Charpy V-notch test

The Charpy V-notch test measures the energy absorbed when a notched, standard-size bar is broken by a single swing of a calibrated pendulum, giving a number in joules that ranks a steel’s notch toughness at a specified temperature. The method is standardized in ISO 148-1 and ASTM E23. Ship steel grades are defined partly by their required Charpy energy at a grade-specific test temperature, so the test is the gatekeeper that separates grades A, D, E, and F and confirms a plate will resist brittle fracture at its design service temperature.