1. (a) State the four classes of engineering materials
(b) Identify the class which each of the following materials belong to. Present your answer in table form Silicone, concrete, chromium, brass, aluminium oxide, wool, silicon carbide, cermet, plain carbon steel, neoprene, carbon fibre reinforced plastic, fibreglass, uranium oxide, copper, zirconium oxide.
2. Two identical sized specimens of materials A and B are made from materials which produce stress v strain graphs as shown below.
Answer the following questions, give reasons for your answers.
(a) Which of the materials has the highest value of Young's Modulus of Elasticity?
(b) Under identical loads, which material will deflect the most?
(c) The specimens are arranged in a press as shown below, the press moves uniformly, which of the specimens would be under the greatest stress?
3. A material which has a Young's modulus of elasticity of 250 GN m-2 and a poisons ratio of 0.32, calculate:
(a) the bulk modulus of the material
(b) the shear modulus of the material.
4. (a) Describe the methods of classifying polymeric materials.
(b) Distinguish between addition and condensation polymerisation and give specific examples of polymers synthesised by each method.
5. (a) What are the two essential constituent elements of plain carbon steel?
(b) What is cementite ?
(c) State the values of hardness for ferrite and cementite. State your answers in the units of Brinell hardness number. Give references for the sources of your answers.
(d) How are the following properties of iron affected when carbon is alloyed with it?
Illustrate your answer with reference to the microstructure of the steel.
• hardness
• strength
• ductility.
(e) What percentage of carbon produces the strongest plain carbon steel?
6. The ultimate tensile strength of a material was tested using 10 samples.
The results of the tests were as follows :
711 N mm-2, 732 N mm-2, 759 N mm-2, 670 N mm-2, 701 N mm-2, 765 N mm-2, 743 N mm-2, 755 N mm-2, 715 N mm-2, 713 N mm-2.
(a) Determine the mean and standard deviation of these results.
(b) Express the values found in (a) in GPa.