Numerical investigation of the scattering of ultrasonic guided wave in hard-to-inspect regions

Fuel weep holes in aircraft wing risers are common fatigue critical locations for crack initiation. Whilst cracks that grow from the surface of the weep holes toward the wing skin can be easily inspected outside the aircraft by traditional ultrasonic and current state-of-the-art stress wave based SHM methodologies, cracks that grow away from the wing-skin on the blind side of the hole pose a much greater challenge. This paper shall present a set of computational investigation to emphasis the merit in the development of 3D finite element models for the analysis of complicated hard-to-inspect geometries in health monitoring applications. The development of reliable and effective health monitoring methodologies for hard-to-inspect structures is dependent on such knowledge of elastic wave scattering from defects. Future work will be focussed on identifying the contributions that individual wave modes make to the scattered wave field such that the physics can be fully exploited for hard-to-inspect sub-surface damage.