An impact test performed on a specimen of a metallic material to evaluate resistance to failure at a discontinuity and to evaluate the resistance of a comparatively brittle material during extension of a crack.
In an Izod test, a small bar of round or square cross section is held as a cantilevered beam in the gripping anvil of a pendulum machine. The specimen is broken by a single overload of the swinging pendulum, and the energy absorbed in breaking the specimen is recorded by a stop pointer moved by the pendulum. The Izod specimen can be tested as an unnotched bar, or it can be prepared with a 45” V-notch in the face struck by the pendulum. The energy absorbed in breaking Izod specimens is reported in joules (1 joule = .0737 ft/lb). Standard methods for impact testing can be found in ASTM E23, Notched Bar Impact Testing of Metallic Materials.
The Izod test of the notched specimen is particularly useful for detecting the presence of embrittling constituents, which might be caused by nitrides that take form during aging or in slow cooling after annealing, and for locating the brittle zone. This test does not reflect the tensile properties of the weld or the parent metal. See CHARPY TEST. See Figure C-4.