5. TORQUE OR TURNING MOMENT OR
TWISTING MOMENT
In factories and workshops, shafts is used to transmit energy
from one end to other end.
To transmit the energy, a turning force is applied either to
the rim of a pulley, keyed to the shafts, or to any other
suitable point at some distance from the axis of the shaft.
The moment of couple acting on the shaft is called torque or
turning moment or twisting moment.
Pinal Patel 5
6. Torque = turning force x diameter of shaft
T = F x 2R
where :
T=Torque
F=Turning force
R=Radius of the shaft
Unit of Torque(T) is N.mm or kN.mm
2R
F
F
Pinal Patel 6
7. Terminology:
1) Shaft: The shafts are the rotating machine elements which
are used to transmit power in machines from one place to
another. Crank shaft is the example of machine shaft.
2) Turning Moment or Twisting Moment: The twisting
moment for any section along the bar / shaft is defined to be
the algebraic sum of the moments of the applied couples
that lie to one side of the section under consideration. The
choice of the side in any case is of course arbitrary.
i.e ∑T up to the section = total twisting moment at section
Pinal Patel 7
8. 3) Shearing Strain: If a generator a – b is marked on the
surface of the unloaded bar, then after the twisting moment
'T' has been applied, this line moves to ab'. The angle ‘γ'
measured in radians, between the final and original
positions of the generators is defined as the shearing strain
at the surface of the bar or shaft.
Pinal Patel 8
9. 4) Modulus of Elasticity in Shear or Shear Modulus:
The ratio of the shear stress to the shear strain is called the
modulus of elasticity in shear or Modulus of Rigidity and in
represented by the symbol G or N or C =τ/γ.
Pinal Patel 9
10. 5) ANGLE OF TWIST (θ):
When the shaft is subjected to Torque (T), point A on the
surface of the shaft comes to A’ position. The angle AOA’ at
the centre of the shaft is called the angle of twist.
∠AOA’= θ =Angle of twist
Angle of twist is measured in radians.
A
A’
θ
Pinal Patel 10
11. γ is shear strain
and θ is angle of twist
Pinal Patel 11
12. 6) SHEAR STRESS IN SHAFT:(τ)
When a shaft is subjected to equals and opposite end
couples, whose axes coincide with the axis of the shaft, the
shaft is said to be in pure torsion and at any point in the
section of the shaft stress will be induced.
That stress is called shear stress in shaft.
Pinal Patel 12
Editor's Notes
NOTE:
To change the image on this slide, select the picture and delete it. Then click the Pictures icon in the placeholder to insert your own image.
