[3B4] Advanced magnetic flux leakage (MFL) system for residual stress characterisation in ferromagnetic materials
T Chen
National Ilan University, Taiwan
Magnetic flux leakage (MFL) testing is an established electromagnetic non-destructive testing (NDT) method for the detection of surface and subsurface discontinuities in ferromagnetic materials. In contrast to the conventional magnetic particle inspection, modern MFL techniques integrate advanced magnetic sensors, offering enhanced sensitivity and novel capabilities. Recent research efforts have expanded MFL applications towards residual stress characterisation, which is the focus of this study.
This study presents the development of an advanced MFL inspection system featuring two-dimensional mapping capabilities, designed to improve detection resolution and data interpretability. The system integrates a motion platform, driven by a servo actuator, and a high-sensitivity quantum well Hall-effect sensor, along with a data acquisition system, enabling automated scanning, real-time signal analysis and magnetic field imaging.
In the experiment, ferromagnetic specimens were subjected to controlled uniaxial tensile loading and thermal stress-relief treatments to investigate the variations in magnetic permeability induced by mechanical elongation and subsequent annealing were captured through MFL mapping. Results demonstrate that the proposed system can detect subtle magnetic field perturbations associated with stress-induced microstructural changes, even in the absence of visible surface defects. Moreover, the MFL signal amplitude correlated with the applied strain and decreased after annealing, confirming the effectiveness of the method for residual stress evaluation.
This study presents the development of an advanced MFL inspection system featuring two-dimensional mapping capabilities, designed to improve detection resolution and data interpretability. The system integrates a motion platform, driven by a servo actuator, and a high-sensitivity quantum well Hall-effect sensor, along with a data acquisition system, enabling automated scanning, real-time signal analysis and magnetic field imaging.
In the experiment, ferromagnetic specimens were subjected to controlled uniaxial tensile loading and thermal stress-relief treatments to investigate the variations in magnetic permeability induced by mechanical elongation and subsequent annealing were captured through MFL mapping. Results demonstrate that the proposed system can detect subtle magnetic field perturbations associated with stress-induced microstructural changes, even in the absence of visible surface defects. Moreover, the MFL signal amplitude correlated with the applied strain and decreased after annealing, confirming the effectiveness of the method for residual stress evaluation.
