AIM
To
conduct torsion test on mild steel or cast iron specimens to find out modulus of rigidity
APPARATUS
1. A torsion testing machine.
2. Twist meter for measuring angles of twist out modulus of rigidity.
2. Twist meter for measuring angles of twist out modulus of rigidity.
3. A steel rule and Vernier
Caliper or micrometer.
THEORY: -
A
torsion test is quite instrumental in determining the value of modulus of rigidity of a metallic specimen. The value of modulus of rigidity can be found out thought observations made during the experiment by using the torsion equation
T=Torque
J= Polar moment of inertia
N= Modulus of rigidity
τ = Shear stress
R = Distance of element from center of shaft
θ = Angle of twist
L= Length of shaft
PROCEDURE
1. Select the driving dogs to suit the size of the specimen and clamp it in the machine by adjusting the length of the specimen by means of a sliding spindle.
2. Measure the diameter at about three places and take the average value.
3. Choose the appropriate range by capacity change lever
4. Set the maximum load pointer to zero.
5. Set the protector to zero for convenience and clamp it by means of knurled screw.
6. Carry out straining by rotating the handweel in either direction.
7. Load the machine in suitable increments.
8. Then load out to failure as to cause equal increments of strain reading.
9. Plot a torque- twist (T- θ) graph.
10. Read off co-ordinates of a convenient point from the straight line portion of the torque twist (T- θ) graph and calculate the value of N by using relation
1. Select the driving dogs to suit the size of the specimen and clamp it in the machine by adjusting the length of the specimen by means of a sliding spindle.
2. Measure the diameter at about three places and take the average value.
3. Choose the appropriate range by capacity change lever
4. Set the maximum load pointer to zero.
5. Set the protector to zero for convenience and clamp it by means of knurled screw.
6. Carry out straining by rotating the handweel in either direction.
7. Load the machine in suitable increments.
8. Then load out to failure as to cause equal increments of strain reading.
9. Plot a torque- twist (T- θ) graph.
10. Read off co-ordinates of a convenient point from the straight line portion of the torque twist (T- θ) graph and calculate the value of N by using relation
OBESERVATION
|
Torque |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
|
Angle
of |
|||||||||||||||
|
Modulus |
RESULT
i) Modulus of rigidity of mild steel rod is
------------- N/mm2
ii) Modulus of rigidity of Aluminum rod is ------------- N/mm2
PRECAUTION
2) Measure the Angle of twist accurately for the corresponding value of Torque.
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