material and processses Flashcards
what is the proper type of nondestructive inspection to use for locating surface cracks in an aluminum alloy casting or forging?
zyglo or dye pnentrant
what inspection method would be most appropriate for checking a nonferrous metal part for inter-granular corrosion?
eddy curd\rent inspection
what inspection method would be most appropriate for checking the internal structure of an airplane wing for corrosion?
x-ray inspection
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 inspection method would be most appropriate for checking a steel landing gear component for stress cracks
magnetic particle inspection
what type of inspection is best suited for detecting a fault within a piece of nonferrous metal?
ultrasonic inspection
explain the procedure to use when making a dye penetrant inspection of a part
clean the part thoroughly, apply the penetrant, and allow it to soak for the recommended dwell time. Remove all of the penetrant from the surface and apply the developer.
why is it important that all parts be thoroughly cleaned before they are inspected by the dye penetrant method?
any grease or dirt in a faul will keep the penetrant from seeping into the fault
explain the procedure to use when performing a magnetic particle inspection of a part
thoroughly clean the part, magnetize it as directed by the appropriate service manual, flow the indicating medium over the surface, and inspect it under a “black” light. when the inspection is complete, thoroughly demagnetize the part
why is it necessary to magnetize a part both circularly and longitudinally when inspecting a steel part by the magnetic particle method?
to detect faults that extend across as well as lengthwise within the part
does cicular magntization detect parts that are across or lengthwise to the part?
lengthwise
why is it important that all engine parts which have been inspected by the magnetic particle method be completely demagnetized?
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
what is the principle of eddy current inspection?
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.
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 within the metal
what is meant by normalizing a piece of steel after it has been welded or machined?
normalizing removes stresses that are locked into the material by welding or machining
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, tempering removes some of this brittleness.
how is steel annealed?
it is heated to just above its upper critical temperature until it reaches a uniform temperature throughout, then it is allowed to cool very slowly in the oven
how is steel hardened?
it is heated to its critical temperature and quenched in water, brine, or oil
what is meant by tempering steel?
the steel is first hardened; then some of the hardness is removed to relieve some of the internal stresses and brittleness
what is meant by case hardening?
the surface of the metal is hardened by the infusion of carbon or aluminum nitride. the interior of the metal remains strong and tough
what are two methods of case hardening?
carburizing and nitriding
how is steel nitrided
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
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.