High-resolution thickness maps of corrosion using SH1 guided wave tomography

Quantifying corrosion damage is vital for the petrochemical industry, and guided wave tomography can provide thickness maps of such regions by transmitting guided waves through these areas and capturing the scattering information using arrays. The dispersive nature of the guided waves enables a reconstruction of wave velocity to be converted into thickness. However, existing approaches have been shown to be limited in in-plane resolution, significantly short of that required to accurately image a defect target of three times the wall thickness (i.e. 3T) in each in-plane direction. This is largely due to the long wavelengths of the fundamental modes commonly used, being around 4T for both A0 and S0 at the typical operation points. In this work, the suitability of the first-order shear-horizontal guided wave mode, SH1, has been investigated to improve the resolution limit. The wavelength at the desired operating point is significantly shorter, enabling an improvement in resolution of around 2.4 times. This is first verified by realistic finite-element simulations and then validated by experimental results, confirming the improved resolution limit can now allow defects of maximum extent 3T-by-3T to be reliably detected and sized, i.e.a long-pursued goal of guided wave tomography has been achieved.

Automated summary

This study investigates the use of the first-order shear-horizontal guided wave mode, SH1, to improve resolution limits in guided wave tomography. The results show a significant improvement in resolution, enabling reliable detection and sizing of defects up to 3T-by-3T, a long-pursued goal in guided wave tomography.