MEB705 MECHANICAL
BEHAVIOUR OF
MATERIALS
MEASURING SPECIMEN USING MICROMETRE AND VERNIER CALLIPER AND
MECHANICAL TESTING (TENSILE TEST, TORSION AND BRINELL HARDNESS TEST)
LAB REPORT BY VINIL PRASAD (2019004152)
SEMESTER 2 2021 || SCHOOL OF MECHANICAL ENGINEERING
OBJECTIVES
The objectives are as follows:
1. To measure dimensions of the respective test specimens using a Vernier
Calliper and a Micrometre.
2. To do a tensile, torsion and hardness testing on the various specimens being
measured and compared it to the 3D printed specimens’ result.
INTRODUCTION
Mechanical testing reveals the properties of a material under dynamic or static
force. Designed to ensure that materials are suitable for their intended
applications, mechanical testing includes methods such as tensile strength,
compression strength, impact resistance, fracture toughness and fatigue.
In this lab three sets of specimens including 3D printed and metal specimens will
be tested and the results compared. The tests are tensile, torsion and hardness
tests. Each set will test both a metal specimen and a 3D printed plastic specimen.
Micrometre
Vernier Calliper
METHODOLOGY
The experiment has three different phases.
1. The first phase involves measuring of the specimen to be tested using
Vernier calliper and micro – meter.
2. The second phase is the drawing and 3D printing of the test specimens. The
3D printed specimens are used as a comparison to the metal specimens and
to determine how strong 3D printed materials really are.
3. The third phase is the actual objective of this laboratory. It includes the
tensile, torsion and hardness test of the 3D printed specimen to the metal
specimens.
Figure of three types of Testing Specimen
RESULTS
Tensile Test
Tensile testing is a destructive test process that provides information about the
tensile strength, yield strength, and ductility of the metallic material. It measures
the force required to break a composite or plastic specimen and the extent to
which the specimen elongated.
The graph below shows the stress – strain graph of Aluminium vs 3D printed Plastic
specimen.
The graph is manually plotted in the Hounsfield Tensiometer. From the scaling
(rolling paper) 1cm is equivalent to 125kg (approx.1.25kN) for the stress. Thus, 1
square is equal to 1 cm2 (1cm x 1cm).
Find:
Material Property
Aluminium
Plastic
UTS
0.044 MPa
0.008 MPa
Yield Strength
0.004 MPa
0.0008 MPa
Young’s Modulus (Slope)
0.02 N/cm2
3.7 x 10-3 N/cm2
The specimen dimensions for both Aluminum and Plastic:
L=110mm
Cross – Sectional Area=πD2/4 =
D=5mm
0.1963 cm2
UTS
Yield Strength
Young’s
Modulus
Aluminum
439.71 MPa
Plastic
50.94 MPa
Aluminum
433.01 MPa
Plastic
89.15 MPa
Aluminum
Slope = 42.39 MPa
Plastic
Slope = 73.56 GPa
Torsion Test
Angular
Displacement
(Deg.)
Torque (Nm)
Cast Iron
Plastic
3D
1
0.49
0.20
2
1.46
0.40
3
2.50
0.60
4
3.58
0.79
5
4.64
0.93
6
5.67
1.15
7
6.55
1.32
8
7.58
1.48
9
8.35
1.65
10
9.16
1.81
15
11.70
2.07
20
13.12
3.48
25
14.72
4.16
30
15.41
4.75
35
15.76
5.17
40
16.22
5.39
45
-
5.63
50
-
5.65
55
-
5.48
60
-
5.42
65
-
5.30
70
-
5.21
75
-
5.05
80
-
4.85
85
-
4.77
90
-
4.55
95
-
4.45
100
-
-
Torsion is the twisting of an object due to an
applied torque. Torsion is expressed in either
the Pascal (Pa), an SI unit for newtons per
square metre, while torque is expressed in
newton metres (Nm).
In this experiment, the Torsion test was
performed on two different materials, cast
iron and plastic.
The table shows amount of displacement in
degree corresponding to the torque in newton
meter for both the cast iron and plastic testing
specimens.
From the results, the cast iron specimen
breaks or fracture at a twisting angle of
40˚with a torque of 16.22 Nm.
Where as in the plastic twisting, angle of twist
reaches 95˚ and beyond with a decreasing
force of 4.45 Nm. However, the maximum
torque force is 5.65 Nm and a displacement of
50˚.
As shown, the cast iron required higher
magnitude of force to be twisted. Whereas the
plastic specimen only needs lower twisting
force with greater angular displacement.
Graph of Torque Vs Angular Displacement
18
16
Torque (Nm)
14
12
10
8
6
4
2
1
2
3
4
5
6
7
8
9
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
0
Angular Displacement (Degrees)
Cast Iron
Plastic
Hardness Test
The hardness of the respective specimens was measured by loading an indenter
onto the surface. The indenter material which is usually a ball made of a material
much harder than the material being tested. The 3000-kilogram force (kg. f) load
is applied slowly by pressing the indenter at 90 degrees into the specimen surface
being tested.
Brinell hardness test is performed to find the hardness typically called the Brinell
hardness.
All the data obtain as a result of experiment is arranged in the table below.
Diameter (D) mm = 10 mm
P(kg) = 3000 kg
BHN =
2𝑃
𝜋𝐷(𝐷−√𝐷 2 −𝑑2
BHN = Brinell Hardness Number (kg. f/mm2)
P
= Applied load in kilogram-force (kg. f)
D
= Diameter of indenter (mm)
d
= Diameter of indentation (mm)
Specimen
Diameter (d)
mm
Calculations
BHN
Aluminium
6.6
(2(3000))/ (π (10) (10-√ (102-6.62))
76.78 kg.f/mm2
Plastic
7.7
(2(3000))/ (π (10) (10-√ (102-7.72))
52.76 kg.f/mm2
Figure 1 A Hardness Test Specimen
CONCLUSION
At the end of this lab, it was concluded that the metals act like ductile materials,
which gives signs of failure before the failure actually occurs rather than plastics,
which act as a brittle material and often fails without any signs. This is why metals
like aluminium in this lab experiment was able to stretch and twist, whereas the
plastic specimen acted like brittle materials and didn’t stretch or twist much
before eventually breaking.