# Torsion Test

Topics: Shear stress, Elasticity, Shear strength Pages: 7 (822 words) Published: May 27, 2014
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Lab (1): Torsion Test

Course Number:
EMC 2043
Course Name :
Mechanics of Materials
Section:

Name
ID
1

2

3

Torsion Test
OBJECTIVES:
To carry out a torsion test to destruction in order to determine the following for a steel rod specimen: 1. To compare the experimental shear modulus (modulus of rigidity) with the tabulated values. 2. The maximum shear stress at the limit of proportionality or the proportional limit shear stress, 3. The general characteristics of the torque, angle of twist relationship.

The proportional limit shear stress: the highest shear stress that the material can withstand and still return to its original geometry is at the limit of the proportional portion of the graph and is known as the proportional limit shear stress.

REFERENCES:
1. Hibbeler, R. C. "Mechanics of Materials", Prentice-Hall, 7th Edition. 2. Instruction Bulletin of Tecquipment Ltd.
MATERIAL:
Mild Steel rod 6 mm diameter over 3" length (overall length including hexagon ends = 5⅝").
EQUIPMENT:
1. Torsion testing Machine and Torsiometer of Tecquipment Ltd. 2. Steel rule and micrometer.
THEORY:

(1)

(2)

(3)
Where,
G = Shear Modulus (GPa)
L = Length (m)
T = Torque (N.m)
J = Polar moment of inertia
EXPERIMENTAL PROCEDURE:
1 Measure the overall length and test diameter of the specimen. 2 Draw a line down the length of the degree of the section of the specimen with a pencil this serves as a visual aid to the degree of twist being put on the specimen during loading. 3 Mount the specimen firmly in the Torsion Testing Machine as indicated in the operating instructions—see later. If the Torsimeter is to be used the fixing procedure should be carried out as prescribed. For each increment of strain record the following:

a) Angle of twist of the specimen () in degrees.
b) Applied torque (T)
c) When the elastic limit has been passed continue to test to destruction with ever increasing increments of strain, recording for each strain increment, I. Angle of twist in degrees.
II. Applied torque.

NOTE: In some tests it may be found unnecessary to use the Torsiometer after the elastic limit has been reached and we may need to remove it.

Fig. 1 Typical torsion-test specimens; it is mounted between The two heads of a testing machine and twisted. MEASUREMENT:
RESULTS:
Specimen no. 1

Specimen Details

Material

Diameter (mm)

Gauge length (mm)

Test Speed (rpm) (reference only)

2. Tabulate the results as follows:

Angle of Twist
 (degrees)
Applied Torque
T (Nm)
Angle of twist

Specimen no. 2

Specimen Details

Material

Diameter (mm)

Gauge length (mm)

Test Speed (rpm) (reference only)

2. Tabulate the results as follows:

Angle of Twist
 (degrees)
Applied Torque
T (Nm)
Angle of twist

Error in the modulus of rigidity:

(4)
Answer the following questions in the body of your report sections: Introduction:
1. Why do we study torsion of beams and members?
2. What is the objective of the experiment?

Apparatus and Procedure:
3. What is the apparatus used to conduct the experiment? Add a picture to the apparatus. 4. Mention the experiment procedure very briefly as you did in the lab.

Data and Figure:
5. Plot the applied torque 'T' against angle of twist  in degrees (for all specimens used during the experiment) for the complete test destruction. Plot your results using Excel. Name it Figure (1) and give it a caption.

6. Plot the applied torque 'T' against angle of twist  in degrees (we will convert it to radians in calculations) for only the elastic region. Use the slope (T/) from the graph to determine the value of modulus of rigidity. Also from this graph determine...