Charpy impact testing involves striking a standard notched specimen with a
controlled weight pendulum swung from a set height. The standard Charpy-V notch specimen is 55mm long, 10mm square and has a 2mm deep notch with a tip radius of 0.25mm machined on one face. In some circumstances, sub-size Charpy specimens can be tested with thickness less than 10mm. The specimen is supported at its two ends on an anvil and struck on the opposite face to the notch by the pendulum. The amount of energy absorbed in fracturing the test-piece is measured and this gives an indication of the notch toughness of the test material. The pendulum swings through during the test, the height of the swing being a measure of the amount of energy absorbed in fracturing the specimen. Conventionally, three specimens are tested at any one temperature and the results averaged. Alternatively, tests are carried out at a range of temperatures in order to generate a ductile to brittle transition curve.