Multi-Frame Imaging And Testing Of Variable-Rank For Linear-Arc Array Of Ultrasonic Guided Waves In Welded Thin Plate

Ultrasonic guided wave synthetic aperture multi-frame variable-rank array can be better used for imaging detection of welded thin plates.Multiple-frame sequence images can fully display the defect scattering information in the acoustic field imaging detection area from different perspectives.Aiming at the problem of ultrasonic guided wave multi-frame variable-rank imaging detection of defects in welded thin plates(welded structures),this paper discusses the design theory and development of ultrasonic horizontal shear(SH)guided wave transducers suitable for multi-frame variable-rank imaging,and studies the ultrasonic guided wave multi-frame variable-rank imaging detection and implementation of typical linear and arc type arrays,including linear arrays and arc arrays.In order to perform ultrasonic guided wave multi-frame variable-rank imaging testing on welded structures,it is necessary to use guided wave transducers as array elements that are more suitable for variable-rank imaging testing.Using the guided wave half wavelength theory and the multiple scattering theory,an acoustic analysis of the excitation of ultrasonic SH guided waves and the front wedge structure of the transducer was conducted.The relationship between the particle density and attenuation of the acoustic matching layer of the transducer was derived to determine the composition of the matching layer.Experiments have verified the effectiveness of analyzing the multiple scattering echo theory for planar and nonplanar front wedge structures of energy converters.The ultrasonic guided wave array multi-frame variable-rank imaging is proposed for the detection of welded structures.The mechanism of ultrasonic guided wave multi-frame variable-rank imaging under the condition of weld scattering is studied for linear arrays.The relationship between the amplitude matrix(transit time matrix)and the rank is analyzed and discussed.The scattered echo matrix is used to describe weld scattering,revealing the inherent characteristic of "multiple peaks" in the guided wave signal during ultrasonic guided wave multi-frame variable-rank imaging.The imaging experiments demonstrate the feasibility of the multi-frame variable-rank imaging mechanism for welded structure linear arrays.The acoustic characteristics and laws of different frame sequence images in linear array multi-frame imaging to characterize defect scatters in welded structural plates were studied.The grayscale value,background grayscale,and signal-to-noise ratio of multi-frame variable-rank images of ultrasonic guided wave linear array in welded structural plates are analyzed.The acoustic characteristics of the scatterers represented by multi-frame variablerank images are discussed as a function of the rank of the receiving matrix.The emphasis is placed on exploring the changes in the acoustic curve of the image when the receiving matrix is single rank,half full rank,or full rank.The use of ultrasonic guided wave arc arrays for multi-frame variable-rank imaging detection of welded structures was studied in order to highlight the natural aggregation characteristics of arc arrays and improve the imaging resolution of defects in the imaging region.The feasibility of multi-frame variable-rank imaging for arc array of welded structures is verified by imaging experiments.The research work in this paper has certain theoretical value and important application prospects for ultrasonic guided wave imaging testing of welded structures(welded thin plates).