Cost-Effective Precracking of Charpy V-Notch Specimens for Fracture-Toughness Testing Using a Piezo-electric Actuator

The evolution in the ASTM standards towards more stringent precracking requirements and the large amount of fracture toughness tests annually performed at SCK•CEN, were the motivations to search for novel techniques to gain more control over the precracking process and to reduce the precracking cost. A piezo-electric actuator was identified as an excellent candidate for this purpose. A dedicated precracking device for Charpy V-notch specimens based on a piezo-electric actuator was developed. The high degree of automation allows full control over the precracking process in agreement with current or future standards. The low power consumption, high precracking frequency, low maintenance and minimum operator intervention significantly reduce the precracking cost. A second piezo-precracking device was installed in a hot cell. An extensive validation demonstrated that the SCK•CEN Piezomatic is capable of producing a fatigue crack in Charpy V-notch specimens (standard, reconstituted, miniaturized, irradiated) in a fast, controllable and accurate way. Both machines have been providing a reliable service for several years.