An ultrasonic SH-guided-wave transducer for image detection of welded structure with multi-frame and in full rank

Ultrasonic transducer of shear horizontal (SH) guided wave has great application value in defect detection in welded structural plate. In order to develop the transducer that could perform multi-frame and full rank imaging detection of welded structures, the theory of half wavelength of guided waves was applied to analyze the excitation of ultrasonic SH-guided waves and the multiple-order scattering inside the transducer. According to the multiple-order scattering theory, the relationship between particle density and attenuation in the matching layer is derived, and the composition of the matching layer is determined. Both the multiple-order scattering echoes inside planar and non-planar front wedge transducers were analyzed experimentally. The research results indicate that the amplitude of the double or more scattered echoes inside the orthogonal front wedge structure has decreased by more than 45%. Performance testing was carried out on the orthogonal front wedge structure of transducer, and the SH-guided waves excited by it reached a signal-to-noise ratio of 14.5 dB for the defect echo signal when a size equivalent to ϕ12 mm in the welded structure was applied. This has demonstrated its superior detection capability. The effectiveness of the theoretical analysis has been verified through experiments. The SH-guided-wave transducer with orthogonal front wedge structure could be used to detect equivalent defects of different sizes in welded structural plates.