Hot working processes involves taking slabsof metal that are thicker width than the roller, then are rolled through therollers to achieve a thinner slab of metal. This occurs by using compressivestresses through the rollers which compresses the metal to the desiredthickness. The hot rolling uses heat so the metal becomes ductile and soft soit can be compresses easier, this process usually uses high temperatures of950-1000 degrees.
However the hardness of the material cannot be controlled, asit depends on the rate of cooling and chemical composition. The surface of hotworking metal depends on the surface oxidation as this can result in scaleformation and poorly finished surface. However if this happens the hot rolledmaterial s further treated and cold rolled to ensure a better surface finish. Cold working processes involves thematerial being rolled through rollers to reduce the material thickness, whenthis happens the material gets compressed and the metal grains are deformed.The benefits of the cold working processes the dimensional accuracy is muchbetter, better surface finish obtained, and there is no costs involved withheating the metal. The disadvantage of this process high forces are requiredfor deformation.
70-30Hotworking processes on the properties and behaviour of 70/30 brass. Theproperties of 70/30 hot working process are stated in the image below. Theheated brass is fed through a series of opposing steel rollers which reducethickness of the brass step by step to about 0.5 inches or less and this willincrease the width. 60-4060-40 brass is an economical alloy with ahigh content of a zinc and copper. This is commonly used for bathroom fixtures,brass brand instruments, and tooling. The properties of 60-40 it has goodforming properties, when hot rolling the microstructure is maintained, and hasa medium strength. But when oxidation happens a poor surface condition canhappen.
Usually cold rolling occurs for 60-40 brass as it achieves a bettersurface finish than hot rolling and the 60-40 brass becomes up to 20% stronger. Describethe effects on properties and behaviour of uni-axial orientation inthermoplastic polymers drawn into fibres. Thermoplastic polymer is a type of plasticwhich changes properties when heated and cooled. When thermoplastic are heatedthey become soft, and have a hard finish when cooled.
A property ofthermoplastic polymer is that they can be heated and shaped many times. Theuni-axial orientation in thermoplastic polymers, the polymer chain areorientated in one direction. This occurs by heating the polymers by doing thisan extensional strain when melted, then a force is applied so they flow througha die to align the polymers in the same direction, then the material isstretched In one direction so that all the chains line up. A property of having uni-axial orientation inthermoplastic polymers is the material becomes tougher and stiffer. Whenthermoplastic polymers drawn into fibres the material is cut into pellets sothey are at fibre length, by doing this it makes fibre length shorter thanother composites fibres. This happens as the cost of material is lower so it’sa cheaper alternative to metal components. Describethe effects on the properties and behaviour of biaxial orientation in filmsheets.Biaxial orientation is the procedure ofstretching a hot plastic film in two directions, which causes a molecularredirection.
As a result of doing this it tends to be much stronger andbalanced in both directions. Theproperties of the biaxial orientation in film sheets is they are transparentand can be made reflective, good gas and aroma barrier properties are achieved,good chemical levels happen during the process, and good electrical insulation. The dimensional stability can be improvedby controlling the crystallization by changing certain processing parameters.The biaxial orientation can be used for food packaging and wrapping crates. Describehow, in an engineering context, the water content of clay affects theproperties and behaviour of the material during processing.
The water content of clay can affect theproperties and behaviour of the material during processing however it candiffer with different types of clay. The first type of clay is raw clay thistype of clay contains no water content and this is extracted in its naturalstate, the properties and behaviours are dry and crumbly this is due to the nowater content. The second type of clayis slip, which is a mixture of water and clay, and this clay is extracted. Theproperties and behaviours of this clay is it cannot be moulded and it has aslime like texture. The third type is plastic, the properties and behavioursare the clay can be joined to other objects, the clay weight can be supportedwhen moulded, and has workable properties. The next type is leather the watercontent will have reduced compared to plastic and slip at this point the clayis viably damp, the properties and behaviours are it can be handled withoutdeformation, and is still joinable to other pieces of clay.
The last stage isgreen ware where there is water content before toughening, the properties andbehaviours of the clay at this point the clay will hold the shape, wetter claycan be joined to the green ware clay, and green ware can be broken easily. Describehow the strength of concrete is improved during processing with the addition ofreinforcement.Concrete is made by mixing together cement,gravel, sand, and water. This sets hard by a chemical reaction taking place.Before concrete is reinforced it is strong in compression, but weak in tensionso this makes it not very useful for many things.
However concrete isreinforced with metal to make it stronger in tension, the metal used toreinforce concrete usually is steel. The steel support is made by joining steelbars or cables together and is surrounded by a mould. Then concrete is pouredaround the mould and is left to set hard. Reinforced concrete is used forbuilding foundations or building. Writea brief outline of so called ‘Smart’ materials and the special properties theypossess for particular applications, quoting examples of applications you mayfind.
A smart material is a material that has oneor more properties that can be changed by an external condition. The externalcondition can be temperature, light, pressure, or electricity. This change canbe repeated many times and is reversible so it can return to its originalstate. A smart material is piezoelectric materials when this material iscompressed an electric voltage is produced for moment, and when a voltage I putacross the material it makes a tiny change in shape. An example of theapplication you may find this is contact sensors for alarm systems. Anothersmart material is shape memory alloys when bent out of shape they will staythat way until heated above a certain temperature, and will return to originalshape. Quantum tunnelling composite is a flexible polymer, when squeezed itbecomes a conductor. Electroluminescent materials produces light when currentpasses through it.
Thermochromic materials changes colour as the temperaturechanges. Photochromic materials changes colour according to differentlightening conditions. Task2(M1): Compareand contrast the properties of low and medium carbon steel to aluminium alloyin relation to their behaviour in the manufacture of a motor vehicle frame,chassis and panels.Aluminium alloy properties are they arelightweight as it has a low density, at low temperatures aluminium doesn’tbecome brittle and its strength increases, but at high temperatures aluminiumstrength decreases, but to make aluminium stronger, you can create aluminiumalloys with Si, Mg, Cu, Zn or heat treatment. Aluminium is easily worked withmost machining methods such as milling, drilling, cutting, punching, bending,etc. This is useful for motor vehicle frame, chassis, and panels as aluminiumcan be machined into parts. Aluminium has a good conductivity this is usefulwhen manufacturing motor vehicle frame, chassis and panels as the aluminium canbe easily shaped. Aluminium reacts with oxygen in the air which forms a thinlayer of oxide which is dense and protects the aluminium from corrosion.
Theproperties of aluminium alloys means there is huge benefits in manufacturing,for example as aluminium is lightweight this enables a good fuel economy andlow emissions which is desired for motor vehicles. A disadvantage of usingaluminium is that it’s difficult to arc weld on this material. Low carbon steel has properties such asgood formability so it easy to form into different shapes, by pouring,moulding, and pressing, and low carbon steel has good weld ability. Low carbonsteel is significantly cheaper than aluminium, but low carbon steel has a poorresistance to corrosion. When comparingboth low carbon steel and aluminium the similarity is they both are easy toshape. Medium carbon steel is made up of compositionof 0.
29%-0.54% carbon, with 0.60%-1.65% manganese.
The properties of mediumcarbon steel is ductile, strong, and has long wearing properties. Whencomparing aluminium and medium carbon steel they both have strong properties,are readily available, both materials can be recycled, and can easily shaped,but medium carbon steel has long wearing properties, this could be a benefit inthe manufacture of a motor vehicle frame, chassis and panels as the parts willhave a long lasting life.