An impact test determines a material's behavior under shock loading by using a pendulum or dropped weight to break a test specimen. It measures the material's toughness and ability to absorb energy without fracturing. Common impact tests include the Izod and Charpy tests which use a swinging pendulum, and drop weight tests. Factors like temperature, composition, and microstructure affect impact properties. Instrumented impact testing provides more detailed data on load over time during fracture compared to basic pass/fail tests. Impact testing is important for evaluating materials used in applications like transportation and power generation where impact resistance affects safety.

1. Materials Characterizations
Centre for Materials Engineering
Materials Engineering (MSc Program )
Impact Test
Prepared by Kidist W.
Submitted to Prof. Gyeong Man Kim
Jan.
16,2019

2. Impact Test
 An impact test is a technique used to determining
the behavior of material subjected to shock loading
in bending, tension or torsion
 The impact test is a method for evaluating the
toughness, impact strength and notch sensitivity of
engineering materials.
 It is a destructive test which requires a specially
prepared specimen.
 This test is designed to determine whether the
material is tough or brittle.

3. Contd’
 Impact resistance is one of the most important
properties for component designers to consider,
as well as the most difficult to quantify.
 Impact resistance is a critical measure of service
life and more importantly, in many applications, it
affects product safety and liability.

4. Application Areas
 Impact testing is required by many industries
in manufacturing products, including steel hull
plate for ships, nuclear plant pressure vessels
and forgings for electric power plant generator
rotors.
 Manufacturing industries that use the impact test
include oil and gas, Aerospace, Power
generation, Automotive, Nuclear)
 It is mostly used to test the toughness of metals,
but similar tests are used for polymers, ceramics
and composites.

5. Factors Affecting Impact Test
 Impact properties can also change when
additives, such as coloring agents, are added to
plastics.
 If the dimensions of specimens are maintained as
indicated in standards, notched-bar impact test
results are affected by;
 the lattice type of materials, (Polymer
orientation)
 testing temperature,
 thermo-mechanical history,
 chemical composition of materials, etc

6. Types of Impact Testing
 Impact Testing of materials is performed to
determine the impact resistance or toughness of
materials by calculating the amount of energy
absorbed during fracture.
 There are basically two types of impact tests:
pendulum and drop weight.
 Izod, Charpy, and tensile impact are the most
common of the pendulum type tests.

7. Pendulum Testing
 This is done by means of a swing pendulum.
A pendulum of a known weight is hoisted to a
known height on the opposite side of a pivot
point.
 By calculating the acceleration due to gravity
the weight falling from a set height will contain
a certain amount of impact energy at the
bottom of the swing.
 By clamping or supporting a specimen on the
bottom, the sample can be released to strike
and break the specimen.

8. sample specimen

9. Contd’
 The pendulum will continue to swing up after the
break event to a height somewhat lower than that
of a free swing. The engineer can use this lower
final height point to calculate the energy that was
lost in breaking the specimen.
E = m.g.(h-h ')
 Many pendulum machines will incorporate a
pointer and energy reading device so that
calculation is unnecessary.
 Izod, Charpy, and tensile impact are the most
common of the pendulum type tests.

10. Charpy Test
 The method determines the toughness or impact
strength of the material in the presence of a flaw
or notch and fast loading conditions.
 The test material is secured horizontally in a
place at both ends and striker hits the center of
the material.
 The amount of energy absorbed by the material
during fracture is measured. Charpy V notch or U
notch test specimens are used.

11. Izode Test
 For this test the specimen is fastened at a vertical
position at the bottom with the notch facing the
striker.

12. Drop/Falling Weight Impact
Test
 A second method is to drop a weight in a
vertical direction, with a tube or rails to guide it
during the "free fall."
 The height and weight are known, therefore
impact energy can be calculated.
 Since the falling weight either stopped dead
on the test specimen, or destroyed it
completely in passing through, the only results
that could be obtained were of a pass/fail
nature.

13. Contd’
 Falling weight impact has several key
advantages over other methods:
 It is applicable for molded samples,
molded parts…
 It is unidirectional with no preferential
direction of failure. Failures originate at the
weakest point in the sample and
propagate from there.
 Samples don't have to shatter to be
considered failures. Failure can be defined
by deformation, crack initiation, or
complete fracture, depending on the

15. Instrumented Impact Testing
 Simple impact tests tests are useful but lack
important information about what was happening
to the test specimen during the impact event and
can be misleading.
 An instrumented impact test is an impact test
where the load on the specimen is continuously
recorded as a function of time and/or specimen
deflection prior to fracture.
 This gives a much more complete representation
of an impact than a single calculated value.
 All of the above impact tests can designed with
electronic sensing instrumentation.

16. Contd’
 The best systems record load vs. time or
deformation for the entire period of the impact
event.
 Another area of improvement with
instrumentation is time. Test times can be
reduced and automation can even be
incorporated into the testing.
 Instrumented drop weight and pendulum testing
is considered to be the best general impact
testing method presently available. By multiple
testing at various rates, a very complete impact
profile can be developed for a polymer.
 This approach can be useful in simulating

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