Mode Identification of Denoised SH Guided Waves Using Variational Mode Decomposition Method

In the non-destructive testing (NDT) for large tank floors and oil pipelines, in addition to noise, the practical detection signal also has mode aliasing problems, which makes it difficult to identify and locate defects accurately. Therefore, in this work, we propose an improved shear horizontal guided wave mode identification method by using a variational mode decomposition (VMD) algorithm. Besides, we use the wavelet denoising method to denoise the original signal before using VMD for mode decomposition. Results show that compared with the traditional EMD method, the VMD algorithm is more effective for identifying aliased mode ultrasonic guided waves, and the wavelet denoising of the original guided wave data can further reduce the errors. Therefore, the proposed ultrasonic guided wave signal method is helpful to improve the defect detection sensitivity and accuracy of the SH EMAT.