Heat Treatment, Forging, Casting, and Material Selection Analysis

This assignment solution delves into various aspects of mechanical engineering, including heat treatment, forging, casting, and material selection. The document explores the impact of heat treatment on welded joints and residual stresses, analyzes different crankshaft manufacturing methods like forging and casting, and discusses the properties and applications of materials like duralumin and fiber-reinforced polymer composites. It also covers the materials used in spark plugs, the process of metal matrix composite synthesis, and the annealing method for improving copper's ductility. Furthermore, it examines the detrimental effects of manufacturing defects and the selection of materials for ballistic helmets and aircraft fuselages. This assignment provides a comprehensive overview of materials science and manufacturing processes relevant to mechanical engineering students.

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TASK 1
Heat treatment is an operation which is costly and time-consuming. It can affect the welded joint,
its corrosion resistance and the level of residual stress. Without heat treatment method, there are
no means of ensuring that the metal manufactured are of high quality and durable.The heating
and cooling rate of the metal greatly determine the quality of the metal and this takes place by
decreasing the metal temperature to its initial level.
The thicker the metal, the more prone the metal will be to falling prey to residual stresses. This is
because welding together of two different materials allows their assemblies to possess the
capacity of changing the structure of the base metal. Introduction of hydrogen during the process
of welding, causes the metal to become prone to cracking and rusting while the shattering and
corrosion increase in case the welded region is tougher than the rest of the steel.
Task 2
Methods of manufacturing crankshaft
Crankshaft material needs to be machined, heat treated and shaped in order to possess suitable
strength, stiffness, hardness and high fatigue strength. The manufacturing of crankshaft is done
from steel either by casting or forging (Totten, 2006, p. 324).
a) Forging method
Forging is a manufacturing process involving the shaping of metal by applying localized
compressive forces and they are mostly grouped based on temperature at which they operate.
The forging of materials into a useful shape is done by pressing or hammering and most

operations involving forging is done in a hot situation though certain materials are cold forged
(Thelning, 2013, p. 109).
The forging machines have the ability to make machines between the size from the bolt to the
rotor of the turbine. This process simply involves deformation of plastic substantial between two
dies in order to achieve the desired configurations. The process of forging is done as open or
closed die forging depending on the complexity.
The compression of material repeatedly and manipulation of its shape manually is done in open
die forging while in closed die forging, the workpiece is squeezed between the two shaped and
closed dies in order to obtain the desired configurations. The die cavity gets completely filled
during squeezing thus making extra materials to find their way out around the periphery of the
dying flash. Both the close and open die forging processes are carried out in cold as well as a hot
state.
There are two popular methods in closed die forging, namely, drop forging and press forging. In
press forging, the mechanical or hydraulic press is used in squeezing the metal slowly and
production of components is done in a single closing of die thus better dimensional accuracy
compared to drop forging. The forged articles got the outstanding grain structures and the best
combination of mechanical properties.
Advantages of forging
 A piece produced by forging is usually stronger compared to the machined part.
 Forging targets a lower total cost when compared to the fabrication or casting.
 Improved microstructure.
 Continuous grain flow.

 Better fatigue resistance.
Disadvantages of Forging
 High cost and high residual stress produced.
 The cost of making dies makes the forging process to be expensive, so long production
runs are normally necessary for reduction of the cost.
 Forging involves high residual stresses which are often released when they are machined
and cause warping when heavy cuts are taken
b) Casting method
The process of casting simply involves pouring of molten metal for producing the desired
product. The heating of metal is firstly done at a required temperature then poured into the mold.
After knockout finishing is done by machining, the crankshaft made of casting has the lowest
strength and it tends to be brittle so that it can be strengthened by some post process heat
treatment and surface treatment process. The procedure for casting process includes; Lobe
hardening, Machining, Heating, Melting, Pouring Molding, Knockout.
Advantages of the casting process
 In this particular method, the cost of material in the crankshaft and machining are
minimized since the crankshaft can be manufactured almost to the essential size and
shape including the counterweights.
 Cast crankshaft can handle loads from all the directions as the metal grain structure is
uniform and random throughout.

 The counterweights on cast crankshaft are slightly larger because the cast material is less
dense.
Disadvantages of the casting process
 High unit cost, labor-intensive and time-consuming in the case of sand casting.
 Poor material strength.
 The further machining process is needed.
 It is not suitable for all materials when using pressure die casting.
TASK 3
The use of duralumin which is an alloy of the aluminum-copper-magnesium alloy is preferred in
the manufacturing of aerospace structures because their hardness. Before the concluding heat
treatment, the alloy is ductile and malleable; after heat treatment, a reaction between the
aluminum and magnesium produces increased hardness and tensile strength. As a result of its
lightness and desirable physical properties, duralumin is widely used in the aircraft industry.
Failing to follow the precautions during the manufacture of the aerospace may lead to excessive
residual stress which results in stress concentration sites and initiates the strike. (Grupta, 2008, p.
67)

TASK 4
Effect of the directional lay of fiber has on properties of a product
Fiber reinforced polymer composite is the widest spread form of polymer composite used
currently and in absence of the reinforcements, poor mechanical properties will be offered by the
polymer. The fiber is providing increased stiffness and the strength of a product while the matrix,
and also, it is responsible for covering the reinforcement thus defending them from chemical and
mechanical damage. They also protect the product from crushing which may be caused as a
result of deformation. (Goebbels, 2009, p. 89).

TASK 5
Identify materials for the main parts in spark-plug
Insulator
In spark-plug, electrodes typically comprise high nickel alloy but when it comes to an insulator,
they are made of aluminum oxide ceramic. The performance of the spark plug can be affected by
the insulator material thus it is necessary to reduce the leakages in electricity or flashover from
the terminal of the plug and to the shell. The material which can also be used instead of
aluminum oxide ceramic is the Sillimanite which can be produced artificially or found in its
natural state (Williams, 2008, p. 45).
The core
An electrode core material has been used in spark plug and it consists of the following materials
 A copper-based material where copper is the largest constituent and a plurality of
precipitates which include phosphorus and iron. The precipitates and copper help in
strengthening the copper matrix so that the core material is a precipitate strengthened
copper alloy. The core is surrounded by nickel-based material where nickel is the single
largest constituents of the nickel-based material (George, 2011, p. 122).

Screw-cap terminal
The topmost of the spark-plug comprises a terminal used in connecting the ignition system.
Sockets which are applied in these applications often have the end of the terminal serve a double
purpose as the nut on a thin threaded shaft (Funatani, 2009, p. 21).
The Body
The body or the metal case assist in withstanding the torque of tightening the plug, serves in the
heat removal from the insulator and pass it on to the cylinder head. The spark plug thread is cold
rolled to prevent thermal cycle fatigue (Dardyshire, 2010, p. 45).
Task 6
Using metal matrix composite, the aluminum matrix is used to synthesize composite showing
high strength. Carbon reacts with aluminum to generate a compound known as aluminum
carbonate which is soluble in water and brittle. The matrix is usually a lighter material and
provides a compliant support for the reinforcement and the composite are created by combining
various materials to form a new material that retains essential properties from the original
element. Production of a composite is done by reinforcing a resin material.
An aluminum metal is heated in the crucible and a motor blade placed in the crucible to in
obtaining a uniform molten metal. At a controlled rate, the reinforcement is poured above the
melt surface to ensure a continuous feed. A homogeneous composite is produced by generating a
uniform mixing of reinforcement particles (Croft, 2009, p. 56)

Fig: Showing process of MMC
Task 7
Identify a suitable process if a cold drawn copper wire was required to have malleable and
ductile properties.
The best method to apply in case copper was required to have ductile and malleable properties is
annealing method since it is heat treatment method which alters both chemical and physical
properties to assist in increasing the ductility and decreasing the hardness of the material. In this
method, a material is heated above its recrystallization temperature then cooling. In annealing,
atoms travel in the crystal lattice while the amount of dislocations drops thus causes an alteration
in hardness and ductility. Diffusion of atoms takes place within the copper so that the material
improvements towards its state of equilibrium. The movement of atoms affect the eradicating
and redistributing the dislocations in metals because the heat provides the energy required to

break the bonds thus increasing the rate of diffusion. The properties can be achieved in copper by
heating the copper metal then allowing it to cool at the temperature of the room in still air.
Copper can be cooled by slowly in air or faster by quenching it in water (Schmitz, 2015, p. 84).
Task 8
Detrimental effects to a finished product that may result from lack of careful control
Weld lines. They are really appearing in the part where a molten plastics encounter each other
while flowing at dissimilar portions of the mold. They are triggered by insufficient bonding of
two or more fronts when there is half-done solidification.
Burn Marks. This is discolorations like colored rust which is formed on the injection molded
prototypes surface (Charity, 2015, p. 412)
Surface delamination. This s a situation where a tinny surface layer shows up on a material as a
result of polluted material and this layer looks like coatings. This is caused by foreign material
finding their means into molten plastic isolated from finished goods (Charity, 2015, p. 225).
Warping. These are deformation which occurs in different parts of the molded component when
there is shrinkage. On-uniform cooling of mold material causes warping
Jetting. This is where the plastic which is molten fails to stick to the mold surface as a result of
injection speed.

TASK 9
Selecting material for a product
Many armed forces use the ballistic helmet in order to protect them from getting injuries such as
traumatic brain injury. There are modern materials currently used in making the helmet namely;
Polymers
There are numerous causes controlling the material response to ballistic effect and the chief
origin of kinetic energy absorption is the straining and breakage of secondary and primary fibers.
Therefore, an important role is played by the fiber tensile in foreseeing the effect response
resulting from the ballistic fibers. In modern body armor system, synthetic fiber established by
DuPont in1965 have been used during manufacture. Helmet made using this material offers
better comfort and higher protection since it has the high tensile strength (Brooks, 2016, p. 312).
Nanomaterials
Carbon nanotubes are examples allotropes of carbon comprising of nanometer diameters, tubular
structure large length to diameter ratio. Carbon nanotubes have good energy absorption of heat,
lightweight, and high strength. The ballistic limit taken for carbon nanotubes is higher meaning
that it is the best material for ballistic application than any other material. For ballistic
operations, polymer matrix Nano-composites where a polymer matrix is reinforced by Nano-
particles like carbo Nano-tubes and this material has high energy absorption capabilities (Berns,
2008, p. 211).

Task 10
Select the suitable material for 3 types of an aircraft fuselage
a) Unpressurized light aircraft
The best material to use in light aircraft is aluminum since it is strong and lightweight.
Aluminum alloy does not corrode easily unlike steel. The problem only arises at high
temperature where they lose strength. Based on the cost, aluminum alloy is cheap compared to
carbon fiber.
b) A mid-altitude commercial passenger carrying the plane
The best material to use in commercial passenger carrying plane is carbon fiber reinforced
polymer or graphite. Commercial aircraft made of carbon fibers embedded in an epoxy resin can
be stacked in numerous ways to maintain integrity during flight. The carbon fiber material is
strong as aluminum but has the weight (Bahadori, 2014, p. 100).
c) High altitude, high-speed military specialization
The best material to use in building military aircraft is titanium since it is a light alloy capable of
withstanding the nearly exterior damage from heat, chemical, industrial, environmental and
corrosive contaminants. Titanium can also be used in making hot sections of the engine since it
has a high melting point which is 1668 degrees Celsius and it is also lighter compared to steel but
the problem is that it is costly (Alinn, 2012, p. 124).

Bibliography
Align, J., 2012. Material Science and Metallurgy. s.l.: Hauffe Grupe.
Bahadori, A., 2014. Corrosion and Material Selection. s.l.:HarperCollins.
Berns, H., 2008. Ferrous Materials. s.l.:Sanoma.
Bogdanovic, V., 2012. Sheet Metal Forming Processes and Die Design. s.l. Scholastic.
Brooks, C., 2016. Principles of the Heat Treatment of Plain Carbon and Alloy Steels. s.l.: Random House.
Charity, B., 2015. Materials Characterisation. s.l.: Thomson-Reuters.
Croft, A., 2009. Heat Treatment of Welded Steel Structures. s.l. Sanoma.
Derbyshire, A., 2010. Mechanical Engineering. s.l.: McGraw-Hill Education.
Funatani, K., 2009. Metallurgical Process Design. s.l.:Simon & Schuster.
George, R., 2011. Wear of Materials. s.l.:Ridders Digest.
Goebbels, K., 2009. Materials Characterization. s.l. OLMA Media Group.
Gupta, M., 2008. Microwaves and Metals. s.l.:Informa.
Schmitz, C., 2015. Aluminum Recycling. s.l.: Pearson.
Thelning, K., 2013. Steel and its Heat Treatment Bofors. s.l.: China Publishing Company.
Totten, G., 2006. Steel Heat Treatment. s.l. Adventure Works Press.
williams, D., 2008. Hydroforming for Advanced Manufacturing. s.l.: Wolters Kluwer.