The standard test for measuring impact energy is the Charpy test. This gives an indication of the characteristics of the material during fracture.
An arm is swung down in a pendulum motion to impact with the test material. The energy required to fracture the sample is recorded.
The Charpy impact specimens are produced as a bar containing a notch. The swinging arm of the impact tester provides the impact. The sample will fracture along the plane indicated by the red line below. The arm continues through after impacting and the height it swings to is a direct indication of the amount of energy absorbed during fracture.
The impact energy can give an indication of the toughness of a material. The test material impedes the motion of the pendulum arm by absorbing the energy of the impact. A higher toughness material will absorb more energy upon impact and will therefore result in a low height to which the pendulum arm will swing to following impact.
Fracture surface of two Charpy specimens after testing, a) ductile material, b) brittle material.