Effects of a remanent magnetization on the sensing signals in magnetic flux leakage type NDT

Sensitive detection of the defect signals in NDT system is critical. Because of a strong magnetic field in magnetic flux type NDT system, the object itself is magnetized and shows a hysteresis characteristics during the sensing, which might cause a distortion of the defect signals. In this research, the magnetization characteristics of a pipeline in the magnetic flux leakage type non-destructive testing are analyzed. Effects of a magnetic hysteresis of a pipeline are analyzed by Preisach modeling and a magnetic flux density due to a remanent magnetization of gas pipeline is computed and verified by real measurement.