THE EFFECT OF CATHODIC POLARIZATION ON FATIGUE BEHAVIOR

摘要

The corrosion-fatigue behavior of cathodically protected ASTM A 710, Grade A, Class 3 steel in seawater was studied. The experimental work consisted of fatigue testing of base- metal specimens and weld joints in seawater and the development of a fatigue model. Corrosion-fatigue testing was performed in synthetic seawater at room temperature using sinusoidal loading at a stress ratio of 0.1 and a frequency of 1Hz. Cathodic polarization levels of -0.09 and -1.13V vs. Ag/AgCl were employed. Base-metal specimens had stress- concentration factors of 1.0, 2.0, 3.5, and 5.0 and were subjected to cyclic axial loads. Weld- joint specimens were full-thickness (19-mm) plate that was either butt-welded or fillet-welded; they were subjected to cyclic three-point bending loads. Fatigue crack growth data were developed for the base metal using compact-tension specimens. Both fatigue crack initiation and growth data were developed for the welded joints. Fatigue strength reduction factors were developed to account for the effects of notch severity and weld-joint configuration. A model that uses a fatigue curve to predict crack-initiation life and crack growth rate data to predict crack-propagation life was developed. This model can be employed in structural design.