TREVOR CHIREMBA                   CONTENTS TITLE PAGE ……………………………………………………………………..2TASK 1:  P4 a) ………………………………………………………………….4                     b)………………………………………………………………… 4 TASK 2: M1 i)…………………………………………………………………. 5                     ii)………………………………………………………………… 8 REFERENCES ………..…………………………………………………………9                     TASK P4 Cold rollingA lot of energy is required to roll a sheet of metal in coldrolling than in hot rolling.

Whereas heating up a sheet of metal makes itmalleable, therefore when rolled between two rollers a flat sheet can be easilyformed. Yet because a cold sheet that is not heated, when put through theroller it will consume more energy so as to push it through. Blow mouldingBlow moulding requires a lot of petroleum in order to beable to produce plastic products. It carries a big risk on the destruction ofthe environment. Slip castingDimensions of low quality can be achieved as compared tothose of dry pressing or powderinjection molding.

The production rate is also lower as compared to that of drypressing, extrusion and injection moulding.  GRP These have poorstiffness and rigidity.                    a)  Piezoelectric crystals in watches Piezoelectric crystals are important factors in a watch, asthese are used to keep time.

A clock circuit consists of a battery, quartzcrystal, oscillator, stepping motor, microchip and a cog. The electrons movingfrom the battery electrifies the quartz crystal, when the quartz crystal iselectrified it begins to vibrate or swing due to piezoelectric effect (theability to produce to produce electricity when mechanical stress is applied).The microchip responds by counting the number of vibrations in the crystaltherefore it then calculates how many times the crystal should vibrate. Afterthe microchip has had a fixed number of vibrations it then sends an electricalpulse to the stepping motor. The polarity of the solenoid changes causing themagnet to rotate, this resulting in the cogs turning every second or asprogrammed.  b) Shape memory alloys for spectacles     These spectacles were designed in a way that they can reshapethemselves as my factors might make them lose their shape such as temperature. Ifone was to fold these spectacles, the stress applied makes the titanium alloyfrom which they are made into an entirely different crystalline structure, ifyou release them the crystal structure reforms again therefore they go backinto their normal shape.

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In other word the molecules are just re-arrangingthemselves in a reversible way, this is known as a solid-state phase change.                           i) UreaFormaldehyde when used in the manufacturing of an electric plug Below is anexplain how the properties and structures of Urea Formaldehyde (UF) effects intheir behavior in the manufacturing process, although to a greater extent UFmay still be used to manufacture electric plugs. To prove this, at some point imight need to compare the properties of UF to those of other materials used tomanufacture plugs such as Acrylonitrile Butadiene Styrene (ABS)  Whenchoosing a material, first we look for a material which can conductelectricity. The safe use of a plug depends on the ability of different partsto conduct electricity. Parts in a plug can be divided like shown in thediagram below. Note that “notevery part in a plug is made of UF”.

 Parts of theplug    Electricplugs are either made by injection moulding or compression moulding.Compression moulding is used for thermosetting plastics like Urea formaldehyde.Plugs have pins which might/are likely to suffer impact therefore these pinshave to be secured.

Toughness isan important factor in this case as the plug body has to be strong. The chartbelow illustrates the strength against toughness for different materialstherefore it allows us to compare different polymers hereby we may be able totell why some polymers are not acceptable. MaterialSelection chart   From thechart above we have seen that there are other materials such as ABS that have more toughness than Ureaformaldehyde(UF), this means ABS a greater impact than UF. Because UF has lowertoughness this means it can only be used for fixed appliances whereby the plugis less likely to suffer any impact (for example a microwave or television).Therefore, under physical properties, UF has high toughness and also high hardnessmaking it more suitable for manufacturing plugs.  Interpretingmaterial selection chart   From thechart, we can easily tell that non-conductive parts in a plug are made frompolymers, this is because they have high resistivity. Also from the chart we see that wood is cheaper than polymers, inthis instance our polymer is UF.

UF can be shaped by various process whereaswood can be machined into a shape, which would not be suitable for massproduction. UreaFormaldehyde is very brittle, this means it is hard but it still can breakeasily. This limits the appliances where it can work, these are applianceswhere it is less likely to break such as a refrigerator.  Conclusion A plug is a3D shape, therefore it is of no use to use a perfect material if it can’t formthe desired shape for example wood, issaid to be far much cheaper than UF but it cannot be used for mass productionas it needs to be machined shaped yet Urea formaldehyde can be shaped bydifferent process making UF the best material to consider over wood.

UF is avery good insulator, plugs made from this polymer are safe to use.     ii) concretewhen used as a structural beam Flexuralstrength – many structures are a subject to flexure and/or bending. When a loadis loaded, the bottom is in tension whilst the upper part is in compressiontherefore some steel bars are inserted (reinforced concrete) therefore theconcrete has very good strength both in tension and compression.       Durability –If well designed and laid properly this structure becomes durable and it canlast for more than 500 years. Ductility –the structure gets ductility from the steel reinforcement. Fireresistance – reinforced concrete beams are more fire resistant as compared toother materials such as steel.

 Seismicresistance – if the structure is designed properly it can be extremelyresistant to earthquakes. Maintenance– Maintenance of a reinforced concrete beam is of low cost as compared to thatof steel and pre-stressed concrete. When settingup this structure it needs a lot of form-work, centering therefore thisrequires a lot of site space and skilled labour. Concrete develops cracks evenif it reinforced these are caused by shrinkage resulting in strength loss.

Whenconcrete is in a fluid material it can be economically moulded into nearly anyshape.