IZOD IMPACT TEST

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Object:Determination of the energy absorbed and impact strength of given specimen using Izod impact testing machine.
Need and scope of the experiment:The necessity for impact tests has arisen due to the failure of materials used in high speed machinery under repeated forces of impulsive character, even when such material has shown satisfactory strength and deformation in a static tensile test. Various forms of impact test has been devised, of which Izod impact test is the only one to try to determine the imperfections in material likely to fracture by "shock". Although the Izod impact test has long been used as the standard form of test for checking the brittleness of metals, the need has arisen for test at elevated and subzero temperatures.
Apparatus:

• Impact testing machine
• Izod specimen of 1Omm x 1Omm. square cross section and 75mm length, with a V -notch 45° angle, 2mm deep and 0.25 mm root radius along the 28mm away from the c/s surface according to ASTM E23. The specimen is kept as a cantilever beam in vertical position. The angle of drop of pendulum is 90°(exact 85° 21') and the impact velocity is approximately 3.856m/sec. The . specimen bends and fractures at high strain rate".
  

Procedure:

1. Without the specimen in the machine, swing the pendulum to ensure free movement.
2. Lift die pendulum and lock it at 90°.
3. Place the Izod test specimen as shown in fig
4. Select the test and its parameter given in the digital indicator.
5. Remove the lock nut and engage the lever.
6. Pendulum will strike the specimen and result will display in digital indicator.

Observations:-
Izod value or Impact Strength
= ^{Energy absorbed N-m}⁄_{Cross section area at nortch $mm^2$} Result:-
Energy required to fracture the Specimen U = ____________ J
Charpy value = _________ $\frac{Nm}{mm^2}$
Main difference between Charpy and Izod tests are: