E. Tada et al., CRACK DETECTION BY HARMONICS ANALYSIS OF THE POLARIZATION CURRENT DURING CORROSION-FATIGUE OF IRON, Nippon Kinzoku Gakkaishi, 62(3), 1998, pp. 276-282
Corrosion fatigue tests of a commercial iron with a hole were carried
out in a berate buffer solution containing 5 mol/m(3) NaCl at a consta
nt passive potential. Polarization current behavior induced by strain
cycles has been investigated in order to detect crack initiation from
the hole and used for the estimation of corrosion fatigue damages. The
amplitude of the polarization current synchronized with the strain cy
cle and the phase shift between the polarization current and the strai
n were calculated from the polarization current behavior. The second h
armonics component of the polarization current was also calculated. In
the early stage of the corrosion fatigue test, the phase shift was al
most constant and the second harmonics component was not detected. How
ever, the phase shift decreased and the second harmonics component of
the polarization current increased with increasing fatigue cycle. It i
s considered that changes of the phase shift and the second harmonics
component of the polarization current result from crack initiation and
the early stage of crack propagation from the hole.