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.