Fatigue life prediction based on crack growth analysis using an equivalent initial flaw size model: Application to a notched geometry

Several methods for fatigue life prediction of structural components have been proposed in literature. The fatigue life prediction based on crack growth analysis has been proposed to assess the residual fatigue life of components, which requires the definition of an initial flaw. Alternatively, Fracture Mechanics crack growth-based fatigue predictions may be used to simulate the whole fatigue life of structural components assuming that there are always initial defects on materials, acting as equivalent initial cracks [1,2]. This latter approach is applied to a notched plate made of P355NL1 steel [3]. Fatigue crack growth data of the material is evaluated using CT specimens, covering several stress R-ratios. Also, S-N fatigue data is available for the double notched plate, for a stress R-ratio equal to 0 [3]. An estimate of the equivalent initial flaw size is proposed, using a back-extrapolation calculation [1,2]. The crack propagation model takes into account the elastic-plastic deformations in the crack-tip area within the calculation, based on the cyclic J-integral method. The performances of predictions are analyzed and deviations discussed. (C) 2015 The Authors. Published by Elsevier Ltd.