Design and development of coercivity meter for nondestructive detection in magnetic materials: a proposed method

This paper presents a proposed design and development of a portable coercivity meter for nondestructive defect detection in ferromagnetic materials. Coercivity, a key magnetic property reflecting the internal microstructure and stress state of a material, is highly sensitive to mechanical damage, fatigue, and heat treatment anomalies. Leveraging this sensitivity, the proposed device uses a controlled magnetic excitation system coupled with high sensitivity magneto resistive sensors to measure the coercive field accurately. To enhance reliability, particularly under field conditions, the system incorporates simultaneous inductance measurement to correct for lift-off variations (air gaps). Calibration and validation are performed using standard steel samples with known hardness and stress levels, and results are benchmarked against conventional nondestructive testing (NDT) techniques such as magnetic particle inspection and eddy current testing. Results on the coding development capability to detect early-stage fatigue damage and subsurface defects, even through protective coatings. The developed system offers a cost-effective, real-time, and portable solution for structural health monitoring in industrial environments.