strength of material lab ,about the impact test.

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Impact test
Student Name: Rawa Abdullah Taha
Class: two – Group A
Course Title: Strength of Material Lab
Department: Mechanic and Mechatronics
College of Engineering
Salahaddin University - Erbil
Academic Year 2019 – 2020

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ABSTRACT
impact test is one of the tests we have in the strength of material lab we
have tested on it before but now we are reporting on it, which we are
testing to see how much the resistance of the material can be to the
material we are using. Many companies in the country are testing the
strengths and weaknesses of the material using the impact test to see what
material should be used for their work, which is very important for
factories. In that report, I will give a general overview of the impact test
and how to use it, and highlight the places that need this device and the
importance of the subject, along with a set of images of the device to get
more familiar with the subject If we do not use the device, we may cause
serious damage to our equipment.for that reason we must be use it to
work in our factory better .

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TABLE OF CONTENTS
Abstract 2
Table of Contents 3
Introduction 4
Introduction 5
Methods 6
Conclusion 7
References 8

4. 4
INTRODUCTION
impact test of metals affords information on failure style under high
velocity loading conditions leading sudden fracture where a sharp stress
raiser is present. The energy riveted at fracture is generally related to the
area under the stress- strain curve which is called as toughness in some
references. Brittle materials have a small area under the stress-strain
curve (due to its limited toughness) and as a result, little energy is
enthralled during impact failure. As plastic deformation capability of the
materials ductility increases, the area under the curve also increases and
absorbed energy and separately toughness increase. Similar
characteristics can be seen on the fracture surfaces of broken specimens.
The fracture surfaces for low energy impact failures, representative brittle
behavior,are relatively smooth and have crystalline appearance in the
metals. On the conflicting, those for high energy fractures have regions of
shear where the fracture surface is inclined about 45° to the tensile stress,
and have rougher and more highly deformed appearance, called fibrous
fracture. Though two standardized tests, the Charpy and Izod, were
designed and used extensively to measure the impact energy, Charpy v-
notched impact tests are more common in practice. The apparatus for
performing impact tests is illustrated schematically.The load is applied
an impact blow from a weighted pendulum hammer that is released from
a position at a fixed height h. The specimen is positioned at the base and
with the release of pendulum, which has a
knife edge, strikes and fractures the
specimen at the notch. The pendulum
continues its swing, rising a maximum
height h ' which should be lower than h
naturally. The energy absorbed at fracture
E can be obtained by simply calculating
the difference in potential energy of the
pendulum before and after the test such as
: E = m.g.(h-h ').,
Figure(1)

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A metal may be very hard (and therefore very strıng and yet be unsuitable
for applications in which it is subjected to sudden loads in examination.
Materials behave fairly differently when they are loaded suddenly than
when they are loaded more slowly as in tensile testing. Because of this
fact, impact test is measured to be one of the basic mechanical tests
(especially for ferrous metals). The term brittle fracture is used to
describe rapid propagation of cracks without any excessive plastic
deformation at a stress level below the yield stress of the material. Metals
that show ductile behavior usually can, under certain circumstances,
behave in a brittle fashion. The stress needed to cause yield rises as the
temperature falls. At very low temperatures, fracture occurs before
yielding. Impact tests are used not also to quantity the energy absorbing
capacity of the material subjected to sudden loading; but also to
determine the transition temperature from ductile to brittle behavior.
Figure(2): Charpy Figure(3): Izod

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METHODS
Pendulum Impact Test: In this test the specimen is located across the
lowest point in the path of a striker straddling at the end of a pendulum as
shown in Figure 4. The striker, having been
initially lifted to a specific height h1, and then
released, swings against the specimen and
breaks it. The striker continues its swing to the
other side of the specimen to a height h2.
Clearly the difference between the two heights
multiplied by the weight of the striker
corresponds to the amount of energy that is
absorbed in fracture.
Figure(4)
Izod Impact Test: In the Izod impact test, the test piece is a cantilever,
fixed upright in an anvil, with a V notch at the level of the top of the
clamp. The test piece is success by a striker carried on a pendulum which
is allowed to fall freely from a fixed height, to give a blow of 120 ft lb
energy. After fracturing the test piece, the height to which the pendulum
rises is verified by a slave friction pointer mounted on the dial, from
which the absorbed energy amount is read.
Charpy Impact Test: The belief of the test differs from that of the Izod
test in that the test piece is tested as a beam supported at each end a notch
is cut across the middle of one face, and the striker hits the opposite face
directly behind the notch. When the results of a number of tests
performed in different temperatures are plotted, ductile-to-brittle
transition curves, may be obtained. As the temperature is reduced through
the transition range, the fracture surface changes from one having a
'fibrous' or 'silky' appearance with much distortion at the sides, to one of
completely crystalline appearance with negligible distortion. There is a
strong association between the energy absorbed and the proportion of the
cross-section which suffers deformation in fracture, and the fracture
surface is frequently described in terms of the percentage of its area
which is crystalline in appearance.

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CONCLUSION
My report, called the impact test, first gave me a brief description and
then I went into detail and described all my methods in general. Of course
the impact test is very important things in factories such as that factories
that needed the steel or iron or at pipe fitting field ,in many places we
need it at my report I talked about it and I explained every things about it
which divide to two (2) Parts which Izod and Charpy I discussed it with
his image's to better understand ,we get this fact that without this test,
maybe we get the serious event in our fields, when we used it we be sure
that our works be success .and for that the factories must be using this
tests because of it's important necessary for many factories that using
metals.

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REFERENCES
[1]. I.A. Collins, Failure of Materials in Mechanical Design
[2]. ASM Metals Handbook, Vol. 10, 8th Edp. 102
[3] . G.E. Dieter, Mechanical Metallurgy (Chap. 12)