Paul's Questions

Question 1

A body is said to be perfectly elastic if…

Answer 1

After it has been deformed by external forces, it returns back to its original shape when the forces are removed.

Question 2

What are the three forms of simple stress?

Answer 2

Tensile stress
Compressive stress
Shearing stress

Question 3

Define toughness

Answer 3

Deformed without breaking

Question 4

Three most important light weight materials in aircraft structure?

Answer 4

Aluminium, titanium and magnesium

Question 5

The selection of materials should be a compromise between what?

Answer 5

quality of material and cost

Question 6

What are the characteristics of iron

Answer 6

Soft malleable and ductile

Question 7

How is iron used to manufacture steel

Answer 7

Alloyed with carbon

Question 8

What process is used to make steel less corrosive

Answer 8

Phosphorus and chromium

Question 9

What principle element is used in steel alloy to create hardness?

Answer 9

Carbon

Question 10

What percentage of carbon is present at low, medium and high carbon steels?

Answer 10

Increases strength hardness and corrosion

Decreases ductility

Question 11

What system is used to identify steel alloys

Answer 11

AISI

Question 12

What is the purpose of tempering?

Answer 12

To relive stresses associated with being hardened.

Makes material less brittle and increases toughness

Question 13

What is the heat treatment process to make steel soft and ductile?

Answer 13

Annealing

Question 14

What process is used to relieve stress after machining?

Answer 14

Normalising

Question 15

Quenching mediums

Answer 15

Water oil and brine and warm oven

Question 16

What does CRES stand for ?

Answer 16

Corrosion resistant steel

Question 17

3 groups of stainless steel

Answer 17

Austenitic, ferritic and martensitic

Question 18

4 disadvantages of stainless steel?

Answer 18

Difficult to cut 
Greater coefficient of expansion
Conducts heat
Looses corrosion resistant under high temps 
Technician required

Question 19

What is hydrogen embrittlement

Answer 19

Mixing carbon and hydrogen which creates methane, putting pressure on the structure.

Question 20

If hydrogen embrittlement is suspected what must be done

Answer 20

Re cooked at 190 degrees for 3 hours

Question 21

Protective treatments for ferrous materials other than steel

Answer 21

Cadmium plate and paint finish. Silver plating

Question 22

Purpose of case hardening

Answer 22

Durable coating for steel components

Question 23

For carburising to be effective what does the steel have to have little of

Answer 23

Carbon

Question 24

3 types of carbonising

Answer 24

Pack gas and liquid

Question 25

In what situations must titanium be protected from the atmosphere

Answer 25

When exposed to high temps

Question 26

What precautions must be taken when grinding titanium?

Answer 26

Hot sparks can ignite. Use liquid coolant

Question 27

When machining titanium what techniques must be used

Answer 27

Low speed high feed
Cutting fluid
Sharp tools

Question 28

Advantages and disadvantages of aluminium

Answer 28

ad;

• corrosion resistant
• very lightweight

Disadvantages
- soft and malleable

Question 29

Differences in grain structure between cast and wrought ally

Answer 29

Cast - coarse grain structure

Wrought - compressed grain structure