Project 2
Tensile Test of Materials
Laboratory Manual
Prepared for 1502ENG Engineering Materials
Outline
Students should work in groups of 5 to complete this assessment item. The aim is to investigate
the tensile properties of the various classes of materials, and relate these properties to real-world
applications, i.e., a bicycle frame.
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CONTENTS
1 Mechanical Properties of Materials 1
1.1 Aim ........................................................................................................................ XXXXXXXXXX1
1.2 Introduction ........................................................................................................... XXXXXXXXXX1
1.3 Scenario ................................................................................................................. XXXXXXXXXX3
1.4 Equipment ............................................................................................................. XXXXXXXXXX3
1.5 Testing Procedure .................................................................................................. XXXXXXXXXX3
1.6 Results ................................................................................................................... XXXXXXXXXX5
References 10
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m2
1 MECHANICAL PROPERTIES OF MATERIALS
1.1 AIM
The of this part is to characterise various specimens by means of the tensile test.
1.2 INTRODUCTION
There are various tests to characterise the properties of a material and they are classified in two main cat-
egories: destructive and non-destructive tests. The latter are mainly utilized to check for defects whereas
the former are used to obtain the material strength and stiffness. Amongst the destructive material tests,
the uniaxial tensile test is the most important of them all (see Fig. 1).
Figure 1: Schematic depiction of a sample under tensile loading, (a) before deformation, and (b) after
deformation. Adapted from (Öchsner 2016, p. 3, Fig. 1.2)
A tensile test is conducted by means of a specialised machine, called the tensile testing machine. In such
machines, a controlled loading of the sample is possible. The deformation of the sample is its response
to the applied load. During the test, the values of the force and deformation are continuously recorded.
Engineering stress (σ ) can be calculated using the recorded forces:
F
σ = , (1)
A0
where F is the instantaneous load applied perpendicular to the specimen cross section in units of newtons
(N), A0 is the original cross-sectional area before any load is applied (m2). The units of engineering stress
is pascal (Pa) which is equivalent to newton per square meter ( N ).
Engineering strain (ε) is the change in the dimension per unit length. Engineering strain can be calculated
y knowing the deformation at every instance:
l − l0
l0
∆l
= , (2)
l0
⑧ Write down the hypothesis of this experiment using the mentioned aim. What was the research
question?
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where l0 is the original length, i.e., the gauge length, before any loading, l is the the instantaneous
length, l − l0 is the deformation elongation or change in length at some instant, as referenced to the
original length. The percentage of strain is the engineering strain times 100.
During the test, the applied force and the displacement, which is the response of the sample to the applied
load, is constantly measured. The tensile testing machine to be used is depicted in Fig. 2.
(a) General view (b) Components of the testing equipment
Figure 2: Tensile testing apparatus.
A tensile sample, or sometimes called a coupon, has a plain geometry (see Fig. 3). It consist of clamping
areas at the two ends of the sample and a prismatic section in the middle. The prismatic section is the area
of interest which incorporates the gauge length. This is the same area in which failure will happen. The
two ends serve the sole purpose of fixating the sample in the apparatus with a better grip. Nevertheless,
other geometries are also possible for the sample.
Figure 3: Flat tensile sample and fixation equipment.
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1.3 SCENARIO
In this activity, your group should conduct some tensile tests and provide the answer for the following
scenario:
1.4 EQUIPMENT
The following equipment will be provided:
1.5 TESTING PROCEDURE
You must work in a group of 5 people and obtain the force-deformation data for each sample. Before
starting the test, you should record the required specimen information, e.g., sample number, material
type, cross-sectional area, length, and other required measurements. Additionally, it is required to mark
the gauge length, i.e., 25 cm, on each specimen.
The very first step is to install and clamp the specimen.
Tip
Do not trust the provided measurements, check everything!
➠ Watch the How to use a digital calliper video.
Tip
You need to get the detailed description of the equipment. Refer to Special Issue: Academic Writing.
Equipment
• a digital calliper,
• an extensometer,
• a data acquisition unit,
• the WP300 Universal Material Tester (20 kN), and
• 8 tensile samples:
– Tempered steel (3 samples),
– Annealed steel (1 sample),
– Copper (1 sample),
– PMMA (Acrylic) (1 sample),
– PVC (1 sample), and
– Plywood (1 sample).
Note
The answer to the question must be incorporated in the discussion and be reflected in the conclusion
part of the report. Therefore, it is an individual component of the report.
Scenario The Scrap Metal Co.
You are employed as the designer engineer in Byke Corp. which is a manufacturer of bicycle frames.
There are a few options available for the frames and you need to compare them in terms of their
mechanical properties. The material options are two types of steel, copper, two polymers, and a
composite. Discuss the mechanical properties of the available materials and choose a suitable material
ased on the results of the tensile test.
http:
youtu.be/zBvJDlljvLA
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Figure 4: Mounted tensile sample with attached extensometer
The force is measured by the load cell, located at the lower part of the machine whereas the defor-
mation of the gauge length is measured by an extensometer (see Fig. 2a). Namely, the deformation is
measured along a specific length in