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A prototype alternating-current potential drop (ACPD) measurement technique has been developed for quasistatic and dynamic J-R curve testing. This well-known technique has classically been used in fatigue crack growth testing, but may find its niche in dynamic testing of conducting materials when more classical compliance and direct current potential drop methods are unsuitable. The system was first optimized and a calibration curve was generated to relate a/W and ACPD output using fatigue crack growth testing for 0.47 < a/W 0.85. Calibration using quasistatic, unloading compliance, elastic-plastic crack resistance (J-R) testing where the higher stress level matches the proposed usage was also conducted for J-R > 0.6. These various calibrations relationships were applied to ACPD output in quasistatic and dynamic J-R curve tests. Preliminary results indicate that calibration relationships must be based on the higher stress, J-R testing to accurately predict the final crack extension in these tests. The quasistatic J-R curves developed from the ACPD technique generally agree well with unloading compliance results. Dynamic J-R curves calculated directly from ACPD also concur with keycurve results although further system development is necessary for system optimization at these high testing rates.
potential drop, ACPD, toughness testing, dynamic fracture testing, J-R curve, HY-130 steel
Mechanical engineer, Naval Surface Warfare Center, Annapolis, MD