Most Charpy impact testing machines are graduated to directly indicate the energies involved. As such, equations are generally not needed. However, the formula used to determine the impact energy – if you need it someday – is as follows:
KV = mgH1 – mgH2 – Ef
Where:
- KV– Impact energy
- m – Pendulum mass
- g– Gravitational constant
- H1– Initial height of the pendulum
- H2 – Final height of the pendulum
- Ef– Energy loss due to friction
Charpy impact test results are measured in joules, the SI unit for energy. This is simply the amount of work performed by a 1-newton force pushing a sample by 1 m in the direction of the force. This value can be used to calculate the impact energy in J/m2 by dividing the joule value by the sample’s cross-sectional area at the sample notch.
