Uchanin V. The development of methods and means for eddy current testing of materials and constructions

The thesis is devoted to the creation of the means and technologies for eddy current inspection of products that are characterized by high levels of noise. The signals of parametric and unaxial type eddy current probes are investigated by volume integral equations method and experimentally. The features of parametric type probe signal distribution for cracks with different length was investigated to determine the optimal probe size. New method for the crack length determination is proposed. The peculiarities of unaxial type probe signal for different orientation relative to crack direction and coil spacing are investigated. The parameter for determination of eddy current probes efficiency is proposed. Its invariant properties relatively on the number of turns and on the winding size while maintaining the aspect ratio are shown. The efficiencies of coils placed on ferrite core are investigated. The number of double differential type eddy current probes for detection of the subsurface defects, such as the defects under protective coating and local subsurface pores in copper products, are developed and investigated. Their effectiveness to determine the vertical section of the inspected object by the eddy current tomography system is shown. The signals from the cracks with different angles relative to the controlled surface are investigated and the method of angle determination is proposed. The influence of the electrical conductivity anisotropy of non-magnetic materials and stresses in ferromagnetic materials to a signal of the double differential type probe is investigated. А number of flaw detectors and technologies for eddy current inspection of products, characterized by high levels of noise, are developed and implemented to industry. Devices for structure analyzing during the monitoring of the aluminum alloys operational degradation in aircraft structures, as well as for gas-filled layers of titanium alloys evaluation are developed. Metrological methodology to support eddy current flaw detection is developed.