1. Normalizing is a heat treatment carried out on all metals.
a) True
b) False
Explanation: Normalizing is a heat treatment method of steel. It closely resembles annealing. But, compared to annealing it is faster and makes the material stronger. Also, annealing is done for several materials.
2. In the process of the hardening of aluminum alloys, what is the temperature above which it should be heated?
a) 1200°F
b) 600°F
c) 2400°F
d) 900°F
Explanation: When a material is heated beyond its critical range, and subsequently undergoes the process of quenching it is called Hardening. Aluminum alloys are heated above temperatures of 900°F to be hardened.
3. Which heat treatment method is also called as “drawing”?
a) Tempering
b) Casehardening
c) Annealing
d) Normalizing
Explanation: Tempering is also called drawing. Tempering, unlike other heat treatment methods, requires the metal to be reheated under the critical range. It is then cooled depending on the material and the requirement of its physical properties.
4. The critical range of steel is between ______
a) 1300°F and 1600°F
b) 2400°F and 2600°F
c) 900°F and 2800°F
d) 900°F and 2400°F
Explanation: The critical range of steel is between 1300°F and 1600°F. Critical range of a material refers to the range between which internal change occurs in a metal. It is important in a lot of heat treatment methods.
5. Materials with ______________ are typically used in aircraft construction.
a) no strain
b) lower strength/weight ratio
c) average strength/weight ratio
d) higher strength/weight ratio
Explanation: The strength/weight ratio is an indication of the material’s ability to sustain the load. Materials with high weight are not preferred. Material with high strength and low weight have good strength/weight ratio, hence they are used.
6. Which of the following is not a property of aluminium that makes it ideal to use as an aircraft material?
a) Resistance to corrosion
b) Light in weight
c) High fuel consumption
d) High strength alloy
Explanation: High fuel consumption is not an advantage. Moreover, aluminium has a low fuel consumption. It is light in weight compared to other metals like steel. It is also a high strength alloy. It is resistant to corrosion.
7. Using materials with good joining properties is an advantage.
a) True
b) False
Explanation: Materials with a good joining property are an advantage. The joining property of a material is the ability to manufacture a structural joint by mechanical methods or welding, soldering, etc. It is useful in fabrication.
8. Which of the following methods would be helpful if a material that is not resistant to corrosion is used?
a) Painting a protective layer
b) Heating to 10°F
c) Increase the quantity of material
d) Disjoining
Explanation: Materials that are not resistant to corrosion can be painted with a protective layer of another metal. A few examples of metals are chromium, nickel or zinc. Increasing the quantity of material or heating will not help.
9. Why is low thermal conductivity important for aircraft systems?
a) To increase the strength of the material
b) To protect from excessive heating
c) To keep aircraft warm for passengers
d) For oxygen
Explanation: Thermal conductivity of a material is the rate at which it conducts heat. Low thermal conductivity is important because it prevents the systems from excessive heating hence preventing failure. It does not affect the oxygen levels or increase the strength.
10. What is fatigue strength?
a) Strength/weight ratio
b) Elasticity
c) Resistance to cyclical stress
d) Strain energy
Explanation: The highest point up to which the material can resist cycles of stress. Aircraft are affected by several stresses and loads. It is important to consider their resistance to these loads and stresses to avoid failure.