Recent advances in magnetic and electric field sensor arrays provide new capabilities for absolute imaging of electrical conductivity, magnetic permeability and dielectric permittivity. Arrays of inductive or magnetoresistive sensing elements are used with magnetic field drives while arrays of capacitive sensing elements are used with electric field drives. Specific inspection examples include magnetic permeability measurements of applied and residual stress in steels, magnetic permeability measurement of precrack fatigue damage in steels, electrical conductivity measurements in a furnace for heat treatment quality control, multiple frequency electrical conductivity measurements for coating age degradation characterization, imaging of hidden damage (e. g., fatigue and corrosion), and complex permittivity monitoring for curing of epoxies and adhesives. This paper reviews shaped field magnetometer and dielectrometer measurement methods and provides a description of inversion methods for property estimation using physical models.
展开▼
