A method for compensation of permanent magnetic field perturbation (PMFP) testing signal based on lift-off measurement

Abstract

This paper proposes a novel composite measurement method for defect detection, which integrates PMFP (permanent magnetic field perturbation) testing and lift-off measurement. The PMFP method is used to detect defects, while the permanent magnet is utilized to construct a magnetic bridge for lift-off measurement. In PMFP testing, the variation of lift-off can significantly affect the signal. To mitigate this effect, the proposed method compensates for the defect signal using the measured lift-off information, which effectively reduces the impact of lift-off variation during the testing. Therefore, this paper constructs a magnetic dipole model based on the PMFP method and analyzes the numerical relationship between the defect signal and lift-off. Based on this, a composite lift-off measurement method for PMFP with a signal compensation function is proposed. This multifunctional sensing method has a compact structure, which significantly reduces the impact of lift-off on the defect signal. The experimental results demonstrate that the confidence level can reach 93% after compensating for the amplitude of the defect signal. The proposed method exhibits excellent performance in practical applications.