| At WMT&R
Izod and Charpy testing are performed at temperatures ranging from
-320°F to over 2000°F. Charpy test are performed on instrumented
machines capable of measuring less than 1ft.lb. to 300ft. lbs. 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 1/4 size. IZOD testing can be done up to
240ft.lbs. on standard single notch and type-X3 specimens.
The Izod impact test was invented in the
early 1900's by a metallurgist named Izod. The Izod 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 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 test. The Izod test differs also in that the notch is positioned
facing the striker.
The Specimen size and shape vary with
the Izod 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 test, like the Charpy 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.