This document discusses different types of stresses, strengths, and couplings used to connect shafts. It defines shear stress, axial force, torsion, tensile strength, compressive strength, shear strength, and torsional strength. It also describes flexible couplings, universal couplings, Oldham couplings, and pin bush couplings; and discusses how they can accommodate misalignment between shafts and transmit torque.

1. Ali Azam (Group leader)
2012-uet-scet-ryk-mech-23
Abddul Malik
2012-uet-scet-ryk-mech-16
Abdul Rayhan Muhammad
2012-uet-scet-ryk-mech-22
Muhammad Naveed
2012-uet-scet-ryk-mech-01
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2. 1. Description about different types of
stresses.
2. Description about different types of
strength.
3. Flexible coupling.
4. Universal, Oldham and bushed pin
coupling.
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4. Shear stress is a stress state in which the shape of
a material tends to change (usually by "sliding" forces
without particular volume change.
Usually Shear Stress is dinoted by :
Unit : Pascal or N/m2
a) Horizontal Shear Stress
b) Transverse Shear Stress
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7. Load, P
P
Area
Ao
Lo
L/2
L/2
Load, P
P
Area
Ao
Lo
L/2
L/2
tension compression
Axial force:
A load directed
along the axis of
the object resulting
in either tension or
compression
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8. Torsion is the twisting of an object due to an
applied torque. It is expressed in newton metres
(N·m) or foot-pound force (ft·lbf).
Torsional stress
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9. Ability of a material to resist deformation.
 Tensile Strength
The tensile strength is defined as the maximum tensile
load a body can withstand before failure divided by its
cross sectional area. This property is also sometimes
referred to Ultimate Tensile Stress or UTS.
Examples:- Typically, ceramics perform poorly in
tension, while metals are quite good.
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10. Compressive strength is defined as the maximum
compressive load a body can bear prior to failure,
divided by its cross sectional area.
examples:-
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11.  Shear strength is the maximum shear load a body can
withstand before failure occurs divided by its cross sectional
area.
 This property is relevant to adhesives and fasteners as well as
in operations like the guillotining of sheet metals.
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12.  Torsional strength is the maximum amount of torsional stress a
body can withstand before it fails, divided by its cross
sectional area.
 This property is relevant for components such as shafts.
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13. A coupling is a device used to connect
two shafts together at their ends for the
purpose of transmitting power.
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14. Coupling
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15.  Rigid coupling is used to connect two shafts which
are perfectly in axial alignment.
 Used to connect shafts that are
precisely aligned.
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16.  Flexible couplings are designed to transmit torque while
permitting some axial, and angular misalignment. Flexible
couplings can accommodate angular misalignment up to a few
degrees and some parallel misalignment.
 flexible coupling can absorb vibration and impact accurately.
It has non lubrication characteristics.
Axial Angular
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17.  Universal coupling is a type of flexible coupling that utilized a
yoke and cross to connect two shafts and allow shafts to be at
an angle relative to each other.
 Common application of Universal joints include car drive
shafts, steering columns.
Center
block
Fork Pin Universal
coupling
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19.  Pin Bush Couplings are used under normal shaft
misalignments. It transmit the torque through rubber
bushes which have an excellent capacity to absorb
shocks.
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21.  The bearing pressure on the rubber or leather
bushes and it should not exceed 0.5 N/mm2
Pin and bush design
 l=Length of bush in the flange,
 d 2=Diameter of bush,
 pb=Bearing pressure on the bush or pin,
 n=Number of pins,
 D1=Diameter of pitch circle of the pins
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22. Pin and bush design
 Bearing load acting on each pin
W = pb×d 2×l
 Total bearing load on the bush or pins
W × n= pb×d 2×l ×n
 Torque transmitted by the coupling
T= W × n × (D1 /2)
T= pb×d 2×l ×n × (D1 /2)
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23. Definition:-
An Oldham coupling is a method to transfer torque
between two parallel but not collinear shafts.
History:-
The coupling is named for John Oldham who
invented it in Ireland, in 1820.
OLDHAM’s COUPLING
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24.  It has three discs, one coupled to the input, one
coupled to the output, and a middle disc is joined by
tongue and groove to both discs.
 The rotation of driver shaft causes the rotation of
middle disc which transmits the motion and power to
the driven shaft.
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25.  The tongue and groove on one side is perpendicular
to the tongue and groove on the other.
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27.  Machine Design (S.I. Units) R. S. Khurmi J. K.
Gupta.
 Mechanics of Engineering and of Machinery,
Vol. III, Wiley, 1883; pages 81-91.
 Theory of Machines 3 from National
University of Ireland.
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