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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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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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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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 orcompression

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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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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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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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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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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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A coupling is a device used to connecttwo shafts together at their ends for thepurpose of transmitting power.

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Coupling

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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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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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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 Universalcoupling

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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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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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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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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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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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The tongue and groove on one side is perpendicular

to the tongue and groove on the other.

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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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