CS237840B1 - Differential inductive sensor for defectoscopy of surface cracks in metallic materials - Google Patents

Abstract

The solution belongs to the department of mechanical engineering and metallurgy and solves the construction of a sensor for defectoscopy of surface cracks in metal materials. Its essence is that the excitation coil of induced eddy currents in an electrically conductive material is placed at equal distances between the sensing coils so that the axes of all three coils are parallel to each other and lie in one plane, while the sensing coils are connected differentially. Both the excitation coil and the sensing coils are pushed onto an E-shaped core with high permeability, whose pole extensions can be shaped according to the geometry of the tested surface.

Description

237840

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential inductive sensor for defectoscopy of surface cracks in metallic materials of dark engineering and metallurgical plants.

Inspection of the material to be processed in the technological process with the aim of automatic sorting of the needles requires sensitive but simple defectoscopic cracks sensors. Defectoscopic devices using differential inductive sensors with through-coils require unidirectional pre-magnetization of the ferromagnetic material under test, accurate guiding objects that must not be deformed. These transducers can be applied to control the burrs formed in the coils, and only detect the beginning or end of the crack.

Better features for detecting surface cracks are those with transducers whose differential coils are symmetrically inserted inside the excitation coil so that their axes are parallel to the axis of the coil. The disadvantage of this arrangement is the relatively large dimensions of the excitation coil, thereby increasing the area of the material in which it induces eddy currents, which increases the required excitation power.

The above-mentioned disadvantages are eliminated by the differential inductive sensor on defectoscopic surface cracks in metal materials based on the principle of induced eddy currents in the electrically conductive material with the differential coil sensing coils according to the invention, the principle being that the excitation coil is disposed at equal distances between the scanning coils so that the coil axes and the sensor coils are aligned and parallel to each other. Further, the pole pieces and the core are shaped according to the geometry of the test element. The advantage of the differential inductive transducer is that it does not require unidirectional magnetization of the ferromagnetic material, nor any adjustment prior to the start of the test, and the distance between the transducer and the test surface is not critical. Neither the position of their start, the end, nor the change in their depth are decisive in the search for surface cracks. Compared with the prior art inductive sensors, the sensor geometry of the invention is simpler in terms of coil formation, which may be the same.

In the accompanying drawing, a differential sensor is shown schematically for defectoscopy of surface cracks in metal materials.

The differential inductive sensor of the invention consists of an excitation coil 2 and of two sensing coils 1 and 3, the axes of which are parallel to each other, in a common plane, the distances of the sensing coils 1 and 3 of the excitation coil 2 being the same. An exciting alternating current flows through the exciter 2, thereby creating a magnetic field around it. The sensing coils 1 and 3 are connected to the plates so as to subtract the induced tensions therein. The resulting differential voltage is a measure of the crack position of the sensor. During testing, the transducer is parallel to the surface of the material so that a portion of the magnetic flux lines cross its surface. The sensitivity of the sensor can be substantially increased by inserting a ferrite coil, or a ferromagnetic core of the Form E, the pole pieces 6 of which can be shaped according to the geometry of the surface-tested material 4.

The differential inductive sensor for de-fectoscopy of surface cracks in metal materials is based on the principle of eddy currents in the tested material-magnetic field and whose geometry of the sensing characteristic is marked by plane symmetry. If the material fracture is outside the magnetic pole range, or lies just in the sensing plane of symmetry, the symmetry of the distribution of the eddy currents in the material will not be impaired. The sensor does not include a crack in such a case. However, if the symmetry of the sensing characteristic is brought into the magnetic pole by the movement of the crack sensor, the eddy current field ceases to be symmetrical and the sensor output produces alternating voltage, whose phase and size depend on the crack position relative to the symmetry plane.

The differential inductive sensor for the detection of surface cracks in metal materials is also suitable for guiding tools, in addition to defectoscopy, in gaps or grooves in metal material, for example in the welding and machining of metal die.

Claims (2)

237840 PREDMET 1. A differential inductive transducer sensor for surface cracks in metal materials based on the principle of induced eddy currents in an electrically conductive material with differentially connected sensing coils is characterized by the ribbing coil (2) being positioned at the same distances between the sensing coils (1 and 3) and the excitation coil axes (2) and the inventive coils (1 and 3J are in one plane and are parallel to each other). 2. A differential inductive sensor according to claim 1, characterized in that the excitation coil and the sensing coil (1, 3) are pushed onto a ferromagnetic or ferrite core (5) of the E-shape, whose pole pieces (6j and the core (5) are formed according to the geometry. 1 sheet of drawings