Numerical Simulation of Fatigue Crack Growth in Straight Lugs Equipped with Efficient Structural Health Monitoring

This paper addresses the influence of the efficient Structural Health Monitoring system (eSHM) on the fatigue life of straight lug components. The eSHM system is a mechanical fatigue crack detection system developed at the Vrije Universiteit Brussel (VUB). It consists in integrating pressurized capillaries into the to-be-monitored component, so that when a fatigue crack breaches the capillary network, a leak flow is created, and the pressure equilibration between the capillary and the open atmosphere is detected by a pressure sensor. The system is therefore aimed for additively manufactured structures. In this paper, one considered the example of straight lugs, quite common in aeronautical structures and well documented in the literature, to assess whether fitting the lug with the eSHM would significantly influence the fatigue crack growth behavior. Therefore, comparisons are made between lugs not equipped with the eSHM and lugs with integrated capillaries, both with identical initial defect. The aim is to determine whether the capillaries have a significant influence on the number of cycles to failure. The evaluation of this influence will be done by numerical computations using the eXtended Finite Elements Method (XFEM). In particular, the computations will be done on the Morfeo software developed by Cenaero. Conclusions from this research will serve as basis for sound implementation of the crack detection system on industrial components. Indeed, the system has to offer a quick detection of the propagating fatigue crack (by being placed as close as possible to the most probable initiation region) while not affecting the component's life (the capillary should not initiate a defect nor reduce the crack growth life of the lug).