Material Science Engineering Answers

The length of Lead piping in the plant is 50 m long at a temperature of 160C. When hot water flows
through it the temperature of the pipe rises to 800C. The coefficient of linear expansion of lead is
29 10-6 0 K
-1
.
i) Determine the change in length of the hot pipe.
This part of the task provides part of the evidence for the grading criterion P8.
ii) Determine the compressive force induced in the pipe if it is rigidly held and expansion is
prevented.
This part of the task provides the evidence for the grading criterion M4.

Using diagrams to illustrate your answers, describe the following failure modes and the
scientific principles that relate to them:
1. ductile/brittle fracture
2. fatigue
3. creep.
For each, make reference, where appropriate, to loading conditions, grain size, surface
finish, stress concentrations, the appearance of the failed surface, stages of creep,
effects of temperature.

A heat exchanger produces dry steam at 100°C from feed water at 30°C at a rate of 1.5 kgs−1. The heat exchanger receives heat energy at a rate of 600 kW from the fuel used. The specific heat capacity of water is 4187 Jkg−1K−1 and its specific latent heat of vaporisation is 2257 Jkg−1.
i) Determine the heat energy received per kilogram of steam produced.

TASK 1
A brass tie bar of length 500 mm and diameter 20 mm undergoes a change in temperature from 25°C to 135°C. The linear expansivity of copper is 19 × 10−6°C−1 and its modulus of elasticity is 84 Gpa.
i) Determine the change of length that takes place.
This part of the task provides part of the evidence for the grading criterion P8.
ii) Determine the compressive force induced in the bar if it is rigidly held and expansion is prevented.

TASK 3
a) A single cylinder petrol engine has a volume compression ratio of 8:1, takes in a mixture of fuel and air at a temperature of 250°C and its pressure is 101 kPa. If the pressure at the end of the compression stroke is 1.5 MPa what will be its final temperature?
b) A compressed air storage cylinder has a volume of 0.5 m3 and contains air at an absolute pressure of 1.8 MPa and temperature 20°C. A quantity of the air is released during which the temperature of the remaining air falls to 15°C and the pressure to 1.5 MPa. Calculate the mass of the air released. The characteristic gas constant for air is 287 Jkg−1K−1.

A brass tie bar of length 500 mm and diameter 20 mm undergoes a change in temperature from 25°C to 135°C. The linear expansivity of copper is 19 × 10−6°C−1 and its modulus of elasticity is 84 Gpa.
i) Determine the change of length that takes place.
This part of the task provides part of the evidence for the grading criterion P8.
ii) Determine the compressive force induced in the bar if it is rigidly held and expansion is prevented.