Non-contact magnetic stress detection method for pipe defects

The invention relates to a non-contact magnetic stress detection method for pipe defects. The method is characterized in that operators hold a magnetic stress detection device, walk along an axial direction of a pipeline just above the pipeline, detect magnetic parameters of a leakage magnetic field above a to-be-detected pipeline by using a sensor probe and record, process data and analyze signals. A threshold Kth of corresponding magnetic field gradients are determined in accordance with different pipelines through experiments; and if sign changes of magnetic field values ??are detected and changes of magnetic field gradients exceed the threshold Kth, the pipeline has the phenomenon of stress concentration. According to relationships of the measured pipeline magnetic field signals with local topography and deeply buried pipelines, and influences of cables, transmission lines and metal objects intersected with the pipelines on the measurement of the magnetic field, impact of outside interference is compensated before data analysis and correlated magnetic field data are corrected. The method can rapidly determine the stress concentration area, and has advantages of small influence of lift-off effect, portable device, rapid and convenient operation, high sensitivity and good repeatability and reliability.