Aim:- To conduct torsion test on mild steel.


1. A torsion test machine along with angle of twist measuring attachment.

2. Standard specimen of mild steel.

3. Steel rule.

4. Vernnier caliper or a micrometer.

Theory:- For transmitting power through a rotating shaft it is necessary to apply a turning force. The force is applied tangentially and in the plane of transverse cross section. The torque or twisting moment may be calculated by multiplying two opposite turning moments. It is said to be in pure torsion and it will exhibit the tendency of shearing off at every cross section which is perpendicular to the longitudinal axis.

Torsion Testing Machne: TORSION TEST OF MILD STEEL


Torsion equation:-

T/J = τ/R= Gθ/L

G = T L/J θ  N/mm2

T= maximum twisting torque (N mm)

J = polar moment of inertia (mm4) = π d4/32

τ = shear stress (N/mm2)

G = modulus of rigidity (N/mm2)

θ = angle of twist in radians

L= length of shaft under torsion (mm)


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 protractor to zero for convenience and clamp it by means of knurled screw.

6. Carry out straining by rotating the hand wheel 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 G by using relation.


1) Measure the dimensions of the specimen carefully

2) Measure the Angle of twist accurately for the corresponding value of Torque.

3) The specimen should be properly to get between the jaws.

4) After breaking specimen stop to m/c.


Gauge length of the specimen, L = ………

Diameter of the specimen, d = ………

Polar moment of inertia, J = π d4/32 = ……..



Result :- Thus the torsion test on given mild steel specimen is done and the modulus of rigidity is ————-N/mm2.

The torsion test is a mechanical test used to evaluate the mechanical properties of a material, particularly its response to torsional or twisting forces. It is commonly used to determine the shear strength, shear modulus, and ductility of materials.

To perform a torsion test on mild steel, here are the general steps involved:

Sample preparation:

Start by preparing cylindrical specimens from the mild steel material. The standard dimensions for the specimen are defined by the testing standards you are following.

Mounting the specimen:

Secure one end of the specimen in a torsion testing machine. The other end should be free to rotate.

Applying the torque:

Apply a twisting or torsional force to the free end of the specimen. This force should be gradually increased until the specimen fractures or until the desired level of deformation is achieved.

Measuring the torque and angle of twist:

As the torque is applied, measure the torque (moment) being applied to the specimen and the corresponding angle of twist. These measurements can be obtained using a torque sensor and an angle measuring device.

Calculating the properties:

Once the test is completed, you can use the measured torque and angle of twist data to calculate various mechanical properties of mild steel. These properties include shear strength, shear modulus, and torsional stiffness.

It is important to note that specific testing procedures, sample dimensions, and calculations may vary depending on the testing standards being followed and the specific equipment available. It is always advisable to consult the relevant testing standards and guidelines for accurate and standardized testing procedures.

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