A shear horizontal phased array steering excitation technique for remnant wall thickness quantification

Precise wall loss quantification in pipe and plate structures is a critical and challenging task, especially in cases where direct access to the component is limited. Accurate knowledge of the remaining wall thickness allows for timely maintenance or replacement to avoid catastrophic failures. In this work, wall loss quantification is performed utilizing the cut-off frequency of mode SH1. The approach requires the excitation of SH1 across a range of frequencies. For this reason, a novel excitation technique using guided wave phased array steering is developed. Specifically, an array generating shear horizontal waves is employed. The influence of the array's length, pitch, element width, and mode excitability on excitation is investigated. By appropriately phasing the elements of the array, mode SH1 is targeted and dynamically excited over a wide frequency-wavelength range. The directionality of SH1 is also studied, as in certain conditions, this can be critical for the success of the quantification. Simulation results show the technique can accurately quantify a 65 % wall thinning defect, offering a 15 % increase compared to established techniques. This is critical, as commonly, wall loss defects above 50 % are considered severe. Additionally, using electronic steering, rapid quantification can be achieved. Experiments using an EMAT and synthetic steering on an intact area and an artificially machined corrosion-like defect validate the technique.