Journal Published Online: 01 May 1988
Volume 16, Issue 3

Crack Length Measurement During Rapid Crack Growth Using an Alternating-Current Potential Difference Method



The object of this project has been to investigate the applicability of an alternating-current potential difference method of crack length estimation to rapid loading fracture mechanics tests in ferromagnetic materials. The more commonly used direct-current method has been demonstrated to be very sensitive to induced magnetization under rapid loadings. The resulting direct-current output signal is complex and not repeatable, and the component related to crack extension cannot be separated from the total response. The tests reported here show calibrations of a 10 kHz alternating-current system on an A533B material and application of the calibration to a static unloading compliance test and to rapid servohydraulic tests. A d-c component dependent on stress-induced magnetization is still present but can now be separated from the high frequency component using Fourier series methods.

The major conclusion is that an alternating-current technique with a properly chosen excitation frequency can be used to detect crack growth in rapidly loaded specimens. Additional comments on developing an improved system are presented.

Author Information

Joyce, JA
U.S. Naval Academy, Annapolis, MD
Schneider, CS
U.S. Naval Academy, Annapolis, MD
Pages: 14
Price: $25.00
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Stock #: JTE10376J
ISSN: 0090-3973
DOI: 10.1520/JTE10376J