Nondestructive testing method and device for detecting and distinguishing internal defect and external defect of wire rope

A nondestructive testing method for detecting and distinguishing an internal defect and an external defect of a wire rope, comprising the following steps:

• step S10:
• acquiring a magnetic flux signal and a magnetic flux leakage (MFL) signal of a detected wire rope;
• step S20:
• preprocessing the magnetic flux signal and the MFL signal of the detected wire rope to obtain a preprocessed magnetic flux signal and a preprocessed MFL signal;
• step S30:
• comparing the preprocessed magnetic flux signal and the preprocessed MFL signal with a preset magnetic flux signal threshold and a preset MFL signal threshold respectively, and calculating a defect position;
• step S40:
• extracting a magnetic flux signal of a defect and an MFL signal of the defect based on the defect position;
• step S50:
• calculating a defect width flw of the detected wire rope based on the magnetic flux signal of the defect and the MFL signal of the defect;
• step S60:
• calculating a defect cross-sectional area loss fs of the detected wire rope based on the defect width flw of the detected wire rope;
• and
• step S70:
• determining whether the defect is the internal defect or the external defect, specifically comprising:
• calculating a peak-to-peak value FV of a waveform of the MFL signal of the defect according to a formula FV=FH−FL, wherein FH represents a peak value of the waveform of the MFL signal of the defect, and FL represents a valley value of the waveform of the MFL signal of the defect;
• designing a relation function ffs=f2(FV, flw), wherein f2 represents a first trained system of higher-degree equations or a first multi-layer neural network, and ffs represents a virtual cross-sectional area loss;
• substituting the defect width flw obtained in step S50 and the peak-to-peak value FV of the waveform of the MFL signal of the defect into the relation function, to calculate the virtual cross-sectional area loss ffs;
• and
• comparing ffs with fs, and when |fs−ffs|>μ, determining that the defect is the internal defect;
• when |fs−ffs|≤μ, determining that the defect is the external defect, wherein
• μ represents a preset defect decision value.