Theoretical Prediction of Ripple-Load Effect on Stress-Corrosion Cracking
NAVAL RESEARCH LAB WASHINGTON DC
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The ripple-load effect RLE is a perplexing phenomenon in which the threshold stress-intensity factor KIscc for stress-corrosion cracking SCC appears to be severely degraded -- at least in some cases, if the constant load condition characteristic of SCC is perturbed by superposition of a small-amplitude cyclic load. In this study, a theoretical framework has been developed to predict the conditions required for a material to exhibit a RLE in a marine environment -- and the extent of such degradation. Insofar as a framework for the RLE necessarily involves the interface between SCC and corrosion fatigue CF, the model presented herein derives from concepts and descriptors used in SCC and CF characterization. Thus, analysis begins with consideration of the relationship between the small amplitude stress-intensity range associated with ripple loading, delta K, the high stress-ratio conditions, R 0.90, the threshold for CF crack growth, delta Kth, the maximum stress-intensity factor in the loading cycle, Kmax, and KIscc. Keywords Stress-corrosion cracking, Corrosion fatigue, Ripple-load cracking, High stress ratio.
- Properties of Metals and Alloys