Material Science

Question 1

What is plastic behaviour/deformation?

Answer 1

The material has permanent change of shape when load is removed.

Question 2

What is elastic behaviour/deformation?

Answer 2

The material returns to original dimensions when load is removed.

Question 3

A researcher is given the task to determine the Young modulus of an alloy in the form of a wire. describe the equipment he should use to carry out the experiment.
(4 points)

Answer 3

1. Wire fixed at one end with load added to wire
2. Suitable scale with suitable marker on wire.
3. Micrometer screw-gauge or calipers for measuring diameter of wire.
4. Reference to safety concerning wire
   snapping

Question 4

A researcher is given the task to determine the Young modulus of an alloy in the form of a wire. Describe what measurements the researcher would make.
(4 points)

Answer 4

1. Original length from fixed end to marker on wire.
2. Diameter of wire.
3. Measure load.
4. New length of wire when load increased.

Question 5

A researcher is given the task to determine the Young modulus of an alloy in the form of a wire. Describe what calculations the researcher should perform.
(4 points)

Answer 5

1. Find extension and/or strain (for each load).
2. Determine cross-sectional area or stress.
3. Plot graph of load-extension or graph of stress-strain. 4. Young modulus = gradient x original, length/area, or Young modulus = gradient
4. Calculate Young modulus from single set of measurements of load, extension, area and length.

Question 6

A researcher is given the task to determine the Young modulus of an alloy in the form of a wire. Describe how the researcher could ensure that his results are reliable.
(4 points)

Answer 6

1. Measure diameter in 3 or more places and take average.
2. Put on initial load to tension wire and take. up ‘slack’ before measuring original length.
3. Take measurements of extension while unloading to check elastic limit has not been exceeded.
4. Use long wire (to give measurable
   extension) Scale or ruler parallel to wire

Question 7

What is ultimate tensile strength?

Answer 7

The maximum stress a material can withstand before

fracture.

Question 8

What is Hooke’s Law?

Answer 8

The extension is proportional to force.

Question 9

What is stress?

Answer 9

The applied force per unit area.

Question 10

What is strain?

Answer 10

The extension produced per unit length.

Question 11

What is Young’s Modulus?

Answer 11

The stress per unit strain when a material is behaving elastically.