| At WMT&R Izod and Charpy impact testing are performed on
instrumented machines capable of measuring less than 1ft.lb. to 300ft. lbs.
at temperatures ranging from -320°F to over 2000°F. 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 Charpy Impact Test was invented by
Georges Augustin Albert Charpy (1865-1945). The Charpy test measures the energy
absorbed by a standard notched specimen while breaking under an impact load.
The Charpy impact test continues to be used as an economical quality control
method to determine the notch sensitivity and impact toughness of
engineering materials.
The Charpy Test is commonly used on
metals, but is also applied to composites, ceramics and polymers.
With the Charpy test one most commonly evaluates the relative toughness of a
material, as such, it is used as a quick and economical quality control
device.
The standard Charpy Test specimen consist of a bar of metal, or other material, 55x10x10mm having a notch
machined across one of the larger dimensions.
V-notch: 2mm deep, with 45° angle and 0.25mm radius along
the base.
U-notch and keyhole notch: 5mm deep notch with 1mm
radius at base of notch.
 The Charpy Test consist of striking a suitable specimen with a hammer on
a pendulum arm while the specimen is held securely at each end. The hammer
strikes opposite the notch. The energy absorbed by the specimen is
determined by precisely measuring the decrease in motion of the
pendulum arm.
Important factors that involve
the toughness of a material include: low temperatures, high strain rates (by
impact or pressurization), and stress concentrators such as notches cracks
and voids.
By applying the Charpy Test to
identical specimens at different temperatures, and then plotting the
impact energy as a function of temperature, the ductile-brittle transition
becomes apparent. This is essential information to obtain when determining
the minimum service temperature for a material. |
