DEVICE FOR EDDY CURRENT DEFECTOSCOPY OF FERROMAGNETIC PIPES ON SIDE OF THEIR INNER SURFACE Russian patent published in 2017 - IPC G01N27/90 

FIELD: physics.

SUBSTANCE: device contains a constant current source, a magnetization system, an eddy current transducer, an electronic unit, a phase shifter. The magnetization system consists of a cylindrical magnetic core with an H-shaped longitudinal section and a winding connected to the output of a constant current source, located on the central rod and made in the form of two identical sections connected and installed with an axial gap symmetrically relative to the center of the magnetic core. The eddy current transducer is placed in the gap between the windings of the electromagnet on a cylindrical frame coaxial with the magnetic core. AC generator is connected to the exciting winding of the eddy current transducer and the electronic unit connected to the output of the eddy current transducer by its input. The electronic unit is capable of amplitude-phase processing of the signal and is connected to the output of the alternator via the phase shifter. The constant current source is adjustable. When the intensity of the magnetic field H produced by the magnetization system changes, the phase difference between the signals associated with the effect of the defects and the signals associated with the influence of the structural inhomogeneity of the metal change. The magnitude of the magnetic field intensity is chosen so that the changes in the applied voltage on the measuring winding of the eddy current transducer, related to the effect of defects and the influence of noise due to the structural heterogeneity of the metal, differ in phase as much as possible. The conditions favourable for separating the signal from defects occur when H<<H_ts, where H_ts is the intensity of the magnetic field required for the technical saturation of the metal.

EFFECT: increased reliability of control by suppressing the influence of interfering factors associated with the electromagnetic heterogeneity of the metal, without bringing it to the state of technical saturation.

2 cl, 9 dwg