Feasibility Study of Alternating Current Potential Drop Techniques for Elastic-Plastic Fracture Toughness Testing

Abstract

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 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 key-curve results although further system development is necessary for system optimization at these high testing rates.