Lecture 1

Manufacturing definition
It is the application of physical and chemical processes to alter the geometry, properties of a given material to
make product.

Importance of manufacturing

Historically Technologically Economically

It is a sign of civilization Raises the wealth level by Adds values for processed
development applying science materials

Material Types

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Metals
A metal is a category of materials generally characterized by properties of ductility, malleability, luster, and high
electrical and thermal conductivity.

Metals
Ferrous Non-Ferrous
based of iron steel all other metals
ex: Cast iron, Steel Aluminum, Magnesium, Copper
Steel: an iron-carbon alloy containing from 0.02% to 2.1% carbon.
Cast iron: an iron-carbon alloy containing from 2.1% to about 4% or 5% carbon.

Parameter Low carbon steels Medium carbon steels High carbon steels
Carbon contain less than 0.20% range between 0.20% and contain carbon in amounts
content C 0.50% C greater than 0.50%
automobile sheet metal machinery components and springs, cutting tools and
Applications parts, plate steel for engine parts such as crankshafts blades, wear-resistant parts
fabrication, railroad rails and connecting rods
Classification of Manufacturing processes

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Shaping processes
Solidification
Heating material → becomes liquid → Pouring → Solidification
Ex: casting

Particulate
Powdered material → applying pressure → product
Ex: any powdered material

Deforming
Material → force exceeds the yield → deformed material
Ex: extrusion and forging

Material removal
Ex: turning, drilling, and milling

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 Lecture 2
Physical and mechanical properties

Most important physical properties

Density: mass/volume (kg/m3) → important for material selection
Thermal expansion: change in length or volume by increasing or decreasing the temperature → important for
shrink fit and welding applications.
Coefficient of thermal expansion α: change in length per degree of the temperature
Δ𝐿
= 𝛼 Δ𝑇
𝐿0
Melting point: needed temperature to transform solid→liquid by energy is called “Heat of Fusion”
Well-known of melting characteristics aids for manufacturing as metal casting and plastic molding.
Mechanical properties of materials
Strength, Toughness, Hardness, Ductility, Malleability, Resilience, Elasticity, Stiffness, etc.
Stress-strain relationship
There are three types of static stresses to which materials can be subjected: tensile, compressive, and shear. The
stress–strain curve is the basic relationship that describes the mechanical properties of materials for all three types.

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Tensile properties
a force is applied that pulls the material, tending to elongate it and reduce its diameter.

Engineering and true stress-strain

Parameter Engineering stress-strain True stress-strain

Curve

𝐹 𝐹
𝜎= 𝜎=
𝐴0 𝐴
Stress F: Applied tension force. F: Applied tension force.
A0: Original cross-section area. A: Instantaneous cross-section area
Stress unit is: N/mm2 (MPa.) Stress unit is: N/mm2 (MPa.)

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 Parameter Engineering stress-strain True stress-strain
𝐿 − 𝐿0 𝐿
𝜖= 𝜖 = ln ( )
𝐿0 𝐿0
L: Specimen length at certain L: Specimen length at certain section.
Strain
section. L0: Original length (Gage length).
L0: Original length (Gage
length).
𝐿𝑓 − 𝐿0 𝐿𝑓 − 𝐿0
𝜖𝑡𝑜𝑡 = × 100 𝜖𝑡𝑜𝑡 = × 100
𝐿0 𝐿0
Elongation % It measures ductility Lf: Length at fracture (Final length).
Note: it is applicable only in elastic
region.
Area reduction does not be 𝐴0 − 𝐴𝑓
accounted in engineering stress- 𝐴𝑅 = × 100
Area 𝐴0
reduction % strain. Af: Area at fracture, A0: Original area.
It measures ductility also.
Hooke’s Law
𝜎 = 𝐸𝜖
It is applied only in elastic region where the stress is directly proportional to the strain.
The relation between stress and strain is straight line has modulus of elasticity, which measures the stiffness of
the material, as a slope.
Stiffness
It is the rigidity of an object.

Yield strength (𝝈𝒀 )

It is the stress level at which large strains take place without increase in stress.
Tensile strength (𝝈𝑼𝒍𝒕 )
Maximum possible engineering stress in tension.

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Ductility
The ability of a material to plastically strain without fracture.

It can be measured by elongation percent or by area reduction percent.

Toughness
Energy to break a unit volume of material. It is Approximated by the area under the stress-strain curve.

Engineering smaller toughness (ceramics)

tensile larger toughness
stress,  (metals, PMCs)

smaller toughness-
unreinforced
polymers

Engineering tensile strain, 

Ex
A tensile test specimen has a starting gage length = 50 mm and a cross-section area = 200mm2. During the test,
the specimen yields under a load of 32000 N (this is the 0.2% offset) at a gage length of 50.2 mm. The maximum
load of 65000 N is reached at a gage length of 57.7mm just necking begins, Final fracture occurs at a gage length
of 63.5mm.
Determine:
a. Yield strength b. Modulus of elasticity
c. Tensile strength d. Engineering strain at max. load
e. Elongation percent

Given 𝐿0 = 50 𝑚𝑚
𝐴0 = 200 𝑚𝑚2
𝐹𝑦 = 32000 𝑁
𝐿𝑦 = 50.2 𝑚𝑚
𝐹𝑚𝑎𝑥 = 65000 𝑁
𝐿𝑚𝑎𝑥 = 57.7 𝑚𝑚
𝐿𝑓 = 63.5 𝑚𝑚
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 Required 𝜎𝑦 , 𝐸 , 𝜎𝑚𝑎𝑥 , 𝜖 @ 𝐹𝑚𝑎𝑥 , 𝑒 (%)
Solution 𝐹𝑦 32000 𝑁
𝜎𝑦 = = = 160 N/mm2 = 160 𝑀𝑃𝑎 (Ans. a)
𝐴0 200 𝑚𝑚2
Δ𝜎 𝜎𝑦 −0 𝜎𝑦 −0 160
𝐸= =𝜖 = 𝐿𝑦 −𝐿0 = 50.2−50 = 80000 𝑀𝑃𝑎 =
Δ𝜖 𝑦 −0.002 ( )−0.002 ( )−0.002
𝐿0 50

80 𝐺𝑃𝑎 (Ans.b)
𝐹𝑚𝑎𝑥 65000 𝑁
𝜎𝑚𝑎𝑥 = = 200 𝑚𝑚2 = 325 𝑀𝑃𝑎 (Ans. c)
𝐴0
𝐿𝑚𝑎𝑥 −𝐿0 57.7−50
𝜖𝑚𝑎𝑥 = = = 0.154 (Ans. d)
𝐿0 50
𝐿𝑓 −𝐿0 63.5−50
𝑒= × 100 = × 100 = 27 % (Ans. e)
𝐿0 50

Hardness
It is resistance to permanent indentation. Good hardness generally means that the material is resistant to scratching
and wear.

Effect of temperature on properties

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 Lecture 3
Metals can be classified as illustrated in lecture 1
Reasons of importance of metals
• High stiffness and strength.
• More tough than other classes of materials.
• Good electrical conductivity.
• Good thermal conductivity.
• Low cost compared with other materials.
Alloy
A mixture or compound of two or more elements, at least one of which is metallic using to improve the mechanical
properties like toughness, strength and hardness.
Solid Solutions:
A solid solution is an alloy in which one element is dissolved in another to form a single-phase structure. In a
solid solution, the solvent or base element is metallic, and the dissolved element can be either metallic or
nonmetallic
Phase:
Any homogeneous mass of material, such as a metal in which the grains all have the same crystal lattice structure.
Phase Diagram: a phase diagram is a graphical means of representing the phases of a metal alloy system as a
function of composition and temperature.
Binary phase diagram: phase diagram of an alloy Consists of 2 elements
Copper-Nickel Phase Diagram

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Determining Chemical Compositions of Phases
Ex:
Determine the proportions of liquid and solid phases for the 50% nickel composition of the copper–nickel system
at the temperature of 1260 oC (2300 oF).
Solution
The proportion of liquid phase present is given by:

The proportion of solid phase present is given by

Using the same horizontal line in the Figure, the distances CS and CL are measured as 10 mm and 12 mm,
respectively. Thus, the proportion of the liquid phase is 10=22 ¼ 0.45 (45%), and the proportion of solid phase is
12=22 ¼ 0.55 (55%).
Plain Carbon Steels
▪ Strength of plain carbon steels increases with carbon content, but ductility is reduced
▪ High carbon steels can be heat treated to form martensite, making the steel very hard and strong

Parameter Low carbon steels Medium carbon steels High carbon steels
contain less than 0.20% range between 0.20% and contain carbon in
Carbon content C 0.50% C amounts greater than
0.50%
automobile sheetmetal machinery components springs, cutting tools and
parts, plate steel for and engine parts such as blades, wear-resistant
Applications
fabrication, railroad crankshafts and parts
rails connecting rods

Stainless Steel (SS)

Highly alloyed steels designed for corrosion resistance
Tool Steels: To perform in these applications, they must possess high strength, hardness, hot hardness, wear
resistance, and toughness under impact
Iron alloys:
Containing from 2.1% to about 4% carbon and from 1% to 3% silicon. This composition makes them highly
suitable as casting metals
Nonferrous Metals
Although not as strong as steels, certain nonferrous alloys have corrosion resistance and/or strength-to-weight
ratios that make them competitive with steels in moderate to high stress applications

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 Properties and Applications
1. High electrical and thermal conductivity
2. Excellent corrosion resistance due to formation of a hard-thin oxide surface film
Aluminum 3. Very ductile metal, noted for its formability
4. Pure aluminum is relatively low in strength, but it can be alloyed and heat treated to compete
with some steels, especially when weight is taken into consideration
1. Low electrical resistivity - commercially pure copper is widely used as an electrical conductor
2. Also, an excellent thermal conductor
3. One of the noble metals (gold and silver are also noble metals), so it is corrosion resistant
Its Alloys:
Copper
Bronze - alloy of copper and tin (typical  90% Cu, 10% Sn)
Brass - alloy of copper and zinc (typical  65% Cu, 35% Zn).
Highest strength alloy is beryllium-copper (only about 2% Be), which can be heat treated to high
strengths and used for springs
1. Coefficient of thermal expansion is relatively low among metals
2. Stiffer and stronger than Al
3. Retains good strength at elevated temperatures
Titanium
Used for:
aerospace applications where its light weight and good strength-to-weight ratio
used for corrosion resistant components, such as marine components and prosthetic implants
dense, low melting point; low strength, low hardness, high ductility, good corrosion resistance
Lead Applications: solder, bearings, ammunition, type metals, x-ray shielding, storage batteries, and
vibration damping
lower melting point than lead; low strength, low hardness, good ductility
Tin
Applications: solder, bronze, "tin cans" for storing food

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 Lecture 4
Sand casting mold

Gating system
Channel through which molten metal flows into cavity from outside of mold.

The casting technology depends on main 3 steps:

Choice the casting process (ex: sand casting as mentioned above)
Heating and pouring:
Heating types: heating till reaches the milting point, required heat of fusion to convert the material form
solid state to liquid one, and heat to increase the molten metal temperature to the desired one.
Pouring: Be ensure that the molten metal occupied all cavities in the mold before solidification occurs
and regard the following factors; pouring temperature, pouring rate, and turbulence.
Example on pouring rate:
The volume flow rate of metal into a mold is 0.01 m3/min. The top of the sprue has a diameter of 20 mm, and its
length is 200 mm. What diameter should be specified at the bottom of the sprue to prevent aspiration? What is
the resultant velocity at the bottom of the sprue if the metal being cast is aluminum?

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Solution
Here, illustrative schematic sketch for the sprue and the molten metal flow

𝑚3
𝑄 = 0.01 60 𝑠 → 1.66667 × 10−4 𝑚3 /𝑠

Let’s denote the sprue top and the sprue down with 1 & 2 respectively.
1.66667×10−4
From continuity equation: 𝑄 = 𝐴𝑉 → 𝐴1 𝑉1 = 𝐴2 𝑉2 → 𝑉1 = 𝜋
(20×10−3 )2
= 0.530516 𝑚/𝑠 → (1)
4

𝜋
Since 𝐴 = 𝑑2
4

Then, we have 2 unknows (𝑉2 & 𝐴2 ), so we need one more extra equation which is “Bernoulli’s Eqn”
𝑃1 𝑉12 𝑃2 𝑉22
+ + ℎ1 = + + ℎ2 + 𝑓𝑟𝑖𝑐𝑡𝑖𝑜𝑛
𝜌𝑔 2𝑔 𝜌𝑔 2𝑔
Assume that 𝑃1 ≅ 𝑃2 and neglect the friction and the datum of h is at h2.

∴ 𝑉2 = √𝑉12 + 2𝑔(ℎ1 − ℎ2 ) = √(0.530516)2 + 2(9.81)(0.2 − 0) = 2.05072 𝑚/𝑠 → (2)

𝑄 4𝑄
∴ 𝐴2 = 𝑉 → 𝑑2 = √𝜋𝑉 = 0.018 𝑚 →≅ 18 𝑚𝑚 (the diameter to avoid the aspiration)
2 2

Solidification of metals
Solidification of alloys (a) and of pure metals (b)

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Solidification time
It is a time required for the casting to solidify after pouring and it is calculated form Chovernov’s rule
𝑉 𝑛
𝑇𝑆𝑇 = 𝐶𝑚 ( )
𝐴
V: mold volume.
A: casting surface area.
n: empirical exponent (~ 2)
Cm: mold constant depends on: mold material – casting thermal properties – how far pouring temperature from
milting point.
Shrinkage in solidification and cooling

Shrinkage of a cylindrical casting during solidification and cooling: (0) starting level of molten metal immediately
after pouring; (1) reduction in level caused by liquid contraction during cooling; (2) reduction in height and
formation of shrinkage cavity caused by solidification shrinkage; and (3) further reduction in height and diameter
due to thermal contraction during cooling of the solid metal. For clarity, dimensional reductions are exaggerated
in our sketches.

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Riser
Reservoir in the mold which is a source of liquid metal to compensate for shrinkage of the part during
solidification
▪ The riser must be designed to freeze after the main casting in order to satisfy its function.
▪ Since the geometry of the riser is normally selected to maximize the V/A ratio, this allows riser volume
to be reduced to the minimum possible value
Core vs pattern

Determines the external shape

May be made of: wood, metal, or plastic
Types:
solid pattern
(b) split pattern
(c) match-plate pattern
(d) cope and drag pattern
Pattern

Determines the internal shape

Core

Buoyancy in casting
During pouring, buoyancy of the molten metal tends to displace the core, which can cause casting to be
defective.
Fb = Wm – Wc
Fb: Buoyancy force.
Wm: weight of molten metal displaced
Wc: weight of the core.

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 Lecture 5
Metal Casting

Sand Casting Production Sequence

Sand Casting Mold

Expendable mold processes Permanent mold processes

mold is sacrificed to remove part mold is made of metal and can be used to
Definition
make many castings
Advantages more complex shapes possible higher production rates
production rates often limited by time to geometries limited by need to open mold
Disadvantages
make mold rather than casting itself
Example Sand casting Centrifugal casting

Desirable Mold Properties:

Strength - to maintain shape and resist erosion
Permeability - to allow hot air and gases to pass through voids in sand
Thermal stability - to resist cracking on contact with molten metal
Collapsibility - ability to give way and allow casting to shrink without cracking the casting
Reusability - can sand from broken mold be reused to make other molds?
Foundry Sands
Silica (SiO2) or silica mixed with other minerals. [ 90% sand – 3% water – 7% clay]
Casting sand properties
1. Sustains high temperature
2. Porous enough to permit the gases escaping
3. Unfortunately, interlocking tends to reduce permeability
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Sand mold types
Green sand molds → mixture of sand, clay, and water; Green" means mold contains moisture at time of pouring
Dry-sand mold → organic binders rather than clay
Skin-dried mold → drying mold cavity surface of a green-sand mold to a depth of 10 to 25 mm, using torches or
heating lamps
Permanent Mold Casting Processes
The mold is reused many times.
The processes include:
▪ Die casting
▪ Centrifugal casting
Die Casting:
A permanent mold casting process in which molten metal is injected into mold cavity under high pressure

Cycle in cold-chamber casting: (1) with die closed and ram withdrawn, molten metal is poured into the chamber.
(2) ram forces metal to flow into die, maintaining pressure during cooling and solidification.
Advantages Limitations
Economical for large production quantities Generally limited to metals with low metal
points
Rapid cooling provides small grain size and Part geometry must allow removal from die
good strength to casting
Good accuracy and surface finish
Thin sections are possible

Centrifugal Casting:
A family of casting processes in which the mold is rotated at high speed so centrifugal force distributes molten
metal to outer regions of die cavity

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 Lecture 6
Metal Forming
Metal forming processes are deformation processes in which applied loads cause plastic (permanent) strains. The
ability to form metals increases with the increase of its ductility.
True Stress-Strain Curve
True stress-strain curve for a typical metallic material is shown

Strain hardening means that the metal is becoming stronger as strain increases.
Material Behavior in Metal Forming
In plastic region, metal's behavior is expressed by the flow curve
𝜎 = 𝑘 𝜖𝑛
k = strength coefficient; and n = strain hardening exponent
Flow Stress: Instantaneous value of stress required to continue deforming the material
𝑌𝑓 = 𝑘 𝜖 𝑛

where Yf = flow stress, that is, the yield strength as a function of strain
Average Flow Stress:
𝑘 𝜖𝑛 𝑌𝑓
𝑌̅𝑓 = =
𝑛+1 𝑛+1
Where 𝑌̅𝑓 = average flow stress; and  = maximum strain during deformation process.

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Hot Working vs. Cold Forming

Cold Forming Hot Working

1. Better accuracy, closer tolerances 1. Workpart shape can be significantly
2. Better surface finish altered
3. Strain hardening increases strength 2. Lower forces and power required
and hardness 3. Metals that usually fracture in cold
Advantages 4. Grain flow during deformation can working can be hot formed
cause desirable directional 4. Strength properties of product are
properties in product generally isotropic
5. No heating of work required 5. No strengthening of part occurs from
work hardening
1. Higher forces and power required in 1. Lower dimensional accuracy
the deformation operation 2. Higher total energy required (due to
2. Surfaces of starting work piece must the thermal energy to heat the work
Disadvantages be free of scale and dirt piece)
3. Ductility and strain hardening limit 3. Work surface oxidation (scale), poorer
the amount of forming that can be surface finish
done 4. Shorter tool life

Recrystallization temperature: It is about one-half of melting point on absolute scale.

▪ In practice, hot working usually performed somewhat above 0.5Tm
▪ Metal continues to soften as temperature increases above 0.5Tm, enhancing advantage of hot
working above this level

Characteristic Parameter Cold Forming Hot Working

Performed at room temperature or slightly above true
No strengthening of part occurs from work hardening true
Better surface finish true
Poorer surface finish true
Lower forces and power required true
Deformation at temperatures above the recrystallization true
temperature
Ductility and strain hardening limit the amount of forming that can true
be done
Higher forces and power required in the deformation operation true
Bulk deformation processes

Rolling Extrusion
Deformation process in which work thickness is Compression forming process in which work metal
reduced by compressive forces exerted by two is forced to flow through a die opening to produce a
opposing rolls desired cross-sectional shape

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 Rolling Extrusion
Direct

(a) Direct extrusion to produce a hollow or

semi-hollow cross sections; (b) hollow and (c)
semi-hollow cross sections.
Types of Rolling: Indirect:
Based on work piece geometry:
1. Flat rolling - used to reduce thickness of a
rectangular cross section
2. Shape rolling - square cross section is formed
into a shape such as an I-beam
Based on work temperature:
1. Hot Rolling – most common due to the large
amount of deformation required.
2. Cold rolling – produces finished sheet and
plate stock

Indirect extrusion to produce (a) a solid cross

section and (b) a hollow cross section.
Flat Rolling: Advantages:
1. Variety of shapes possible, especially in hot
extrusion
Limitation: part cross section must be uniform
throughout length

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 Rolling Extrusion
2. Grain structure and strength enhanced in cold
and warm extrusion
3. Close tolerances possible, especially in cold
extrusion
4. In some operations, little or no waste of material
Ao
Extrusion ratio rx = Af
Ao = initial cross-section area of the billet.
Af = final cross-section area of the billet.

Draft= D=t0-tf
Reduction=r=D/ t0

Direct vs. Indirect Extrusion

Hot vs. Cold Extrusion

Characteristic Parameter Hot Extrusion Cold Extrusion

Increases ductility of the metal true
Generally used to produce discrete parts true
Heating of billet to above its recrystallization temperature true
No oxidization takes place true
Permitting more size reductions true
Good surface finish true
Also called impact extrusion at high speed operations true
Permitting more complex shapes true

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