Statistical evolution of small fatigue crack in 1Cr18Ni9Ti weld metal

Statistical evolution of small fatigue crack behavior is analyzed. Three co nsiderations an given, They consist of the total fit, the consistency of st atistical parameters with test data, and the practice of commonly used dist ributions, namely Weibull (two- and three-parameters), normal, lognormal, e xtreme minimum, extreme maximum, and exponential. The crack growth rate dat a of 1Cr18Ni9Ti stainless steel-weld metal reveal that fatigue damage is a gradual process involving an initial non-ordered (chaotic) or load history- independent random state to an ordered load history-dependent random state. The seven distributions are examined. Different from existent conclusion, appropriate assumed distribution for characterizing the evolution data is t he normal or extreme minimum value model rather than the Weibull two- or th ree-parameter. The other distributions do not fit the data as they violated two or all three of the mentioned considerations. (C) 1999 Published by El sevier Science Ltd. All rights reserved.