Vol 54, No 10 (2018)

The question is considered of the relationship between the divergence of a longitudinal (400 mm) groove in the rail web, used as an indirect residual-stress–based rejection criterion, with internal stresses measured by acoustic strain gaging across the rail section. The internal stresses have also been evaluated in individual rail elements after cutting. A finite element simulation in the COMSOL Multiphysics software environment has been performed in order to establish connection between groove divergence and stresses. Results are presented for experimental measurements over 49 sections of different rails. The relationship is demonstrated between the stress level in rail elements and the level of stresses measured by an electromagnetic-acoustic structuroscope in an experiment on the side of the railhead. Based on the modeling and experimental results, an acoustoelastic technique is proposed for monitoring residual stresses in rails as an expert method with a rejection level of 80 MPa when sounding a rail section on the side of its head.

The technical condition of high-voltage insulators was inspected for the first time at several substations of OAO “Kazanskie elektricheskie seti” (Kazan Power Grid PLC) using the previously developed two-channel remote method for measuring the characteristics of partial discharges. Based on the results of preliminary bench tests with model samples and field measurements of a set of partialdischarge parameters and on computer-aided analysis of these results, diagnostic features have been established that make it possible to determine the type and location of the most dangerous defects and the degree of their influence on the operability of the insulators.

Thickness measures for electrically conductive coatings applied to electrically conductive bases are described, for which not only geometrical but also electrophysical parameters such as the specific electrical conductivity and complex relative permeability of the measure base and the specific electrical conductivity of the measure coating are prescribed. The procedure and a technique for measuring the specific electrical conductivity of the base of a measure using the van der Pauw method, the complex relative magnetic permeability of metal on ring-shaped samples using a permeameter, a technique for transferring the value of this parameter to the measure base of an arbitrary shape with a flat surface, and also the procedure and a method for measuring the specific electrical conductivity of the coating-measure material with the use of an eddy current probe with a wave-like drive winding are described.

The magnetic properties and specific features of giant magnetoimpedance in rapidquenched amorphous wires of composition (Co_0.94 Fe_0.06 )_72.5Si_12.5 B₁₅ are investigated. The working interval and sensitivity to changes in an external quasistatic magnetic field have been calculated for the alternating current frequencies from 1 MHz to 1 GHz. Parameters that are optimum for using such wires as sensitive elements in magnetic field sensors have been calculated, and the probe sensitivity to the external magnetic field has been determined. A sensor prototype was designed that, when tested, confirmed the possibility of using the giant magnetoimpedance in sensors based on amorphous CoFeSiB wires for flaw detection.

Ultrasonic infrared thermography is a rapid and informative method of nondestructive testing, used to inspect materials and products in aviation and rocket and space industries. High-power piezoelectric emitters stimulate various materials by ultrasound and help revealing hidden flaws by local temperature changes, which can amount to tens of degrees. The possibility of optimizing the procedure of ultrasonic infrared thermography by choosing the frequency of acoustic waves so as to match the frequencies of local resonances of defects of different sizes has been investigated.