A new imaging method of microwave NDT for butt fusion defect detection in polyethylene pipes

Polyethylene (PE) pipes are extensively utilized in both industrial and civil applications due to their exceptional corrosion resistance and cost-effectiveness. However, defects that arise during the heat fusion welding process, such as bubbles, cracks, and incomplete fusion, can significantly compromise the structural integrity and operational safety of the pipeline, potentially leading to leakage incidents. In this paper, a new imaging method based on microwave non-destructive testing (NDT) data for detecting the above defects is presented. Originating from the imaging concept of geophysics, the proposed method firstly uses the inverse fast Fourier transform (IFFT) to convert the frequency domain data into the time domain and then combines singular value decomposition (SVD) and principal component analysis (PCA) algorithms to remove direct waves and noise, forming the desired high-quality B-scan image. This method has been validated through electromagnetic simulation and experiments. By comparing the experimental images and tensile results, the proposed method can effectively present the detection signal characteristics and defect locations of slag inclusion, holes, low temperature, and grease defects, proving the effectiveness of the method.