Kerbschlagtests

Kerbschlagtests are a family of notched impact tests used to assess the notch toughness and impact resistance of materials, particularly metals. In the test, a small, notched specimen is clamped in a support and struck on a prepared edge by a swinging pendulum. The energy absorbed by the specimen until fracture is derived from the loss of the pendulum’s kinetic energy and is reported as impact energy, typically in joules. A higher value indicates greater toughness at the test temperature.

The term Kerbschlag translates from German as “notch impact.” The tests are the German counterpart to the Charpy impact test and share the same basic principle, though they may refer to similar specimen geometries and notch types with regional naming differences.

Specimens are notched bars, usually of a standardized cross-section, with a V-shaped or occasionally U-shaped notch, and are tested in a transverse orientation relative to the notch. The exact specimen size, notch geometry, and testing temperature are defined by national or international standards.

Procedure: The pendulum is released from a fixed height to strike the specimen; the machine measures the energy lost by the pendulum to fracture the specimen. Tests are often conducted at room temperature but temperature-controlled variants determine the ductile-to-brittle transition.

Use and interpretation: Kerbschlag tests provide a measure of material toughness and notch sensitivity, informing material selection and quality control, especially for structural steels and cast alloys. They are not direct measures of fracture toughness (K_IC) but correlate with it under certain conditions. Limitations include sensitivity to notch quality, specimen preparation, and strain rate effects.

Standards: The method is standardized by various bodies (for example ISO, EN, and ASTM), with regional variants such as Charpy and Izod tests describing related approaches.