Inspection of plate-like structures in the petrochemical industry is vital. Ultrasonic guided waves have been used extensively to detect various types of defect by monitoring reflected and transmitted signals; however, testing becomes difficult for sharp, shallow defects as current inspection techniques suffer from a lack of sensitivity to such features. Previous studies, obtained by comparing various inspection techniques, suggest that the SH1 mode in particular, at around 3 MHz-mm, would be suitable when testing for shallow defects; however, it is clear that both the SH0 and SH1 mode can exist at this frequency-thickness product which can complicate the inspection process and therefore limit defect detectability. This paper investigates the possibility of single mode excitation of the SH1 mode at around 3 MHz-mm. the ability of this method towards detecting very shallow defects (<10% cross-sectional thickness loss) has also been studied. Using finite element analysis simulations and verification experiments it is shown that a signal dominated by the SH1 mode can be generated using PPM EMATs. Furthermore, it is shown that, by studying the reflection coefficient of the SH1 mode, the pure SH1 mode can be used to detect vary shallow defects (< 10% thickness loss) that will be missed by standard, lower frequency guided wave testing.
How to Cite:
Khalili, P. . & Cegla, F. ., (2019) “Excitation of pure SH1 mode and evaluation of its sensitivity to very shallow crack-like defects”, Review of Progress in Quantitative Nondestructive Evaluation .