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BACKGROUND
The impact is defined as the impedance of material to rapidly applied loads.1 An Impact test is a dynamic test in which a selected specimen which is usually notched in struck and broken by a single bow in a specially designed machine. The foremost purpose of this test is to measure the ability to resist high-rate loading on an object.
Izod and Charpy Impact tests are comparable in many respects. However, both use different sample specimen, such as in Izod testing size of the part is 10 × 10 × 75 mm, whereas in Charpy test, the specimen size is 10 × 10 × 60 mm.2 Impact energy is the amount of work done to fracture a test specimen. The material is tested to determine its impact strength until it yields. In general, notch-type samples are used for impact testing. The presence of notch on the surface of the test area of a specimen creates a concentration of stress or localization of strain during tests.3 Keyhole notch and the V notch are generally used in Izod and Charpy Impact tests.
Izod Impact Test
The Izod Impact test is named after its inventor Edwin Gilbert Izod (1876-1946). A vice type hammer is connected to the impact testing machine instead of an anvil type hammer, which is used for Charpy impact testing. Up to 0-164 Joules or N-m, Izod testing can be achieved. Izod test specimens deviate depending on what material is being tested. Metallic samples tend to be square in cross-section, while polymeric test specimens are often rectangular, being struck parallel to the long axis for the rectangle.
Charpy Impact Test
The Charpy Impact test was developed in 190 by French Scientist Georges Charpy (1865-1945). This test measures the energy absorbed by a standard notch specimen while breaking under an impact load. The Charpy Test continues to be used as an economical quality control method to determine the notch sensitivity and impact toughness of engineering materials. This test is commonly applied to materials, but it is also applicable to composites, ceramics, and polymers.
The prime objective of this experiment is to determine the impact strength of materials by Izod and Charpy testing methods.
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REQUIREMENTS
Materials: Impact testing machine
A steel specimen for 10 × 10 × 75 mm (for Izod test)
10 × 10 × 60 mm (for Charpy test)
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PROCEDURE
Izod Impact Test
First of all, hold the steel specimen in impact testing machine’s vice in such a way that the notch faces the vice type hammer and it is placed half inside and half upside above the vice’s surface. Be sure that the striking hammer is set in safe test position before putting the specimen. Bring the striking hammer to the uppermost position and lock it at that position. After bringing the indicator to zero, release the hammer. Due to the effect of gravity, the hammer will fall breaking the specimen through its momentum. At the leading position of the indicator when it stops moving.2 Note down the reading and bring back the hammer to its idle position.
Charpy Impact Test
First of all, hold the steel specimen in impact testing machine’s vice in such a way that the notch faces the anvil type hammer and it is placed half inside and half upside above the vice’s surface. Be sure that the striking hammer is set in safe test position before putting the specimen. Then the indicator of the machine is set to zero, similar to as in Izod impact test. At the uppermost position of the indicator note down the reading. Then place the specimen on support or anvil, so that blow of hammer remains opposite to the notch.2
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CONCLUSION
The process of finding impact strength of a material through Izod and Charpy testing methods has been discussed successfully. The material is placed in a vertical position in Izod test while it is placed in horizontal position in Charpy test to perform the experiment.
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REFERENCES
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P. V. Brown, “Impact testing machine”. US Patent US2755658A, 24 07 1956.
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N. Singh, “Experimental study and parametric design of impact testing methodology,” Thapar University, Patiala, 2009.
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J. M. W.J. Cantwell, “The impact resistance of composite materials — a review,” Journal of Applied Polymer Science banner, vol. 22, no. 5, pp. 347-362, 2003.
