FEASIBILITY OF LOW‐FREQUENCY STRAIGHT‐RAY GUIDED WAVE TOMOGRAPHY

Many aging pipelines and aircraft are suffering from corrosion and the corrosion patches are often inaccessible. There is therefore a need for a rapid, accurate, long range inspection technique to measure the remaining thickness in corrosion patches. Low‐frequency guided wave tomography is a potentially attractive technique to rapidly evaluate the thickness of large sections of partially accessible structures. This paper demonstrates that in the low‐frequency regime the ray theory may not be valid which compromises the use of any straight‐ray tomography algorithm. This paper also shows, in simulations and experimentally, that the same frequency regime can be used to successfully reconstruct thickness reduction in plates with diffraction tomography.