P1 Describe the structure (including the atomic structure) associated with a given metal, polymer, ceramic, composite and smart material
Describe the structure (including the atomic structure) associated with each of the following materials. Identify the nature of the bonds between atoms and molecules, in particular identifying where you will find covalent, ionic and metallic bonds.
(i) With reference to tin-lead solder, explain what a eutectic mixture is. Show a phase diagram and explain what it shows.
(ii) With reference to a suitable micrograph or sketch, including the scale, show the typical granular structure of typical plain carbon steel.
Explain how the grains form from the melt.
Identify and describe the lattice structure associated with ferrite.
Pearlite is a layered structure. What are the layers?
Identify and describe the lattice structure associated with cementite.
What effect does increased carbon content have on the number of pearlite grains?
Explain what you would expect to see at the microscopic level as the carbon content exceeds 1.7%
(iii) With reference to the molecular bonds and cross links, explain why it is possible to melt and reuse a thermoplastic polymer, but not a thermosetting polymer. Show a polymer molecule, for example a polythene polymer, and identify the elements and bonds it contains.
(iv) Explain what is meant by the glass transition temperature in polymers.
(v) Using examples explain how ceramics can have an amorphous structure, a crystalline structure or a bonded structure.
(vi) Using examples of composite materials describe what the matrix is and what the reinforcement is. Explain how a composite can be particulate, fibrous or laminated.
(vii) With reference to piezoelectric materials, electro-rheostatic or magneto-rheostatic materials, and shape memory alloys, explain how smart materials can have crystalline, amorphous or metallic structures.
P2 classify given engineering materials as either metals or non-metals according to their properties.
Link each of the materials below to one or more categories and say why the material belongs in those categories. The materials are:-
a) Latex
b) Copper
c) Stainless steel
d) Brass
e) Fibre glass
f) PVC
g) Piezoelectric crystal
h) Bakelite
i) Concrete
j) Wood
The categories are:-
i) Ferrous alloy.
ii) Non-ferrous metal.
iii) Non-ferrous alloy
iv) Thermoplastic polymer
v) Thermosetting polymer
vi) Elastomer
vii) Ceramic
viii) Composite
ix) Smart material
x) Natural material.
P3 describe mechanical, physical, thermal and electrical and magnetic properties and state one practical application of each property in an engineering context.
The mechanical properties you need to describe are: tensile strength, shear strength, compressive strength; hardness; toughness; ductility; malleability; elasticity; brittleness.
The physical properties are: density; melting temperature.
The thermal properties are: expansivity; conductivity.
The electrical and magnetic properties are: conductivity; resistivity; permeability; permittivity.
P4 (See also M1) describe the effects on the properties and behaviour of processing metals, polymers, ceramics and composites and of post-production use of smart materials.
(i) With reference to the relative grain structures produced by the annealing, quenching and tempering of steel, explain how the properties of steel is affected by these processes.
(ii) Describe the effect of alloying steel with chromium and other metals effects the behaviour of the stainless steel in service.
(iii) Describe how the processing temperature and evenness of cooling affect the properties of products made from thermoplastic polymers when they are in service.
(iv) Explain why curing is important in thermosetting polymers and describe the effects of incomplete curing.
(v) Describe what is meant by sintering in the context of ceramic processing and its importance to the finished product.
(vi) Explain the importance of fibre alignment in composites with regard to direction of stress in service.
(vii) Explain some of the causes of de-lamination in composites.
(viii) Explain the importance of the matrix to reinforcement ratio in composites.
(viiii) Explain the function of the particle reinforcement in a cermet, for example those used in cutting tools.
(x) Describe how a change of stress in a piezoelectric material can produce an electric charge.
P5 (See also D1) use information sources to select a different material for two given applications, describing the criteria considered in the selection process.
(i) With reference to BS EN 13261:2009 describe the principal selection criteria for a railway carriage axle. Your answer should include information on the mechanical properties, surface finish and durability of the axle.
(ii) Select a suitable material for the mass production of sports drink bottles, based on a variety of information sources including from material manufacturers and stockholders. Among the criteria you should consider are safety (e.g. toxicity), cost, economies of scale, availability, modes and forms of delivery, recyclability, material properties such as strength, weight and elasticity, modes of production and finish.
P6 describe the principles of the modes of failure known as ductile/brittle fracture, fatigue and creep.
(i) Compare the processes of ductile and brittle fracture. Describe the appearance of the fracture surfaces in each case. Explain how grain size can affect these processes, and how the loading rate (gradual or impact loading) can affect these processes.
Explain, with a relevant diagram, the transition temperature for steel.
(ii) Explain, with a relevant diagram, for example an S-N curve, what is meant by fatigue in the context of cyclic loading in components. Describe the appearance of the fracture surfaces that would indicate fatigue stress. What are the stress concentrators that will promote fatigue stress? How can surface finish reduce these effects?
(iii) Explain, with a suitable diagram, such as a strain versus time curve, what is meant by creep in the context of components subjected to constant stress. Describe the processes of primary, secondary and tertiary creep. How is the rate of creep affected by temperature, grain size and the magnitude of the applied stress? What is the creep limit?
P7 perform and record the results of one destructive and one non-destructive test method using one metal and one non-metallic material.
Write a report based on the following two tasks. In addition to the report you will be observed performing the test and a witness statement will be signed.
Task 1: Use the tensile testing machine and the associated computer software to produce a graph of stress against strain for a given polymer sample. Ascertain Young`s modulus, ultimate tensile strength and the yield stress of the sample.
Task 2: Conduct a visual inspection of a galvanised steel crash barrier and lamp post and record the results. For example, do you see what you would expect to see?
P8 (See also M3) describe a different process of degradation associated with each of metals, polymers and ceramics.
Describe the processes of galvanic corrosion in metals, radiation effects on polymers, and thermal shock in ceramics.
M1 explain how the properties and structure of different given engineering materials affect their behaviour in given engineering applications.
This is an extension of the work you will do for P1 and P4. Choose two or more materials and describe how their performance in an engineering application is related to their properties and structure.
For example, when a force is applied to a piezoelectric material it produces an electric charge which can be used to trigger a car`s airbag in the event of an accident. This effect is related to the atomic structure and composition of the material.
You have also studied how the quality of steels affects their behaviour in service, for example how this affects the transition temperature in steels. It is the internal structure of metals which determines their resistance to failure in service.
In rubber it is the arrangement of the polymer molecules which allow considerable reversible extension and make it a suitable material for car tyres.
M2 (See P7, D2) explain how one destructive and one non-destructive test procedure produces useful results.
This will follow on from the work you did for P7.
Task 1. Explain the relevance of tensile testing to the real life application of materials, for example in components that will be subjected to loads in service.
Task 2. Explain the importance of visual inspection in ensuring that street furniture is fit for purpose. Consider, for example, the safety implications and the costs of not maintaining these items.
M3 explain how two given degradation processes affect the behaviour of engineering materials.
This will be an extension of the work you did for P8. For example, how does the corrosion of a component experiencing a tensile or compressive load affect the stress in the component?
D1 justify your selection of an engineering material for one given application describing the reasons the selection meets the criteria.
This can follow on from your work for P5. In particular, you need to give reasons for selecting a particular material and why other materials considered for the application were not selected. You need to consider the service environment, loads, forces, design life, relative cost, safety and efficiency among other factors.
D2 evaluate the results of one test procedure.
This will follow on from the work you did for P7 and M2. You need to write a report which evaluates the results of the tensile tests you carried out for P7 and M2. Compare the results for LDPE and glass filled nylon, and say why the results obtained reflect the inner structure of the respective materials.
You should also consider the relevance, validity and accuracy of the test.