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INTERNATIONAL JOURNAL FOR RESEARCH IN EMERGING SCIENCE AND TECHNOLOGY, VOLUME-2, ISSUE-5, MAY-2015
E-ISSN: 2349-7610
Design and Development of a Notched Ring Shaped
Miniature Specimen and Its Test Setup to Study the
Mechanical Behavior of Metals
F.Hafeez1 and A.Husain2
1
Assistant Professor, 2Associate Professor
1
Department of Mechanical Engineering, College of Engineering, University of Shaqra, Saudi Arabia
1
farrukh6aug@gmail.com
2
Department of Civil Engineering, Jamia Millia Islamia, New Delhi,India – 25
2
asif_iitd@rediffmail.com
ABSTRACT
The paper presents in detail the design and development of a notched ring shaped miniature specimen as well as the experimental
setup used for testing the miniature specimen. The experimental setup is simple and possesses salient features which help in
meeting the desired objectives of miniature testing. In the present study, notched ring shape specimen are developed from
cylindrical rods of different materials using minimum number of machining operations so that the test could be performed in
tension mode without affecting its material properties and the proposed notched ring shaped miniature specimen can easily be
modeled in plane stress condition in finite element method. The aim of this paper is to develop a methodology for determining
mechanical and damage properties of metals from the resultant load displacement curve, obtained by means of a tension test on a
Zwick-Z250 universal testing machine.
Keywords: Miniature Tests, Mechanical Properties
1. INTRODUCTION
The ball or spherical head punch test is the most studied
The miniature specimen test is a very useful technique to
method used to obtain several mechanical properties such as
determine the mechanical properties of materials in those
strength, ductility, ductile–brittle transition temperature, and
situations where it is impossible to extract large volumes of
fracture toughness with little volume of material [3] [4] [5].
material
conventional
The various shapes and dimensions of the punches, and
specimens. Miniature specimen test technique has specifically
circular disks have been used by various research groups [1]
emerged to solve practical problem related to monitor the
[6] [7] [8] [9] [12]. One of the limitations imposed on such test
performance of components used in nuclear power generation
is the accurate requirement of alignment through the guide
systems, petroleum industry, chemical plants, thermal power
cylinder of the axis of the punch, specimen and die. Manahan
stations etc. Manahan et al [1] have successfully developed the
et al. [5] discussed the reasons for this and suggested that the
application of small specimen test technique for designing
eccentricity of loading should not exceed ~ 0.025mm on
large system and nuclear systems in particular. Lucas [2] has
samples of 3mm in diameter. In most of the literature on such
shown that miniature specimen test technique can be applied
type of tests [7] [8] [10] [11] [12], the samples are clamped in
successfully to obtain the mechanical properties of metals in
place to minimize the misalignment of the miniature specimen
the form of either tensile tests, micro hardness, creep, impact
with respect to the axis of symmetry of the test rig. Although
tests, bend tests, fracture toughness, or punch tests (ball, shear
researchers have succeeded in accurately measuring the
punch).
mechanical properties of samples of various shapes and
required
for
VOLUME-2, ISSUE-5, MAY-2015
standard/full-size
COPYRIGHT © 2015 IJREST, ALL RIGHT RESERVED
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INTERNATIONAL JOURNAL FOR RESEARCH IN EMERGING SCIENCE AND TECHNOLOGY, VOLUME-2, ISSUE-5, MAY-2015
E-ISSN: 2349-7610
thickness using various tests but due to several limitations
from the same test. The procedure for making this specimen is
placed over design of their test apparatus and specimen the
easier as compared to that of making conventional sub size
tests become complicated and uneconomical. Owing to the
tension test specimens. The selected geometry has additional
simplicity of tension test need arises to design a test apparatus
advantage due to its convenience in finite element modeling
and a simple miniature specimen that can be successfully used
and economy in computation time. Fig. 1 shows the mode of
to demonstrate and simulate the strength of miniature test
failure of specimens prepared and tested as per testing
technology in the laboratory. The paper presents the design of
requirements.
basic components of the experimental setup i.e. specimen
holder, loading pin and miniature specimen that can be used
on any universal testing machine such as MTS, INSTRON and
Zwick etc.
Figure- 1: Specimen after Testing
2.2 Specimen Holder
2. DESIGN FEATURES OF MINIATURE
The designed specimen holder is made from non shrinkable
SPECIMEN TEST APPARATUS
die steel having a diameter of 12mm at one end and 6mm
The basic components of the experimental setup used in
diameter at the other end with a gauge length of 125mm. The
present work consist of specimen holder, loading pin,
holder is provided with a 10 mm deep slit of 2mm width at
miniature specimen, and Zwick/ Z250 universal testing
one end (to hold the specimen with the help of a loading pin)
machine. The specimen designed for the present investigation
and the other end left for firm gripping. A through 2mm
is ring shaped with a V notch added diametrically to the
diameter hole, drilled laterally, at the depth of 3mm from the
miniature specimen. To hold the above notched ring shaped
top, is provided for holding the specimen with the help of
specimen in the machine, versatile miniature specimen holder
2mm diameter loading pin, shown in Fig. 2. Special attention
of die steel which is capable to accommodate different
is given to ensure that the slit in the top and bottom holder lie
thicknesses of specimens has been designed. The miniature
along the same line when both holders are gripped in testing
testing is tensile in nature. The miniature specimen
machine along with the specimen through the loading pins.
experiences tensile load through the loading pin, which holds
The arm of the specimen holder is designed in such a way that
the miniature specimen in specimen holder. The extension of
it can accommodate different specimen thicknesses. After
the specimen upon tensile load is recorded automatically with
machining, the holders were austenitized at 1000°C for 30
the help of Test-Xpert software interfaced directly with the
minutes, followed by air-cooling, and then tempering at 700°C
Zwick machine.
for an hour to achieve the final hardness of HRC 60. Loading
pins used to fix the miniature specimen in the specimen
2.1 Specimens
holders were made of martensitic steel so that they would not
The miniature specimen in the present investigation has been
bend when the tension force is applied.
prepared in the following steps. Initially the samples of
different materials were produced in the circular rods of 12mm
diameter. A precise hole of 8mm diameter was drilled, along
the axis of the circular rod, on each of them by marking the
centre of the hole. The rings of 0.5mm, 0.8mm and 1.0mm
thickness were sliced from these circular rods on EDM wire
cut machines. A V-shaped notch of 1mm depth and 60o angle
of cut was developed manually on all rings, along same
diametrically opposite ends, using a fine grade triangular cross
cut file. A V-notch is being added diametrically to obtain both
the uniaxial mechanical properties and fracture properties
VOLUME-2, ISSUE-5, MAY-2015
Figure 2. Ring specimen attached in the holder
COPYRIGHT © 2015 IJREST, ALL RIGHT RESERVED
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INTERNATIONAL JOURNAL FOR RESEARCH IN EMERGING SCIENCE AND TECHNOLOGY, VOLUME-2, ISSUE-5, MAY-2015
E-ISSN: 2349-7610
The test specimen is subjected to tensile loading through the
deformable body with bonded strain gauges. Strain gauges are
pin in the bottom holder. Fig. 2 shows a complete assembly of
connected together to a measurement bridge. The value of the
specimen holder, loading pins and ring specimen. At first the
measurement voltage at the measuring bridge output is
top specimen holder is gripped along with the specimen using
analogous to the force to be measured. This force acts on the
wedge grips. Then the specimen is attached with the bottom
deformed body and on the entire sensor system. Fig. 3 shows
holder by passing the pin through the hole provided in the
the specimen in a holder attached on Zwick machine with a
specimen and holder. As the bottom holder is gripped in the
5kN load cell used for measuring the force.
lower wedge grip, it tries to push the holder along with the
specimen and gets rotated. Now, when the tensile load is
applied through the loading pin the lower cross head displaces
itself and tries to become straight so that the specimen
experiences tensile load uniformly.
2.3 Testing Machine
In the present investigation Zwick/ Z250 universal testing
machine is used for applying the load, as shown in Figure 3.
The basic unit of the Z250 material testing machine consists of
a load frame and an electronic control console, for testing
varieties of materials. The material testing machine is
Figure 3. Photograph of specimen in a holder attached on
designed for quasi static loading with continuous, pulsating or
Zwick Machine
cyclic sequences. It has been designed for tensile, compressive
and flexural tests. The machine is a floor model where the
3. CONCLUSION
load frame basically consists of a base with lead screw drive,
The complete apparatus for testing miniature specimen is
guide columns, ball lead screws, and a height adjustable and
described in this paper. The apparatus includes the description
movable crosshead. The base consists of a base plate with lead
of designed miniature specimen, specimen holder, and pins.
screw bearings and column clamps, the lead screw drive and
The results revealed the potential of simple tension test on
shock absorbing elements. The base plate and each crosshead
designed test apparatus used successfully to simulate the
contain a central hole of 70 mm diameter as well as 8
strength of miniature test technology in the laboratory and
coaxially arranged M16 threaded holes of radius 110 mm and
hence to assess the mechanical properties of metals.
8 coaxially arranged M8 threaded holes of radius 57.5 mm.
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VOLUME-2, ISSUE-5, MAY-2015
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