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The directivity of the quasi-static component (QSC) is quantitatively investigated for evaluating the orientation of a micro-crack buried in a thin solid plate using the numerical simulation method. Based on the bilinear stress–strain constitutive model, a three-dimensional (3D) finite element model (FEM) is built for investigating the nonlinear interaction between primary Lamb waves and the micro-crack. When the primary Lamb waves at A0 mode impinge on the micro-crack, under the modulation of the contact acoustic nonlinearity (CAN), the micro-crack itself will induce QSC. The amplitude of the QSC generated can be used for directly charactering the micro-crack orientation. The finite element simulation results show that the directivity of the QSC radiated by the micro-crack is closely related to the orientation of the micro-crack, allowing for the characterization of micro-crack orientation without the need for baseline signals. The results indicate that the directionality of the QSC can be used for characterizing the orientation of the micro-crack. The amplitude of the QSC is affected by the contact area between two surfaces of the micro-crack. It is demonstrated that the proposed method is a feasible means for the characterization of micro-crack orientation. [ABSTRACT FROM AUTHOR]

This paper investigates acoustic field characteristics of shear-horizontal feature guided waves (SH-FGWs) propagating through topographic waveguides like welds and stiffeners in plate-like structures. It establishes mathematical models of second harmonic and quasi-static component (QSC) generated by SH-FGWs in a welded joint and analyzes their theoretical characteristics. Using two-dimensional semi-analytical finite element and three-dimensional finite element methods, it studies the dispersion characteristics of FGWs and acoustic field distribution at specific frequencies of SH-FGWs, as well as their nonlinear response. This study provides new physical insights into the acoustic field distribution and nonlinear response of SH-FGWs in topographic waveguides. [ABSTRACT FROM AUTHOR]

The utilization of ultrasonic-guided wave array imaging in the detection of weld structural plates holds significant importance. This study presents a novel approach for full-rank imaging of shear horizontal-guided wave arc sparse arrays in welding structure imaging detection, the paper discusses the mechanism behind the ultrasonic-guided wave arc sparse array, specifically focusing on its full-rank imaging of multi-frames (FRIMR) capabilities in the presence of weld scattering. The receiving aperture of the arc sparse array is analyzed and discussed using the amplitude matrix and time-transition matrix. Both synthetic aperture and FRIMR of the arc sparse array are examined. The research findings demonstrate that FRIMR detection using ultrasonic-guided wave arc sparse array effectively captures scattering information equivalent to the wavelength size in the imaging detection area. This results in an average SNR improvement of 39.2% in full-frame imaging compared to multi-frames imaging. The imaging experiment validates the feasibility of the proposed imaging principle, highlighting its potential for imaging detection of welded structures. The research presented in this paper serves as a crucial foundation for future studies and applications of array imaging detection using ultrasonic-guided waves in welded structural plates. [ABSTRACT FROM AUTHOR]