Flashcards in Materials & Processes Deck (82)
Why is an alloy steel that heat treats well not good to weld?
It becomes brittle and cracks.
What is the difference between a thermoplastic and a thermosetting resin?
Thermoplastics can soften or melt and harden again, while a thermosetting resin will char and burn at elevated temperatures.
Name a purpose for thermoplastics and thermosetting resins.
Thermoplastics are used to make plexiglas, and thermosetting resins are used as the matrix in composites.
Name materials used in composites.
3. Carbon fiber
Name one substance used as a matrix in composites?
Polyester resin or epoxy resin.
What is the advantage of using pre-impregnated materials?
Proper matrixes, fibers evenly coated, and correct mix of resin and harden.
Why is it important that a piece of aluminum alloy be quenched immediately after it is removed from the heat-treating oven?
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.
Explain the way a steel structure is normalized after it has been welded.
Heat the steel structure to a temperature above its critical temperature and allow it to cool in still air.
Why is a piece of steel tempered after it has been hardened?
When steel is hardened, it becomes brittle and tempering removes some of this brittleness.
What is meant by an icebox rivet?
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.
How tight should the nut be installed on a clevis bolt that is used to attach a cable fitting to a control surface horn?
The nut on a clevis bolt should not be tight enough to prevent the clevis bolt turning in the cable fitting and the horn.
Why is it very important that the surface of a piece of clad aluminum alloy not be scratched?
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.
What determines the size of tip that is to be used when gas welding steel?
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.
How is the welding flux removed from a piece of aluminum that has been gas welded?
It should be removed by scrubbing it with hot water and a bristle brush.
What must be done to a welded joint if it must be rewelded?
All traces of the old weld must be removed so the new weld will penetrate the base metal.
What kind of measuring instrument is used to measure the runout of an aircraft engine crankshaft?
A dial indicator.
What measuring instruments are used to measure the fit between a rocker arm shaft and its bushing?
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.
What is the smallest size cable that is allowed to be used in the primary control system of an aircraft?
What type of control cable must be used when pulleys are used to change the direction of cable travel?
Extra-flexible cable (7 x 19).
Describe the method of solution heat treatment of an aluminum alloy.
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.
Describe the method of precipitation heat treating of an aluminum alloy.
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.
How does filiform corrosion usually appear on an aircraft structure?
As thread-like lines of puffiness under a film of polyurethane or other dense finish system topcoats.
What type of composite material is used when stiffness is the prime requirement?
What type of composite material is used when toughness is the prime requirement?
What does the Magnetic Particle process consist of?
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.
What method of NDI could be used to check for surface cracks in aluminum fittings?
Dye penetrant, X-ray, Eddy Current, Ultrasonic, or Visual.
What occurs when penetrant is applied and removed from a part?
Penetrant enters a fault and stays, and a developer is applied to make the fault visible.
List the steps used for dye penetrant inspection.
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.
What is the proper type of NDI to use for locating surface cracks in an aluminum alloy casting or forging?
Zyglo or dye penetrant.