ENGINEERING MATERIALS Essay Example
- Category:Engineering and Construction
- Document type:Article
The two specific metals are aluminium and copper
Recrystallization of metallic materials
Recrystallization of metallic materials helps in the development of grain microstructure through slip plastic deformation. The realignment of grains in the structure gives the material its softness and ductability.
Similarly, recrystallization of copper microstructure impart mechanical properties such as its malleability as a wire.
Hot or cold working
The mechanical properties of aluminium can be improved by cold working and hot working. Hot working is carried out to make aluminium soft and ductile while cold working is done to compact and increase dimensional accuracy of aluminium.
Copper can also be strengthened by both hot working and cold working to impart different properties. The ductility of copper is enhanced by hot working.
Alloying of aluminium is carried out to impart specific properties to meet end application. Aluminium alloys can be used for various applications including packaging and cooking wares among others. Elements or metallic impurities are added to impart needed properties. For instance, the addition of boron, which is a grain refiner gives the material high conductivity required when used as overhead electric cables (Total Materials, n.d). Arsenic, which is a semiconductor, is added in aluminium to improve the semi-conductor property to enable its use as a foil for packaging food to keep them hot.
Various properties of copper metal are attributed to alloying of the material. Unalloyed copper is always soft. When tin is added, it gives bronze, an alloy of copper, which is stronger and harder than pure copper. Zinc is added to copper to give brass, which is equally stronger as bronze, but mostly used when the conductivity of the material is not a concern as zinc reduces both the electrical and thermal conductivity of copper (MatWeb, n.d).
The materials for discussion are polystyrene and low density polyethylene (LDPE)
High processing temperature reduces the strength of both polystyrene and LDPE. Those produce under high temperatures have higher melting points than those produced under low temperatures.
Other properties process parameters
Cooling temperature and speed also influences the properties of thermoplastics. Slow and air cooling impart better strength than faster cooling. Therefore, both types of materials will have better mechanical properties when cooled over a long period of time.
Pressure, injection speed
Injection pressure has very little effects on mechanical properties of thermoplastic. However, injection speed determines the strength of the materials. High injection speed improves the mechanical properties for both materials.
Thermosetting polymeric materials
Phenolic and epoxy are the materials of discussion
Phenolic is one of the hardest thermosetting polymer. It is a high-temperature resistance material a property imparted by high-temperature moulding. It moulded at high temperatures to give it a glossy finish and a hard surface (Rebling Plastics, n.d). Epoxy is also compressed at high temperatures of between 165 to 175-degree centigrades. The temperature homogenises the moulding materials to give it the abrasion resistance property.
Moulding pressure and time
Phenolics are moulded at pressures around 21 to 42 MPa with an injection time of 3 to 8 seconds imparting strength and hardness to the material (Plastic Engineering Company, 2011).
Epoxies are moulded at moderate pressures of around 60 to 100MPa for a short period with injection time of around 5 seconds. This gives the material the arc resistance property.
Curing temperature and time
Phenolics cures at temperatures below the moulding temperatures and they are allowed to harden in the open. Curing time is around 30 seconds per mm of the material.
Epoxies harden faster as the temperature reduces below the moulding temperature. It cures between 25 and 40 seconds per mm of the material. The curing process allows for the inter-linkages of bonds that make the material arch and abrasion resistant.
Bricks and porcelain are the materials for discussion.
Water content of clay
Bricks are one of the traditional ceramics made out of clay. Water content of clay determines the curing process of bricks and eventual properties. Too much water content would weaken the bricks making it more brittle. Low water content reduces curing time and at low temperatures that may reduce the strength of the material.
Porcelain sizing is an important aspect of getting the right mould. High water content will shrink the material, and, as a result, the curing and firing process are controlled to avoid shrinkage. The control ensures hard and strong porcelain products that are less brittle.
Sintering press force
Sintering press force is applied at the moulding stage of bricks. Sintering gives brick shape and determined the final properties after firing. Bricks are moulded using moderate sintering press force, as they will be dried in natural air before firing. The closing of gaps between the clay materials improves the mechanical strength.
The porcelain sintering process reduces the porosity, thus impact the material enhancing its physical strength. The higher the sintering press forces the harder the material is expected to be.
Firing temperatures depend on the level of water content in the clay. A lot of heating would be required to remove water in the clay. The higher the temperature, the stronger and less brittle the bricks are.
Similarly, porcelain needs high temperatures to harden and cure. It needs around 2300 degree Fahrenheit to achieve full vitrification (The American Ceramic Society, 2014). The higher the temperature, the harder the product and less brittle it becomes.
The materials used are fibreglass and carbon fibre composite
The orientation of the materials for the composites determines the strength of the composite material. The glass fibres used to reinforce the plastic must be consistent throughout the matrix. Properly aligned enhance the mechanical properties of the material. The fibreglass is strong along the orientation and weak perpendicular.
Similarly, carbon fibres composite is stronger along the fibre direction and weak in the perpendicular direction.
Lamination is carried out to add strength by adding layers of composite materials to make a structure. Fibre delamination weakens the strength of fibreglass by removing various layers.
Delamination of carbon fibre reduces its mechanical properties due wearing caused by the removal of the layers.
Matrix /reinforcement ratio
The higher the reinforcement ratio, the stronger the composite material. When high and recommended ratios of glasses added to the plastic matrix, the resultant fibre matrix will be stronger and harder.
Higher ratios of reinforcement in the matrix strengthens the composite. The higher the carbon fibre in the matrix the stronger and lighter the composite becomes (University of Virginia, 2014).
Particles dispersion in cermets
Particles dispersion in cermets does not have significant effects on the strength of the firbreglass because it does not have a metallic matrix.
Dispersion in cermets has little effects on the strength and application of carbon fibre composite.
Smart grease and polymorph
Applied force to grease reduces its viscosity and makes it more slippery, which is slower due to its stickiness.
Polymorph is hard and will resist any force applied to it.
Presence of electric fields does have significant effects on the function of smart grease. Polymorph is an insulator, and the electric fields do not interfere with its performance.
Smart grease is not affected by magnetic fields. Polymorph is not affected by magnetic as well.
Smart grease does not have colour change. Similarly, polymorph does not change colour under any external stimuli.
Wind turbine blade choices
There is a range of materials that can be used to design a wind turbine blade. They include steel, wood, aluminium, fibres and composite materials
Wood has been used as engineering construction materials, but cannot be used design the blade for a wind turbine. It has low stiffness and difficulties in limiting the deflection for large blades. Its durability does not make it feasible for the design.
Steel has been the traditional choice material for the design of wind turbine blades. They are strong and have high inertia that stabilized the turbine rotation for a consistent power supply. Nickel alloy was used due to its resistance to corrosion and oxidation. Steel is no longer a popular choice for fabrication due to its low fatigue level, and they are also heavy.
Although aluminium is ductile and a good heat conductor, they have a low fatigue level compared to steel. As a result, they have never been used in fabrication of the wind turbine blades. Aluminium are less stiff and weaker compared to steel.
Fibres and matrix composites are becoming better materials for the design of wind turbine blades. Fibreglass is designed to be stronger, good mechanical and electrical properties that make them ideal for fabrication of the wind turbine blades. Fibre composites have moderate stiffness, strength, and density eliminating most of the problems steel and aluminum had.
The best material for fabrication of wind turbine blades is the fibre-reinforced materials such as fibreglass. Although they might be cheap to manufacture, they offer long term solutions and benefits over other materials. They have good electrical properties and mechanical properties required for a turbine blade.
Material for making car bodies
There is a wide range of materials that can be used to make the body of a car. The materials include plastic, glass, aluminium, rubber, steel, and copper among others. Steel still forms the larger part of the total weight of a car. However, designers have been shifting from steel to better materials. Steel or iron has been used due to its durability, but performance is now taking centre stage in manufacturing cars. Glass in their fibre-reinforced form is still being used for windows and windscreens. Pure plastics are now being used less on body parts and are being replaced by fibreglass composite materials for their strength and durability.
Aluminium is the best material to use for making the body of a car for various reasons. First, aluminium is stronger and equally durable as iron. However, it is lighter with a density of 2.7000kg/m3 a third of steel (Aluminium Design, 2013). Its alloys have tensile strengths of range 150 to 300MPa. It has a higher formability than other metals, making it ideal for moulding. It is also a good conductor of electricity and heat. In addition, it iscorrosion resistant a property that lacks in steel.
Criteria used in selecting the right material include durability, lightness (density), strength, good mechanical and electrical properties, and flexibility of the material among others. Aluminium encompasses most of the properties required of a material in making the body of a car.
Aluminium Design (2013). Properties of aluminium. Available at: <http://www.aluminiumdesign.net/why-aluminium/properties-of-aluminium/> [Accessed 24 April 2015]
MatWeb(n.d). How alloying elements affect the properties of copper alloys. Available at: <http://www.matweb.com/reference/copper-alloys.aspx>[Accessed 24 April 2015]
Rebling Plastics (n.d). Thermosetts. Available at: <http://www.reblingplastics.com/thermosets.htm>[Accessed 24 April 2015]
Plastics Engineering Company (2011). Injection moulding guidelines. Available at: < https://www.plenco.com/tips/mptips.html> [Accessed 24 April 2015]
The American Ceramic Society (2014). Structure and properties of ceramics. Available at: < http://ceramics.org/learn-about-ceramics/structure-and-properties-of-ceramics> [Accessed 24 April 2015]
Total Material (n.d). Aluminum alloys – Effects of alloying elements. Available at: <http://www.totalmateria.com/Article55.htm>[Accessed 24 April 2015]
University of Virginia (2014). Composites. http://www.virginia.edu/bohr/mse209/chapter17.htm
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