Stress intensity factors from stress analysis of an equivalent hole

In this paper, on the basis of the stress analysis of an equivalent model, the stress intensity factors (SIF) of a crack have been evaluated. In the stress analysis, the crack is substituted by an equivalent hole equal in size to the length of the crack. The method is based on the evaluation of the hoop stress on the free border of the equivalent hole and the subsequent calculation of the J-integral (JVρ) as a parameter related to the SIF. Alternatively, if the hoop stress on the free border cannot be evaluated, the stress analysis can be performed on the surface in the neighbourhood of the hole. In order to validate the method, two experimental cases have been considered: a plate with two different bore diameters of 50% and 20% of the plate width, respectively. The stress analysis was performed by means of strain gauges attached to the free border. For the plate with the smaller bore, the strain gauges were also attached to the surface near the hole. In this way, the strain approach can be extended to thin plates or when it is not possible to attach the strain gauges to the free border of the hole.