The convenient and cheap instrumented Charpy impact test used for the evaluation of dynamic fracture toughness suffers many disadvantages and limitations. As an effort to enhance the reliability and accuracy of the instrumented impact testing, a new pendulum type of test apparatus has been designed and constructed at the Technical Research Centre of Finland (VTT).
The new tester contains several novel features which help to avoid the drawbacks of the normal designs and which make the impact testing more reliable and appropriate from the fracture mechanics point of view. For that purpose the tester is equipped with a fully computerized data acquisition system and an optical COD measuring device. The latter has been developed and constructed through the co-operation between Materialprüfungsanstalt (MPA) and VTT. In the new testing facility the determination of fracture toughness is based on the application of the optical COD measuring device. In this paper testing equipment and procedures are described and discussed.