Inspection of defects in welds is challenging but of great interest to industry. Having the most effective inspection setup allows for greater potential in detecting critical flaws. An improved inspection approach can be achieved by understanding the interaction between the fundamental shear horizontal guided wave mode (SH0) and defects of different sizes [1]. This understanding will result in the selection of suitable wavelengths and methods of inspection, enabling the&nbsp;detection of flaws of the required dimension.The total reflection from a defect comes from the interference between reflections from the near and far end of the defect relative to the incident wave [2]. The length of the defect determines the separation of these two reflection sources and how they interfere, resulting in an oscillatory behaviour of the magnitude of the reflection with defect length. Previous work has not considered how the defect width impacts this oscillatory behaviour. The effect that the width has on the reflection behaviour was investigated in this work, looking at how different size defects affect the SH0 reflection, as well as studying the SH0 diffraction and the mode converted S0 Lamb wave. An extensive range of defect sizes have been investigated by using both finite element analysis and experimental work. The defects were in 1 mm thick titanium sheets; the testing was performed using 6 mm wavelength SH0. Electromagnetic acoustic transducers (EMATs) have been used to generate the SH wave. EMATs are very efficient generators of SH waves when using a periodic permanent magnet array (PPM), and despite conventional wisdom stating that they are not suitable for generation in titanium, this work shows that with optimisation, inspection using EMATs is capable. Results show that the defect width affects the length at which the maximum SH0 reflection occurs, especially as the width size decreases. This is also the case for the S0 reflection. By understanding the reflection and diffraction behaviour in more detail, and combining results from different waves, an inspection method can be used which is optimised for very small (around 0.5 mm diameter target size) defects which may be present in welds.[1]&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; P. A. Petcher and S. Dixon, “Weld defect detection using PPM EMAT generated shear horizontal ultrasound,” NDT E Int., vol. 74, pp. 58–65, 2015, doi: 10.1016/j.ndteint.2015.05.005.[2]&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; A. Demma, P. Cawley, and M. Lowe, “Scattering of the fundamental shear horizontal mode from steps and notches in plates,” J. Acoust. Soc. Am., vol. 113, no. 4, pp. 1880–1891, 2003, doi: 10.1121/1.1554694.&nbsp;&nbsp;

Detection of Defects in Titanium Using Shear Horizontal Guided Waves

Paper Proceedings: https://asmedigitalcollection.asme.org/qnde/QNDE2021/volume/85529

ASME 2021 48th Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE2021)

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