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Materials & Processes Flashcards

0
Q

What is the difference between a thermoplastic and a thermosetting resin?

A

Thermoplastics can soften or melt and harden again, while a thermosetting resin will char and burn at elevated temperatures.

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1
Q

Why is an alloy steel that heat treats well not good to weld?

A

It becomes brittle and cracks.

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2
Q

Name a purpose for thermoplastics and thermosetting resins.

A

Thermoplastics are used to make plexiglas, and thermosetting resins are used as the matrix in composites.

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3
Q

Name materials used in composites.

A
  1. Kevlar
  2. Fiberglass
  3. Carbon fiber
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4
Q

Name one substance used as a matrix in composites?

A

Polyester resin or epoxy resin.

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5
Q

What is the advantage of using pre-impregnated materials?

A

Proper matrixes, fibers evenly coated, and correct mix of resin and harden.

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6
Q

Why is it important that a piece of aluminum alloy be quenched immediately after it is removed from the heat-treating oven?

A

Any delay in quenching aluminum alloy after it is removed from the oven will allow the grain structure to grow enough that intergranular corrosion is likely to form in the metal.

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7
Q

Explain the way a steel structure is normalized after it has been welded.

A

Heat the steel structure to a temperature above its critical temperature and allow it to cool in still air.

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8
Q

Why is a piece of steel tempered after it has been hardened?

A

When steel is hardened, it becomes brittle and tempering removes some of this brittleness.

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9
Q

What is meant by an icebox rivet?

A

A rivet made of 2017 or 2024 aluminum alloy. These rivets are heat-treated and quenched, then stored in a subfreezing ice box until they are ready to be used. The cold storage delays the hardening of the rivet.

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10
Q

How tight should the nut be installed on a clevis bolt that is used to attach a cable fitting to a control surface horn?

A

The nut on a clevis bolt should not be tight enough to prevent the clevis bolt turning in the cable fitting and the horn.

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11
Q

Why is it very important that the surface of a piece of clad aluminum alloy not be scratched?

A

The pure aluminum used for the cladding is noncorrosive, but the aluminum alloy below the cladding is susceptible to corrosion. If the cladding is scratched through, corrosion could form.

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12
Q

What determines the size of tip that is to be used when gas welding steel?

A

The thickness of the material being welded. The size of the tip orifice determines the amount of flame produced, and thus the amount of heat that is put into the metal.

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13
Q

How is the welding flux removed from a piece of aluminum that has been gas welded?

A

It should be removed by scrubbing it with hot water and a bristle brush.

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14
Q

What must be done to a welded joint if it must be rewelded?

A

All traces of the old weld must be removed so the new weld will penetrate the base metal.

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15
Q

What kind of measuring instrument is used to measure the runout of an aircraft engine crankshaft?

A

A dial indicator.

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16
Q

What measuring instruments are used to measure the fit between a rocker arm shaft and its bushing?

A

The outside diameter of the shaft is measured with a micrometer caliper. The inside of the bushing is measured with a telescoping gauge and the same micrometer caliper.

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17
Q

What is the smallest size cable that is allowed to be used in the primary control system of an aircraft?

A

1/8-inch diameter.

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18
Q

What type of control cable must be used when pulleys are used to change the direction of cable travel?

A

Extra-flexible cable (7 x 19).

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19
Q

Describe the method of solution heat treatment of an aluminum alloy.

A

The metal is hardened by heating it in a furnace to a specified temperature and immediately quenching it in water. It is soft when it is removed from the quench, but as it ages it regains its hardness.

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20
Q

Describe the method of precipitation heat treating of an aluminum alloy.

A

The metal is heated and quenched, then it is returned to the oven and heated to a lower temperature. It is held at this temperature for a specified time, then removed from the oven and allowed to cool in still air. This increases the strength and hardness of the metal.

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21
Q

How does filiform corrosion usually appear on an aircraft structure?

A

As thread-like lines of puffiness under a film of polyurethane or other dense finish system topcoats.

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22
Q

What type of composite material is used when stiffness is the prime requirement?

A

Graphite (carbon).

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23
Q

What type of composite material is used when toughness is the prime requirement?

A

Kevlar.

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24
Q

What does the Magnetic Particle process consist of?

A

First magnetize the part to be inspected, then apply ferromagnetic particles (very fine iron oxide). Any flaw or fault within the component interrupts the magnetic lines of flux, and the particles will form a pattern on the surface indicating its location. When the inspection is complete, thoroughly demagnetize the part.

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25
Q

What method of NDI could be used to check for surface cracks in aluminum fittings?

A

Dye penetrant, X-ray, Eddy Current, Ultrasonic, or Visual.

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26
Q

What occurs when penetrant is applied and removed from a part?

A

Penetrant enters a fault and stays, and a developer is applied to make the fault visible.

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27
Q

List the steps used for dye penetrant inspection.

A

Part to be inspected is cleaned, and a penetrant is applied. After the appropriate dwell time the penetrant is washed from the surface and a developer is applied. Inspect for results.

  • Fluorescent dye is inspected under a black light, a fault shows up as bright yellow-green, against a dark background.
  • If the dye is visible under ordinary light, a fault shows up as a highly visible red mark on the white background.
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28
Q

What is the proper type of NDI to use for locating surface cracks in an aluminum alloy casting or forging?

A

Zyglo or dye penetrant.

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29
Q

What inspection method would be most appropriate for checking a nonferrous metal part for intergranular corrosion?

A

Eddy current inspection.

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30
Q

What inspection method would be most appropriate for checking the internal structure of an airplane wing for corrosion?

A

X-ray inspection.

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31
Q

Why is it important that all engine parts which have been inspected by the magnetic particle method be completely demagnetized?

A

If the parts are not completely demagnetized, they will attract steel particles that are produced by engine wear and will cause damage to bearing surfaces.

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32
Q

Why is it important that all parts be thoroughly cleaned before they are inspected by the dye penetrant method?

A

Any grease or dirt in a fault will keep the penetrant from seeping into the fault.

66
Q

How are bolts indentified?

A

By coded markings on the bolt head.

67
Q

What do rivet head markings indicate?

A

The material composition and strength of the rivet.

68
Q

How do you torque hardware when no information is available?

A

Using a standard torque table.

69
Q

What determines the correct grip length of a bolt used in an aircraft structure?

A

The grip length of the bolt should be the same as the combined thicknesses of the materials being held by the bolt.

70
Q

How do you keep quenched rivets from hardening?

A

By refrigerating lower than 32 degrees Fahrenheit.

71
Q

What type of loading should be avoided when using a self-locking nut on an aircraft bolt?

A

A self-locking nut should not be used for any application where there are any rotational forces applied to the nut or to the bolt.

72
Q

What is the difference between a general purpose bolt and a close tolerance bolt?

A

Close tolerance bolts are machined more accurately, and identified by a triangle on the bolt head enclosing the material mark.

73
Q

How is work hardening achieved?

A

By cold working metal.

74
Q

What is the most common control cable in use?

A

The 7 x 19 flexible stainless steel cable.

75
Q

What is the proper penetration of a fillet weld?

A

25 to 50%

76
Q

What are the undesirable characteristics of a cold weld?

A

Improper penetration, rough irregular cold laps, and not being feathered into the base metal.

77
Q

What are the characteristics of a welding bead in a butt weld?

A

The weld bead should be three to five times the material thickness in width, have a smooth taper into the base metal, and have one hundred percent penetration.

78
Q

What is used to make “outside” measurements?

A

Outside micrometers or vernier calipers.

79
Q

What tools are used to inspect welds?

A

Magnifying glass and a bore scope.

80
Q

When must micrometers be calibrated?

A

If they are dropped, if the frame is sprung due to improper use, or general wear.

81
Q

What inspection method would be most appropriate for checking a steel landing gear component for stress cracks?

A

Magnetic particle inspection.

82
Q

What type of inspection is best suited for detecting a fault within a piece of nonferrous metal?

A

Ultrasonic inspection.

83
Q

Why is it necessary to magnetize a part both circularly and longitudinally when inspecting a steel part by the magnetic particle method?

A

To detect faults that extend across as well as lengthwise within the part.

84
Q

Does circular magnetization detect faults that are across or lengthwise to the part?

A

Lengthwise.

85
Q

What is the principle of eddy current inspection?

A

A current is induced into the metal being tested by a test probe. The amount of induced current is determined by the conductivity, mass, and permeability of the material, and the presence of any faults or voids.

86
Q

What is meant by normalizing a piece of steel after it has been welded or machined?

A

Normalizing removes stresses that are locked into the materials by welding or machining.

87
Q

How is steel annealed?

A

It is heated just above its upper critical temperature until it reaches a uniform temperature throughout, then it is allowed to cool very slowly in the oven.

88
Q

How is steel hardened?

A

It is heated to its critical temperature and quenched in water, brine, or oil.

89
Q

What is meant by tempering steel?

A

The steel is first hardened; then some of the hardness is removed to relieve some of the internal stresses and brittleness.

90
Q

What is meant by case hardening?

A

The surface of the metal is hardened by the infusion of carbon or aluminum nitride. The interior of the metal remains strong and tough.

91
Q

What are two methods of case hardening?

A

Carburizing and nitriding.

92
Q

How is steel nitrided?

A

The steel part is heated in a retort in which there is an atmosphere of ammonia (a compound of nitrogen and hydrogen). Aluminum, an alloying element in the steel, combines with the nitrogen to form an extremely hard aluminum nitride on the surface of the steel.

93
Q

What is another name for precipitation heat treatment?

A

Artificial aging.

94
Q

What are the two most commonly used rivet heads?

A

MS20470 universal head and MS20426 100 degree countersunk head.

95
Q

What alloy is identified by the following rivet codes: A, AD, D, DD, B?

A 
A is 1100 aluminum.
AD is 2117-T aluminum alloy.
D is 2017-T aluminum alloy.
DD is 2024-T aluminum alloy.
B is 5056-T aluminum alloy.
96
Q

What is the meaning of this rivet designation: MS20470AD4-6?

A 
MS20470 = Universal head.
AD = 2117-T aluminum alloy
4 = 4/32 (1/8) inch diameter.
6 = 6/16 (3/8) inch long.
97
Q

What mark on the head of a rivet identifies the following alloys: 2117-T, 2017-T, 2024-T, 5056-T?

A

2117-T recessed dot.
2017-T raised dot.
2024-T raised double dash.
5056-T raised cross.

98
Q

What bolt is identified by this number AN6-14A?

A 
AN6 = Hex head bolt, 6/16 (3/8) inch diameter.
14 = Length = 1-4/8 (1-1/2) inch long.
A = The shank is not drilled for a cotter pin.
99
Q

What is indicated by a triangle on the head of a steel bolt?

A

This is a close tolerance bolt.

100
Q

What is a correct application for self-tapping sheet metal screws on an aircraft?

A

They may be used to hold nonstructural components onto the aircraft.

101
Q

How can you tell when a self-locking nut must be discarded?

A

When you can screw the nut onto a bolt without having to use a wrench.

102
Q

What is a channel nut?

A

A series of nuts mounted loosely in a channel that is riveted to the aircraft structure. You can install screws in a channel nut without having to hold the nut with a wrench.

103
Q

Of what two materials are cotter pins made?

A

Low-carbon steel and corrosion-resistant steel.

104
Q

What is the basic wood used for aircraft wing spars?

A

Sitka spruce.

105
Q

What type of fabric is most widely used for covering aircraft structures?

A

Heat-shrinkable polyester fabric.

106
Q

What is the alloy number of the most commonly used aluminum alloy for aircraft structural use?

A

2024-T

107
Q

What is the alloy number of a high strength aluminum alloy that has zinc as an alloying component?

A

7075

108
Q

How does filiform corrosion usually appear on an aircraft structure?

A

As thread-like lines of puffiness under a film of polyurethane or other dense finish system topcoats.

109
Q

In what increments can a vernier micrometer caliper be read?

A

One ten thousandth (0.0001) inch.

110
Q

What is an advantage of a vernier caliper over a micrometer caliper?

A

The range of a vernier caliper is far greater than that of a micrometer caliper.

111
Q

What precision tool is used to measure piston ring side clearance?

A

Thickness gage.

112
Q

What precision tools are used to measure the inside diameter of a cylinder?

A

A telescoping gage and a micrometer caliper.

113
Q

What precision tools are used to measure the inside diameter of a small hole?

A

A small hole gage and a micrometer caliper.

114
Q

What is the principle upon which ultrasonic inspection is based?

A

Any fault within a material will change the material’s resonant frequency. Comparing the resonant frequency of a known sound material with the material under test will indicate the presence of a fault.

General (12 decks)

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