Cut-off thickness identification of defects with single and two-step geometries using SH1 mode conversion

Abstract

The utilization of the cut-off property of higher-order SH wave modes, particularly SH1, holds promise for assessing the remaining thickness of structures. However, the mode conversion behavior of SH wave modes poses a significant challenge to the accuracy of the cut-off method in quantifying remnant thickness. The occurrence of mode conversion depends on factors such as the slope and defect thickness, leading to situations where the SH1 mode can persist below the cut-off frequency after transmission through the defect. This mode conversion introduces errors during the defect quantification process. This study focuses on investigating the potential of using the cut-off feature of the SH1 mode for remnant thickness quantification under various defect geometry scenarios, including single and double step defects with different slopes and thickness reductions. The capability to identify cut-off frequencies originates from the innate potential for mode conversion within geometries featuring minor defect angles. When notable mode conversion occurs, particularly in cases involving larger defect angles, the mode conversion process hinders the precise determination of the cut-off frequency.