Abstract
The aim of this work is to evaluate the applicability of the Wheeler and Willenborg models to predicting fatigue crack growth retardation in a flash welded structural steel subjected to a single overload during constant amplitude (CA) fatigue crack propagation test. Compact tension specimens, in different microstructural conditions, were subjected to a single overload at a given crack length during CA fatigue loading and crack growth rate da/dN vs. the stress intensity factor range deltaK was monitored, evidencing the retardation in crack propagation over an interval of crack length. The size of the delay zone as well as the number of the delay cycles were predicted by both the Wheeler and Willenborg models and then compared with the experimental data. Finally, the results are presented and discussed focusing on the comparison between the predictions made by the two models in the light of the experimental data.
Highlights
The rate of fatigue crack propagation and the critical crack size are considered essential for structural integrity assessment based on damage-tolerance considerations
The purpose of the present work was to evaluate the applicability of the models proposed by Wheeler and Willenborg to predicting fatigue crack growth retardation in a structural steel largely adopted for fabricating offshore mooring chains
Under the same constant amplitude (CA) loading conditions, fatigue crack growth is invariably higher in the welded joints than in the base metal
Summary
The rate of fatigue crack propagation and the critical crack size are considered essential for structural integrity assessment based on damage-tolerance considerations. The fatigue crack starts to advance into the overload (OL) plastic zone and the residual compressive stresses in an element just behind the crack tip are relaxed. This contributes to the level of crack closure in the wake of the crack tip, retarding fatigue crack propagation. As the crack exits the OL plastic zone, the propagation rate is generally back again at the baseline level corresponding to the constant amplitude (CA) loading Other retardation mechanisms such as crack blunting and strain hardening of the material within the OL plastic zone can be activated following overloading and contribute to the extension of fatigue life
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