Optimised Shear Horizontal Guided Wave Inspection Set-Up for Titanium Welds.

Abstract

The inspection of welds in thin titanium sheets is vital to ensure that all components meet their required criteria. Shear horizontal (SH) guided waves may offer particular benefits for defect detection, especially the fundamental mode (SH0), which is non-dispersive. Electromagnetic acoustic transducers (EMATs) are efficient generators of SH waves. However, titanium is traditionally a difficult material to inspect using EMATs. Through finite element analysis and experiments, this work proposes an inspection set-up using a 6 mm wavelength SH0 mode as the incident wave. When the SH0 mode interacts with a defect, reflections occur. The primary reflection is the SH0 mode, but mode conversions occurring at the defect result in the reflection of a mode converted Lamb wave. The Lamb guided wave mode reflected in our work is the S0 mode. The weld inspection approach presented uses both of these guided wave modes. The intention of detecting multiple wave modes is to provide more information about the inspected region, improving the reliability of the results by providing an increased probability of detection and a reduced likelihood of false positives. The results show initial testing and validation of the proposed set-up, highlighting how the SH0 mode reflection is sensitive to the weld quality. The positioning of the transducers sensitive to the S0 mode is also presented, showing the defect size's effect on the angle of reflection.