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This International Standard specifies methods for the verification of pendulum impact-testing machines used for the Charpy impact test, Izod impact test and tensile impact test described in ISO 179-1, ISO 180 and ISO 8256, respectively.

The test machines covered by this International Standard are of the pendulum type. The impact energy W (see 3.12) absorbed in impacting a test specimen is taken as being equal to the difference between the potential energy E (see 3.11) of the pendulum and the energy remaining in the pendulum after impacting the specimen. The impact energy is corrected for friction and air-resistance losses (see Table 2 and 5.6).

Methods are described for verification of the geometrical and physical properties of the different parts of the test machine. The verification of some geometrical properties is difficult to perform on the assembled instrument. It is therefore assumed that the manufacturer is responsible for the verification of such properties and for providing reference planes on the instrument that enable proper verification in accordance with this International Standard.

These methods are for use when the machine is being installed, is being repaired, has been moved or is undergoing periodic checking.

This International Standard is applicable to pendulum-type impact-testing machines, of different capacities and/or designs, with the geometrical and physical properties defined in clause 5.

A pendulum impact-testing machine verified in accordance with this International Standard, and assessed as satisfactory, is considered suitable for impact testing with unnotched and notched test specimens of different types.

Annex A describes the relationships between the various characteristic pendulum lengths, the potential energy and the moment of inertia of the pendulum.

Annex B explains how to calculate the ratio of frame mass to pendulum mass required to avoid errors in the impact energy.

Annex C describes, for Charpy impact testing, the changes in pendulum velocity just after impact as a function of impact energy and gives the ranges of impact energies for the measurement of which pendulums of specified capacity have to be used.

Annex D discusses the stiffness of the base of the frame necessary to avoid resonant oscillations in the frame due to reaction forces caused by the moving pendulum.

Annex E gives the dimensions of a gauge plate suitable for the verification of Charpy impact-testing machines.