Two Methods for Determination of Fatigue Crack Propagation LimitCurves and their Applicability for High Strength Steels

摘要

There are different documents containing fatigue crack propagation limit or designrncurves and rules for the prediction of crack growth. The research work aimed to characterise thernfatigue crack propagation resistance of different steels using limit curves and determination of limitrncurves for different structural steels and high strength steels, and their welded joints, under differentrnloading conditions, based on statistical analysis of test results and the Paris-Erdogan law. With thernhelp of the characteristic values of threshold stress intensity factor range (△Kth), two constants ofrnParis-Erdogan law (C and n), and fatigue fracture toughness (△Kfc) two reliable methods – arnsimplified method and a two stages method – can be proposed. Our testing results were comparedrnwith the testing results can be found in the literature. The limit curves calculated by the new methodrnrepresent a compromise of rational risk (not the most disadvantageous case is considered) andrnstriving for safety (uncertainty is known).