Questions Flashcards
What happens to the steel at ‘arrest’ or ‘critical’ points as it is heated?
The metal temperature stops rising, heat absorbed changes the micro-structure
Steel containing .83% carbon has how many arrest points?
One
What is the softening heat treatment?
Annealing
Which heat treatment restores the crystalline structure and therefore increases strength?
Normalising
What other heat treatment process is carried out prior to tempering?
Hardening
What properties does small amounts of Molybdenum bring to chrome alloy steel?
Helps to improve the properties of the steel.
What are the advantages of Maraging steel?
Tougher, simpler heat treatments, less distortion during heat treatment, easier to work, easier to weld, resistance to corrosion and hydrogen embrittlement
What is surface hardening?
Given the material a hardener external surface, supported by a tough and
shock-resisting core.
Why is aluminium not often used in aircraft construction in its pure state?
It has very little strength
Aluminium alloys are classified as wrought or casting. How are they further classified?
Heat treatable and non-heat treatable
How are non heat treatable aluminium alloys strengthened?
By Cold working
What is Alclad?
A sandwich type of sheet metal with a core of 95% of the thickness which is an aluminium alloy with upper and lower surfaces of pure aluminium for corrosion protection
What process must be carried out before forming or shaping aluminium?
Annealing
How can age hardening be delayed?
Storing the solution heat treated material in a refigerator
How many times can Alclad be heat treated?
3 times, any more the alloying materials start to bleed into the pure aluminium cladding.
Describe a malleable metal.
One that can be deformed by compression before it shows signs of cracking
Describe a ductile metal.
One which can be deformed a great deal by Tension before it fractures.
What is measured by an impact test?
A test of the toughness of a material and its ability to resist mechanical shock.
What is the yield point?
The point where the properties of a material under tension go from Elastic to Plastic.
Define Creep.
The permanent extension of a material when subjected to tension and heat.
How is hardness determined when using Brinell or Vickers hardness test equipment?
A ball or diamond shape indenter is fired into the surface of a material. The hardness is indicated by the dimensions of the- indent left in the material.
Which test for toughness would be used at low or high temperatures?
When there is a requirement for testing at low or high temperatures the Charpy test is recommended.
What causes cyclic fatigue?
Repeated fluctuating loads, such as take-off, landing, turbulence and pressurisation
What type of test results in a graph where stress(S) is plotted against number of reversals(N)?
Fatigue testing.
What affect has surface finish be found to have on the endurance limit of a test piece?
A polished test piece has a much greater endurance limit than a roughly
turned test piece.
