問題一覧
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Metals which contain
iron is ferrous metals
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The carbon content in medium carbon steel is
0.3-0.8 %
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• A steel with 1.3 % carbon content is
high carbon steel
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At normal temperature High Carbon Steel is harder because
of the percentage of carbon in the granules
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Pearlite is a laminate microstructure of steel consisting of
ferrite and cementite
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Cementite is
Strong but hard and brittle
7
Grinding of a steel reveals a
dull but spark pattern (lots of forking). It is likely to be high carbon steel
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a material to fracture when subjected to a shock loading or blow : a
brittleness
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Plasticity is
the opposite to elasticity
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Toughness is the opposite of
brittleness
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is the ability to resist off-set (scissor action) load
Shear strength
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An Impact Test measures
toughness
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The Charpy and Izod tests are types of
impact tests
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The brinell hardness testers uses a
steel ball indenter
15
the effects of annealing steel
decrease in internal stress and softening of the metal
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Steel annealing process it
relieves internal stress suffered After engineering processes
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Fatigue tests can be carried out
either on individual components or on complete aircraft structure
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Case hardening is
heat-treating process of metal produces a hard, wear-resistant surface over a strong, tough core
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Thermal conductivity
ability of a material to conduct a certain amount of heat within a given time, copper is a good example is
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Normalizing heat treating
Iron- base metals
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Nitriding of steel by
ammonia gas
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the aluminum will have a
lower VPN Vickers pyramid hardness than the steel
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The Bayer process to convert
bauxite to alumina
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Duralumin
2000 series of aluminum alloy
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Primary aircraft structure (skin and spars etc.)
made of C-110M • titanium
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The ‘Nimonic’ series of alloys are
high temperature, corrosion resistance
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The melting point of titanium is
1668˚C
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The two classes of aluminum alloy is done to
Wrought (worked) and Cast (moulded)
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The mechanical properties of pure aluminium are
silvery white metal which is soft and ductile
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Adding other elements to aluminum alloys, such as copper, manganese or magnesium
decrease corrosion resistance of the aluminum
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Clad aluminum alloy (alclad
5% of alloy thickness
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The heat treatment of clad aluminum alloys must not be carried out more than
three (3) times
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The purpose of rivets Refrigeration
to make rivets the soft formable condition
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The identification No. of zinc in aluminum alloy is
7
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The 6000 series of aluminum alloy principle alloying element of
magnesium and silicon
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Refrigeration of heat-treated aluminum alloys is sometimes done in order to
delay the precipitation process
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For aluminum alloy, the maximum time between removal from heat treatment furnace and quenching must be not more than
7 Seconds
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A salt bath is a heated tank containing mineral salts, typically
90% nitrate and 10% sodium nitrate
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Quenching is required to be done in hot or boiling water
to reduce quenching stress
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Aluminium Solution heat treating is
the process of heating aluminium at prescribed temperature for a prescribed time and then cooling rapidly usually by quenching in water
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Precipitation heat treatment of aluminum alloy is done to
speed up age hardening process
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Following solution treatment aluminum alloy can be placed into service
after 5 days
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In aircraft engineering terms, a composite usually consists of
plastic resin matrix and reinforcing fibres of various materials
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Epoxy resins
are the most widely used resin types for aerospace adhesive and composite applications
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Epoxy resins advantage that they
do not react with the solvents and dopes used for fabric coverings
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thermosetting resin
once cured, it cannot be become liquid again by heating
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A disadvantages of Thermoplastics
lack rigidity not commonly used for aeronautical composite resins
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a resin characteristics
Have ambient temperature storage
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Cyanate esters
the material’s has dielectric properties for manufacturing high speed radomes
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The composite part must be as strong and durable as
the original
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the fibres in composite can be wound tightly to increase
strength
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Non-heat treatable aluminum alloys can be hardened by
strain hardening
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In (5052-H24) the letter H indicates
Strain hardening
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The composite structural defect of separation of composite panel plies is called
delamination
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Common method of
non-destructive
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Specific repair instruction and limitations of damage of composite are provided in
Structural Repair Manual
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Adhesive joints are liable to experience main types of stress
Tensile ▪ Shear ▪ Cleavage and ▪ Peel
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proposed repair scheme should meet all the original design requirements
the structure
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Strength
is the name of the ability to support load without breaking
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Impact resistance
the ability of a material to withstand impact without shattering
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Stiffness
the ability of a material to support a load without bending too much
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The name given to the longitudinal direction of the fiber in woven fabric is
warp
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standard soda glass in common use for windows , etc
A’ Glass
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is high resistance to corrosive materials. It is normally produced and used only as a surface matt to reduce cost
C’ Glass
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is an improved electrical grade of glass for modern radome
D’ Glass
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A fibre made
of glass
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do not resist flame well and burn through more quickly than other fibres
Aramid fibres
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are made from pure carbon and are black in colour
Carbon fibres
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Carbon fibre composites are known of these general characteristics
High tensile strength and High compressive strength
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Ceramic fibres are used in heat resistant blankets and to weave fireproof cloth for engine and pylon protection
high temperature application is required ,e.g. a firewall
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Phenolics are fairly brittle system but they have
good fire/smoke toxicity performance
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Polyesters are two or three-part systems have good environmental resistance and heat resistance up
to150˚C
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Polyester fabric, used on a fabric covered airplane may be attached to the structure by
strings or by use of fabric adhesives
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is a simple structure built-up from layers of cloth impregnated with resin
A laminate
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Plastics are made from materials obtained from
animal or vegetable products and coal or petroleum by-products
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Most aircraft control system pulleys are made from
Tufnol
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The best type of wood to be used in the construction of aircraft is
Sitka Spruce
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The standard wood type for aircraft wood structures is
Spruce
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When selecting wood suitable for aircraft structural use, the growth
rate should be more than 6 rings per inch (25 mm)
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The usual method of repairing elongated bolts in a wooden structure is done by
fitting steel bushes
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Ring shake defect of wood is indicated by a parting of the
annular rings
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A visible wrinkle found across the face of piece of wood , in a wooden structural member , is most likely
a compression shake caused by compression load
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On a wooden aircraft structure if there is no evidence of fiber adhesion in the glue in a failed glued joint
this may indicate glue deterioration
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Curved wooden parts are made by
soaking or steaming wood strips then clamping in a jig to set the bend
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wood shrinkage occurs greatest in the
tangential direction to the growth ring
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Fish – eyes are small areas which have not dried uniformly due
surface • contamination with oil, wax or silicone products
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Iron oxide is sometimes added to aircraft dope to improve it's
durability to adhesion
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Retarder is used to slow the drying time of dope finishes to prevent
blush
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is the only inspection method for identifying excess tension in aircraft fabric covering
Observation
90
Excessive tension in aircraft fabric is
usually caused by excessive dope film on new covering
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Fabric repair seams on a fabric covered aeroplane should be
covered with tape
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Lacing cord or stringing chord used on aircraft fabric covering must have a minimum breaking strength of
60 Ib
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Lap seam is the only seam type in a fabric covering requires that the selvedge be left on ,or the fabric edge cut with
pinking shears