Charpy Impact Tester

The Charpy impact tester measures a material's toughness, its ability to absorb energy before fracturing, by swinging a heavy pendulum from a fixed height to strike and break a notched bar specimen and recording how much of the pendulum's energy the fracture absorbed from how high it swings afterward. The French engineer Georges Charpy standardized the test in 1901, refining an existing pendulum impact method into the specific notched-bar configuration and calculation that carries his name, developed to give industry a quick way to detect steels that were strong under slow loading but dangerously brittle under sudden impact. The Charpy test's finding that many steels fail suddenly below a specific transition temperature became central to understanding brittle fractures, including the wartime failures of welded Liberty ship hulls, and the test remains a standard specification requirement for structural and pressure-vessel steel.