NATIONAL UNIVERSITY OF SCIENCES & TECHNOLOGY
MS DESIGN AND MANUFACTURING 20112nd Semester
DESIGN, DEVELOPMENT AND PROCESS MAPPING OFAIRCRAFT RADIAL
TYRE
Product Design and Development
ASSIGNMENT
Submitted to:
Prof. Dr. Liaquat Ali
Submitted by:
Arshad Chaudhry2011-NUST-MS-DME-28Waqas
Saleem2011-NUST-MS-DME-21Sajjad Alam2011-NUST-MS-DME-05Yasir
Anwar2011-NUST-MS-DME-06Imran Wattoo2011-NUST-MS-DME-04
Date of Submission: 31May, 2012
1.INTRODUCTIONAn aircraft tyre is as a ring shaped covering
rubber covering that is installed on a wheel hub. The basic purpose
is to protect the wheel and provide a flexible medium that allow
absorbing of shocks. The wheel remains in close contact to the
surface through the rubber tyre, where any damage to the tyre
consequently results in damage to the main wheel hub.Synthetic,
natural rubber, fabric and wire, along with other compound
chemicals are used as main materials for manufacturing the rubber
tyres. The aircraft tyres consist of two main parts i.e., tread and
a body.
The purpose of tread is to provide the traction while the wheel
body provides support to bear the load of aircraft. Prior to
invention of rubber and mere strip of metal was attached to the
outer circumference of the wheel hub to protect against wear and
tear. Today, the vast majorities of tyres are pneumatic inflatable
structures, comprising a doughnut-shaped body of cords and wires
encased in rubber and generally filled with compressed air to form
an inflatable cushion. Pneumatic tires are used on many types of
vehicles, such as cars, bicycles, motorcycles, trucks, earthmovers,
and aircraft.
2.CONCEPT DEVELOPMENTTyres are an integral and most essential
part of the aircraft as they play a vital role during takeoff and
landing phase. During these phases, these are subjected to enormous
loading and momentum and thus are prone to much wear and tear as
compared to wheels and tyres installed on ground transport
vehicles.
We have recently come across with a problem of short life of
aircraft wheels on Super-MU. In fact, life of an aircraft tyre and
its wheel hub are measured separately and in number of landings and
takeoffs. A shortened life of aircraft tyre would entail its
replacement much frequently and incur increased cost.
Thus the design team thought of redesigning the tyre for
aircraft Super-MU with an increased life and at competitive price
as being offered by other manufacturers. It is important that the
facilities for rubber production and subsequent processing are
already held with Rubber Shops at Aviation Complex. This is mainly
a reverse engineering approach while referencing to other aircraft
tyre manufacturers and their best practices. The team would focus
on manufacturing processes of the aircraft tyre and in this effort
wheel hub would not be included as part of effort. The approach
would be to make a design, develop manufacturing processes, develop
prototype, and devise client acceptability and inspection
criteria.
UNDERSTANDING THE OPPORTUNITY3.1MISSION STATEMENT
PRODUCT DESCRIPTIONThe product is an aircraft radial tyre.
BUSINESS CASEProduct would be used on commercial aircraft
(Boeing 747).
GOALSTo capture 30% of market share by introducing better
quality and durability and extended life of tyres at affordable
cost than available in market.
PRIMARY MARKETAll Boeing 747 aircraft operating airlines
SECONDARY MARKETAll individual / private aircraft owners.
ASSUMPTIONS Low Cost Greater number of landings Less wear and
tear Low premature failure rate Consistent quality Less care and
maintenance requirements
COMPETITORS Good Year Michelin General Bridgestone
STAKE HOLDERS Users (Aircraft operators) Retailers /
Distributors Sales & Marketing Service Centers Production
Facility Aviation MROs Private aircraft owners
3.2GATHERING THE RAW DATA FROM CUSTOMERSThree methods for data
collection were employed Interviews Focus groups Observing the
product in useChoosing the customers (10-50 interviews)
The art of eliciting customer needs data Go with the flow Use
visual stimuli Suppress preconceived hypothesis about the product
technology Have the customer demonstrate the product and/ or
typical tasks related to the product Be alert for surprises and the
expression of latent needs Watch for non-verbal information
Documenting the interaction with the customers Audio tape
recording Notes Video tape recording Still photography
3.2.2Interviews with Users
1. Number of Landings should be greater.2. Premature failure
rate should be low.3. Installation/ removal easy.4. No extensive
care and maintenance requirements.5. Not of a higher cost.6. Better
quality.7. Protection against Weather effects8. Less wear and
tear9. Should get fixed on existing wheel hub.10. Should support
existing aircraft braking system.11. Should have adequate cooling
mechanism after brake applications.12. Should operate in a wide
range of temperatures even under extreme weather conditions.13.
Should operate at varying nature of landing surfaces.14. Easy
access to charge air pressure.15. Must retain the air pressure.
3.3INTERPRETING RAW DATA IN TERMS OF CUSTOMER NEEDS
Express the needs in terms of what the product has to do andnot
in terms of how it will do Express the needs as specifically as the
raw data Use positive and not negative phrasing Express the need as
an attribute of the product Avoid the words must and should
3.3.1Data collection
About 10 to 15 users including technicians, pilots and
maintenance engineers working in airlines and aviation MROs were
interviewed for seeking customer needs. Additionally, maintenance
facilities were visited for studying the existing tyres and the
range provided by different manufacturers. All collected customer
needs and interpreted needs are being summarized below :
CUSTOMERXYZADDRESSCHAKLALATELEPHONE05190990WILLING TO FOLLOW
UPYESINTERVIEWERSPROJECT TEAMDATED15 APRIL, 2012CURRENT
USEMICHELINTYPE OF USERCOMMERCIAL
CUSTOMER STATEMENTINTERPRETED NEEDS
Number of Landings should be greater.Tyre life is measured
against the number of landings that should be higher enough to
match aircraft inspections.
Premature failure rate should be low.Tyre should not fail before
completion of assign life in terms of number of landings.
Installation/ removal easy.Procedure and access for
removal/installation should be easy and less time consuming.
No extensive care and maintenance requirements.Reduced
maintenance at operational and inspection level.
Not of a higher cost.Cost should be affordable vis--vis
utility.
Better quality.Rubber of tyre should be of good quality to
support described functions and usage.
Protection against Weather effectsWeather effects should have
minimal or zero effect on tyre surfaces and rubber.
Less wear and tearCut marks, bruises, blisters and minimal
frictional effects should be encountered during the operational
life
Should get fixed on existing wheel hub.Tyre design and
dimensions should allow it to get installed on existing wheel hub
without requiring any modifications in hub assembly.
Should support existing aircraft braking system.Design,
dimensions and weight loading capacity of tyre should be enough to
support existing aircraft braking system without requiring any type
of modification.
Should have adequate cooling mechanism after brake
applications.Tyre design should allow instant cooling after brake
application under high loading and momentum.
Should operate in a wide range of temperatures even under
extreme weather conditions.Tyre should remain intact and in
operational condition between temperature ranges from -25C to
60C.
Should operate at varying nature of landing surfaces.Should be
able to support aircraft landing at rough surfaces, landing strips,
ice and unpaved surfaces.
Easy access to charge air pressure.Charging of air pressure and
its checking for inspection should have easy access.
Must retain the air pressureTyre should be able to retain
maximum pressure for a longer period of time without requiring
frequent charging of pressure.
3.4ORGANIZE THE NEEDS INTO HIERARCHY
Print or write each need statement on a separate card or
self-stick note Eliminate redundant statements Group the cards
according to the similarity of the needs they express Choose a
label for each group Consider creating super groups consisting 2-5
groups Review and edit the organized needs statement
3.5HIERARICHAL NEEDS ARE AS GIVEN BELOW:
S NOINTERPRETED NEEDS
1Tyre life is measured against the number of landings that
should be higher enough to match aircraft inspections.
2Reduced maintenance at operational and inspection level.
3Cut marks, bruises, blisters and minimal frictional effects
should be encountered during the operational life
4Weather effects should have minimal or zero effect on tyre
surfaces and rubber.
5Rubber of tyre should be of good quality to support described
functions and usage.
6Tyre should not fail before completion of assign life in terms
of number of landings.
7Cost should be affordable vis--vis utility.
8Should be able to support aircraft landing at rough surfaces,
landing strips, ice and unpaved surfaces.
9Procedure and access for removal/installation should be easy
and less time consuming.
10Tyre design and dimensions should allow it to get installed on
existing wheel hub without requiring any modifications in hub
assembly.
11Tyre design should allow instant cooling after brake
application under high loading and momentum.
12Design, dimensions and weight loading capacity of tyre should
be enough to support existing aircraft braking system without
requiring any type of modification.
13Tyre should remain intact and in operational condition between
temperature ranges from -25C to 60C.
14Charging of air pressure and its checking for inspection
should have easy access.
15Tyre should be able to retain maximum pressure for a longer
period of time without requiring frequent charging of pressure.
3.6ESTABLISH THE RELATIVE IMPORTANCE OF THE NEEDSGive Numerical
importance to each customer need Feature is un-desirable I would
not consider a product with this feature Feature is not important I
would not mind having it Feature would be nice to have but it is
not important Feature is highly desirable but I would consider a
product without it Feature is critical I would not consider a
product without this feature
S NORELATIVE IMPPORTANCEINTERPRETED NEEDS
15Tyre life is measured against the number of landings that
should be higher enough to match aircraft inspections.
25Reduced maintenance at operational and inspection level.
35Cut marks, bruises, blisters and minimal frictional effects
should be encountered during the operational life
44Weather effects should have minimal or zero effect on tyre
surfaces and rubber.
54Rubber of tyre should be of good quality to support described
functions and usage.
64Tyre should not fail before completion of assign life in terms
of number of landings.
74Cost should be affordable vis--vis utility.
85Should be able to support aircraft landing at rough surfaces,
landing strips, ice and unpaved surfaces.
93Procedure and access for removal/installation should be easy
and less time consuming.
103Tyre design and dimensions should allow it to get installed
on existing wheel hub without requiring any modifications in hub
assembly.
114Tyre design should allow instant cooling after brake
application under high loading and momentum.
124Design, dimensions and weight loading capacity of tyre should
be enough to support existing aircraft braking system without
requiring any type of modification.
133Tyre should remain intact and in operational condition
between temperature ranges from -25C to 60C.
143Charging of air pressure and its checking for inspection
should have easy access.
153Tyre should be able to retain maximum pressure for a longer
period of time without requiring frequent charging of pressure.
3.6LIST OF METRICS AND NEEDS METRICS MATRIX Metrics should be
dependent and not independent or variable Metrics should be
practical Some needs cant be transferred into quantifiable metrics
The metrics should include the popular criteria for comparison in
the market place
4.INITIAL DESIGN METHODOLOGYIn order to approach the design and
then manufacturing process, the team considered following areas
vital to the manufacturing process of aircraft tyres.
1. Functional Requirements2. Material Selection3. Manufacturing
and Assembly consideration4. Cost consideration
4.1FUNCTIONAL REQUIREMENTSThe main functional requirements for
aircraft tyres are4.1.1 BalanceThe centrifugal forces exerted on
the main wheel hub and axle during the rotation of the tyre depends
mainly on center of mass and the orientation of their moment of
inertia, referred to as balance, imbalance, or unbalance.
4.1.2 Camber thrustIt is the force generated perpendicular to
the direction of travel of a rolling tyre due to its Camber
angle.
4.1.3Centrifugal growthA high speed rotating tyre develops
larger diameter due to the centrifugal forces moving the rubber
tread away from the center, which may cause speedometer errors.
4.1.4 Circle of forcesThe circle of forces, traction circle,
friction circle, or friction ellipse is a useful way to think about
the dynamic interaction between a vehicle's tire and the road
surface.
4.1.5 Contact patchThe contact patch is the area of the tread
that is in contact with the surface.
4.1.6 Cornering forceCornering force or side force is the
lateral force produced during turnings.
4.1.7 Dry tractionIt is the ability of tyre to deliver traction,
or grip, under dry conditions.
4.1.8 Force variationThe tire tread and sidewall elements
undergo deformation and recovery as they enter and exit the center
line area of tyre foot print.
4.1.9 Load sensitivityIt is measured in terms of behavior of
tyres under loading and off loading conditions.
4.1.10 Rolling resistanceRolling resistance is the resistance to
rolling caused by deformation of the tyre in contact with the
surface.
4.1.11 Self aligning torqueIt is the torque that a tire creates
as it rolls along that tends to steer it, i.e. rotate it around its
vertical axis.
4.1.12 Slip angleIt is the difference between a rolling wheel's
actual direction of travel and the direction towards which it is
pointing.
4.1.13 Stopping distancePerformance-oriented tyres have a tread
pattern and rubber compounds designed to grip the road surface, and
so usually have a slightly shorter stopping distance.
4.1.14 Work loadThe work load of a tire is the determination of
under undue stress conditions that ,may lead to premature failures
of the he tyre.
4.1.15 Tread wearThe tread wear is the wearing and tearing to
which the tread of the tyre is subjected during its life span.
4.1.16 et tractionIt refers to the tyre grip under wet
conditions on a surface.
4.2MATERIAL SELECTIONKeeping in view the functional requirements
of the aircraft tyre as described above, team decided to choose
synthetic rubber as one of main fundamental material for aircraft
tyre manufacturing. A number of polymers are used to manufacture
the aircraft type, brief description of each is given below.
4.2.1 Natural RubberNatural rubber has the chemical name
poly-isoprene and consists of polymer chains all having an almost
perfect structure. Natural rubber can attain a good regularity when
stretched. Hence it crystallizes on stretching, resulting in a high
gu, tensile strength. natural rubber is vulcanized with sulphur
compounds that can cross link the chains because of presence of
reactive double bonds making it stronger.
4.2.2 Poly-Butadiene RubberStereo specific catalysts can be used
to polymerize butadiene to a high structure. Most of the
poly-butadiene products are of the cis type but may have mix chain
structure.
4.2.3 Styrene-Butadiene RubberThese are obtained by mixing two
monomers butadiene and styrene. the chains contain random sequence
of monomer chains, which gives them rubber like behavior but does
not allow to crystallize upon stretching.
4.2.4 ButylThis polymer contains mostly iso-butylene units with
just a percentage of iso-prene units. Hence, unlike butadiene and
natural rubber products, this polymer contains only a few
percentages of double bonds.
4.2.5 Ethylene Propylene RubberThis elastomer is a butadiene
with one chlorine atom replacing one hydrogen atom.
4.2.6 NitrileThis is a co-polymer of two monomers, butadiene and
acrylonitrile, Like SBR it has an irregular chain structure.
4.2.7 HydrinIt is a copolymer of epichlorohydrin and ethylene
oxide that is primarily amorphous with small amounts of
crystallite.
4.2.8 RoyalthermIt is a relatively nw compound and is silicone
modified EPDM. It is a good value for mechanical properties.
4.2.9 ParelParel elastomer is a sulphur-capable copolymer of
propylene oxide and allyl glycidyl ether. This polymer elastomer is
finding use in applications where good dynamic properties and
flexibility at extremely low temperatures are important.
4.3DESIRED CHARACTERISTICS IN AIRCRAFT TYRE RUBBERSFollowing are
few material characteristics that need to be taken into
consideration while selecting a material for aircraft tyres.
4.3.1 Tensile StrengthSince the polymer is never extended to
more than a fraction of its ultimate elongation and tensile
strength because of the presence of reinforcements, there is a
considerable amount of controversy regarding the value of the
properties. However, the tensile strength is a good estimate of
quality of the rubber. It is measured in pounds per square inch. A
high value of tensile strength is preferred.
4.3.2 Percentage ElongationThe percentage elongation of the
rubbers is the ratio of the change in length to the original
length. The percentage elongation is a good indicatot of the
quality of rubber and is measured in interval scales ranging from
zero to 800.
4.3.3 ModulusThe modulus of rubber is measured usually as the
stress in the compound when stretched to three to four times of its
original length, the stress is calculated on the basis of the
specimens original ;length, a higher value of modulus is
preferred.
4.3.4 Heat GenerationThe heat generated in the tyre is the most
important factor resulting in its premature failure during the
service life. The properties of most polymers changes with heat. A
low rate of heat generation would allow greater life for
operation.
4.3.5 High TemperaturesHigh temperatures reduce the properties
of the polymers and cause the cords to separate.
4.3.6 Fluid ResistanceThe resistances of elastomer to liquids
lie in the volume changes that occur with time and temperature, the
change in physical properties as the rubber absorbs the liquid, the
low temperature flexibility.
4.3.7 AbrasionAbrasion is initiated by the local stress
concentrations at the contact between the track asperities and
rubber. The abrasion causes the formation of ridges perpendicular
to the direction of abrasion. These ridges are saw tooth shaped
with the teeth pointing against the direction of abrasion.
4.3.8 TractionTraction is the adhesion of the tyre to the
surface. The tract of the tyre depends on three variables, tread
design, tyre construction and tread compound.
4.3.9 AdhesionThe capability of the adhesive system is important
in determining the mass of tread, the angular speed that this mass
can be rotated and the displacement that the tread mass can
tolerate when it passes through the surface contact point.
4.3.10 ProcessibilitySince the tyre has to be built on the drum
and then cured in the mold, r rheological properties of rubber such
as green strength, building tack, and creep resistance are very
important properties.
Considering above factors, Butyl was selected as the most
appropriate material form manufacturing of the aircraft tyres.
4.4DESIGN AND MODELINGFor the designing and modeling of the
aircraft tyres, The Pacejka "Magic Formula" tire models was
employed. Pacejka has developed a series of tire design models over
the last 20 years. They were named the 'magic formula' because
there is no particular physical basis for the structure of the
equations chosen, but they fit a wide variety of tire constructions
and operating conditions. Each tire is characterized by 10-20
coefficients for each important force that it can produce at the
contact patch, typically lateral and longitudinal force, and
self-aligning torque, as a best fit between experimental data and
the model. These coefficients are then used to generate equations
showing how much force is generated for a given vertical load on
the tire, camber angle and slip angle.
The Pacejka tire models are widely used in professional vehicle
dynamics simulations, and racing car games, as they are reasonably
accurate, easy to program, and solve quickly. A problem with
Pacejka's model is that when implemented into computer code, it
doesn't work for low speeds (from around the pit-entry speed),
because a velocity term in the denominator makes the formula
diverge. An alternative to Pacejka tire models are brush tire
models, which can be analytically derived, although empirical curve
fitting is still required for good correlation., and tend to be
less accurate than the MF models.
The general form of the magic formula is
where b, c, d and e represent fitting constants and R is a force
or moment resulting from a slip parameter k.
4.5Manufacturing Considerations and Major PartsFew of the major
considerations that are to be emphasized during the manufacturing
of the aircraft tyre are discussed as under.4.5.1 TreadThe tread is
the part of the tire that comes in contact with the road surface.
The portion that is in contact with the road at a given instant in
time is the contact patch. The tread is a thick rubber, or
rubber/composite compound formulated to provide an appropriate
level of traction that does not wear away too quickly. While
designing thetread, void ratios would be kept small to provide more
rubber in contact with the road for higher traction, but may be
compounded with softer rubber that provides better traction.
4.5.2 BeadThe bead is that part of the tire that contacts the
rim on the wheel. The bead is typically reinforced with steel wire
and compounded of high strength, low flexibility rubber. The bead
seats tightly against the two rims on the wheel to ensure that a
tire holds air without leakage. The bead fit is tight to ensure the
tire does not shift circumferentially as the wheel rotates. The
width of the wheel hub in relationship to the tire is an important
factor in decideing the shape of tyre bead.
4.5.3 SidewallThe sidewall is that part of the tire that bridges
between the tread and bead. The sidewall is largely rubber but
reinforced with fabric or steel cords that provide for strength and
flexibility. Sidewalls are molded with manufacturer-specific
detail, government mandated warning labels, and other consumer
information, and sometimes decorative ornamentation, like
whitewalls. Thus the team decided to take guidelines from
regulations issued by US Department of Transportation.
4.5.4 ShoulderThe shoulder is that part of the tire at the edge
of the tread as it makes transition to the sidewall. The team
decided to take guidelines from regulations issued by US Department
of Transportation.
4.5.5 PlyPlies are layers of relatively inextensible cords
embedded in the rubber to hold its shape by preventing the rubber
from stretching in response to the internal pressure. The
orientations of the plies plays a large role in the performance of
the tire and is one of the main ways that tires are
categorized.
4.6ESTIMATED COSTS4.6.1Design CostIn design phase, majority of
costs were associated with accessing US Department of
Transportation Regulations, internet; A Modeling Software, Rubber
Specifications, World Rubber Manufacturer Catalog, Human Resource
Pay.
EntityRough Order of Magnitude CostUS Department of
Transportation Regulations2500 USDInternet25 USDModeling
Software5000 USDRubber Specifications500 USDWorld Rubber
Manufacturer Catalog500 USDHuman Resource Pay25 USD Avg/Hour
4.6.2 Manufacturing CostThe manufacturing cost would involve the
following costs.
EntityRough Order of Magnitude CostRaw Material100
USD/tyreSpinning and Weaving Process50 USD/tyreCompounding
Process75 USD/tyreBead Wiring and Forming25 USD/tyreCarcass
Forming25 USD/tyreBuffing15 USD/tyreVulcanizing100
USD/tyreFinishing85 USD/tyreInspection Cost35 USD/tyreHuman
Resource50 USD/tyreMachine35 USD/tyreTools15 USD/tyreCost of
Quality50 USD if rework required
These costs are estimated to be on average of 610-660 USD per
aircraft tire where the company was already buying an aircraft tire
from foreign vendor at a price of 2000 USD.
4.6.3 Total Project CostThe total project cost is the sum of
both design and manufacturing costs and is estimated to be around
50000 USD on a rough order of magnitude.
5.DFM AND DFA PRINCIPLESFollowing DFM principles were applied
during this project.1. The Team decided to use Butyl Rubber for the
reasons that it was full filling the requirements for functional
parameters and was easily available with rubber manufacturer and
retailers and distributors in required grade having desired
physical and chemical properties.2. Part features and tolerances
were such that these do not require any special processes.3. No
special tooling was emphasized except for NDI equipment.4. General
tooling was recommended to undertake manufacturing process.5. Most
of the dimensions are with general tolerances except the tight
tolerance at the Bead.6. Most of the operations involved are low
labor cost except the NDI that required high skill and special
equipment.7. The process was progressive one as the final part was
a single entity.8. Step-by-step and one directional manufacturing
technique is applied here.
6.GENERAL PROCESS MAP
Original Design Review
Review Client RequirementClient Requirement
Handed Over to CustomerTesting and EvaluationSimulation and
ModelingConceptual DesignDesign ReviewQuality
InspectionManufacturingDesign ApprovalDetailed
Design6.1MANUFACTURING PROCESS MAP
Cord TwistingWeavingHigh Tensile
MachineCalendaringCuttingBandingDipping MachineBanbury MixingBatch
Off MachiningHeat RollingTread ExtrudingBead
FormingCarcassingVulcanizingFinishingTread
SkiveringInspectionRelease
6.2MANUFACTURING PROCESS SCHEMATIC DIAGRAM
7.ACCEPTANCE CRITERIAFollowing acceptance criteria was reversed
engineered from the design of the aircraft tyre of company RICHELIN
(name changed for confidentiality) for our design.Tyre
Size6.00-6Ply Rating6Speed Rating 120 mphLoading1750 lbsPressure42
psiThread DesignRBSkid Depth0.18 inchTyre Weight7.8 lbsMax
Unbalance6.0 Oz-inOutside Diameter16.90-17.50 inchSection
Width5.90-6.30 inchShoulder Dia15.30 inchShoulder Dia5.8 inchLoaded
Radius6.9 InchAspect Ration0.91
8.INSPECTION CRITERIAFollowing is the inspection criteria for
the tyre that have been manufactured after processing through above
manufacturing steps. The conditions given below are not
acceptable.
1.Cuts
2. Swirl Wraps
3.Thread Separation
4.Groove Cracking
5.Rib Undercutting
6.Rubber Heating
7.Cut or Snug
8.Ozone or Weather Cracking
9.Kinked Bead
10.Inner Tyre Damage
9.REJECTION CRITERIA Tires with cuts penetrating into the inner
liner and with cuts reaching to more than 40% of the actual number
of plies. For Radial tires, cuts reaching 40% of the belt
plies.
Tire with cuts and weathering reaching the carcass plies on the
sidewall and the bead area.
Tires with spot wearing exposing the carcass or belts.
Tires with signs of cord-melting from overheating at the bead
base.
Tires with broken, bent or exposed bead wire.
Tires with wrinkles on the inner liner surface.
Dually mounted tires where one has burst in operation (Both
should be scrapped).
Tires with casing separation.
10.TESTING AND VALIDATIONFollowing test would be conducted to
check for the good tyre.1.Geometric Test.This test allows for a
complete analysis of the tire sidewall and tire tread width areas.
These measurements ensure that the tire will not have any defects
that were not able to be detected by the uniformity and
dynamicbalance tests. These defects could include bulges or
depressions in the tiresidewall, as well as in the tire tread that
could compromise the integrity ofthe tire and the ride quality of
the vehicle.
2.Compression Test.This test helps to determine if the tyre
manufactured has the capacity to sustain the loads and aircraft
momentum for what it has been designed.
3.Elastomer Check.Elastomer of the tyre rubber after
manufacturing is verified to be within the required and specified
limits as per the design requirwements.
4.Radiographic Testing.This test helps to detect the subsurface
cracks in the rubber of the tyre that can not be detected by normal
visual methods.
5.Dynamic Balancing.This test measures tires according to
static, couple, and upper and lower plane imbalance. If not
properly checked, these forces can cause an aircraft to bounce,
have tire wobble, and not steer properly.
6.Uniformity Test.This test measures force variation, run out,
and sidewall appearance. Without properly checking these forces,
the integrity of tire and quality is dramatically affected. These
forces can cause a vehicle to bounce, vibrate, and not steer
properly.
7.Wear Rate.Real time simulation of the tyre would be carried
out to measure its wearing during brake application under dry and
wet conditions. These would provide a good estimate for the life to
be assigned to the tyre.
11.CONCLUSIONWith the financial challenges arising from the
deregulation of the air-travel industry, the airlines are faced
with the challenge of reducing operating costs to remain
competitive. As a result, the airlines have demanded that the
aircraft manufacturers produce new designs with high reliability
and low maintenance requirements. In basic design, costs associated
with the aircraft tyre may be reduced by aiming at simplicity,
compactness, and minimum weight and maintenance requirements.
Simplified design and improved manufacturing techniques, are being
used to reduce the part-count.
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