A novel method for underwater pipeline crack detection via active electric field and frequency inflection point analysis

Abstract Subsea pipelines are essential for offshore oil and gas transportation, as they enable the delivery of resources over extended distances. However, over time, the structural integrity of these pipelines is frequently compromised by defects such as corrosion, cracking, and mechanical deformation. Traditional defect detection techniques have many limitations, including low operational efficiency, complex procedures, and sensitivity to environmental conditions. This study introduces an innovative defect detection approach for underwater pipelines, which is based on active electric field principles inspired by the electrolocation mechanisms of weakly electric fish. The proposed method incorporates frequency inflection point (FIP) analysis, and utilizes joint time-frequency spectrum (JTFS) analysis of detection signals and computational algorithms to identify characteristic frequency inflection points associated with defects. The experimental results show that FIP is related to the shape and material of the object, enabling defect detection through FIP analysis. The successful identification of artificially processed notches demonstrates the great potential of this method in underwater pipeline defect detection, especially in identifying crack damage. It can be integrated with autonomous underwater vehicles (AUVs) to automate the inspection process, thereby enhancing operational efficiency. At present, this research is limited to laboratory-scale conditions. The simulation of natural cracks through mechanically machined notches has laid a preliminary foundation for future field verification. However, to evaluate the practical application potential of this active electric field-based detection method in marine environments, further research will be necessary, particularly in addressing the challenges posed by environmental interference and operational variability.