Subject E - Materials and Processes

Question 1

What is a suitable nondestructive testing method for detecting surface cracks on aluminum castings and forgings?

Answer 1

The dye penetrant inspection method detects surface cracks with equal success on aluminum, magnesium, brass, copper, and titanium. It can also be used on ceramics, plastics, and glass.

Question 2

List the steps in a dye penetrant inspection

Answer 2

1. Thoroughly clean the materials surface.
2. Apply the penetrant for the specified dwell time.
3. Remove the penetrant with water or emulsifying cleaner.
4. Dry the part
5. Apply the developer
6. Inspect the results.

Question 3

Describe the procedure for performing a magnetic particle inspection?

Answer 3

Thoroughly clean all grease, oil, and dirt from the metal part which must be of ferrous material such as iron or steel. Magnetize the part and then apply the ferromagnetic particles, either held in liquid suspension or in dry powder form, to the area to be inspected. If a discontinuity is present, the
magnetized particles will form a pattern in the approximate shape of the discontinuity.

Question 4

What are two types of self-locking nuts?

Answer 4

All metal, and fiber-lock, or elastic stop nuts.

Question 5

What is the general rule for using self-locking nuts?

Answer 5

Do not use self-locking nuts at joints which are subject to rotation.

Question 6

What type of cable is used in primary control systems?

Answer 6

Extra flexible 7 x 19 stainless steel cable.

Question 7

How can the correct “grip length” of a bolt be determined?

Answer 7

Generally speaking, the grip length should equal the total thickness of the materials being joined together. The grip of a bolt is the unthreaded portion of the bolt shank.

Question 8

The length of AN standard bolts are measured in what fraction?

Answer 8

8ths of an inch.

Question 8

What does the triangle mean on the head of a steel bolt?

Answer 8

That it is a close tolerance bolt.

Question 9

What numbers are used for close tolerance bolts?

Answer 9

AN-173 through AN-186 for hex-head bolts, and NAS-80 through NAS-86 for countersunk.

Question 10

What is the difference between a standard bolt and a close tolerance bolt?

Answer 10

A close tolerance bolt is machined to more precise (accurate) dimensions and is used in high performance applications.

Question 11

A solid rivet diameter is always measured in what fraction?

Answer 11

32nds of an inch.

Question 12

Describe a rivnut?

Answer 12

It is a threaded body that is riveted to the aircraft structure.

Question 13

What is the purpose of a channel nut and nutplate?

Answer 13

Both nuts allow a screw or bolt to be installed without needing to hold the nut with a wrench.

Question 14

What are common materials for cotter pins to be made from?

Answer 14

Low carbon steel, and stainless steel.

Question 15

What is the smallest cable that can be used in primary control systems?

Answer 15

One-eighth inch in diameter.

Question 16

What are the penetration requirements for a fillet weld?

Answer 16

Penetration should be 25 to 50 percent of the thickness of a base metal.

Question 17

What precision measuring instruments are used to measure outside dimensions?

Answer 17

Outside micrometer and Vernier calipers.

Question 18

What term describes a metal that is based on iron?

Answer 18

Ferrous alloy

Question 19

What width should a welding bead have and what should be the depth of penetration in a butt weld?

Answer 19

The bead width should be 3 to 5 times the thickness of the base metal and there should be 100 percent penetration of a butt weld.

Question 20

What system is used to identify AN type aircraft bolts?

Answer 20

Aircraft bolts have code markings on the bolt heads for identification. Bolt diameter is measured in 16th of an inch and length is measured in 8th of an inch increments.

Question 21

What is the difference between a close-tolerance and regular AN bolt?

Answer 21

Close tolerance bolts are used in applications where the bolted joint is subjected to severe vibrations and load reversals. Also, close tolerance bolts are machined to more precise standards and must be driven in by a hammer.

Question 22

What are the steps for solution heat treating aluminum alloys?

Answer 22

The alloy must be heated to a predetermined temperature, heat, soaked for a specified period of time, and then rapidly quenched to a relatively low temperature, heat, souk, and quenched.

Question 23

In what state is aluminum alloy immediately after solution heat treating and quenching?

Answer 23

The alloy is in a comparatively soft state, so the material must be naturally aged or precipitation hardened.

Question 24

What is done to prevent certain aluminum alloy rivets (D and DD) from becoming hard after heat treating and quenching?

Answer 24

The rivets are stored in a refrigerator at a temperature lower than 32°F. The rivets will remain soft for several days. They are also called "Ice box rivets.

Question 25

What do rivet head markings indicate?

Answer 25

The alloy of the rivet.

Question 26

Why is alloy steel that is responsive to heat treatment usually less suitable for welding?

Answer 26

Because of its tendency to become brittle (weak)and loose ductility (flexibility) in the area of the weld.

Question 27

Why should steel be normalized after welding or machining?

Answer 27

To remove internal stress of the metal, that way to reducing brittleness.

Question 28

What are two methods of case hardening?

Answer 28

Carburizing and nitriding.

Question 29

What are the characteristics of a cold weld?

Answer 29

A cold weld has improper penetration and cold laps caused by insufficient heat. It appears rough and irregular and its edges are not feathered into the metal base.

Question 30

What tools are used to measure the outside dimensions of shafts, thickness of sheet metal stock, diameter of drills, and for many other similar applications?

Answer 30

Outside micrometer or caliper.

Question 31

What should be used to make a visual inspection of a weld?

Answer 31

A magnifying glass of at least ten power.

Question 32

what nondestructive testing methods could be used for detecting surface cracks in aluminum fittings?

Answer 32

Eddy current, dye penetrant, x-ray, aultrasonic testing, and visual inspection.

Question 33

How may AN standard steel bolts be identified?

Answer 33

AN bolts can be identified by the code markings on the bolt heads.

Question 34

What does the magnetic particle inspection basic process consist of?

Answer 34

The basic process consists of magnetizing a part and then applying ferromagnetic particles to the surface area to be inspected. If a discontinuity (defect) is present, the particles will form a recognizable pattern on the surface.

Question 35

What is the procedure for performing penetrant inspection?

Answer 35

The steps are Clean the surface, apply penetrant; remove the penetrant with emulsifier or cleaner, dry the part; apply developer; and inspect and interpret results.

Question 36

Why should a micrometer be periodically calibrated? (Give at least one of the answers below.)

Answer 36

Continually sliding objects between the anvil and spindle may wear the surfaces OR If it is dropped, its accuracy may be affected OR If the spindle is overtightened, the frame may be permanently sprung (bent).

Question 37

Which Casehardening process is accomplished on steel alloys, after heat treating, to produce a wear resistant surface on engine parts, such as crankshafts?

Answer 37

Nitriding

Question 38

Name 2 types of hardness testers used on steel and other alloys such as aluminum.

Answer 38

Rockwell, Brinnell, Barcol.

Question 39

What hardware is used as a threaded bushing to repair threads?

Answer 39

Helicoils

Question 40

What are some of the purposes for which thermoplastic and thermosetting resins are commonly used in modern aircraft?

Answer 40

Thermoplastic acrylic is commonly used for windshield and side windows. Thermosetting resins are commonly used as the matrix material in composites.

Question 41

Which steel alloy is noted for its toughness and is most commonly used for aircraft tubular structure, such as frame members, engine mounts, landing gear parts, and other structural parts?

Answer 41

Chrome-Molybdenum steel

Question 42

What is another, commonly known name for an aramid material?

Answer 42

Kevlar

Question 43

In what class of threaded fit are aircraft bolts commonly manufactured?

Answer 43

Class 3, medium fit

Question 44

What are two basic types of washers?

Answer 44

plain, lock, and special

Question 45

The diameter and the length of AN standard steel bolt, as in the part number AN3-5, is measured in what fractional increment?

Answer 45

The diameter is 1/16th of an inch; ( the AN3 is 3/16 inch diameter bolt). The length is 1/8th of an inch; (the AN3-5 is a 5/8 inch bolt in length).

Question 46

What does the grip length of a bolt correspond to?

Answer 46

The thickness of the material being fastened with the bolt.

Question 47

What may be accomplished to prevent heat treated aluminum alloy rivets from becoming hard after the quenching sequence?

Answer 47

The rivets may be stored in a refrigerator at a temperature lower than 32 F. They will remain soft for several days.

Question 48

What is the term used that applies to a combination of materials such as fiber, whisker or particle, surrounded and held in place by a resin forming a structure?

Answer 48

Composite structure

Question 49

What do the markings on the heads of solid shank rivets indicate?

Answer 49

The material of which they are made and their strength.

Question 50

What portable hardness tester is commonly used for testing aluminum alloys, copper, brass, or other relatively soft materials?

Answer 50

Barcol Tester

Question 51

How is work hardening obtained?

Answer 51

By cold working metal.

Question 52

In the aluminum alloy 2xxx through 8xxx series, as in 2004-T3, what do the first digits indicate?

Answer 52

The primary alloying element.

Question 53

Name 4 advantages of composites.

Answer 53

High strength to weight ratio; fiber-to-fiber transfer of stress allowed by chemical bonding; Modulus (stiffness to density ratio) 3.5 to 5 times that of steel or aluminum; Longer life than metals; higher corrosion resistance; tensile strength 4 to 6 times that of steel or aluminum; Greater design flexibility; Bonded construction eliminates joints and fasteners; Easily repairable

Question 54

Which NDT (nondestructive testing) method can be performed without removing the surface coatings such as primer, paint, and anodized films and is effective in detecting surface and subsurface corrosion?

Answer 54

Eddy Current Inspection Method.

Question 55

What occurs during the preparation stages when penetrant inspection liquid is applied to, and then removed from, a part that is cracked?

Answer 55

The penetrating liquid enters the cracks and remains there in order to make the crack visible after developing is applied.