Hong Kong Institute of Vocational Education (Tsing Yi)
Department of Construction
Concrete and Structure Laboratory
Laboratory Test Instruction Sheets
Torsion Test
______________________________________________________________________________________________________________________
Course:
Higher Diploma in Civil Engineering
Experiment: Torsion Test
Hours
Unit:
Structural Analysis I
Expected Duration:
1.25
Objective:
1.
2.
3.
To determine the shear modulus of the metal specimens.
To determine the shear stress at the limit of proportionality of the test specimens.
To study the different failure modes of ductile and brittle specimens.
Apparatus
1.
2.
3.
TecQuipment Torsion Testing Machine as shown in Fig. 1.
Torsion Test specimens as shown in Fig. 2
Steel rule and micrometer.
Theory
From the general torsion theory of a circular specimen:
T Gθ τ
=
=
J
l
r
where
T = Applied Torque (Nm).
J = Polar moment of inertia (mm4 ) = πd4/32
G = Shear Modulus (Nmm-2 ).
θ = Angle of twist (over length) in radians.
l = Gauge length (mm).
τ = Shear stress at radius r (Nmm-2 ).
r = Radius (mm).
Experimental Procedures
1.
Measure the overall length (l) and diameter (d) of the test section of the specimen
before and after testing.
Pg. 1
Hong Kong Institute of Vocational Education (Tsing Yi)
Department of Construction
Concrete and Structure Laboratory
Laboratory Test Instruction Sheets
Torsion Test
______________________________________________________________________________________________________________________
2.
Draw a line down the length of the test 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 and use the levelling
wheel to reset the dial gauge reading to its original value at the start of the
experiment. For each increment of angle of twist record the following to
destruction:a)
angle of twist of the specimen in degrees (θ). (later convert to radian)
b)
applied torque (T).
Suggested Increment of Twist Angle
To ensure that an adequate number of values are obtained from the test, particularly during
the elastic region of strain, the following is recommended:Specimen
Code
Angular
Increment
0.15% carbon steel (as drawn)
MT15
3o
Cast Iron
MCI
2o
Remark:
Two specimens of MT15 and MCI will be used for the experiment.
Results:
1.
Dimensions of the specimens before and after testing:
Dimensions of the specimens (mm)
Type of specimen
0.15% Carbon Steel (MT15) Cast Iron (MCI)
Initial diameter (mm)
Final diameter (mm)
Gauge length (mm)
Initial overall length (mm)
Final overall length (mm)
Pg. 2
Hong Kong Institute of Vocational Education (Tsing Yi)
Department of Construction
Concrete and Structure Laboratory
Laboratory Test Instruction Sheets
Torsion Test
______________________________________________________________________________________________________________________
2.
Test data for the torsion test:
Mild Steel (MT15)
Angle of twist, θ, ( o)
Applied torque, T (Nm)
0
3
6
9
12
15
18
21
24
27
30
Angle of twist, θ, ( o)
Applied torque, T (Nm)
33
36
39
42
45
48
51
54
57
60
63
Angle of twist, θ, ( o)
Applied torque, T (Nm)
66
69
72
75
78
81
84
87
90
93
96
Angle of twist, θ, ( o)
Applied torque, T (Nm)
99
Angle of twist, θ, ( o)
Applied torque, T (Nm)
Cast Iron (MCI)
Angle of twist, θ, ( o)
Applied torque, T (Nm)
0
2
4
6
8
10
12
14
16
18
20
Angle of twist, θ, ( o)
Applied torque, T (Nm)
22
24
26
28
30
32
34
36
38
40
42
Angle of twist, θ, ( o)
Applied torque, T (Nm)
44
46
48
50
52
54
56
58
60
62
64
Angle of twist, θ, ( o)
Applied torque, T (Nm)
Angle of twist, θ, ( o)
Applied torque, T (Nm)
Pg. 3
Hong Kong Institute of Vocational Education (Tsing Yi)
Department of Construction
Concrete and Structure Laboratory
Laboratory Test Instruction Sheets
Torsion Test
______________________________________________________________________________________________________________________
3.
4.
Graphical Presentation for the Test Data:
a)
Plot a graph of applied torque “T” (Nm) against the angle of twist “θ“ (in
radian) of each specimen for the complete test to destruction.
Hints: T as y-axis and θ as x-axis.
b)
Calculate the slope of the graph of the elastic region in order to determine the
values of the shear modulus of each specimen.
Hints: By using the given formula
c)
From the graphs, determine the torque and then calculate the shear stress at
the limit of proportionality for each specimen.
Hints: By using the given formula.
Observation of the Modes of Failure
Record and sketch the modes of failure of each specimen.
Discussion of Results
1.
2.
3.
Comment on the modes of failure of the test specimens.
State and comment upon the values (shear moduli, shear stresses at the limit of
proportionality) obtained from the test.
Discuss the errors involved in this experiement and make suggestions for the
improvement.
Laboratory Report
1.
Each student shall submit his / her laboratory report which includes the following
items:
(a)
(b)
(c)
(d)
(e)
(f)
2.
Name of Test
Objectives of Test
Test Data
Test Data presented in Graphical Form.
Shear moduli and torsional shear stresses at the limit of proportionality of
specimens obtained in (d).
Report and explain the modes of failures of specimens.
Hand in the report on / before _______________.
Pg. 4