Anatoly Sagalakov

Subminiature eddy current transducers for studying metal-dielectric junctions

Based on a transformer eddy current transducer (ECT), a probe has been designed to study metal-dielectric-metal structures. The structural diagram of the probe is given and the basic technical data are stated (the number of windings is 10–130 turns, and the value of the initial permeability of the core μmax = 500). The scheme that uses the computer as a generator and receiver of signals from windings is considered. The measurement procedure allowing one to detect defects in laminate composites with a high accuracy is described. The transducer was tested on the layered structure consisting of paper and aluminum layers with a thickness of 100 μm each in which the model defect was placed. The dependences of the ECT signal on the defect in this structure are given.

Flaw detection of alloys using the eddy-current method

A subminiature transformer eddy-current transducer (ECT) that is intended for the study of different nonuniform materials, alloys, miniature parts, printed-circuit boards, and microscopic defects has been designed. A block diagram of the transducer is given and its basic technical characteristics ensuring localization of the magnetic field on areas of approximately 50 × 50 μm are stated. A scheme that uses a computer as a generator and receiver of signals from windings is proposed. It is capable of automatically changing the filtering cutoff frequency and operating frequency of the device. The designed measuring system eliminates the main drawback of eddy-current transducers (the small area of the electromagnetic field), simultaneously significantly reducing the noise level due to the use of high-quality amplifiers and filters, and searches for defects in printed circuit boards, metal–dielectric–metal-junctions, and alloys of different metals. A measurement procedure that allows one to perform high-accuracy monitoring of flaws in different alloys is described. The eddy-current transducer was successfully tested on several objects, e.g., a 5.5-μm thick Al–Mg alloy and welded seams of 5-mm thick titanium plates, as well as other objects. The dependences of the ECT signal on the flaws in these structures are given.

Eddy-current measuring system for analysis of alloy defects and weld seams

A measuring system based on an eddy-current transformer permits the detection of defects in plates of duralumin and aluminum–magnesium alloys.

Flaw inspection of welded joints in titanium alloys by the eddy current method

Abstract The eddy current transducer (ECT) of the transformer type is used to construct a sensor for investigating titanium sheets joined by a welded joint. The characteristics of the ECT are presented. The measurement method for controlling the occurrence of defects in the welded joints in titanium alloys is described. The experimental results obtained by the ECT on two welded titanium sheets are presented. The depth of penetration of the field of eddy currents into the investigated object is determined and the dependences describing the response of the ECT at different depths of the defect are outlined. The relationships can be used for evaluating the quality of welded joints and determining the reliability of welding.

Subminiature eddy-current transducers for conductive materials research

On the basis of the eddy-current transducer (ECT) of transformer type sensor has been developed. It allows exploring metal-insulator-metal, aluminum-magnesium alloy structure and titanium. Block diagram of the sensor, basic technical information were presented (the number of 10-130 turns, the value of initial magnetic permeability of the core μmax=500). The scheme of computer application as a generator and receiver of signals from the windings has been considered. Measurements technique which allows high-precision control of defects in composite materials, titanium and aluminum-magnesium alloy has been described. As a part of the study, the transducer has been tested at a number of facilities: aluminum-magnesium alloy 5.5 mm thick and titanium 5 mm thick. The article shows the dependence of the (ECT) signal from the defect in these structures.

An alloy flaw measuring system using subminiature eddy-current transducers

The measuring system based on subminiature eddy-current transducers is developed to carry out local investigations into aluminum-magnesium alloy plates with flaws. The Delianna filter has been modified to allow a significant increase in the signal-to-noise ratio. The transducer has been tested on a number of aluminum-magnesium alloy plates with flaws. The paper presents data on the relationship between the eddy-current transducer response and the presence of flaws in alloys as hidden slots at signal frequencies ranging between 300 and 700 Hz on an exciting winding.

Subminiature Eddy-Current Transducers for Conductive Materials and Layered Composites Research

The measuring system based on subminiature eddy-current transducers has been developed to carry out local investigations of aluminum-magnesium alloy plates for flaws. The Delianna filter has been modified to allow the significant increase of signal-to-noise ratio. A scheme that uses a computer as a generator and receiver of signals from windings is proposed. It is capable of automatically changing the filtering cutoff frequency and operating frequency of the device. The transducer has been tested on a number of aluminum-magnesium alloy plates with flaws. The article presents data on the relationship of eddy-current transducer response to the presence of flaws in alloys as hidden holes at signal frequencies comprised between 300–700 Hz on an exciting winding.

Subminiature eddy current transducers for studying semiconductor material

Based on an eddy-current transducer (ECT), a probe has been designed to study the semiconductor material. The structural diagram of the probe is given and the basic technical data are stated (the number of windings is 10-130 turns, and the value of the initial permeability of the core μ max = 500). Due to the high confinement of the magnetic field, it is possible to acquire data from small areas of semiconductor plates. Response versus ECT positioning diagram is also provided.

Letter: An origin of magnetohydrodynamic reverse flow in 90° bends

A two-dimensional flow in a 90° bent channel is considered. A magnetic field is uniform and parallel to the inlet branch of the channel. A spectral element method was used for liquid motion calculations. Three types of steady flows were detected. It was found that magnetic forces can suppress a pressure gradient and eject liquid from the inlet. Consequently, a perceptible reverse flow appears.A two-dimensional flow in a 90° bent channel is considered. A magnetic field is uniform and parallel to the inlet branch of the channel. A spectral element method was used for liquid motion calculations. Three types of steady flows were detected. It was found that magnetic forces can suppress a pressure gradient and eject liquid from the inlet. Consequently, a perceptible reverse flow appears.A two-dimensional flow in a 90 degree bent channel is considered. A magnetic field is uniform and parallel to inlet branch of the channel. A spectral/hp element method was used for liquid motion calculations. Three types of steady flows were detected. It was found that magnetic forces can suppress a pressure gradient and throw out liquid from the inlet, a relatively large reverse flow appears.

Investigation of steel to dielectric transition using microminiature eddy-current converter

The research aims to develop a microminiature converter for electrical steel investigation. The research topic is considered relevant due to the need for evaluation and forecasting of safe operating life of electric steel products. The authors determined the capability to study steel characteristics at different depths based on variations of eddy-current converter amplitude at the steel-dielectric boundary. A microminiature transformer-type converter was designed, which enables to perform local investigations of ferromagnetic materials using eddy-current method based on local studies of the steel electrical conductivity. Having the designed converter as a basis, a hardware-software complex was built to perform experimental studies of steel at the interface boundary. A system was developed for automated converter relocation above the studied object at a specified velocity. Test results are reported for a specimen with continuous and discrete measurements taken at different frequencies. Response dependence of eddy-current converter was found to demonstrate non-linear behavior at steel to dielectric transition. The effect of gap between the eddy-current converter and the test object is investigated.