AMT- Materials Flashcards
Critical Temperature
The temperature in which metal structure cannot carry the service load it was designed to do due to softening from critical temperature.
Hot working
Metal is worked above critical temperature
Cold working
Metal is worked below critical temperature
Rolling
Can be hot or cold working process. Metal is compressed between rollers.
Forging
Metal is shaped by pressing, dropping, hammering at above critical temperature
Extruding
Hot or cold process. Metal is forced through a die to create seamless superior product.
Casting
Liquid state metals poured in mold to form shape. Widely used for parts such as turbine blades.
Why is cold rolling preferred over hot rolling
Cold rolling makes the metal stronger due to work hardening
Why does cold working provide a more accurate finish and dimensions
No thermal expansion
What must be done to cold worked metal for further forming?
Annealing. Work hardening occurs when cold worked which makes the metal hard and brittle. Annealing relives the stresses and softens the metal so it can be worked further.
What metals can be extruded?
Lead, tin, aluminum, alloys, copper, titanium, molybdenum, vanadium, steel
What is an advantage of cold extruding?
No oxidation, good surface finish and mechanical properties
What is a non-ferrous metal?
A metal that does not contain iron (Fe)
What is an alloy?
A mixture of metallic solid solution composed of two or more elements that adhere to certain desired properties
What advantages come from allowing aluminum?
Aluminum can exceed mechanical properties of some steel. Strength increased.
Advantage of alloying molecular-wise
Stops dislocations of molecules from spreading. Resist deformation.
Identify: AA 1140-H14
AA- Aluminum Association
1-Commercially pure Aluminum
1- Alloy mod once
40- 40 points above 99% pure (99.4%)
H1-Alloy hardened by working
4- Worked to harden to one half of potential
Temper designations
O
Annealed
Temper designations
H1
Strain hardened by cold working
Temper designations
H12
Strain hardened by cold working
2 indicates 1/4 hardness
Temper designations
H14
Strain hardened by cold working
4 indicates 1/2 hardness
Temper designations
H18
Strain hardened by cold working
8 indicates full hardness
Temper designations
H19
Strain hardened by cold working
9 indicates extra hard
Temper designations
H2
Strain hardened by cold working and partially annealed
Temper designations
H3
Strain hardened and stabilized
Heat treatment
O
Annealed
Heat treatment
F
As fabricated
Heat treatment
T
Heat treatable alloy
Heat treatment
T3
Solution Heat treated and strain hardened
Heat treatment
T36
Solution Heat treated and strain hardened
6= amount strain hardening, reduction of 6%
Heat treatment
T4
Solution Heat treated and room temp aging
Heat treatment
T6
Solution Heat treated and artificial aging
Aluminum Alloying Elements
1xxx
Aluminum (99% pure)
Aluminum Alloying Elements
2xxx
Copper
Aluminum Alloying Elements
3xxx
Manganese
Aluminum Alloying Elements
4xxx
Silicon
Aluminum Alloying Elements
5xxx
Magnesium
Aluminum Alloying Elements
6xxx
Magnesium and silicon
Aluminum Alloying Elements
7xxx
Zinc
Aluminum Alloying Elements
8xxx
Other Elements
Identify AA 2024-T3
AA- Aluminum association
2- copper
0- no mods
24- 24th alloy in the family
T- heat treated
3- solution Heat treated and strain hardened
Solution Heat treatment
Heating of an alloy to a temperature at which a particular constituent will enter into solid solution followed by cooling at a rate fast enough to prevent the dissolved constituent from precipitating
Precipitation heat treatment
A treatment involving the heating or aging of an alloy at elevated temperature to cause a constituent to precipitate from solid solution. To separate
Purpose of heat treating
Used to alter physical/chemical properties of a material and achieve desired results such as hardening or softening.
Annealing
Heating to just above critical point, soaking in that temp then cooling slowly.
Natural aging
Cooling at room temp/air temp
An alloyed aluminum that has a thing pure aluminum layer mechanically attached that provides corrosion protection. Layer has a thickness of 5% total thickness on each side.
ALCLAD
How does the pure aluminum on ALCLAD prevent corrosion
Oxide layer forms on pure aluminum. Aluminum oxide is impervious (non-porous) to water, protects alloy. The alloy itself would not do this as the copper, zinc etc. would react with aluminum in presence of water.
Why is magnesium a useful alloy/metal for Aircraft materials?
Magnesium weighs two thirds that of aluminum. Hexagonal unit shaoe makes toughness a property.
Disadvantage of magnesium?
Burns/ignites, hard to extinguish.
Advantages of titanium
High strength to weight ratio Resistant to stress cracking Low coefficient thermal expansion Resistant to most corrosive substances Short term, extreme heat properties ideal for use in aircraft firewalls
Bright white Starbursts at end of stream would indicate which metal?
Titanium
Why is copper limited in its uses for structural material
Limited because of its weight.
This metal is used for spark plug gaskets due to its electrical conductivity
Copper
What is composed in bronze
Copper (75-90%) and tin( 10-25%)
What is composed in brass
Copper (55-70%) and zinc (30-45%)
What is brass commonly used for in aircraft?
Bearing metal and seal applications
Describe sintered metals and an advantage of sintered brass and bronze.
Sintering: objects created from metal powders held in molds, pressed then heated BELOW melting point.
Brass and bronze used as bushings that self lubricate due to oil retention of sintered form
Galling
Rubbing or mating of surfaces. Transfer of material between metallic surfaces via heat from motion. Metal gets hot it welds and the surface metal is destroyed.
Brinelling
Caused by excessive impact. Permanent indentation of hard surface
Spalling
Chipped away portion of hardened surface
Fretting
Corrosion due to vibration and slip in contact areas between materials
What are the 4 nickel alloys used in aviation?
Monel
K-Monel
Inconel
CRES (Corrosive Resistant Steel)
Monel
Nickel with 31.5% COPPER alloyed
Used in lockwire
High temp environment
K-Monel
Nickel alloy with small amount of aluminum
Preferred choice for landing gear components
Toughness and corrosive resistant
High fatigue strength
High UTS levels with proper hardening
Inconel
Nickel with 7.2% IRON and 15.8% CHROMIUM
Lockwire
CRES (Corrosive Resistant Steel)
High iron content but included as nickel alloy
Austenitic CRES used for hardwire and lockwire
Fasteners prone to galling
Ferrous metals
Metals with iron in them (Fe)
How is iron ore reduce to iron metal?
What is the reduction process called?
Mixing ore with limestone and coke (pure carbon) and heating.
Carbon combines with oxygen forming superheated Co (carbon monoxide). Removes oxygen from iron ore.
Limestone melts and absorbs impurities from iron (flux)
Reduction process called SMELTING
What is pig iron
High carbon form of iron that is brittle and useless. Results after smelting.
How is steel made from pigs of iron?
Carbon is burned out of the metal then quantities of other elements are added into purified iron. Steel then poured into ingots.
SAE
Society Automotive Engineers
AISI
American Iron and Steel Institute
10xx-13xx are what type of steel groups?
Plain carbon steels
Identify
SAE 1020
SAE- Society Automotive Engineers
1- plain carbon steel
0- nothing added besides carbon
20- 20 points or 0.2% carbon added
Identify
SAE 1130
SAE- Society Automotive Engineers
1- plain carbon steel
1- Sulphur added, free machining steel
30 -30 points carbon 0.3%
Percentage of carbon in LOW carbon steels
0.10% to 0.30%
Percentage of carbon in MED carbon steels
0.30% to 0.50%
Percentage of carbon in HIGH carbon steels
0.50% to 1.05%
Steel alloys
1xxx
Plain carbon steel-low
Steel alloys
2xxx
Nickel
Steel alloys
3xxx
Nickel chromium
Steel alloys
4xxx
Molybdenum
Steel alloys
5xxx
Chromium
Steel alloys
6xxx
Chromium vanadium
Steel alloys
8xxx
Nickel, chromium, molybdenum
Steel alloys
11xx
Sulfur mod
Steel alloys
12xx
Sulfur and phosphorus mod
Steel alloys
13xx
Sulfur, phosphorus and manganese mod
Identify
SAE 2330
SAE- Society Automotive Engineers
2-nickel major alloy element
3- approx percentage of nickel
30- carbon points 0.3%
In 4130, what does the “1” stand for
4= Molybdenum family
1=Percentage of chromium
Hardness
Ability of metal to resist abrasion, penetration, permanent distortion
When quenching what should you do when submerging metal in substance?
Agitate it, so you reduce boundary layer from insulating and resulting uneven temperatures
Quenching
Results change in microstructure, gives tool high hardness and brittleness
Purpose of tempering
Trade brittleness for plasticity
Normalizing
Carried out by heating to above critical temperature then cooled at room temperature
Casehardening
Hardness process where the outer shell of metal goes through a chemical reaction to harden and become stronger around the core.
Carburizing
Carbon used as hardening agent in casehardening
Nitriding
Raising temperature to 900⁰-1150⁰ F then introducing ammonia gas (NH3) Gas decomposes into nitrogen gas.
Nitrogen infuses and reacts with elements in metal to form nitrites which harden the surface. Creates a 0.060 layer. Copper used on areas not to be nitrided
Babbit
Mixture of soft metals (lead, aluminum, copper) with metals (zinc, cadmium) resulting a metal alloy capable of long life. Used as bearings due to resistance of galling.
_____ is the #1 issue in aircraft design
Weight
Why are aircraft structures easily damaged?
Because they are lightweight
Primary structure
Portion of an airplane that would seriously endanger its safety if it failed.
Examples of primary structures
Wing spars, wing, fuselage skins, control surfaces, engine mounts
Secondary structures
Structure not critical to flight and ground safety.
Examples of secondary structures
Cowlings, fairings, interior furnishing, unpressurized windows, stringers
What type of fuselage construction is this
Truss
Longitudinal members that extend across several frame members and help the skin support primary bending loads.
Longerons
____relies on triangles to make it strong
Truss
A ___truss uses mostly diagonal bracing
Warren
A ____truss uses perpendicular bracing
Pratt
Gusset
Plate used to strengthen joint in a structure
This type of construction is extruded as one piece which makes it stronger than welded portions. It does not have longerons or stringers and the outer skin carries the primary loads
Monocoque (single shell)
Former
A structure that gives shape to the fueslage much like a rib would in a wing
Bulkhead
A structure that gives shape to the fuselage, a “face” to a sub-structure
What kind of construction type is this
Semi-monocoque
Short pieces between longerons. Provide shape and attachment for skin
Stringers
Extend over several formers helping skin support primary bending loads
Longerons
Advantages of semi-monocoque
Additional internal structure helps lighten weight as skin can be thinner. Design choice for pressurized cabins
Full cantilever
Semi-cantilever
What are the small structures attached to the struts called
Jury struts
Identify parts of wing construction
When you tighten drag wires, why are you able to tighten both ends
There are right hand and left hand threads on each end
Primary load carrying component in a wing, horizontal stabilizer, vertical stabilizer, most control surfaces etc.
Spar
If height is doubled in a Spar….
Carry ability is quadrupled
Secondary structure component in a wing. Gives aerodynamic shape, holds spars upright, gives rigidity, transfers loads
Ribs
In combination with spars and ribs, what is designed to carry part of flight and ground loads?
Wing skin
What is a wet wing
Wing that carries fuel, sealed with fuel resistant sealant.
Smooth airflow, non-load carrying, tertiary structure. Reduces interference drag
Wing root fairings
This landing gear is located between nose wheel and main wheels
Tricycle
This landing gear has a wheel at the tail end
Conventional
Methods of checking relative alignment of an aircraft
Special dihedral board with spirit level
Incidence board
Symmetry check on small aircraft
Measurements between points taken with steel tape
Symmetry check on large aircraft
Spring scale to obtain equal tension. Dimension position chalked on floor using plumb bobs.
Can also use a construction transit
What is the primary objective of aircraft repair?
To restore damaged parts to original condition.
What do you look for in the case of damage from a lightning strike?
Bearing damage, melted resin in composites
What’s the main thing to look for to identify a hard landing?
Wrinkling skin
How do you check a float for leaks
Put plane in after for 24 hours or fill float.
Should you use blind rivets on floats?
No, they create leaks
A location where cross-sectional area of a part changes abruptly
Stress riser
What must you do after repainting an aircraft control surface. And why?
Rebalance it as the weight may have changed from the paint and could cause flutter.
True or false.
Any time a repair is made to an aircraft, the same material (alloy) must be used
True
As an AME basic knowledge of aircraft materials is used to:
Correct choice of material for repair
Correct choice of surface treatments needed for corrosion
Understand load levels of fasteners
3 classes to describe material properties and their descriptions
Mechanical, how a material acts/works (torsion)
physical, how a material described (balsa wood, Sitka spruce)
chemical, how a material reacts with other materials
Examples of mechanical properties
Plasticity Ductility Malleability Brittleness Elasticity Strength Fatigue Creep
Examples of physical properties
Electrical/conductivity Thermal conductivity Magnetic conductivity Melting point Specific gravity Density Colour Thermal coefficient
Examples of chemical properties
Oxidization
Reduction
Corrosion
Phenomenon of progressive failure of a material due to cyclical induced cracking
Fatigue
If we prevent tension loading on the surface ____can be prevented if not postponed
Fatigue failure
A process that puts compressive load on the surface to counter tension loads which normally break a part. Done with metal balls, accurately shot at surface until smooth.
Shot peening
Metal fatigue cracks can only start where metal is in ____ not ____
Tension, not compression
Slow plastic deformation, change in geometry when parts subjected to load. Caused by load valued below materials yield point over time
Creep
How do you check for blade creep
Use a feeler gauge to measure thickness between blade and encasing ring
Temperature which material will change from solid to liquid
Melting point
Comparison of weight of given volume with equal volume of demineralized water.
Specific gravity
Weight per unit volume of a material
Density
Ability of material to reflect and absorb different wavelengths of light energy
Colour
The change in the physical dimension of a material due to its level of thermal energy
Thermal coefficient of expansion
Two metals bonded with different coefficients of expansion.
Bimetal strip
Combination of an element with oxygen to form an oxide. Result physical, chemical and mechanical properties differ drastically from the original element properties
Oxidation
Removal of oxygen from a compound or oxide to isolate element
Reduction
Undesirable attack on a material. May take form of atmospheric, submarine, subterranean or electrolytic attack.
Corrosion
Derives it’s scale numbers from the DEPTH of the imprint it makes in the metal. Uses diamond cone
Rockwell
Diagonal measurement of hardness testing. Measure impression diagonals
Vickers
Hardness number derived from DIAMETER of indentation in test piece. Use microscope
Brinell
Derived by depth of indentation. Used for soft metals.
Barcol
Ability of material to resist tearing under bending or tensile loads
Toughness
Materials resistance that opposes deformation due to applied external load. Measured in kpi
Stress
The degree of deformation due to stress
Strain
Testing materials to their failure point to find their ultimate strength
Destructive testing
Point where permanent deformation takes place. Plastic
Yield point
Point just prior to failure
Ultimate tensile strength
What region precedes the yield point
Elastic region
Columns of stacked cells
Cellulose Fibre
Complex of thermoplastic matrix which holds the fibers in position.
Lignin
The living rings of cells between the heartwood and outside of the tree (bark)
Sapwood
The dormant rings of cells starting with the pith and radiating out. Preferred lumber source
Heartwood
The very center column of cells, the first growth of the tree
Pith
Growth layer. The cell manufacturing layer between the sapwood and the bark
Cambium
The covering of the tree which provides the tree with protection. Dead and dry
Bark
The large cell concentration produced in cooler wetter conditions
Springwood
Smaller more dense cell concentration produced during warmer, drier conditions
Summerwood
This wood comes from deciduous trees. Angiosperms (seeds have coverings like fruit)
Hardwood
This wood comes from coniferous (cone-bearing) trees. Gymnosperms (no seed covering)
Softwood
The standard wood for all wood used in aircraft structures.
Sitka spruce
Method of sawing dimensional lumber from a log to produce a board with the growth rings perpendicular to the face of the board. Results most stable, highest quality lumber being produced
Quarter sawing
Quarter sawn exhibits ____grain
Vertical
Plain or flitch sawn lumber exhibits ____grain
Angular or flat
Refers to alternating regions of darker and lighter wood resulting from the differing growth parameters in different seasons
Grain
This shrinkage occurs perpendicular to growth lines
Lineal shrinkage
Shrinkage occurs parallel to growth rings
Tangential
What shrinkage is the largest dimension of shrinkage that often causes checking
Tangential
A form of wood, one piece
Solid
A form of wood, more than one piece with grain running the same direction
Laminated
Form of wood, more than one piece with grain running different directions
Plywood
Max grain deviation
1:15 rise over run
Ac43.13 lists minimum and naxinum ring count for Aircraft wood at ______rings per inch
6 and 15
What ring count is preferred according to ac43.13
12-15
When viewed from end, a board face edge will have an angle between it and growth rings, between ______
45-90⁰, 45 is minimum. 90 is ideal
A portion of a branch that is embedded in wood of a tree trunk
Knot
When two growth rings separate along their circumferential surfaces, a sticky solution fills the gaps
Pitch pocket
Environmental imbalance causes tree to compensate by growing dense wood on one side of trunk. A pith is offset from center. Excess of summerwood. Too brittle for use.
Compression wood
Natural result of bound water reduction in logs from saturated state to required equilibrium water content less than 15% of the weight. Not permitted in certified wood
Checks
A moisture content of ____ in wood is approved. ___is preferred
8-15%, 10-12% preferred
Separation of cells in any direction from mechanical force. Can be caused by a check in drying process
Splits
What are indications of decay
Softening, swelling, discolored, bad odor
How do you check wood for decay
Pick at it with knife, chunks out means rot. Can also check for hollow sound with tap test.
What must wood be protected with
Quality marine varnish (2 part epoxy)
Plasticized lacquer that is applied to fabric covered aircraft. Tightens and stiffens.
Dope
The gold standard glue used in wood repairs
Resorcinol formaldehyde synthetic resin glue
Obsolete glue used in aviation due to short life in hot moist conditions
Urea formaldehyde resin glue
Sometimes reduced in hot moist environments
Epoxy resin araldite
Plastic that can be reheated and reformed. Ex: Lignin
Thermoplastic Resin
Plastic that once set, cannot be reheated and reformed. Ex: Epoxy
Thermosetting Plastic Resin
Unique low frictional coefficient, high toughness, electrical insulation, resists heat, high impact strength, gear used to drive distribution wiper in aircraft magneto
Nylon
Thermoplastic resin with nylon slipperiness. Proper name is polytetrafluoroethylene. Toughness of this and low friction coefficient makes it a good bearing material. No lubrication needed due to low friction
Teflon
Disadvantages of polyester resin
High cure shrink, limited working time, moderate mechanical properties,
2 part adhesive that gives off heat due to chemical reaction. Exothermic reaction.
Epoxy
This can be a brittle substance of a 2 part adhesive used to paint aircraft. Adding softeners can make it not chip at all
Epoxy paint
What is an example of a phenol formaldehyde resin or phenolic.
Micarta, bakelite, formica
Reinforcing fiber that is added to phenolic too give toughness
Flox
Examples of flox used in phenolic formaldehyde resins
Linen, cotton, glass, nylon , paper
____ agents used to thicken and reinforce thermosetting plastic resins.
Thixotropic
Examples of thixotropic additives
Microbaloons,
A chemical process for converting rubber or related polymers into more durable materials via addition of Sulfur or other relevant curative or accelerators
Vulcanization
Aviation sealants are 2 parts mixed by __
Weight
Organic natural sources of covering fabric
Cotton, linen and silk
Synthetic sources of fabric covering
Polyester, glass, nylon
Grade A cotton must have a min tensile strength of ___per inch
80lbs
How can you test integrity of fabric
With seyboth or Maule test
Service strength of fabric must be __ of original
70%
Process of dipping fabric into caustic soda then rolling in a calendar mill to increase strength, Lustre and lay out knap (little stray fibers)
Mercerizing
More threads, one direction
Uni-directional
Same number of threads in both directions
Bi-directional
Where is the warp of the fabric located?
Along the salvage edge, running down the roll
Where is the fill located
Across the fabric, from salvage edge to salvage edge.
Used originally on cotton, highly flammable, cotton fibers dissolved with nitric acid along with other additives.
Nitrate dope
Developed by the US Navy, cellulose fibers dissolved in acetic said and butyric acid plus additives. Less adhesive, less flammable
Butyrate dope
Why is butyrate dope added on top of nitrate dope?
Nitrate dope is more adhesive and will stick to fabric better. Butyrate sticks better directly to nitrate dope
What is added to dope to protect from UV rays
Aluminum powder
Glass resistant to electricity, good resistance to fatigue, high strength, 98% of fibers borosilicate glass.
E-Glass
Structural glass, lighter and stronger than E-glass,
S-Glass
This material is made from nylon, impact resistant “bulletproof”, high tensile strength, low compressive strength, not used on critical structures, absorbs water, requires special tools to cut
Aramid Fibers (Kevlar)
This material is high tensile strength, lightweight, black in colour, fails without warning when stress limit is reached, negative coefficient of thermal expansion, causes issues with thermal balance
Carbon fiber
This material is very stiff and has Hugh tensile and compressive strength. Usually prepreg, large diameter makes it hard to bond to curved surfaces, used to repair aluminum, barbed molecules hazardous to health
Boron fibers
The performance of a composite structure depends on what.
The orientation of the fibers
What are some honeycomb core materials?
Paper, nomex, carbon, fiberglass, metal,
How do you inspect for delamination
Tap test, soft/desd sound indicates delamination
Impact damaged honeycomb is repaired with a ____or ____ type repair
Scarf or patch
Heat sources used for composite repair
Oven, autoclave, heat blanket, heat lamp, hot air systems.
Corrosion resistant steel most often used in aviation?
18-8 (chromium and nickel)
What is quasi-isotropic layup
Multiple layers of materials all differing by 45 degrees in orientation
Three designs of wing construction?
Monospar, multispart and box beam
Carbon fiber advantages
High strength, corrosion resistance
Tempering always follows ____ never precedes
Hardening
What’s the difference between carbon and graphite planes?
Graphite is 3d, carbon is 2d
Types of wooden ribs?
Plywood web, lightened plywood web, truss types
Max years fabric can be in service
15-20 years
What does magnesium silicon allow in an alloy?
Makes alloy heat treatable
What does the first digit in the wrought aluminum designation indicate?
Identifies the alloy type
Main types of aircraft structures?
Truss and monocoque
Firewalls can be made of what steel?
Stainless steel
How do you cut dry prepreg fabric?
With a special knife
What does Sulfur do when added to metal?
Improves machinability
Aluminum alloy mostly used for fuel tanks?
5052, 3003
Purpose of stringers?
Give shape, attach skin, prevent tension and compression from bending fuselage
Aluminum alloys commonly hardened by?
Cold working