explanation about first law of thermodynamics, engineering materials and manufacturing processes

1. Prof. M. P. Poonia
Professor, Department of
Mechanical Engineering
Malaviya National Institute of
Technology Jaipur

3. CARNOT HEAT
ENGINE

6. Thermodynamic properties are those that
describe the state of a system in terms of its
energy. The four most common
thermodynamic properties are enthalpy,
entropy, Gibbs free energy, and internal
energy.
Internal energy is the energy within a system
at any time, while Gibbs free energy is energy
that is available to be given off to do work.

7. Properties, such as Mass M, , Volume V,
Internal energy U, Enthalpy H and
Entropy S are extensive properties.
Values change accordingly as the mass of
a system changes.
Intensive properties are independent of
the mass of a system. Pressure P,
Temperature T, Specific Volume v,
Specific Internal Energy u, Specific
Enthalpy h, Specific Entropy s
EXTENSIVE AND INTENSIVE PROPERTIES

8. A Pump full of compressed gas is
allowed to expand and 80 kJ of work
is done by the gas on an object in the
lab. At the same time, the gas is
warmed by the addition of 100 kJ of
heat energy. If the initial internal
energy of the gas is 500 kJ, calculate
the final internal energy.

9. Unit III - Classification, properties, criteria for material
selection. (no. of lectures- 1)
COURSE CONTENTS (contd.)

10. • Metals and Alloys
• Ceramics and Glasses
• Polymers
• Composites
Classification of Engineering
Materials

11. 1. Metals and Alloys: The primary
difference between alloy and pure metal is
that an alloy is a mixture of two or more
metals, while a pure metal is made up of
only one type of element. Alloys are
usually created in order to combine the
desirable characteristics of each
component material into one product.
Properties

12. •They are good thermal and electrical
conductors.
•They maintain their good strength at high
and low temperatures.
•Many metals have high elastic strength
and high elastic modulus.
•They are the least resistant to corrosion.
•They have sufficient ductility.
•One more important characteristic, they
can be strengthened by alloying and heat
treatment.
Metals and Alloys (Continued)

13. 2. Ceramics and Glasses
Inorganic materials consisting of both
metallic and non-metallic materials
bonded together chemically.
•They have high hardness, high modulus of elasticity,
and high-temperature strength.
•Since they are brittle, they cannot be used as good as
metals.
•Generally, they have a high melting point and high
chemical stability.
•Ceramics are generally poor conductors of electricity.
•Ceramics have high strength on compression.

14. Organic materials consist of long molecular
chains or networks containing carbon.
•They generally have low densities and low rigidity.
•Their mechanical properties may vary considerably.
•Most polymers are non-crystalline but some consist of
a mixture of both crystalline and non-crystalline regions.
•Most of them are corrosion resistant, but they cannot
be used at high temperatures.
•Most of them are poor conductors of electricity due to
the nature of atomic bonding.
•They generally have good strength to weight ratio.
3. Polymers

15. Materials where two or more of the
above materials are brought together on
a macroscopic level.
• They are designed to combine the best
properties of each of its components.
• Usually, they consist of a matrix and a
reinforcement.
.
4. Composites

17. Selection Criteria
1. Mechanical Properties: Strength, Ductility,
Toughness, Hardness, Strength to Weight Ratio
2. Physical Properties: Density, Melting Point,
Weight, Specific Heat, Thermal Expansion,
Conductivity etc
3. Chemical Properties: Oxidation, Corrosion,
Flammability, Toxicity,
4. Manufacturing Properties: Weld ability,
Machinability, Cast ability, Formed
5. Availability, Service Life
6. Others: Colors, Surface Dimensions, Texture

18. •Strength: It is the property of a material which
opposes the deformation or breakdown in presence
of external forces or load. Materials must have
suitable mechanical strength to be capable to work
under different mechanical forces or loads.
•Toughness: It is the ability of a material to absorb
the energy and gets plastically deformed without
fracturing. Its numerical value is determined by the
amount of energy per unit volume. Its unit is Joule/
m3.
Mechanical Properties of Materials

19. •Hardness: It is the ability of a material to resist to
permanent shape change due to external stress.
There are various measure of hardness – Scratch
Hardness, Indentation Hardness and Rebound
Hardness.
•Hardenability: It is the ability of a material to attain
the hardness by heat treatment processing. It is
determined by the depth up to which the material
becomes hard. Hardenability of material is inversely
proportional to the weld-ability of material.
Mechanical Properties of Materials

20. •Brittleness: Brittleness of a material indicates that
how easily it gets fractured when it is subjected to a
force or load. Brittleness is opposite to ductility of
material.
•Malleability: Malleability is a property of solid
materials which indicates that how easily a material
gets deformed under compressive stress.
Malleability is often categorized by the ability of
material to be formed in the form of a thin sheet by
hammering or rolling. This mechanical property is an
aspect of plasticity of material. Malleability of
material is temperature dependent. With rise in
temperature, the malleability of material increases.
Mechanical Properties of Materials

21. •Ductility: Ductility is often categorized by the ability
of material to get stretched into a wire by pulling or
drawing. This mechanical property is also an aspect
of plasticity of material and is temperature
dependent. With rise in temperature, the ductility of
material increases.
•Creep :Creep is the property of a material which
indicates the tendency of material to move slowly
and deform permanently under the influence of
external mechanical stress. It results due to long
time exposure to large external mechanical stress
with in limit of yielding. Creep is more severe in
material that are subjected to heat for long time.
Mechanical Properties of Materials

22. Mechanical Properties of Materials
Resilience: Resilience is the ability of material to
absorb the energy when it is deformed elastically by
applying stress and release the energy when stress is
removed. The modulus of resilience is defined as the
maximum energy that can be absorbed per unit
volume without permanent deformation. Its unit is
joule/m3.
Fatigue: Fatigue is the weakening of material caused
by the repeated loading of the material. When a
material is subjected to cyclic loading, and loading
greater than certain threshold value but much below
the strength of material (ultimate tensile strength limit
or yield stress limit), microscopic cracks begin to form
at grain boundaries and interfaces.

23. TYPES OF LATHES
1. A Speed Lathe Machine is
a high-speed, hand-operated,
mainly used by woodworkers.
It can provide a spindle speed
from 1200 to 3600rpm.
The machine comes with a
very simple design, it
contains headstock, bed,
tailstock, and tool post.
These machines are used for
woodturning, furniture
making, metal polishing,
spinning, and centering.

24. TYPES OF LATHES
2. Engine Lathe – These lathes emerged during the
Industrial Revolution and originally used steam power
for operation before later being fitted with gas or electric
motors. The engine lathe is considered as the most
common type of manual lathes, which are widely used
in all machine shop applications. The engine lathe or
center lathe can perform operations such as turning,
end face, grooving, knurling, and threading.

25. Tool-Room Lathe – A high precision lathe having a
gearbox in the headstock offering a extended range of
thread pitches for both internal end external threads
and feeds. It has a low spindle runout and precision
guideway and leadscrews offering high stability, low
clearances and backlash. It is used for making
precision components in the tool room.
TYPES OF LATHES

26. Capstan and Turret Lathes – A capstan and turret lathe
is a production lathe. The turret head is mounted on the
ram fitted with turret slides longitudinally on the saddle.
Turret head has a hexagonal block having six faces with
a bore for mounting six or more than six tools at a time.
TYPES OF LATHES
The main difference between the capstan and turret
lathe machine is the capstan lathe is fast because of
light construction but the turret lathe is slow (rigid
construction).These machines are used for mass
production.

27. DIFFERENCE BETWEEN TURRET AND
CAPSTAN LATHE

28. TYPES OF LATHES
These lathes utilize a computerized system that
results in high precision and accuracy. The popularity
of these lathes has led to them replacing many other
lathe types in machinist shops.
CNC Lathes: The CNC meaning can be defined as a
process in which pre-programmed computer software
dictates the movement of factory machinery and tools.
As a result, manufacturers can produce parts in less
time, reduce waste and eliminate the risk of human
error.

29. LATHE SPECIFICATIONS

30. LATHE SPECIFICATIONS
1. Speed
2. Feed
3. Depth of Cut

31. LATHE SPECIFICATIONS

32. Brief Technical Specifications
Bed Length- 7' to 24'
Distance between Centers-2'7" (800) to 19'6" (5950)
Bed Width -18" (457), 20" (508) & 24" (610)
Centre Height 15" (381), 18" (457), 20" (508), 22"
(558) & 24" (610)
Spindle Hole- 2-1/8" (54) to 6-1/8" (156)

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