Speaker
Mr
Johan Schuurmans
(SCK-CEN)
Description
Experience has shown that it is practically impossible to obtain a reproducible, sharp, narrow machined notch using conventional manufacturing techniques that will simulate a natural crack well enough to provide a satisfactory fracture toughness test result. Consequently, all specimens used for the determination of the fracture toughness of metallic materials must contain notches sharpened with fatigue cracks. The fatigue crack is produced by cyclic loading the notched specimen on a servo-hydraulic testbench or resonant fatigue testing equipment.
The evolution in the ASTM standard to more stringent precracking requirements and the large amount of fracture toughness tests annualy performed at SCK-CEN, was the motivation to search for novel techniques to gain more control over the precracking process and to reduce the precracking cost. A feasibility study identified the piezo-electric actuator as an excellent candidate for this purpose.
A dedicated precracking machine for PCCV 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 yield loss, low maintenance and minimum operator intervention significantly reduced the precracking cost.
A second piezo-precracking was installed in a hot-cells and is already providing a reliable service for several years.
Primary author
Mr
Johan Schuurmans
(SCK-CEN)
Co-author
Dr
Marc Scibetta
(SCK-CEN)
