ランダム荷重下での疲労亀裂伝播(第1報) : 単一および多重の過大荷重による疲労亀裂伝播の遅延現象

概要

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The importance of fatigue analysis under service loading conditions has recently been recognized in design of ship structure, offshore structure, pressure vessel and so on. But fatigue crack growth retardation following overloads is now an obstacle to the accurate pre-diction of fatigue life of structural components. In the present study, an experimental analysis was conducted on fatigue crack growth following single, multiple and intermittent overloads, as the first stage of fatigue analysis under random loading. Experimental results showed two eminent features :(1) the greater the overload is, the larger the crack growth retardation becomes (2) likewise, the larger the number of overload cycles is, the larger the crack growth retardation becomes. But in the case of intermittent overloads, the crack growth acceleration was observed when the interval between overloads was less than about 50 cycles. The abrupt falling of the crack growth rate and its recovery was commonly observed in the retardation process. The model to predict the behaviour of crack growth following overloads was proposed assuming a bilinear relation between the effective stress intensity range and the amount of crack growth. The model agrees well with experiments for the prediction of the number of cycles spent in retardation process.
社団法人日本船舶海洋工学会の論文