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ELECTRICAL POTENTIAL MONITORING OF CRACK FORMATION AND SUBCRITICAL GROWTH FROM SMALL DEFECTS
Author(s) -
GANGLOFF R. P.
Publication year - 1981
Publication title -
fatigue and fracture of engineering materials and structures
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.887
H-Index - 84
eISSN - 1460-2695
pISSN - 8756-758X
DOI - 10.1111/j.1460-2695.1981.tb01372.x
Subject(s) - superalloy , materials science , cracking , calibration , paris' law , fracture mechanics , fatigue testing , composite material , structural engineering , metallurgy , crack closure , microstructure , engineering , mathematics , statistics
—An experimental method was developed to quantify the formation and subcritical propagation of small cracks emanating from artificial surface defects. Continuous crack depth information was obtained from dc electrical potential measurements employing an analytical model. Fatigue experiments were conducted to evaluate the crack monitoring procedures for conditions relevant to the elevated temperature defect tolerance of superalloys. Cracking progressed uniformly and predictably from small surface defects (0.1 mm deep and 1.4 mm long) in A286, 304 and 10Ni steels and in René 95 and MP–159 superalloys. Crack depths, computed based on analytical calibration of measured electrical potentials, agreed to within ±18% of corresponding values measured optically. Similar results were obtained for a penny‐shaped defect, 75 μm deep. Applications of the technique were investigated, including characterizations of fatigue crack formation and growth in René 95.