An automated system for fatigue crack growth and fracture toughness measurements has been developed for irradiated stainless steels tested at temperatures up to 925 K. The system, including a microcomputer, is based on the d-c potential-drop technique for crack extension measurements. Specimens of the compact-tension type are used for the experiments. A description is given of the potential-drop method and the automated data acquisition system. The method of collecting N-a data pairs is given as well as the calculation and analysis of the fatigue crack growth rate (da/dN) and stress-intensity factor (ΔK). The measurement of load, deflection, and crack extension data to determine the J-versus-Δa curves is also discussed.
Calculations and interpretations of the results are in good agreement with the ASTM standards.
The system for crack growth experiments has proven to be very reliable, with a high resolution and accuracy.
In practice, good experience has been gained using the system for testing irradiated specimens under remote handling conditions.