The development of a computer-controlled single-specimen J-test procedure is described. The results of a sensitivity study to determine the effect of analog-to-digital converter resolution and transducer signal noise on elastic unloading compliance crack length measurements are presented. The results are used to estimate the minimum equipment performance specifications needed for successful J-test automation. The actual test system is described along with the details of the automated procedure.

A comparison is made between results obtained using the automated procedure and the more conventional heat-tinting technique for HY-130 at room temperature (tested as part of the American Society for Testing and Materials J-Integral R-Curve Round Robin Program) and nuclear pressure vessel grade steels at 200 to 290°C. Good agreement in the generation of J-Δa data was found in all cases. However, some difficulty was encountered in predicting absolute crack lengths by compliance in the round-robin tests, apparently due to specimen design.