Torsion Test

Torsion Test Submitted By: Ankit Suchanti Roll no: 10003013 Mechanical Engineering Name:

Objective: To familiarize oneself with torsion test technique and equipment and determine the values of  maximum torque , ultimate shear strength and fracture strength for the given specimens.

Standard: ASTM A938-07

Apparatus: Torsion testing machine

Specimen: Aluminium, Mild Steel, Stainless Steel, Brass, Grey cast iron

Schematic Diagram:

Movable Chuck

Stationary (Rotating) Chuck 

Specimen

Weights Manual Control Board

Figure shows a representtion of the torsion machine.

Procedure:

1. Measure the diameter of the specimen rods using vernier callipers at three different points and take their mean as the mean diameter of the rod. 2. Measure the length of the rod. 3. Next the software, TestXpert II is started on the computer attached to the machine. 4. Switch on the main power supply. 5. Turn on the UPS. 6. Switch on the machine and establish the link between the machine and the computer. o 7. Now set the position of the rotating chuck to 180 . 8. The lid of the machine is opened and the specimen is mounted in the chucks after which the lid is closed and locked. 9. Now set the torque initial value (if non zero) to zero. 10. Now input the parameters of the specimen such as shape, diameter and length into the software. 11. Next set the rotation speed and ensure other settings before starting the test. 12. Once the settings are done start the test and wait until t he specimen breaks down. 13. The software records the test results continuously over time and stops as soon as the specimen breaks down. 14. Then open the lid and remove the specimen and rstore the machine to default settings for testing other specimens.

Observations: Observations made during the test are as summarized in the table below.

Specimen Brass

D1(mm)

D2(mm)

D3(mm)

D avg

(Order of  performing the Exp.)

7.08

7.08

7.1

7.086

1

Stainless Steel

7.1

7.08

7.1

7.093

3

Cast iron*

7.1

7.12

7.14

7.12

4

Aluminum

7.04

7.06

7.02

7.04

2

Mild Steel

7.08

7.06

7.06

7.066

5

* This experiment was performed by me.

Experiment performed by: Nakul Nuwal Shubham Bhargav Ankit Suchanti Shashank Agarwal Dhwanil Shukla

The Test Report for all the specimen:

Calculations: 3

Ultimate Shear Strength (τmax) = MR/J =16M/pi(d ) Modulus of Rigidity (G) = ML/Jβ M is Torque applied L is Length of specimen 4 J is Area moment of inertia ( πd  /32) β is angle of twist

Results: The values of maximum torque, ultimate shear strength and fracture strength for the given specimens are:

Specimen

Maximum Torque (in Nm)

Ultimate Shear Strength (in MPa)

Fracture Strength (in Nm)(mod)

1

Brass

16.54

236.87

10.63

2

Mild Steel

24.07

347.65

9.14

3

Aluminum

5.67

82.8

1.02

4

Grey Cast Iron

9.51

134.26

9.63

5

Stainless Steel

65.46

934.71

11.7

Serial number

Discussion: 1. The breakage occurred only due to shear force applied. 2. Cast Iron being brittle fractured in the least time and in the least strain angle. 3. The application of torque was at a speed well below the prescribed maximum speed(As per ASTM standard). 4. The specimen fractured at its centre(roughly) making the result of the test valid. 5. The fracture of brittle material and ductile material were completely different while the fracure was parallel to its surface for ductile material, it was at 45 deg for brittle material.

Figure shows the difference in fracture for brittle(left) and ductile(right) material.