Analysis and Fabrication of Magneto-Rheological Damper

8/10/2019 Analysis and Fabrication of Magneto-Rheological Damper

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ANNA UNIVERSITY: CHENNAI 600 025

BONAFIDE CERTIFICATE

Certified that this project report ANALYSIS AND FABRICATION OF

MAGNETO RHEOLOGICAL DAMPER is the bonafide work of

KRISHNAKUMAR.D (21109101301), RAJASELVAM.R (21109101041) &

ARULDINESH.L (21109101007) who carried out the project work under my

supervision.

SIGNATURE SIGNATURE

Mr. Yogesh Kumar Sinha Mr.S.Sivakumar

HEAD OF THE DEPARTMENT ASSOCIATE PROFESSOR

Department of Aeronautical Engineering Department of Aeronautical Engineering

Rajalakshmi Engineering College Rajalakshmi Engineering College

Thandalam, Chennai - 602105 Thandalam, Chennai - 602105

INTERNAL EXAMINER EXTERNAL EXAMINER


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ACKNOWLEDGEMENT

We express our gratitude to our guide, Mr. S. Sivakumar for suggesting,

encouraging and guiding us to doing the project for Analysis and fabrication of

magneto rheological fluid.

We also like to convey our heart-full thanks to our

H.O.D, Mr.Yogesh kumar sinha, for his continuous support, involvement and

back up throughout the project.

We would like to extend our gratefulness to Mr. S. Sivakumarfor

invaluable guidance to fabricate and testing the MR damper through UTM

machine.

We thank all the teaching and non-teaching faculty members for their

complete support and encouragement. We like to thank our management and

chairperson, for their support and promise in the realization our tunnel design.

We also thank our parents and friends for their continuous encouragement

and support.

(i)


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NOMENCLATURE

SYMBOL DESCRIPTION UNIT

D Diameter of the cylinder (shock-strut) mm

Df Differential Force N

Dp Differential Pressure psi

Fa Air spring Force N

FD Damping Force N

FF Frictional Force N

FS Total Force N

Po Pressure inside the cylinder psi

A Area of the piston mm

Ys Stroke length mm

V0 Volume of the upper chamber mm

3

N Polytrophic constant No unit

P Density Kg/m3

Orifice co-efficient No unit

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A0 Area of the orifice mm2

Viscosity of the oil Ns/m2

K Stiffness N/mm

n Natural frequency of the system Rad/sec

M Mass Kg

Frequency HertzY Stroke velocity m/sec

t time sec

ABBREVIATIONS

UTM UNIVERSAL TESTING MACHINE

D.O.F DEGREE OF FREEDOM

W.R.T WITH RESPECT TO

(iv)


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LIST OF FIGURES

Fig:1.1 Single degree of freedom

Fig:2.1 Landing gear configuration

Fig:3.1 Without magnetic field effect

Fig:3.2 With magnetic field effect

Fig:3.3 Basic working concept of MR fluid

Fig:3.4 MR fluid working system

Fig:3.5 Iron powder grade sizes

Fig:4.1 UTM setup

Fig:4.2 MR damper testing

Fig:4.3 Dial gauge

Fig:5.1 Model view of landing gear and MR fluid

Fig:5.2 MR fluid chemicals

Fig:5.3 Making of MR fluid

Fig:5.4 Factory views

Fig:5.5 Schematic diagram for MR damper

Fig:5.6 Fabricated model(MR damper)

Fig:5.7 piston(with magnetic coil) and cylinder

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LIST OF TABLES

Table: 2.1 Fixed and retractable landing gear

Table: 3.1 Modes of operation

Table: 3.2 MR fluid properties

Table: 3.3 Comparison of iron powder grade sizes

Table: 5.1 Properties of MR fluid

Table: 5.2 Hydraulic oil(hydro 68) properties

Table: 6.1 WITHOUT MAGNET EFFECT READINGS

Table: 6.1.1 Air-spring force calculation results

Table: 6.1.2 Damping force calculation results

Table: 6.1.3 Frictional force calculation results

Table: 6.1.4 Total force calculation results

Table: 6.1.5 Stiffness calculation results

Table: 6.1.6 Frequency calculation results

Table: 6.2 WITH MAGNET EFFECT READINGS

Table: 6.2.1 Air-spring force calculation results

Table: 6.2.2 Damping force calculation results

Table: 6.2.3 Frictional force calculation results

Table: 6.2.4 Total force calculation results with magnetic effect

Table: 6.2.5 Stiffness calculation results

Table: 6.2.6 Frequency calculation results

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LIST OF PLOTS

Plot: 7.1 Load Vs Pressure

Plot: 7.2 Load Vs Deflection

Plot: 7.3 Load Vs Air - spring force

Plot: 7.4 Load Vs Frictional force

Plot: 7.5 Load Vs Damping force

Plot: 7.6 Load Vs Total force

Plot: 7.7 Load Vs Stiffness

Plot: 7.8 Load Vs Natural frequency

Plot: 7.9 Load Vs Time

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CONTENTS PAGE NO

ACKNOWLEDGEMENT (i)

ABSTRACT (ii)

NOMENCLATURE (iii)

ABBREVIATIONS (iv)

LIST OF FIGURES (v)

LIST OF TABLES (vi)

LIST OF PLOTS (vii)

CONTENTS (viii)

CHAPTERS

1. INTRODUCTION

1.2:MR DAMPER 1

1.3: MR FLUID 3

2. AIRCRAFT LANDING GEAR

2.1: LANDING GEAR 4

2.2: LANDING GEAR CONFIGURATION 5

2.3: FIXED & RETRACTABLE LANDING GEAR 14

2.4: TYPES OF SHOCK STRUT 17

2.4.1: AIR-OLEO 17

2.4.2: SPRING OLEO 18

3. MAGNETO-RHEOLOGICAL FLUID

3.1: INTRODUCTION TO MR FLUID 19

3.2: MR FLUID WORKING PROCEDURE 20

3.2.1: WITHOUT APPLYING MAGNETIC FIELD

3.2.2: WITH APPLYING MAGNETIC FIELD

3.3: BACK GROUND TO MAGNETIC FLUID TECHNOLOGY 22

3.4: MODES OF OPERATION 24

3.5: PROPERTIES OF MR FLUID 26


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3.6: SCANNING OF IRON POWDER 27

3.7: APPLICATION OF MR FLUID 28

3.8: ADVANTAGES OF MR FLUID 31

4. UNIVERSAL TESTING MACHINE

4.1: UTM INTRODUCTION 33

4.2: COMPONENTS

4.3: DESCRIPTION OF UTM 34

4.3.1: THE HYDRAULIC POWER UNIT 35

4.3.2: THE LOAD MEASUREMENT UNIT

4.4: CONTROL DEVICES 364.5: UTM TEST 37

4.5.1: GAP TESTS

4.5.2: ANGULAR MOTION TESTS

4.5.3: COMPRESSION TESTS

4.5.4: LEAKAGE TESTS

4.6: TESTING PROCEDURE 38

4.7: USES 41

5. FABRICATION WORK

5.1: MAKING OF MR FLUID 42

5.1.1: CHEMICALS

5.1.2: PROCEDURE 43

5.1.3: SPECIFICATION 44

5.2: HYDRAULIC OIL (HYDRO 68) 45

5.2.1: MATERIAL SAFETY DATA SHEET FOR HYD OIL 68

5.2.2: ACCIDENTAL RELEASE MEASURES 46

5.2.3: HANDLIG AND STORAGE 47

5.2.4: PHYSICAL AND CHEMICAL PROPERTIES

5.3: MAKING OF MR DAMPER 48

5.3.1: FACTORY VIEW


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5.3.2: PROCEDURE

5.3.3: FABRICATED MODEL 50

5.3.4: DIMENSIONS OF THE COMPONENTS 51

5.4: MILD STEEL

5.4.1: INTRODUCTION 52

5.4.2: PROPERTIES OF MILD STEEL 53

5.4.3: USES OF MILD STEEL 54

6. CALCULATIONS

6.1: WITHOUT MAGNETIC EFFECT OBSERVATION 55

6.1.1: AREA & VOLUME CALCULATION 566.2: FORCE CALCULATION

6.2.1: AIR-SPRING FORCE CALCULATION

6.2.2: DAMPING FORCE CALCULATION 58

6.2.3: FRICTIONAL FORCE CALCULATION 59

6.2.4: TOTAL FORCE CALCULATION 60

6.3: MODELING OF THE LANDING GEAR STRUT 61

6.3.1: PROCEDURE

6.3.2: STIFFNESS CALCULATION 62

6.3.3: FREQUENCY CALCULATION 63

6.4: WITH MAGNETIC EFFECT OBSERVATION 65

6.4.1: AIR-SPRING FORCE CALCULATION 66

6.4.2: DAMPING FORCE CALCULATION 67

6.4.3: FRICTIONAL FORCE CALCULATION 69

6.4.4: TOTAL FORCE CALCULATION 70

6.4.5: STIFFNESS CALCULATION 71

6.4.6: FREQUENCY CALCULATION 72

7. GRAPHS 74

8. CONCLUSION 80

9. REFERENCES 81


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CHAPTER 1

1.1 INTRODUCTION

Landing gear is one of the essential part of an aircraft used during landing,

take off, taxing, towing etc. During the landing phase it is subjected to severe loads

and shocks. Moreover landing gears are designed based on the weight and impact

load of an aircraft, so it is important to measure the load on the landing gear and

analyze the same.

1.2 MR DAMPER:

Single degree of freedom:

Inmechanics, the degree of freedom(DOF) of amechanical system is the

number of independent parameters that define its configuration. It is the number of

parameters that determine the state of a physical system and is important to theanalysis of systems of bodies inmechanical engineering,aeronautical

engineering,robotics,andstructural engineering.

Fig 1.1: single degree of freedom

1
http://en.wikipedia.org/wiki/Classical_mechanicshttp://en.wikipedia.org/wiki/Mechanical_systemhttp://en.wikipedia.org/wiki/Mechanical_engineeringhttp://en.wikipedia.org/wiki/Aerospace_engineeringhttp://en.wikipedia.org/wiki/Aerospace_engineeringhttp://en.wikipedia.org/wiki/Roboticshttp://en.wikipedia.org/wiki/Structural_engineeringhttp://en.wikipedia.org/wiki/Structural_engineeringhttp://en.wikipedia.org/wiki/Roboticshttp://en.wikipedia.org/wiki/Aerospace_engineeringhttp://en.wikipedia.org/wiki/Aerospace_engineeringhttp://en.wikipedia.org/wiki/Mechanical_engineeringhttp://en.wikipedia.org/wiki/Mechanical_systemhttp://en.wikipedia.org/wiki/Classical_mechanics


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The horizontal vibrations of a single-story building can be conveniently modeled as

a single degree of freedom system. The position of a single car (engine) moving

along a track has one degree of freedom, because the position of the car is defined

by the distance along the track. A train of rigid cars connected by hinges to an

engine still has only one degree of freedom because the positions of the cars behind

the engine are constrained by the shape of the track.

An automobile with highly stiff suspension can be considered to be a rigid body

traveling on a plane (a flat, two-dimensional space). This body has three

independent degrees of freedom consisting of two components of translation and

one angle of rotation. Skidding ordrifting is a good example of an automobile's

three independent degrees of freedom.

The position of a rigid body in space is defined by three components

oftranslation and three components ofrotation,which means that it has six degrees

of freedom. TheExact constraint mechanical design method manages the degrees

of freedom to neither under constrain nor over constrain a device.

An air-oleo strut is designed and fabricated with the known dimensions.

Testing is carried on the fabricated model by gradually applying load using

universal testing machine. The air spring force, damping force and frictional force

is calculated for four different loads applied using the UTM. Further the Air-oleo

strut is modeled as a spring mass system with single D.O.F and the natural

frequency, stiffness is calculated using known formulae. Graphs of different

quantities are plotted.(e.g. load vs pressure, load vs stroke length).

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http://en.wikipedia.org/wiki/Drifting_(motorsports)http://en.wikipedia.org/wiki/Translation_(physics)http://en.wikipedia.org/wiki/Rotationhttp://en.wikipedia.org/wiki/Exact_constrainthttp://en.wikipedia.org/wiki/Exact_constrainthttp://en.wikipedia.org/wiki/Rotationhttp://en.wikipedia.org/wiki/Translation_(physics)http://en.wikipedia.org/wiki/Drifting_(motorsports)


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1.3 MAGNETO-RHEOLOGICAL FLUID:

A Magneto rheological fluid commonly known as MR fluids are

suspensions of solid in liquid whose properties changes drastically when exposed to

magnetic field. A magneto rheological fluid (MR fluid) is a type ofsmart fluid in a

carrier fluid, usually a type of oil. When subjected to a magnetic field, the fluid

greatly increases its apparent viscosity, to the point of becoming a visco elastic

solid.

Magneto rheological (MR) fluids are materials that respond to an applied field with

a dramatic change in their rheological behavior. The essential characteristic of these

fluids is their ability to reversibly change from a free-flowing, linear, viscous liquid

to a semi-solid with controllable yield strength in milliseconds when exposed to a

magnetic field.

MR fluids find a variety of applications in almost all the vibration control systems.

It is now widely used in automobile suspensions, seat suspensions, clutches,

robotics, design of buildings and bridges, home appliances like washing-machines.

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http://en.wikipedia.org/wiki/Smart_fluidhttp://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Apparent_viscosityhttp://en.wikipedia.org/wiki/Viscoelastichttp://en.wikipedia.org/wiki/Viscoelastichttp://en.wikipedia.org/wiki/Apparent_viscosityhttp://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Smart_fluid


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CHAPTER 2

AIRCRAFT LANDING GEAR

2.1 LANDING GEAR:

Landing gear is one of the essential part of an aircraft used during landing, take

off, taxing, towing etc. During the land phase it is subjected to severe loads and

shocks. Moreover landing gears are designed based on the weight and impact load

of an aircraft, so it is important to measure the impact load on the landing gear andanalyze the same.

In order to allow for a landing gear to function effectively, the following design

requirements are established:

1. Ground clearance requirement

2. Steering requirement

3. Take-off rotation requirement

4. Tip back prevention requirement

5. Overturn prevention requirement

6. Touch-down requirement

7. Landing requirement

8. Static and dynamic load requirement

9. Aircraft structural integrity

10. Ground lateral stability

11. Low cost

12. Low weight

13. Maintainability

14. Manufacturability

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2.2 LANDING GEAR CONFIGURATION:

Landing Gear Configuration The first job of an aircraft designer in the

landing gear design process is to select the landing gear configuration. Landing

gear functions may be performed through the application of various landing gear

types and configurations. Landing gear design requirements are parts of the aircraft

general design requirements including cost, aircraft performance, aircraft stability,

aircraft control, maintainability, producability and operational considerations.

In general, there are ten configurations for a landing gear as follows:

1. Conventional gear

2. Unconventional gear

3. Single main

4. Bicycle

5. Tail-gear

6. Tricycle or nose-gear

7. Quadricycle

8. Multi-bogey

9. Releasable rail

10. Skid

11. Seaplane landing device

12. Human leg

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Fig 2.1 landing gear configurations

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Conventional landing gear:

Conventional landing gear, or tail wheel-type landing gear, is an aircraft under

carriage consisting of two main wheels forward of the center of gravity and a small

wheel or skid to support the tail. The term conventional persists, having begun in

the time when the majority or conventional of airplanes was thus configured,

even though nowadays most aircraft are configured with Tricycle landing gear.

The term tail dragger is aviation jargon for an aircraft with a conventional

undercarriage, although some writers have argued that the term should refer onlyto an aircraft with a tailskid and not a tail wheel.

In early aircraft, a tailskid made of metal or wood was used to support the tail on

the ground. In most modern aircraft, a small, articulated wheel assembly is

attached to the rearmost part of the airframe in place of the skid. This wheel is

steered by the pilot through a connection to the rudder pedals, allowing the rudder

and tail wheel to move together.

Advantages:

The tail wheel configuration offers several advantages over the tricycle

landing gear arrangement.

Due to its smaller size the tail wheel has less parasite than a nose wheel,

allowing the conventional geared aircraft to cruise at a higher speed on the

same power.

Tail wheels are less expensive to buy and maintain than a nose wheel. If a

tail wheel fails on landing, the damage to the aircraft will be minimal. This

is not the case in the event of a nose wheel failure, which usually results in

propeller damage.

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Due to the increased propeller clearance on tail wheel aircraft less stone chip

damage will result from operating a conventional geared aircraft on rough or

gravel airstrips

Because of the way airframe loads are distributed while operating an rough

ground, tail wheel aircraft are better able to sustain this type of use over a

long period of time, without cumulative airframe damage occurring.

Tail wheel aircraft are also more suitable for operating on skids.

Disadvantages:

Tail wheel aircraft are much more subject to nose-over accidents, due to

main wheels becoming stuck in holes or injudicious applications of brakes

by the pilot.

Tail wheel aircraft generally suffer from poorer forward visibility on the

ground, compared to nose wheel aircraft. In some cases this necessitates

S turning on the ground to allow the pilot to see while taxing.

Tail wheel aircraft are more difficult to taxi during high wind conditions,

due to the higher angle of attack on the wings. They also suffer from tower

cross wind capability and in some wind conditions may be unable to use

cross wind runways or single-runway airports.

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Single Main:

The simplest configuration of landing gear is the single main includes one

large main gear that carries a large portion of the aircraft weight and load; plus a

very small gear under the nose. In terms of size, the main gear is much larger

(both strut and wheel) than the secondary one. Both of these gears are in the

aircraft symmetrical plane. The main gear is close to the aircraft cg, while the

other gear is far from it. In majority of cases, the main gear is located in front ofthe aircraft cg and the other one is behind cg (under the tail section). In case,

where the main gear is aft of aircraft cg, the secondary gear is usually converted

to a skid under the fuselage nose. Majority of sailplanes are employing single

main landing gear because of its simplicity.

Bicycle:

Bicycle landing gear, as the name implies, has two main gears one aft and

one forward of aircraft cg; and both wheels have a similar size. To prevent the

aircraft from tipping sideways, two auxiliary small wheels are employed on the

wings. The distance between two gears to the aircraft cg is almost the same, thus,

both gears are carrying a similar load.

The bicycle landing gear has some similar features with single main and in

fact is an extension to the single main. This arrangement is not popular among

aircraft designers due to its ground instability. The main advantages of this

configuration are the design simplicity and the low weight.

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Tail-gear:

Tail-gear landing gear has two main wheels forward of the aircraft cg and a

small wheel under the tail. The wheels in front of the aircraft cg is very close to it

(compared with aft wheel) and carries much of the aircraft weight and load; thus

is referred to as the main wheel. Two main gears are in the same distance from

the cg in the x-axis and the same distance in y-axis (in fact left and right sides);

thus both are carrying the same load. The aft wheel is far from cg (compared

with main gear); hence it carries much smaller load and then is called an

auxiliary gear. The share of the main gear from the total load is about 80 to 90percent of the total load, so the tail gear is carrying about 10 to 20 percent.

Tricycle landing gear:

Tricycle gear is aircraft under carriage, or landing gear, arranged in a tricycle

fashion. The tricycle arrangement has one wheel in the front, called the nose

wheel, and two or more main wheels slightly aft of the center of gravity. Because

of ease of operating tricycle gear aircraft on the ground, the configuration is most

widely used on aircraft.

Tricycle gear is easier to land because the attitude required to land on the

main gear is the same as that required in the flare, and they are less vulnerable to

crosswinds. As a result, the majority of modern aircraft are fitted with tricycle

gear. Almost all jet-powered aircraft are fitted with tricycle landing gear, to

avoid the blast of hot, high speed gases causing damage to the ground surface, in

particular runways and taxiways. The few exceptions have included the

Yakovlev Yak-15, the super marine Attacker, and prototypes such as the Heinkel

He 178, the first four prototypes (VI through V4) of the Messerschmitt Me 262,

and the Nene powered version.

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Quadricycle:

As the name implies a quadricycle landing gear utilizes four gears; similar to

a car conventional wheel system. Two wheels at each side where two wheels are

in front of aircraft cg and other two aft of cg. The load on each gear depends on

its distance to cg. If aft and forward wheels have the same distance to cg, they

will have to carry the same load. In this case, it is very hard to rotate the aircraft

during take-off and landing; so the aircraft will perform a flat take-off and

landing. This characteristics causes the aircraft to have a longer take-off run,compared with tricycle configuration. This feature enables the aircraft to have a

very low floor which permits an easier loading and unloading.

Multi-bogey:

As the aircraft gets heavier, number of gears needs to be increased. A

landing gear configuration with multiple gears of more than four wheels also

improves take-off and landing safety. When multiple wheels are employed in

tandem, they are attached to a structural component referred to as bogey that is

connected to the end of the strut. An aircraft with multi- bogey landing gear is

very stable on the ground and also during taxiing. Among various landing gear

arrangement, a multi-bogey is the most expensive, and most complex for

manufacturing. When the aircraft weight is beyond 200,000 lb, multiple bogeys

each with four to six wheels are used. Large transport aircraft such as Boeing B-

747 and Airbus A- 380 utilize multi-bogey landing gear. Boeing B-747 is

equipped with a four four-wheel bogies main gear and a twin-wheel nose unit.

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Releasable Rail:

For those aircraft which are designed to take-off while airborne and are not

expected to land on the ground or sea, there is a special type of gear. Rockets and

missiles are in the same category in terms of landing gear configuration. These

air vehicles are either launched, or released to get airborne. Take-off or launch

gear usually consists of two to three fixed pieces.

One piece is a flat plate of T-shape part that is attached to the mother vehicle

or launcher. The main function of this attachment is to hold the vehicle whilelaunched.

Skid:

Some vertical take-off and landing aircraft and helicopters do not need to

taxi on the ground, so they are equipped with a beam-type structure referred to as

skids instead of regular landing gear. The configuration of skids mainly

comprises of three to four fixed cantilever beams which are deflected outward

when a load (i.e. aircraft weight) is applied. The deflection of skids plays the role

of a shock absorber during landing operations. However, due to the nature of the

beams, they are not as efficient as oleo shock absorbers. The design of skids

compared with regular landing gear which are equipped with wheels is much

simpler.

Basic equations for beam deflection and bending stress might be employed in

the design and analysis of skids. In addition, fatigue loading and fatigue life must

be taken into account to predict the skid endurance.

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Seaplane Landing:

Device Take-off and landing on the sea requires special landing gear

configuration. The technical features of the water runway are totally different

than a hard surface tarmac. Thus, a sea-plane is not able to employ the

advantages of wheels on the water. The sea-plane landing gear and the shape of

the hull are governed by the following design requirements:

1. Slipping

2. Water-impact load reduction

3. Floating4. Lateral static stability

A sea-plane usually lands on the water first by its fuselage and then by

utilizing a special skid to remain stable. The fuselage (or hull) bottom shape

constitutes the primary part of a sea-plane landing gear. The fuselage shape must

be designed to satisfy above-going requirements as well the fuselage original

design requirements for accommodating payload. The slipping and the reduction

of the water-impact load requirements often influence the design of the fuselage

bottom shape.

Human Leg:

When an aircraft is very light and the cost is supposed to be as low as

possible, human leg can function as the landing gear. This is the case for hang

glider and paraglider. Pilot must use his/her leg to during take-off and landing

operation. Due to human physical weaknesses, the landing speed must be very

low (e.g. less than 10 knot) in order to have a safe landing. Pilot skill and

nimbleness is a requirement besides the leg for a successful landing. In such a

case, there is no need for landing gear design; just assume that it has been

designed and fabricated and is ready for flight.

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2.3 FIXED, RETRACTABLE, OR SEPARABLE LANDING GEAR:

Another design aspect of the landing gear is to decide what to do with it

after take-off operation. In general, there are four alternatives as follows:

1. Landing gear is released after take-off.

2. Landing gear hangs underneath the aircraft (i.e. fixed).

3. Landing gear is fully retracted inside aircraft

(E.g. inside wing or fuselage).

4. Landing gear is partially retracted inside aircraft.

Each of these four alternatives has various advantages and disadvantages

which must be evaluated prior to decision making. In the first case, the landing

gear is released after take-off; so the aircraft does not have to carry it during

flight mission. Hence the aircraft weight will be reduced after take-off and it is

assumed as an advantage.

However, this alternative does not have anything to do with landing. It

means that the aircraft is not supposed to land; which is the case for drones that

are used as a target for missile test. Or, the aircraft must use another landing gear

to land safely. Such wheels are sometimes mounted onto axles that are part of a

separate dolly (for main wheels only) or trolley (for a three wheel set with a

nose-wheel) chassis. The major advantage of such arrangement is the weight

reduction which results is a higher performance. If the aircraft is planned to land

at the end of its mission, this option is not recommended, since landing on a

moving cart is not a safe operation. There is a very few number of aircraft with

such landing gear configuration.

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In the case of a retractable landing gear, it folds after takeoff into the

fuselage where it is stored during flight until shortly before landing. Related

features of a retractable landing gear are:

1. Retracting system design,

2. Provision of sufficient room for landing gear after retraction.

Most mechanisms for landing gear retraction system are based upon a four-

bar linkage, by using three members connected by pivots. The fourth bar is the

aircraft structure. A retraction mechanism clearly increases aircraft weight,design complexity, and maintenance; and reduces the internal fuel volume.

The major options for main landing gear home are:

1. In the wing,

2. In the fuselage,

3. Wing-podded,

4. Fuselage-podded,

5. Wing-fuselage junction, and

6. In the nacelle.

In a high-wing configuration, retracting and locating landing gear in the

fuselage makes the strut shorter. In general, a retracted position inside aircraft

will chop up aircraft structure which consequently increases aircraft weight. The

examples are locating the landing gear in the wing, in the fuselage, on in the

wing-fuselage. On the other hand, a podded bay configuration tends to increase

aircraft frontal area that causes additional aerodynamic drag. The example is

locating the landing gear in a pod beside fuselage. In terms of aircraft structural

design complexity, a landing gear bay in the wing requires a wing cutout that

leads in stronger spars.

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The best candidate for a bay in the wing is the room between main spar and

rear spar. A landing gear bay in the fuselage also requires a fuselage cutout that

leads in stronger frames and longerons. The aerodynamic benefits of in the wing

or in the fuselage bay arrangements outweigh the drawbacks for high-speed

aircraft.

Table 2.1fixed and retractable landing gear

No ItemFixed(non-retractable)

Landing

Retractable Landing

Gear

1 Cost Cheaper Expensive

2 Weight Lighter Heavier

3 Design Easier to design Harder to design

4 Manufacturing Easier to manufacture Harder to manufacture

5 Maintenance Easier to maintain Harder to maintain

6 Drag More drag Less drag

7Aircraft

performance

Lower aircraft

performance(e.g.

maximum speed )

Higher aircraft

performance(e.g.

maximum speed)

8Longitudinal

stabilityMore stable (stabilizing)

less stable

(destabilizing)

9 Storing bay Does not require a bay Bay must be provided

10 Retraction systemDoes not require a retraction

System

Requires a retraction

system

11 Fuel volume More available internal fuelVolume

Less available internalfuel volume

12 Aircraft structure Structure in un-interrupted

Structural elements need

reinforcement due to

cutout

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2.4 TYPES OF SHOCK STRUT:

A strut is a structural component designed to resist longitudinal compression.

Struts provide outwards- facing support in their lengthwise direction, which can

be used to keep two other components separate, performing the opposite function

of the tie. They are commonly used in architecture and engineering, for instance

as components of an automobile chassis, where they can be passive braces to

reinforce the chassis and/or body, or active components of the suspension. In

piping, struts restrains movement of a component in one direction while allowing

movement or contraction in another direction.

An automotive suspension strut combines the primary function of a shock

absorber(as a damper), with the ability sideways loads not along its axis of

compression, somewhat similar to a sliding pillar suspension, thus eliminating

the need for an upper suspension arm. This means that a strut must have a more

rugged design, with mounting points near its middle for attachment of such

loads. A shock strut serves the purpose of a shock absorber by observing the

heavy loads and shock impacted during landing.

Shock strut is classified into,

Air-oleo

Spring-oleo

2.4.1 AIR-OLEO

An AIR-OLEO strut is an air-oil hydraulic shock absorber used on the landing

gear of most large aircraft and many smaller ones. It cushions the impacts of

landing and while taxing and damps out vertical oscillations.

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OPERATION:

An oleo strut consists of an inner metal tube or piston, which is attached to

the wheel axle, and which moves up and down in an outer (or upper) metal tube,

or cylinder, that is attached to the airframe. The cavity within the strut and piston

is filled with air and oil (usually hydraulic fluid), and is divided into two

chambers that communicate through a small orifice. When the aircraft is

stationary on the ground, its weight is supported by the compressed air in the

cylinder.

During landing, or when the aircraft taxis over bumps, the piston slides up and

down. It compresses the air, which acts as a spring, and forces oil through theorifice, which acts as a damper. A tapered rod may be used to uncover additional

orifice so that damping during compression is less than during rebound. Oleo

struts are often inflated with nitrogen instead of air, since it likely to cause

corrosion. The various parts of the strut are sealed with O-rin

gs or similar elastomeric seals, and a scraper ring is used to keep dust and grit

adhering to the piston from entering the strut.

2.4.2 SPRING OLEO:

It is one of the shock strut that wide application in the past. A spring oleo shock

strut uses a combination of spring and oil to absorb shock. Oleo in Greek means

oil.

Spring provides the cushioning effect

Oil acts as a damper

This combination is capable of observing heavy shocks and loan thereby

providing necessary cushion while landing. The shocks are observed in the

spring and the damper opposes the shock once the shock is observed it is

released during extension of spring.

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CHAPTER 3

MAGNETO RHEOLOGICAL FLUID

3.1 Introduction:

A Magneto rheological fluid commonly known as MR fluids are

suspensions of solid in liquid whose properties changes drastically when exposed to

magnetic field. A magneto rheological fluid (MR fluid) is a type ofsmart fluid in a

carrier fluid, usually a type of oil. When subjected to a magnetic field, the fluid

greatly increases its apparent viscosity, to the point of becoming a visco elastic

solid. Importantly, the yield stress of the fluid when in its active ("on") state can be

controlled very accurately by varying the magnetic field intensity. The upshot of

this is that the fluid's ability to transmit force can be controlled with an

electromagnet,which gives rise to its many possible control-based applications.

Magneto rheological (MR) fluids are materials that respond to an applied fieldwith a dramatic change in their rheological behavior. The essential characteristic of

these fluids is their ability to reversibly change from a free-flowing, linear, viscous

liquid to a semi-solid with controllable yield strength in milliseconds when exposed

to a magnetic field.

MR fluids find a variety of applications in almost all the vibration control systems.

It is now widely used in automobile suspensions, seat suspensions, clutches,

robotics, design of buildings and bridges, home appliances like washing-

machines.The key to success in all of these implementations is the ability of MR

fluid to rapidly change its rheological properties upon exposure to an applied

magnetic field.

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3.2 MR FLUID WORKING PROCEDURE:

3.2.1 WITHOUT APPLYING MAGNETIC FIELD:

In the absence of an applied field, MR fluids are reasonably well

approximated as Newtonian liquids. For most engineering applications a simple

Bingham plastic model is effective at describing the essential, field-dependent fluid

characteristics. A Bingham plastic is a non-Newtonian fluid whose yield stress

must be exceeded before flow can begin; thereafter, the rate-of-shear vs. shear

stress curve is linear. In this model, the total yield stress is given by,

Yield stress caused by the applied magnetic field,

Magnitude of magnetic field,

Shear rate,

Independent plastic viscosity defined as the slope of the measured Shear

stress Vs Shear strain relationship. i.e., at H=0.

Fig 3.1 without magnetic field effect

3.2.2

WHILE APPLYING MAGNETIC FIELD:

Applying a magnetic field to magneto rheological fluids causes particles in

the fluid to align into chains. When some low-density MR fluids are exposed

to rapidly alternating magnetic fields, their internal particles clump together.

Over time they settle into a pattern of shapes that look a bit like fish viewed

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from the top of a tank. Such clumpy MR fluids don't stiffen as they should

when magnetized. The fish tank pattern is fragile and takes about an hour to

fully develop. The structure of particles in an MR fluid gradually changes

when an alternating magnetic field is applied.

Fig 3.2 with magnetic field effect

As the fluid flows through the MR valve, it is subjected to a magnetic field in

the active valve regions. Over this portion of MR valve, the fluid develops its

yield stress and allows for controllability in the force. As the fluid enters the

active valve region, the transition from Newtonian-like flow to Bingham

plastic flow occurs. Though it is known that MR fluid response to a magnetic

field occurs in a matter of milliseconds [2, 3], the degree of response

achieved by the fluid has yet to be addressed.

Fig 3.3 Basic working concept of MR fluid

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3.3 BACK GROUND TO MAGNETIC FLUID TECHNOLOGY:

Present electric field based micro-electromechanical system (MEMS)

technology of solid capacitive structures can be extended to include magnetic field

interactions with ferrofluids and submicron size magnetic particles for micro/nano-

electromechanical system (MEMS/NEMS) devices. Ferrofluids, which are

synthesized as a stable col-loidal suspension of permanently magnetized particles

such as magnetite of 10nm diameter, are an excellent choice for such NEMS

magnetic field technology.

Brownian motion keeps the 10nm size particles from settling under gravity,and a surfactant is placed around each particle to provide short range steric

repulsion between particles to prevent particle agglomeration in the presence of

non-uniform magnetic fields (Rosensweig, 1985). Conventional ferrofluid

applications use DC magnetic fields from permanent magnets for use as a liquid O-

ring in rotary and exclusion seals, as dampers in stepper motors and shock

absorbers, and for heat transfer in loudspeakers (Berkovsky & Bashtovoy, 1996).

These applications concern macroscopic systems but because the ferrofluid

particles have a particle diameter of order 10nm, there are also many potential new

MEMS/NEMS applications using ferrofluid particles, with and without carrier

fluid, for nano-duct flows, nano-motors, nano-generators, nano-pumps, nano-

actuators, and other similar nano-scale devices (Gazeau et., 1997).

Ferrofluids also have very interesting lines, patterns, and structures that can

develop from ferrohydrodynamic instabilities as illustrated in Figures a and b for

the ferrofluid peaking behavior resulting from a magnetic field perpendicular to the

free surface of a ferrofluid layer; in Figure c for the gear-like structure resulting

from the radial perpendicular field instability when a small magnet is placed behind

a ferrofluid drop confined between closely spaced glass plates

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Figure a: Hexagonal peaking patterns of about 1cm spacing result when a

perpendicular magnetic field is applied to a layer of magnetic fluid with saturation

magnetization of 400G. The peaks initiate when the magnetic surface force exceeds

the stabilizing effects of the fluid weight and surface tension. The left picture shows

the chocolate-drop like shape with an applied perpendicular field of about 200G

while the right picture shows the sharp peaks with a hexagonal base pattern with a

magnetic field of about 330G.

Figure b: Another view of the perpendicular field instability including a crown of

peaks on the glass container wall edge when

a400Gmagneticfieldisapplied.Thecontainingvesselhas15cm diameter.

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Figure c: Gear-like structure that results when a small 5mm diameter permanent

magnet with strength of about 1200G is placed behind a small ferrofluid droplet

confined between glass plates with 1mm gap.

3.4 MODES OF OPERATION

An MR fluid is used in one of three main modes of operation, these being

flow mode, shear mode and squeeze-flow mode.

These modes involve, respectively, fluid flowing as a result of pressure

gradient between two stationary plates; fluid between two plates moving

relative to one another; and fluid between two plates moving in the directionperpendicular to their planes.

In all cases the magnetic field is perpendicular to the planes of the plates, so

as to restrict fluid in the direction parallel to the plates.

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Table 3.1 modes of operation

Operational

mode Valve mode Shear mode Squeeze mode

Functional

Principle

Fig 3.4 MR fluid working system

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3.5 PROPERTIES OF MAGNETO RHEOLOGICAL FLUID:

Typical magneto rheological fluids are the suspensions of micron sized,

magnetizable particles suspended in an appropriate carrier liquid such as mineral

oil, synthetic oil, water or ethylene glycol. The carrier fluid serves as a dispersed

medium and ensures the homogeneity of particles in the fluid. A variety of

additives are used to prevent gravitational settling and promote stable particles

suspension, enhance lubricity and change initial viscosity of the MR fluids. The

stabilizers serve to keep the particles suspended in the fluid, whilst the surfactants

are adsorbed on the surface of the magnetic particles to enhance the polarization

induced in the suspended particles upon the application of a magnetic field.

Table 3.2 MR fluid properties

Property: Typical value:

Maximum yield strength, y(field)50-1

00 MPa

Maximum field strength 250 kAm-1(0.3 Tesla)

Plastic viscosity, p 0.1-1.0 Pas

Operable temperature range -40C to +150C(limited carrier fluid)

Contaminants Unaffected by most impurities

Response time < milliseconds

Density 3-4 g/cm3

p/ y (field), figure of merit 10-10-10-11s/Pa

Maximum energy density 0.1 J/cm3

Power supply (typical) 2-25V @ 1-2 A (2-50 watts)

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3.6 SCANNING OF IRON POWDER :

The carbonyl iron powder was obtained from ISP Technologies. Two kinds of Fe

powder were used which are referred as GRADE AS and 3700. GRADE A grade is

the reduced iron grade with an average particle size of 7 m.

This grade was reduced in hydrogen atmosphere, therefore carbon, oxygen, and

the nitrogen concentrations are lower than that of the GRADE B grade, known as

straight grade, which wasnt exposed to a reduction process. The average particle

size for GRADE B is ~ 2 m. The impurity contents of the powders are given inThe oxygen concentration in GRADE B is ~0.4 wt% which suggests that FeO,

Fe3O4, Fe2O3 may be formed.

Scanning electron micrographs which show the morphology of as-received iron

grades that were used in this research are given for GRADE A and GRADE B

grades, respectively.

GRADE A GRADE B

Fig 3.5 Iron powder grade sizes

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Table 3.3 Comparison of iron powder grade sizes

AVERAGE

FE

GRADES

SIZE (M)%IRON %CARBON %OXYGEN %NITROGEN

GRADE A 7 9 >99.5


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linear MR dampers for real-time active vibrational control systems in heavy

duty trucks,

linear and rotary brakes for low-cost, accurate, positional and velocity

control of pneumatic actuator systems,

rotary brakes to provide tactile force-feedback in steer-by- wire systems,

linear dampers for real-time gait control in advanced prosthetic devices,

adjustable real-time controlled shock absorbers for automobiles,

MR sponge dampers for washing machines,

Magneto rheological fluid polishing tools,

very large MR fluid dampers for seismic damage mitigation in civil

engineering structures,

Large MR fluid dampers to control wind-induced vibrations in cable-stayed

bridges.

The MR brake operates in a direct-shear mode, shearing the MR fluid filling the

gap between the two surfaces (housing and rotor) moving with respect to one

another. Rotor is fixed to the shaft, which is placed in bearings and can rotate in

relation to housing. Resistance torque in the MR brake depends on viscosity of the

MR fluid that can be changed by magnetic field. MR brake allows for continuous

control of torque.

When there is no magnetic field the torque is caused by viscosity of carrier

liquid, bearings and seals. MR brake is especially well suited for a variety of

applications including pneumatic actuator control, precision tension control and

hap tic force feedback in applications such as steer-by-wire [15]. MR clutch similar

to MR brake operates in a direct-shear mode and transfers torque between input and

output shaft.

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3.7.1 Mechanical engineering:

Magneto rheological dampers of various applications have been and continue to be

developed. These dampers are mainly used in heavy industry with applications

such as heavy motor damping, operator seat/cab damping in construction vehicles,

and more.

As of 2006, materials scientists and mechanical engineers are collaborating to

develop stand-alone seismic dampers which, when positioned anywhere within a

building, will operate within the building's resonance frequency, absorbing

detrimentalshock waves andoscillations within the structure, giving these dampers

the ability to make any building earthquake-proof, or at least earthquake-resistant.

3.7.2 Military and defense:

The U.S. Army Research Office is currently funding research into using MR fluid

to enhance body armor. In 2003, researchers stated they were five to ten years away

from making the fluid bullet resistant. In addition, Humvees, and various other all-

terrain vehicles employ dynamic MR shock absorbers and/or dampers.

3.7.3 Optics:

Magneto rheological finishing,a magneto rheological fluid-based optical polishing

method, has proven to be highly precise. It was used in the construction of the

Hubble Space Telescope's corrective lens

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3.7.4 Automotive and Aerospace:

If theshockabsorbers of a vehicle'ssuspension are filled with magneto rheological

fluid instead of plain oil, and the whole device surrounded with anelectromagnet,

the viscosity of the fluid, and hence the amount ofdampingprovided by the shock

absorber, can be varied depending on driver preference or the weight being carried

by the vehicle. This is in effect a magneto rheological damper. For example, the

Magneride active suspension system permits the damping factor to be adjusted

once every millisecond in response to conditions.

GeneralMotors (in a partnership withDelphiCorporation)has developed this

technology for automotive applications. It made its debut in both Cadillac (Seville

STS build date on or after 1/15/2002 with RPO F55) as "Magneride" (or "MR") and

Chevrolet passenger vehicles (AllCorvettes made since 2003 with the F55 option

code) as part of the driver selectable "Magnetic Selective Ride Control (MSRC)"

system) in model year 2003. Other manufacturers have paid for the use of it in their

own vehicles. As of 2007, BMW manufactures cars using their own proprietaryversion of this device, while Audi and Ferrari offer the MagneRide on various

models.

General Motors and other automotive companies are seeking to develop a magneto

rheological fluid based clutch system for push-button four wheel drive systems.

This clutch system would useelectromagnets to solidify the fluid which would lock

the driveshaft into the drive train. Porsche has introduced magneto rheological

engine mounts in the 2010 Porsche GT3 and GT2. At high engine revolutions, the

magneto rheological engine mounts get stiffer to provide a more precise gearbox

shifter feel by reducing the relative motion between the power train and

chassis/body.

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3.7.5 HUMAN PROSTHESIS:

Magneto rheological dampers are utilized in semi-active human prosthetic legs.

Much like those used in military and commercial helicopters, a damper in the

prosthetic leg decreases the shock delivered to the patients leg when jumping, for

example. This results in an increased mobility and agility for the patient.

3.8 ADVANTAGES OF MR FLUID:

Easy to control and have higher magnitude of yield stress.

Real-time, continuously variable control of Damping, Motion and position

control, Locking, Haptic feedback.

High dissipative force independent of velocity.

Greater energy density.

Simple design (few or no moving parts).

Quick response time (10 milliseconds).

Consistent efficacy across extreme temperature variations (range of 140C to

130 C).

Minimal power usage (typically 12V, 1 Amp max current; fail-safe to

battery backup, which can fail-safe to passive damping mode).

Inherent system stability (no active forces generated).

MR fluids can be operated directly from low-voltage power supplies. MR

technology can provide flexible, reliable control capabilities in designs.

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CHAPTER 4

UNIVERSAL TESTING MACHINE

4.1 INTRODUCTION:

A universal testing machine, also known as universal tester, materials testing

machine test frame, is used to test the tensile stress and compressive strength of

materials. It is named after the fact that it can perform many standard tensile andcompression tests on materials, components, and structures. A

Universal Testing Machine also known as a materials testing machine and can be

used to test the tensile and compressive properties of materials. This type of

machines are called Universal Testing Machine because it can perform all the tests

like compression, bending, tension etc to examine the material in all mechanical

properties. These machines generally have two columns but single column types

are also available. Load cells and extensometers measure the key parameters of

force and deformation which can also be presented in graphical mode in case of

computer operated machines.. These machines are widely used and would be found

in almost all materials testing laboratory.

4.2 COMPONENTS:

Load frame- usually consisting of two long supports for the machine. Some

small machines have a single support.

Load cell- A force transducer or other means of measuring the load is

required. Periodic calibration is called for.

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Cross head- A movable cross head (crosshead) is controlled to move to

move up or down. Usually this is at a constant speed: sometimes called as a

constant rate of extension (CRE) machine. Some machine can program the

cross head speed or conduct cylindrical testing, testing at constant force,

testing at constant deformation, etc. Electromechanical, servo-hydraulic,

linear drive and resonance drive are used.

Means of measuring extension or deformation- Many tests require a

measure of the response of the test specimen to the movement of the cross

head. Extensometers are sometimes used.

Output device- A means of providing the test result is needed. Some older

machines have dial or digital displays and chart recorders. Many newer

machines have a computer interface for analysis and printing.

Conditioning- Many test require controlled conditioning (temperature,

humidity, pressure,etc.). The machine can be in the controlled room or a

special environmental chamber can be placed around the test machine for

the test. Text fixtures, specimen holding jaws, and related sample making

equipment are called for many test methods.

4.3 DESCRIPTION OF UTM :

The Universal Testing Machine consists of two main parts, viz. the loading

unit and the control panel. The loading unit consists of a robust base at the centre of

which is fitted the main cylinder and piston. A rigid frame consisting of the lower

table, the upper cross head and the two straight columns is connected to this piston

through a ball and socket joint. A pair of screwed columns mounted on the base

pass through the main nuts to support the lower cross-head.

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Each cross-head has a tapering slot at the centre into which are inserted a

pair of racked jaws. These jaws are moved up or down by the operating handle on

the cross-head face and is intended to carry the plate (grip) jaws for the tensile test

specimen. An elongation scale, which measures the relative movement between the

lower table and the lower cross-head, is also provided with the loading unit.

The control panel contains the hydraulic power unit, the load measuring unit and

the control devices.

4.3.1THE HYDRAULIC POWER UNIT:

The Hydraulic Power Unit consists of an oil pump driven by an electric motor and

a sump for the hydraulic oil. The pump is of the reciprocating type, having a set of

plungers which assures a continuous non-pulsating oil flow into the main cylinder

for a smooth application of the test load on the specimen. Hydraulic lines of the

unit are of a special design to enable them to perform various functions.

4.3.2 THE LOAD MEASURING UNIT:

The load measuring unit, in essence is a pendulum dynamometer unit. It has a small

cylinder in which a piston moves in phase with the main piston under the same oil

pressure. A simple pendulum connected with this small piston by a pivot lever thus

deflects in accordance with the load on the specimen and the pivot ratio. This

deflection is transmitted to the load pointer which indicates the test load on the dial.

The pivot lever has four fulcrum -knife-edges, giving fo4ir ranges of test load, (viz.

0-100 kN; 0-250 kN; 0-500 kN and 0-1000 kN). The required range can be selected

by just turning a knob provided for the purpose. The overall accuracy of the

machine depends mainly on the accuracy of the measuring unit.

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4.4 CONTROL DEVICES :

These include the electric control devices, the hydraulic control devices and the

load indicating devices.

1.The Electric Control Devices are in the form of four switches set on the

left side of the panel face. The upper and lower push switches are for moving

the lower cross-head up and down respectively. The remaining two are the

ON and OFF switches for the hydraulic pump.

2.The Hydraulic Control Devices are a pair of control valves set on the

table or the control panel. The right control valve is the inlet valve. It is a

pressure compensated flow control valve and has a built-in overload relief

valve. If this valve is in the closed position, while the hydraulic system is on,

oil flows back into the sump. Opening of the valve now, cause the oil to flow

into the main cylinder in a continuous non-pulsating manner. The left control

valve is the return valve. If this valve is in the closed position, the oil

pumped into the main cylinder causes the main piston to move up. The

specimen resists this, movement, as soon as it gets loaded up. Oil pressure

inside the main cylinder (and elsewhere in the line) then starts growing up

until either the specimen breaks or the load reaches the maximum value of

the range selected. A slow opening of this valve now causes the oil to drain

back into the sump and the main piston to descent.

3.The Load indicating Devices consist of a range inflating dial placed

behind a load indicating dial. The former move and sets itself to the range

selected when the range adjusting knob is turned. The load .on the specimen

at any stage is indicated by the load pointer which moves over the load

indicating dial and harries forward with it a dummy.

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4.5 UTM TEST:

A test set-up was designed to characterize the voltage output and power

output of the generator at various road conditions. Shock absorber testing

machine was made available by institute. The mechanism for variation of

amplitude & frequency of excitation to simulate road profiles.

The following tests will be conducted for normal landing gear.

4.5.1 GAP TESTS:

Caution should be taken when doing gap tests since using too much force

can damage the landing gears. When testing NLGs the first step is to lock thesteering so that the turn cylinder does not move freely. The gap tests are made by

manipulating the rotary actuator. The actuator is set to apply a torque of 100Nm

and the angular deviance is measured. This is done in both directions.

4.5.2 ANGULAR MOTION TESTS:

The angular motion tests are only made for the NLGs. First the weights

simulating the wheels are fastened if so required. Before any testing can take place

the angular movement restrictors must be checked. Then the NLG is driven through

the motions by the rotational actuator and the torque and angular displacement are

recorded.

4.5.3 COMPRESSION TESTS:

Before doing compression tests the force, speed and stroke restrictors must

be checked. If the tests requires the landing gear to be pressurised this must be done

before the test is started. During the test compression force and distance is

measured and the data saved and plotted.

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4.5.4 LEAKAGE TESTS:

The landing gear pressurised are by either dry nitrogen ( Boeing ) or hydraulic fluid

(Messier-Dowty). The filling port on landing gear is connected to the appropriate

feeding port on the pressure port console. When the correct pressure is reached the

control valve is closed and the landing gear let to stand. The pressure is monitored

from the main control table. So there is no need for going into the room with the

landing gear.

But we are going to test the Magneto Rheological damper in UTM to find the

pressure, load, various forces, time and deflection by with magnetic effect and

without magnetic effect.

4.6 TESTING PROCEDURE:

Before doing the testing the pressure gauge in model and load indicator in

UTM should be in zero condition.

The dial gauge will be move after some amount of load that load is called

threshold weight, the reading should be taken after that threshold weight. The fabricated model is placed precisely between the jaws of the universal

testing machine.

Load is applied slowly on the model by turns in UTM.

The initial deflection or the stroke is measured.

The load for which the pressure gauges starts to raise is noted down.

Once the load starts increasing the following are measured for8KN,12KN,16KN,20KN..

a) Deflection or stroke length

b)

Time

c)

Pressure in the lower chamber

d)

Final deflection.

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The jaws are raised and model is removed from jaws and allowed to extend.

The pressure in the chamber is noted from the pressure gauges fitted in the

lower chamber.

Same procedure to be carried out by passing 6V DC current in the MR fluid

to make the magnetic effect inside the cylinder.

Note the reading and plot the graph for both cases, without magnetic effect

and with magnetic effect.

Fig4.1 UTM setup

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Fig4.2 MR Damper testing

Fig4.3 Dial Gauge

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4.7USE:

The set-up and usage are detailed in a test method, often published by the

standard organization. This specifies the sample preparation, fixturing, gauge

length (the length which is under study or observation), analysis etc.

The specimen is placed in the machine between the grips and the extensometer if

required can automatically record the change in gauge length during the test. If the

extensometer is not fitted, the machine itself can record the displacement between

its cross heads on which the specimen is held.

However, this method not only records the change in length of the specimen

but also all other extending/elastic components of the testing machine and its drive

systems including any slipping of the specimen in the grips. Once the machine is

started it begins to apply an increasing load on specimen. Throughout the test the

control system and its associated software record the load and extension or

compression of the specimen.

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CHAPTER 5

FABRICATION WORK

Fig 5.1 model view of landing gear and MR fluid

5.1 MAKING OF MAGNETO-RHEOLOGICAL FLUID:

5.1.1 Chemicals:

Ammonia -250 ml

Ferric chloride -100ml (10gms)

Ferrous chloride -50ml (5gms)

Oleic acid -20ml

Kerosene -100ml

Volume fraction for these solution to be making by 5gm ferrous chloride and

10gm ferric chloride contents. Add these content with proper ammonia to makes

the solution for 50ml ferrous chloride and 100ml ferric chloride.

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Fig 5.2 MR fluid chemicals

5.1.2 PROCEDURE:

Fig5.3 making of MR fluid

First add ferric & ferrous chlorides. Mix it with Ammonia and heat at 20C. After

15 minutes add oleic acid. Shake or mix it properly by Safe condition. Oleic acid

reacts and makes the solution overflow in the test glass. After 30 minutes add

kerosene to that solution. Finally kerosene reacts with iron-acid solution resulting

in the formation of MR fluid.

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5.1.3 SPECIFICATION:

Stroke length : 2.5 cm

MR fluid : 200 ml

Density : 3.28g/cm

Magnetic field : 0 to 200 KA/m

Current : 6 volts and 4.5amp

Inductance : 40 MHz

Coil Resistance : 1.33

Temp range : -40 to 150C

Force : up to 20000N

Table 5.1 MR fluid properties:

PROPERTIES MR FLUID

Viscosity, temperature

@25 [C]0.240.85 [Pa.s]

Density 2.98 to 3.18 [g/cm3]

Solids content by weight 80.98%

Operating temperature -40 to 130 [C]

Flash point >150 [C]

Appearance Dark grey

Yield point 50-100 (Kpa)

Magnetic field strength 150-250 (KA/m)

Reaction time Few milliseconds

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5.2 HYDRAULIC OIL (HYDRO 68):

Table 5.2 Hydraulic oil (hydro 68) Properties:

PropertyValue in

metric unit

Value in

metric unit

Value

in US unit

Value

in US unit

Density at

60F (15.6C)

0.880 *10 kg/m 54.9 lb/ft

Kinematicviscosity at

104F (40C)

68.0 cSt 68.0 cSt

Kinematic

viscosity at

212F

(100C)

10.2 cSt 10.2 cSt

Viscosity

index

135 135

Flash point204 C 204 F

Pour Point

Aniline Point

-40

88

C

C

-40

88

F

F

Colormax.7.0 max.7.0

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5.2.1 MATERIAL SAFETY DATA SHEET FOR HYD OIL 68:

Composition comments:

Refer to section eight for exposure limits on ingredients. Exposure limits regulated

as a mist. Chemical ingredients not regulated by osha or sara are treated

confidentially.

Health warnings:

INHALATION. Oil mist can irritate airways and lungs. Heating can generatevapors that may cause respiratory irritation,nausea and headaches. Inhalation

hazard at room temperature is unlikely due to the low volatility of this product.

SKIN CONTACT.Slightly irritating. Repeated or prolonged contact can result in

drying of the skin. EYE CONTACT.Irritating.May cause slight eye irritation.May

cause very slight transient (temporary) corneal injury.INGESTION.Can cause

stomach ache and vomiting. Main hazard, if ingested, is aspiration into the lungs

and subsequent pneumonitis.

5.2.2 ACCIDENTAL RELEASE MEASURES:

Precautions to protect the environment:

Keep product out of sewers and watercourses by diking or impounding. Advise

authorities if product has entered or may entersewers, watercourses or extensive

land areas. Assure conformity with applicable government regulations.

Spill clean-up procedures:

Contain spill. Neutralize and absorb small amounts. Collect and return large

amounts to shipping container. Rinse spill area with water.

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5.2.3 HANDLING AND STORAGE:

Handling precautions:

Do not reuse container. Keep lid closed when not in use. Keep away from heat,

sparks and open flame. Ventilate well, avoid breathing vapors. Use approved

respirator if air contamination is above accepted level.

Do not store or mix with strong oxidizers. Avoid spilling, skin and eye contact.

Eye wash station should be available at the work place.Storage precautions:

Keep container closed when not in use. Keep away from heat, sparks and open

flame. Store separate from strong acids andoxidizers.

5.2.4 PHYSICAL AND CHEMICAL PROPERTIES:

Appearance/physical state: Liquid.

Color: amber.

Odor: mild (or faint). Petroleum.

Solubility description: insoluble in water.

Boiling point (f, interval): >500 pressure: 760mmhg

Density/specific gravity (g/ml): ~0.87 temperature (f): 61

Vapor density (air=1): >5

Vapor pressure:


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5.3 MAKING OF MR DAMPER:

Fabrication of the landing gear shock strut involves precise positioning and

accurate engineering even a small deviation from the original will result in

devastation. Generally moulding process is used for fabricating the landing gear

strut.

5.3.1 FACTORY VIEW:

Fig 5.4 factory views

5.3.2 PROCEDURE

1.The inner cylinder and the outer cylinder are fabricated to the dimension using

moulding process.

2.The piston head is now inserted into the hollow outer cylinder.

3.An orifice and a plate is placed inside the outer cylinder.

4.The inner cylinder is filled with oil and outer is filled with air.

5.Pressure gauge is fitted to the outer and the inner cylinder.

6.The inner and outer cylinder is sealed to avoid leakage of oil.

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Fig 5.5 SCHEMATIC DIAGRAM FOR MR DAMPER

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5.3.3 Fabricated model:

Fig 5.6 Fabricated model (MR damper)

Fig 5.7 piston(with magnetic coil) and cylinder 50


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5.3.4 DIMENSIONS OF THE COMPONENTS:

PISTON

Piston diameter : 98.6 mm

Piston rod diameter : 50 mm

Piston thickness : 50 mm

CYLINDER

Cylinder outer diameter : 114 mm

Cylinder inner diameter : 103 mm

Cylinder height : 520 mm

SPRING

Spring diameter : 46 mm

Spring height : 212 mm

Number of springs : 15 rolls

Space b/w two rolling : 15 mm

SEAL

Seal thickness : 60 mm

Outer diameter : 114 mm

Inner diameter : 52 mm

WINDING SETUP

Outer diameter : 80 mm

Inner diameter : 52 mm

Thickness : 25 mm

Distance b/w layer : 15 mm

Coil thickness : 1 mm

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BATTERY SPECIFICATIONS

Current : 4.5 Amps

Voltage : 6 volts

WEIGHT OF THE COMPONENTS

Cylinder wt : 10.5 kg

Piston rod wt : 8.1 kg

Spring wt : 0.3 kg

Cylinder top seal wt : 2.9 kg

Tyre wt : 14 kg

5.4 MILD STEEL

5.4.1 INTRODUCTION:

Steel is derived from iron. Iron ore requires great thermal energy (around1,500C) to reduce to its metallic form of iron. The iron is then alloyed with carbon

and metals such as nickel or tungsten to produce steel.

Steels are described as mild, medium- or high-carbon steels, according to the

percentage of carbon they contain.

Mild steelis a type ofsteel that only contains a small amount ofcarbon and

other elements. It is softer and more easily shaped than higher carbon steels. It also

bends a long way instead of breaking because it is ductile. Mild steel is an iron

alloy that contains less than 0.25% carbon. Mild steel is very reactive and will

readily revert back to iron oxide (rust) in the presence of water, oxygen and ions.

The readiness of steel to oxidize on exterior exposure means that it must be

adequately protected from the elements in order to meet and exceed its design life.

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Prior to painting, new mild steel surfaces should be inspected for mill scale,

rust, sharp edges, laminations, burr marks and welding flux, forming or machine

oils, salts, chemical contamination or mortar splashes on them, all of which must be

removed. It is used innails and some types of wire; it can be used to make bottle

openers, chairs, staplers, staples, railings and most common metal products. Its

name comes from the fact it only has less carbon than steel.

5.4.2 PROPERTIES OF MILD STEEL:

Mild Steel is one of the most common of all metals and one of the least

expensive steels used. It is to be found in almost every product created from

metal.

It is weldable, very durable (although it rusts), it is relatively hard and is

easily annealed.

Having less than 2 % carbon it will magnetize well and being relatively

inexpensive can be used in most projects requiring a lot of steel. However

when it comes to load bearing, its structuralstrengthis not usually sufficient

to be used in structural beams and girders.

Most everyday items made of steel have some milder steel content. Anything

from cookware, motorcycle frames through to motor car chassis, use this

metal in their construction.

Because of its poor resistance to corrosion it must be protected by painting or

otherwise sealed to prevent it from rusting. At worst a coat of oil or grease

will help seal it from exposure, and help prevent rusting.

Being a softer metal it is easily welded.Its inherent properties allow

electrical current to flow easily through it without upsetting its structural

integrity.

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This mild variant of harder steel is thus far less brittle and can therefore give

and flex in its application where a harder more brittle material would simply

crack and break.

Mild steel is used in almost all forms of industrial applications and industrial

manufacturing. It is a cheaper alternative to steel, but still better than iron.

5.4.3 USES OF MILD STEEL:

Mild steel has a maximum limit of 0.2% carbon. The proportions of

manganese (1.65%), copper (0.6%) and silicon (0.6%) are approximately

fixed, while the proportions of cobalt, chromium, niobium, molybdenum,

titanium, nickel, tungsten, vanadium and zirconium are not.

A higher amount of carbon makes steels different from low carbon mild-type

steels. A greater amount of carbon makes steel stronger, harder and very

slightly stiffer than a low carbon steel. However, the strength and hardness

comes at the price of a decrease in the ductility of this alloy. Carbon atoms

get trapped in the interstitial sites of the iron lattice and make it stronger.

What is known as mildest grade of carbon steel or 'mild steel' is typically low

carbon steel with a comparatively low amount of carbon (0.16% to 0.2%). It

hasferromagneticproperties, which make it ideal for manufacture of many

products.

The calculated average industry grade mild steel density is 7.85 gm/cm3. Its

Young's modulus, which is a measure of its stiffness, is around 210,000

MPa.

Mild steel is the cheapest and most versatile form of steel and serves every

application which requires a bulk amount of steel.

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CHAPTER 6

CALCULATIONS

6.1 WITHOUT MAGNETIC EFFECT OBSERVATION:

Without magnetic effect readings to be noted during the testing time and

those values are tabulated.

Table 6.1 without magnet effect readings

LOAD(KN) PRESSURE(PSI)DEFLECTION(STROKE

LENGTH)mmTIME(sec)

8 525 19 18.4

12 860 24 24.7

16 1210 33 29

20 1530 37 38.3

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6.1.1 AREA & VOLUME CALCULATION:

Area of the cylinder = /4*D

Diameter of the cylinder = 103mm

Area =4

103 106

A = 0.008332m

Volume of the cylinder = = 51.5 520 109

V= 4.3327 1033[1PSI = 6894.5 N/m]

6.2 FORCE CALCULATIONS

6.2.1 AIR-SPRING FORCE CALCULATION:

= P0 A v0v0 AyS 1)

For 8 KN

= 525 6894.5 0.008332 4.3327 1034.3327 103 0.008332 19 103= 31302.334 N

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2)

For 12 KN

= 860 6894.5 0.008332 4.3327 10

3

4.3327 103 0.008332 24 103=51793.09 N

3)

For 16 KN

= 1210 6894.5 0.008332 4.3327 10

3

4.3327 103 0.008332 33 103= 74218.36 N

4)

For 20 KN

= 1530 6894.5 0.008332 4.3327 10

3

4.3327 103 0.008332 37 103= 94623.54 N

Table 6.2 air spring force calculation

S.NO LOAD(KN)AIR-SPRING

FORCE(N)

1 8 31302.33

2 12 51793.09

3 16 74218.36

4 20 94623.54

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6.2.2 DAMPING FORCE CALCULATION:

= 0.5 3

2

202 1)

For 8 KN

= 0.5 (912 + 1.225) (0.008332)3 (0.00098)2(0.4)2 (1 8 1 03)2 = 4.893 106

2) For 12 KN

= 0.5 (912 + 1.225) (0.008332)3 (0.00163)(0.4)2 ( 1 8 1 03) = 1.3536 105

3)

For 16 KN

= 0.5 (912 + 1.225) (0.008332)3 (0.00279)(0.4)2 ( 1 8 1 03) = 3.9658 105

4)

For 20 KN

= 0.5 (912 + 1.225) (0.008332)3 (0.0031)(0.4)2 ( 1 8 1 03) = 4.8961 105

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Table 6.3 damping force calculation

S.NOLOAD(KN) DAMPING FORCE(N)

1 8 4.893 1062 12 1.3536 1053 16 3.9658 1054 20 4.8961 105

6.2.3 FRICTIONAL FORCE CALCULATION:

= 1)

For 8 KN

= 0.38 31302.334

= 11894.88 N

2)

For 12 KN

= 0.38 51793.09= 19681.37 N

3)

For 16 KN

= 0.38 74218.36= 28202.97 N

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4)

For 20 KN

= 0.38 94623.54=35956.94 N

Table 6.4 frictional forces calculation

S.NO LOAD(KN)FRICTIONAL

FORCE(N)

1 8 11894.88

2 12 19681.37

3 16 28202.974 20 35956.94

6.2.4 TOTAL FORCE CALCULATION:

=

+

+

1) For 8 KN

Total force F = 43197.214 N

2)

For 12 KN


3)

For 16 KN

Total force F = 102421.33 N60


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4)

For 20 KN


Table 6.5 Total force calculation

S.NO LOAD(KN) TOTAL FORCE(N)

1 8 43197.214

2 12 71474.46

3 16 102421.33

4 20 130580.48

6.3 MODELING OF THE LANDING GEAR STRUT:

6.3.1 Procedure:

Modelling of the landing gear shock strut can be done with some with some valid

assumption such as,

The air and oil combination to act as a spring.

The oil to be damper.

Assuming both ends are fixed and load taken by the strut to be the

mass acting on the spring mass system with single degree of freedom.

Where,

Stiffness K = Force/Deflection

=2

= /61


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6.3.2 STIFFNESS CALCULATION:

Stiffness offered by the spring for four different loads can be calculated by,

Stiffness K = Force / Deflection (stroke length)

1. For 8 KN

Stiffness K =8 1 03

1 9 1 03

= 421052.63 2.

For 12 KN

Stiffness K =12 103

24 103

= 500000 3.

For 16 KN

Stiffness K =16 103

33 103

= 484848.48

4.

For 20 KN

Stiffness K =20 103

37 103

= 540540.54 62


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Table 6.6 stiffness calculation

S.NO LOAD(KN) STIFFNESS(N/m)

1 8 421052.63

2 12 500000

3 16 484848.48

4 20 540540.54

6.3.3 FREQUENCY CALCULATION:

Natural frequency of the system can be found by the formula,

= 2

1)

For 8 KN

=

421052.63 9.81

8 1 03= 22.72

/

= 22.722 = 3.616 Hertz

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2)

For 12 KN

=500000 9.81

12 103 = 20.21 /

= 20.212 = 3.216 Hertz

3)

For 16 KN

=484848.48 9.8116 103 = 17.24 /

=

17.24

2

= 2.74 Hertz

4) For 20 KN

=540540.54 9.81

20 103 = 16.28 / = 16.282

= 2.59 Hertz

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Table 6.7 frequency calculation

S.NO LOAD(KN) FREQUENCY(Hertz)

1 8 3.616

2 12 3.216

3 16 2.74

4 20 2.59

6.4 WITH MAGNETIC EFFECT OBSERVATION:

With magnetic effect readings to be noted during the testing time and those

values are tabulated.

Table 6.8 with magnetic effect readings

LOAD(KN) PRESSURE(PSI)DEFLECTION(STROKE

LENGTH)mmTIME(sec)

8 755 17 21.3

12 1170 22 29.7

16 1635 29 37.5

20 2280 34 44

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6.4.1 AIR-SPRING FORCE CALCULATION:

= P0 A v0v0 AyS

1)

For 8 KN

= 755 6894.5 0.008332 4.3327 103

4.3327 103 0.008332 21.3 103= 45223.34 N

2)

For 12 KN

= 1170 6894.5 0.008332 4.3327 1034.3327 103 0.008332 29.7 103=71281.85 N

3)

For 16 KN

= 1635 6894.5 0.008332 4.3327 1034.3327 103 0.008332 37.5 103= 101222.102 N

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4)

For 20 KN

= 2280 6894.5 0.008332 4.3327 1034.3327 103 0.008332 44 103= 143081.24 N

Table 6.9 Air spring force calculation(MR Effect)

S.NO LOAD(KN)AIR-SPRING

FORCE(N)

1 8 45223.34

2 12 71281.85

3 16 101222.102

4 20 143081.24

6.4.2 DAMPING

Analysis and Fabrication of Magneto-Rheological Damper

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