Results of a DVM round robin on instrumented Charpy testing

The DVM-group on "Instrumented Impact Testing" (DVM-Deutscher Verband für Material-forschung und-prüfung, i.e. German Society of Materials Research and Testing) was running a round robin exercise in 1992, in order to support the development of an international standard on instrumented Charpy testing. Seventeen international participants from research institutes and industry performed about 400 instrumented Charpy-tests using a German pressure vessel steel at four different temperatures. The specimens were prepared with standardized V-notches, spark-eroded crack-similar slits or fatigued cracks. The tests were based on existing standards and specifications and on a draft standard for instrumented Charpy-tests. Standardized material data like the Charpy-energy, lateral expansion, and percentage of shear fracture were measured. In addition, characteristic forces and partial energies were determined and fracture mechanical quantities were evaluated. One interesting observat ion was a "cleavage-gap", i.e. a region of crack extension, where transition to cleavage was not observed with pre-cracked specimens but with notched specimens. The results of the participants showed an excellent agreement and a very good accuracy of the force measurements was observed. Therefore, these results supported international activities to standardize the instrumented Charpy test as ISO 14 556 (2000).