A hybrid pulsed electromagnetic-acoustic transducer and testing method for broad-range defect inspection in ferromagnetic metallic structures

Large-scale ferromagnetic metallic structures, such as storage tanks and wind turbine towers, are critical equipment in the energy and infrastructure sectors. They operate in complex environments and are prone to surface defects such as pitting and corrosion thinning. Single detection methods often face challenges such as missed detection and incomplete coverage. Existing electromagnetic non-destructive testing (NDT) hybrid methods suffer from issues including limited detection range, complex sensor structure, and low signal-to-noise ratio (SNR). To address these problems, this paper proposes a hybrid pulsed electromagnetic-acoustic non-destructive testing method. An integrated probe is designed, which uses a U-shaped electromagnet structure to magnetise the near-surface region of the material. Both pulsed electromagnetic signals and ultrasonic signals are collected simultaneously by a single sensing unit, and the signals are separated based on their differences in the time domain and frequency domain. In addition, a one-dimensional scanning strategy and a two-dimensional f-k filtering algorithm are proposed. Experimental results verify that the proposed hybrid detection sensor exhibits excellent detection performance for both near-field and far-field defects, and the detection range is more than doubled. This work provides a novel method for the detection of surface defects in large-scale ferromagnetic metallic structures.