Government College of Engineering,
Karad
First Year B. Tech
FE 1209 Basic Engineering
Prof. Swati S. Jadhav.
Content
• Manufacturing Processes: Turning, milling, drilling.
• Material properties, tensile, compressive
and shear strength, ductility, malleability, hardness.
• Mechanical Power Transmission: Machine elements:
Axle, shaft, keys, pulleys, etc. Belt drives, gear
drives, chain drives, Applications of these devices
(Numerical treatment on Torque, speed, power for
belt and gear drive only)
• What is manufacturing?
“act
of making something (a product) from raw
materials”
Manufacturing Processes
• Two basic types:
• 1.Processing operations- transform a work material from one
state of completion to a more advanced state–Operations that
change the geometry, properties,
–Operations that change the geometry, properties, or
appearance of the starting material
• 2.Assembly operations - join two or more components to
create a new entity
Classification of manufacturing
processes
Processing Operations
Three categories of processing operations:
1.Shaping operations - alter the geometry of the starting work
material
2.Property-enhancing operations - improve physical properties
without changing shape
3.Surface processing operations - to clean, treat, coat, or deposit
material on exterior surface of the work
Shaping Processes – Four Categories
• Solidification processes - starting material is a
heated liquid or semifluid
• Particulate processing - starting material consists
of powders
• Deformation processes - starting material is a
ductile solid (commonly metal)
• Material removal processes - starting material is a
ductile or brittle solid
Solidification Processes
Starting material is heated sufficiently to
transform it into a liquid or highly plastic state
• Examples: metal casting, plastic molding
Particulate Processing
Starting materials are powders of metals or ceramics
Usually involves pressing and sintering, in which
powders are first compressed and then heated to bond
the individual particles
Steps: Pressing and sintering
Deformation Processes
Starting workpart is shaped by application of
forces that exceed the yield strength of the
material
• Examples: (a) forging, (b) extrusion
Material Removal Processes
Excess material removed from the starting piece
so what remains is the desired geometry
• Examples: machining such as turning, drilling,
and milling; also grinding and nontraditional
processes
TURNING
DRILLING
MILLING OPERATION
According to Newton's third law, the cylinder will experience a force downward on the
lower surface of the cylinder and an equal and opposite force on the upper surface of
the cylinder. My cylinder has an original length of Io and surface area of Ao. As I pull
on my material with the force F the cylinder will lengthen and the resulting length will
be l. Stress, σ, is defined as the force divided by the initial surface area, σ=F/Ao. This
pulling stress is called tensile stress. Strain is what results from this stress. Strain, ε, is
defined as the change in length divided by the original length, ε=ΔI/Io. Before we
proceed further with stress and strain, let's define some other types of stress.
If instead of pulling on our material, we push or compress our
cylinder we are introducing compressive stress. This is
illustrated in the following figure:
If instead of applying a force perpendicular to the surface, we
apply parallel but opposite forces on the two surfaces we are
applying a shear stress. This is illustrated in the following figure:
Stress related to shear is torsional stress. If we hold one end of
our cylinder fixed and twist the other end as shown in the figure
below, we are applying a torsional (or twisting) stress.
• DUCTILITY: It is a measure of the amount of
deformation of a material can withstand before
breaking. It is also the ability of a material by which
it can be drawn into wires.
• MALLEABILITY: It is the ability of a material by
which it can be rolled into sheets. Malleability is the
ability of a material to exhibit large deformation
subjected to compressive force whereas ductility is
the ability of a material to deform upon the
application of tensile force. Aluminium, Copper and
gold have good malleability.
• HARDNESS: It is the ability of a material to offer
resistance to penetration or indentation. It is also the
ability to resist wear, abrasion, scratch or cutting.
Mechanical Power Transmission
What is Machine?
Machine is a device consisting of various elements
arranged together, so as to perform the prescribe task to
satisfy human needs.
Machine Elements
•Machine element is an individual component or a group
of components of a machine which performs a specific
function.
•Its function may be of holding the components together,
to transmit power or to give supports.
•Depending upon these functions only, the machine
elements are following types.
1) Machine elements used for holding the components.
2) Machine elements used for transmitting the power.
3) Machine elements used for support of other
components.
Shaft
Types of shafts
Axles
•It is non-rotating machine element which is
used to support rotating machine elements
like : wheels, pulleys etc.
Types of Shafts
A ) Machine shaft:These shafts form an integral part of the machine
itself. e.g. crank shaft of an I.C. engine .
1) Axle An axle is stationary shaft i.e. Non rotating member,
which supports a rotating element like wheel or hoisting
drum and fitted to the housing by means of bearings. Axle
is subjected to bending load only and does not transmit
any useful torque.
e.g.
• rear axle of railway wagon
• axle of motor car
• supporting wheels.
2) Spindle: A spindle is a short rotating shaft. Spindles are used
in all machine tools to give motion to a cutting tool or to a
work piece.
e.g.
• spindle of drilling machine.
• drive shaft of lathe.
B) Transmission shaft:
These shafts transmit power from the source of power to the machine which absorbs
that power.
e.g. the power is transmitted from motor to compressor by means of a
transmission shaft.
The transmission shaft is usually circular in cross section. The shaft is always stepped
(having different cross sections of shafts) for positioning transmission elements like
gears, pulleys and bearings. Transmission shafts may be solid or hollow.
Type:
1. main shaft
It is a primary shaft, which is
driven by the machine shaft and from
which the power is supplied to the
counter shaft.
2) Countershaft
It is a secondary shaft, which is
driven by the main shaft and from
which the power is supplied to the
machine components.
Types based on structure of Shafts
• Hollow shafts are lighter than
solid shafts. They have more
strength per kg weight of
material compared to solid
shaft.
• The various types of shafts are
as shown in Fig.
• The examples of the hollow
shafts are propeller shafts.
• Main shaft between air
compressor and gas turbine in
air craft engine.
Shaft Material
• The material used for the shaft should have the following
properties
1) It should have high strength.
2) It should have good machin ability.
3) It should have good heat treatment properties.
4) It should have high wear resistant properties.
5) It should have sufficient hardness.
6) It should be corrosion resistant in marine or corrosive
environments.
7) It should have high modulus of elasticity.
• The material commonly used for shaft is mild steel. The carbon
steel is also used where strength, wear resistance and facility
of heat treatment is needed.
Keys
• A key is a machine element used on shafts to secure the rotating elements
like gears, pulleys or sprockets and prevent the relative motion between the
two. It is always inserted parallel to the axis of the shaft. Keys are used as
temporary fastenings and are subjected to considerable crushing and
shearing stresses.
A keyway is a slot or recess in a shaft and hub of the pulley to accommodate a
key.
• Materials used:
• Plain carbon steels
• Alloy steels
• A key performs following two basic functions.
1) The primary function of key is to transmit the torque from the shaft to the
hub of machine element and vice-versa.
2) The second function of the key is to prevent relative rotational motion
between the shaft and mounted machine element like gear or pulley.
• In most of the cases, key also prevents axial motion between the
elements.
• A keyed joint consisting of shaft, hub and key is illustrated in Fig.
• A recess or slot machined on the shaft and or in the hub to
accommodate the key is called as key way.
• One key way is usually cut by milling machine.
• Keys are designed in order to withstand shear and compressive stresses
resulting from transmission of torque.
• Generally, material of the key is selected, which has less strength than the
shaft material.
Types of Keys
• Keys are broadly classified as
a) Saddle keys
b) Sunk keys
c) Round key
d) Splines
Keys
Belts
• The belt drives are of the following types :
(a) open belt drive, and
(b) cross belt drive.
• Open Belt Drive
• Cross belt drive
•
•
Let d1 and d2 be the diameters of driving and driven pulleys, respectively. N1 and
N2 be the corresponding speeds of driving and driven pulleys, respectively.
The velocity of the belt passing over the driver
•
If there is no slip between the belt and pulley
•
If thickness of the belt is ‘t’, and it is not negligible in comparison to the diameter,
•
Let there be total percentage slip ‘S’ in the belt drive which can be taken into
account as follows :
Chain
Gears