Paul's Questions Flashcards
A body is said to be perfectly elastic if…
After it has been deformed by external forces, it returns back to its original shape when the forces are removed.
What are the three forms of simple stress?
Tensile stress
Compressive stress
Shearing stress
Define toughness
Deformed without breaking
Three most important light weight materials in aircraft structure?
Aluminium, titanium and magnesium
The selection of materials should be a compromise between what?
quality of material and cost
What are the characteristics of iron
Soft malleable and ductile
How is iron used to manufacture steel
Alloyed with carbon
What process is used to make steel less corrosive
Phosphorus and chromium
What principle element is used in steel alloy to create hardness?
Carbon
What percentage of carbon is present at low, medium and high carbon steels?
Increases strength hardness and corrosion
Decreases ductility
What system is used to identify steel alloys
AISI
What is the purpose of tempering?
To relive stresses associated with being hardened.
Makes material less brittle and increases toughness
What is the heat treatment process to make steel soft and ductile?
Annealing
What process is used to relieve stress after machining?
Normalising
Quenching mediums
Water oil and brine and warm oven
What does CRES stand for ?
Corrosion resistant steel
3 groups of stainless steel
Austenitic, ferritic and martensitic
4 disadvantages of stainless steel?
Difficult to cut Greater coefficient of expansion Conducts heat Looses corrosion resistant under high temps Technician required
What is hydrogen embrittlement
Mixing carbon and hydrogen which creates methane, putting pressure on the structure.
If hydrogen embrittlement is suspected what must be done
Re cooked at 190 degrees for 3 hours
Protective treatments for ferrous materials other than steel
Cadmium plate and paint finish. Silver plating
Purpose of case hardening
Durable coating for steel components
For carburising to be effective what does the steel have to have little of
Carbon
3 types of carbonising
Pack gas and liquid
In what situations must titanium be protected from the atmosphere
When exposed to high temps
What precautions must be taken when grinding titanium?
Hot sparks can ignite. Use liquid coolant
When machining titanium what techniques must be used
Low speed high feed
Cutting fluid
Sharp tools
Advantages and disadvantages of aluminium
ad;
- corrosion resistant
- very lightweight
Disadvantages
- soft and malleable
Differences in grain structure between cast and wrought ally
Cast - coarse grain structure
Wrought - compressed grain structure
