PPT: Torsion | Strength of Materials (SOM) - Mechanical Engineering PDF Download

 Page 1


TORSION OF CIRCULAR SHAFT
? 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.
Page 2


TORSION OF CIRCULAR SHAFT
? 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.
Torque = turning force x diameter of shaft
T = F x 2R
where :
T=Torque
F=Turning force
S=Radius of the shaft
Unit of Torque(T) is N.mm or kN.mm
R
F
F
Page 3


TORSION OF CIRCULAR SHAFT
? 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.
Torque = turning force x diameter of shaft
T = F x 2R
where :
T=Torque
F=Turning force
S=Radius of the shaft
Unit of Torque(T) is N.mm or kN.mm
R
F
F
ANGLE OF TWIST (?)
? 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’= ? =Angle of twist 
? Angle of twist is measured in radians.
A’                                                                   
o                                  
A
Page 4


TORSION OF CIRCULAR SHAFT
? 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.
Torque = turning force x diameter of shaft
T = F x 2R
where :
T=Torque
F=Turning force
S=Radius of the shaft
Unit of Torque(T) is N.mm or kN.mm
R
F
F
ANGLE OF TWIST (?)
? 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’= ? =Angle of twist 
? Angle of twist is measured in radians.
A’                                                                   
o                                  
A
SHEAR STRESS IN SHAFT:(t)
? 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. 
Page 5


TORSION OF CIRCULAR SHAFT
? 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.
Torque = turning force x diameter of shaft
T = F x 2R
where :
T=Torque
F=Turning force
S=Radius of the shaft
Unit of Torque(T) is N.mm or kN.mm
R
F
F
ANGLE OF TWIST (?)
? 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’= ? =Angle of twist 
? Angle of twist is measured in radians.
A’                                                                   
o                                  
A
SHEAR STRESS IN SHAFT:(t)
? 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. 
STRENGTH OF SHAFTS
Maximum torque or power the shaft can transmit from one 
pulley to another, is called strength of shaft.
(a) For solid circular shafts:
Maximum torque (T)is given by :
where, D = dia. of the shaft
t=shear stress in the shaft
3
16
D T ? ? ? ?
?