For more than a century the Charpy test has been employed as an acceptance test characterizing the impact toughness of a material. The original parameter is the energy consumed during breaking a standard notched specimen with net cross-section of 80 mm 2 . If this energy is plotted versus temperature, many steels show small values at low temperatures which rise in a transition regime and enter a plateau at elevated temperatures (upper-shelf toughness).
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Safe operation of a structure or component is only possible if the operating temperature is well above the transition regime. The unexpected breaking-apart of liberty ships operating in cold polar seas during World War Two could later be explained by the fact that for the steel used to build the hull had a transition temperature higher than the water temperature. |
The development of finite element techniques and in particular damage mechanics concepts enabled researchers to extract much more information from instrumented Charpy tests: |
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