MATERIAL ENGINEERING

The Airbus A330 is a large capacity, wide body, twin-engine airliner capable of medium to

long range commercial passenger flights.

The A330-200 engines:

Rated ETOPS-180min (Extended-range Twin-

engine Operation Performance Standards)

Thrust range: 303-320 kN (68,000-72,000 lb).

The types used:

General Electric CF6-80E1

Pratt & Whitney PW4000

Rolls-Royce Trent 700

The PW 4000 engine:

The most advanced nacelle and the lightest weight.

The first engine in the industry to qualify for ETOPS-180min

Service-proven technologies in material and aerodynamics.

Meets all present noise and emission regulations.

Maximum performance, reliability and durability.

PW4170 Advantage70™ provide upgrades.

The pylon box is the

primary structure. It

supports the engine

through two points and is

attached in two points to

the half wing.

Material composition of pylon box

Pylon box structure

Steel

Alloy consisting iron with carbon content ( 0.2% to 2.14%)

Carbon acts as hardening agent – prevents dislocations of iron atom crystals

Increased carbon content increase hardness and strength but also brittleness.

Two types of steel:

> Carbon steel

> Alloy steel

Advantages of alloy steel over carbon steel:

Greater strength, resistance to wear, springiness and resistance to corrosion.

Improved mechanical properties obtained by less drastic heat treatment than required by plain carbon

steel.

Chromium molybdenum steel:

It is an alloy steel.

Molybdenum reduces grain size of steel and increases impact strength and elastic limit.

Extremely wear resistant

High fatigue strength

Tensile strength

Ideal for high-strength structural application such as a pylon holding an engine of significant weight.

Inconel 718

A nickel alloy containing chromium.

It has a 50-55% content of nickel and 17-21% content of chromium

and small percentages of iron, aluminium and titanium.

Properties of INCONEL® alloy 718:

Corrosion-resistance

Excellent welding characteristics

Good tensile strength

Fatigue strength

Creep and rupture strength

Use in pylon: 3 sleeve/thread pin assembly on Rib 18a (attachment point of pylon to wing)

Threaded pins are used to assemble 2 pieces together and must support the load hence Inconel 718 is an appropriate

material choice. It has high tensile strength, creep and ruptures strength and fatigue strength that is ideal for the

function of supporting load and allows durability and reliability. Its corrosion resistive property also allows more

durability and reliability. The material can withstand high temperature (423° to 1300°F) which is ideal considering the

high temperature operation of the engine. The economical fabrication procedures enable the best mechanical

properties to be formulated.

Aluminium alloy

Aluminium alloys are mixtures of aluminium with other metals like copper, zinc, manganese, silicon, or

magnesium.

They are much lighter and more corrosion resistant than plain carbon steel, but not as corrosion resistant as pure

aluminium.

Bare aluminium alloy surfaces will keep their apparent shine in a dry environment due to the formation of a clear,

protective oxide layer.

Use in pylon Forward access doors between ribs 10 and 11

7000 Aluminium alloy series is an appropriate material choice for the forward access doors. It is light in weight and

has high tensile strength which makes it ideal for the function of supporting loads and allows durability and

reliability.

Properties of 7000 series-

Alloyed with zinc

Precipitation hardened to the highest strengths of any aluminium alloy.

Primarily used due to its low weight, the ease with which they can be formed and fabricated, and their corrosion

resistance in many atmospheric and immersion environments.

Not resistant to corrosion in many marine environments and are subject to crevice corrosion, pitting.

Some of the 7000 series alloys are subject to stress corrosion cracking when heat treated to high strength levels.

Subjected to galvanic corrosion as they have an anodic potential with respect to most other metals.

Heat treatable to obtain high strengths..

Heat treatment of 7000 series

Aluminium base 7000 series alloys can have improved tensile properties when, after heat treatment and

subsequent quenching, they are subjected to a three-step aging process comprising a first aging step at 190°-

230° F., a second aging step at over 230° F. and a third aging step at 315°-380° F.

Stainless steel

o Stainless steel is an iron alloy with about 11% chromium.

o The chromium content in stainless steel alloys prevents corrosion.

o Types of stainless steel based on the crystalline structures: Austenite, Ferrite, Martensite, Duplex (austenite – ferrite)

and Precipitation-hardening martensitic stainless steels.

Use in pylon Spigot fitting and lower arm spar

o Spars are a means of providing extra strength to the structures and hence 17-4HP, a precipitate hardening stainless

steel is an appropriate material choice. It has high tensile strength, creep and ruptures strength and fatigue strength that is

ideal for the function of supporting load and allows durability and reliability. Its corrosion resistive property also allows more

durability and reliability

Properties of Precipitation hardening stainless steel

o Moderate to good corrosion resistance in a range of environments

o Good oxidation resistance

o Easy machinability

o High Tensile strength

o Low cost

o High fatigue and creep strength

Manufacture and heat treatments

o Stainless steel is formed by solution annealing and precipitation hardening (age hardening)

Titanium Silvery grey white metal.

Very reactive and because of that it is often use for alloying deoxidizing other metals.

Titanium and titanium alloys are heat treated for the following purposes:

To reduce residual stresses developed during fabrication

To produce an optimal combination of ductility, machinability, and dimensional and structural stability.

To increase strength (solution treating and aging)

To optimize special properties such as fracture toughness, fatigue strength, and high-temperature creep strength.

Welding generally increases strength and hardness

Welding generally decreases tensile and bend ductility

Welds in unalloyed titanium grades 1, 2 and 3 do not require post-weld treatment unless the material will be highly stressed in a strongly reducing

atmosphere

Titanium properties:

High resistance to corrosion, stress, and cracking

It withstands high temperatures

It has high resistance to creep and fatigue .

High strength to weight ratio and tensile strength

Has low electrical conductivity

Titanium alloysApplications:

High strength to weight ratio - Aircraft, fuselage skin, frames, compressor blades, nozzle guide vanes, and sporting equipment, etc.

Excellent corrosion resistance - Chemical processing, desalination, power generation equipment, valve and pump parts, marine hardware, and

prosthetic devices.

In pylon construction such as primary structure, pylon to engine, pylon to wing, secondary structure and etc..

Ti-5Al-2Sn-2Zr-4Mo-4Cr and Ti-10V-2Fe-3Al used for primary part of pylon Rib 12, Pylon to engine and pylon to wing part Rib 18A which contains 4

shackles made up of Beta titanium alloys.

Alpha Alloys:

Typically contain aluminium and tin, though they can also contain molybdenum, zirconium, nitrogen, vanadium, columbium, tantalum, and silicon.

Do not generally respond to heat treatment, but they are weld able.

Commonly used for applications like airplane parts, and chemical processing equipment.

Ti-8AL-1Mo-1V, Ti-6AL-2Sn-4Zr-2Mo are the alpha alloys designed for resistance to creep at elevated temperature.

Alpha-Beta Alloys:

for service up to 595 C, such as Ti-1100 and IMI-834 are being developed as casting. Can be strengthened by heat treatment and aging, and therefore

can undergo manufacturing while the material is still ductile, then undergo heat treatment to strengthen the material, which is a big advantage.

As aircraft engine manufactures seek to use cast titanium at higher operating temperatures, Ti-6Al-2Sn-4Zr-2Mo and Ti-6Al-2Sn-4Zr-6Mo are being

specified more frequently.

Other advanced high temperature titanium alloys

Beta Alloys:

Smallest groups of titanium alloys

Have good harden ability, good cold formability when they are solution-treated, and high strength when they are aged.

Slightly denser than other titanium alloys.

High creep resistant alloys, they are weld able, and can have yield strengths up to 1345 MPa. They are used for

heavier duty purposes on aircraft.

Fabrication

Difficult to fabricate because of its susceptibility to oxygen, nitrogen, and hydrogen impurities which cause the titanium

to become more brittle.

Elevated temperature processing must be used under special conditions in order to avoid diffusion of these gasses into

the titanium.

Commercially produced titanium products are made in the following mill wrought forms; plate, tubing, sheet, wire,

extrusions, and forgings.

Titanium can also be cast, which must be done in a vacuum furnace because of titanium's reactive nature.

Primer on steel

There is a very large range of different primer systems that can be applied to bare steel, aluminium sprayed

surfaces or galvanized surfaces.

For protecting internal suraces, component is usually galvanized first and any required cosmetic painting

applied on the visible external surfaces. Steel primers provide additional corrosion resistance and improve the

appearance of decorative top coat finishes.

Special properties

Non toxic – safe to use.

Designed to match electrical resistivity

Contains no chlorides or carbon particle dispersions

Alkaline in nature, will increase passive protection

Contains a powerful corrosion inhibitor

Application

It is widely used in aviation particularly in pylon construction. Such as primary part Rib 1 pyramid structure, Rib

2 to 8, in two caps at upper spars, two side panels.

Sandblasting Sandblasting is a process of smoothing, shaping and cleaning a hard surface by forcing solid particles

across a surface at high speeds.

Mainly done to clean or etch a surface.

t is also known as bead blasting or blast cleaning (similar effect as using sand paper.)

Provides a more even finish, especially at corners with ease.

Sandblasting equipment

The abrasive itself used for cleaning the surface

An air compressor

Blaster gun

Applications

Sandblasting is primarily used for two different types of applications.

Clean a surface of anything that might be clinging to it

Either etch, carve designs into materials or to shape a material

It is mainly used as a method of priming (removal of all imperfections and giving a smooth surface) a

surface for the application of paint or a sealant.

Aluminium thermal spray

Thermal spraying is used to provide:

Anti-Corrosion.

Heat Shield.

Erosion Prevention.

Insulation

Benefits of Thermal Spraying

Comprehensive choice of coating materials: metals, alloys, ceramics, cermets and

carbides.

Thick coatings can be applied at high deposition rates.

Coatings are mechanically bonded to the substrate can often spray coating materials

which are metallurgically incompatible with the substrate, e.g., materials with a higher

melting point than the substrate.

Components can be sprayed with little or no pre- or post-heat treatment, and component

distortion is minimal.

Parts can be rebuilt quickly and at low cost, and usually at a fraction of the price of a

replacement.

By using a premium material for the thermal spray coating, coated components can

outlive new parts.

Thermal spray coatings may be applied both manually and automatically.

Types of Thermal Spraying Processes

Cadmium plating Cadmium Plating is electroplating process which provides a deposition of corrosion resistant cadmium coating on metals Provides a high degree of corrosion protection unmatched by other coating systems. Protects even in aggressive corrosion conditions including atmospheric, saline and alkaline conditions. Unique ‘sacrificial’ action, meaning the protective coating, even after receiving damage or scratches, will itself corrode before

allowing the base material (steel and other structural metals) to corrode leaving it undamaged.

Features Superb corrosion protection; (> 2,000hrs salt spray) Low coefficient of friction (0.15 vs steel) Ductile Can be chromate coated for enhanced corrosion protection

Benefits Provides prolonged corrosion protection to key components Prevents galvanic corrosion between steel fasteners and aluminium Reduces the tightening torque of fasteners and allows repeated dismantling Helps guarantee the safety of highly stressed components  Good lubricity, easy solderability Attractive polishable silvery finish

Applications In aerospace industries , Cadmium plating prevents bimetallic corrosion between high tensile steel fasteners and aluminium

alloys. Important for bolts used with engines, major structural members and landing gear and for fasteners for aluminium sheet. Use of this process has been restricted in many industries to places where alternative coatings cannot be used, due to its

health hazards.

Pylon operating conditions

significant tension exerted on the pylon as it acts as a bridge between wing

and engine.

 thermal expansion and contraction while the aircraft is parked, engine warm-

up, take-off, reverse thrust, and cruise.

thermal shock, cracking and unrestrained expansion weakens the structure

and it cracks.

Wing flutter

High number of cycles.

Conclusion Material properties required by the pylon:

High Tensile strength

High Compressive ,shear , yield strength

Tough – resistance to bending

Thermal properties

Thermal stability

Withstand high temperatures.

Non- Flammable

Chemical properties

High Corrosion resistance

In conclusion the materials in the pylon are appropriate for its function of supporting the engine to the wing. Steel

the major constituent of the pylon has the property of very high tensile strength making it a wise choice for the

pylon

along with all the other materials such as stainless steel, titanium, Aluminium alloy and Inconel 718. The cadmium

plating and the Aluminium spray with primer coating enables the corrosion resistant property of steel.