.org/wiki/Split-ring_resonator

http://www.ruland.com/shaft-collars.asp

http://www.udco.com/sseries.shtml