A finite element simulation methodology of the fatigue behaviour of punched and drilled plate components

Abstract In order to analyse the fatigue behaviour of punched and drilled plates under tensile loading it is necessary to know the stress intensity factors (SIF) for the different crack fronts and crack sizes that are originated in this geometry throughout the number of cycles. The results available in the literature for the SIF for drilled plates are based on a quarter-elliptical crack front, and consider only either symmetrical cracks initiated simultaneously at both edges of the hole or a single crack initiated at one edge. The fractographic analysis of fatigue tests performed has shown that neither the quarter-elliptical crack front nor the symmetrical cracks are real for most of the tests. This can lead to erroneous results in the later studies of the fatigue life. This paper shows the finite elements methodology to define the SIF for a plate with a central hole considering any crack front and their numerical results. The methodology and the obtained results have been validated through the simulations of the SIF for elliptical cracks. Using the SIF for several points of the crack front and the Paris law of the material, the evolution of any crack front can be estimated after a set of fatigue cycles and, consequently, the fatigue life of the samples under study from a given initial crack can be predicted. Finally, fatigue life predictions have been compared with the real experimental results from the S – N curves of the samples, in order to define an equivalent initiation defect due to processing conditions, which can be used in the design or integrity assessment of any component.