Contribution of the striker design on the measured energy of low-energy Charpy reference specimens

What is it about?

The correct operation of a pendulum impact tester is verified by testing reference specimens at different energy levels. This verification tends to fail at the low-energy level for instrumented strikers optimized for accurate force measurement. This was attributed to the elastic energy stored in the striker. A method to subtract the energy stored in the striker from the indicated energy is proposed.

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Why is it important?

A discrepancy in the obtained absorbed energy is noticed when different laboratories certify the same low-energy material. By subtracting the elastic energy stored in the striker from the obtained energy, the dependency of the obtained certified value, will be reduced. The requirements of ASTM E23 are in conflict with ASTM E2298. Optimizing the design of an instrumented striker for accurate force measurement, generally increases the striker compliance (especially for U-hammer machines), and hence elastic energy stored in the striker. The indicated absorbed energy, when using optimized instrumented strikers, is therefore higher and often outside the verification requirement of ASTM E23.