At Westmoreland Mechanical Testing & Research, Inc. Izod impact tests and Charpy impact tests are performed at temperatures ranging from -320°F to over 2000°F. Charpy impact test are performed on instrumented machines capable of measuring less than 1foot-pound. to 300 foot-pounds. Specimen types include notch configurations such as V-Notch, U-Notch, Key-Hole Notch, as well as Un-notched and ISO (DIN) V-Notch, with capabilities of testing subsize specimens down to ¼ size. Izod impact testing can be done up to 240foot-pounds. on standard single notch and type-X3 specimens. The Izod impact test was named for english engineer Edwin Gilbert Izod. The Izod impact test consists of a pendulum with a determined weight at the end of its arm swinging down and striking the specimen while it is held securely in a vertical position. The impact strength is determined by the loss of energy of the pendulum as determined by precisely measuring the loss of height in the pendulum's swing.
Some years later the Izod impact test this test was modified by Georges Charpy to hold the specimen in a horizontal rather than a vertical position. This is the primary difference between the Izod and the Charpy impact test. The Izod impact test differs also in that the notch is positioned facing the striker.
The specimen size and shape vary with the Izod impact test according to what materials are being tested. Specimens of metals are usually square, and polymers are usually rectangular being struck perpendicular to the long axis of the rectangle.
The Izod impact test, like the Charpy impact test, is also used to test materials at low temperature to try to simulate conditions that may occur in the actual use of the material.
The Ductile to Brittle Transition Temperature may be obtained by testing a number of identical specimens at different temperatures, and then plotting the impact energy as a function of temperature, the ductile-brittle transition becomes apparent as the resulting curve shows a rapid decline in impact strength as the temperature increases. This is essential information to obtain when determining the minimum service temperature for a material.