Abstract: The present disclosure provides a method and a device for detecting and evaluating a defect with electromagnetic multi-field coupling. The method includes magnetizing a pipeline with the electromagnetic multi-field coupling; detecting a defect of the pipeline along an axial direction of the pipeline at a constant speed; collecting signals at a position of the defect to obtain magnetic leakage signals in three dimensions and an electrical impedance signal; pre-processing the collected signals; decoupling the pre-processed signals, to obtain decoupled magnetic leakage signals and a decoupled electrical impedance signal; performing impedance analysis on the decoupled electrical impedance signal, and determining a type of the defect based on a phase angle of the decoupled electrical impedance signal; and performing quantification analysis on the decoupled magnetic leakage signals and performing quantification evaluation on a size of the defect using a neural network defect quantification method.

Abstract: A method for reconstructing a defect includes: S1, establishing a database of magnetic flux leakage signals of a unit defect and acquiring a magnetic flux leakage signal of the unit defect; S2, acquiring a target magnetic flux leakage signal; S3, initially setting a scaling factor k; S4, constructing a forward model; S5, inputting the k into the forward model and performing forward prediction according to the k to acquire a predicted magnetic flux leakage signal for the defect to be detected; S6, calculating an error between the target magnetic flux leakage signal and the predicted magnetic flux leakage signal, and determining whether the error is smaller than an error threshold ?, if yes, executing S7; otherwise, executing S5 after the k is corrected; and S7, scaling the unit defect according to the k to acquire a final size of the defect to be detected.

Abstract: The present disclosure provides a method and a device for detecting and evaluating a defect with electromagnetic multi-field coupling. The method includes magnetizing a pipeline with the electromagnetic multi-field coupling; detecting a defect of the pipeline along an axial direction of the pipeline at a constant speed; collecting signals at a position of the defect to obtain magnetic leakage signals in three dimensions and an electrical impedance signal; pre-processing the collected signals; decoupling the pre-processed signals, to obtain decoupled magnetic leakage signals and a decoupled electrical impedance signal; performing impedance analysis on the decoupled electrical impedance signal, and determining a type of the defect based on a phase angle of the decoupled electrical impedance signal; and performing quantification analysis on the decoupled magnetic leakage signals and performing quantification evaluation on a size of the defect using a neural network defect quantification method.

Abstract: An imaging method based on guided wave scattering of omni-directional EMATs includes: selecting an nth omni-directional EMAT from N omni-directional EMATs uniformly arranged in a detection region of a metal plate to be detected as an excitation EMAT; selecting m omni-directional EMATs as omni-directionally receiving EMATs to omni-directionally receive an ultrasonic guided wave signal, and calculating a travel time and intensity of the ultrasonic guided wave signal; judging whether the excitation EMAT and the omni-directionally receiving EMATs form a scattering group, if yes, calculating a position of a scattering point; judging whether the position of the scattering point is within a preset scattering region, if yes, determining the position of the scattering point as an effective scattering point; repeating the above steps until all N omni-directional EMATs have excited omni-directional ultrasonic guided waves, and performing curve fitting on all effective scattering points to obtain a defect profile image.

Abstract: A method for reconstructing a defect includes: S1, establishing a database of magnetic flux leakage signals of a unit defect and acquiring a magnetic flux leakage signal of the unit defect; S2, acquiring a target magnetic flux leakage signal; S3, initially setting a scaling factor k; S4, constructing a forward model; S5, inputting the k into the forward model and performing forward prediction according to the k to acquire a predicted magnetic flux leakage signal for the defect to be detected; S6, calculating an error between the target magnetic flux leakage signal and the predicted magnetic flux leakage signal, and determining whether the error is smaller than an error threshold ?, if yes, executing S7; otherwise, executing S5 after the k is corrected; and S7, scaling the unit defect according to the k to acquire a final size of the defect to be detected.

Abstract: An imaging method based on guided wave scattering of omni-directional EMATs includes: selecting an nth omni-directional EMAT from N omni-directional EMATs uniformly arranged in a detection region of a metal plate to be detected as an excitation EMAT; selecting m omni-directional EMATs as omni-directionally receiving EMATs to omni-directionally receive an ultrasonic guided wave signal, and calculating a travel time and intensity of the ultrasonic guided wave signal; judging whether the excitation EMAT and the omni-directionally receiving EMATs form a scattering group, if yes, calculating a position of a scattering point; judging whether the position of the scattering point is within a preset scattering region, if yes, determining the position of the scattering point as an effective scattering point; repeating the above steps until all N omni-directional EMATs have excited omni-directional ultrasonic guided waves, and performing curve fitting on all effective scattering points to obtain a defect profile image.