Электромагнитные методы контроля изменений напряженно-деформированного состояния диэлектрических материалов

Mechanical-electrical and acoustic-electrical complex methods of testing cracking while changing the stress-strain state in dielectrics are discussed on the example of rock samples. The paper discusses the results of numerical and experimental studies of changes in the electromagnetic responses parameters under the pulse deterministic acoustic excitation of rock samples with different composition and texture. Also the results of mathematical calculations of the stress concentration on cracks located along the sample axis are presented, perpendicular to which deterministic acoustic pulses were introduced. The experimental studies results of sample electromagnetic emission with containing calcite and magnetite under uniaxial compression to fracture are shown. Regularities in the electromagnetic signals amplitudes changes during acoustic sounding in the process of «stepwise» uniaxial loading by compression to destruction are given.

МАКРОСКОПІЧНА НЕОДНОРІДНІСТЬ ОПТИЧНИХ, ДІЕЛЕКТРИЧНИХ І ФОТОДІЕЛЕКТРИЧНИХ ВЛАСТИВОСТЕЙ КРИСТАЛІВ ZnSe

The subject matter of study in the article is the optical, dielectric and photodielectric properties of ZnSe crystals containing macroscopic structural inhomogeneities. The goal of this work is to study large-scale inhomogeneities in ZnSe crystals, which is important for determining the suitability of their application in technology. The tasks to be solved are: in a crystalline ZnSe ingot of cylindrical shape in the optical range at perpendicular to the light flux orientation of the sample axis to detect macroscopic inhomogeneities and establish their relationship with the features of the dielectric properties of the local regions of the ZnSe ingot; to investigate the influence of nonmonochromatic light flux on the distribution of dielectric parameters along the axis of the ZnSe ingot containing areas of macroscopic inhomogeneities. The problems were solved by the following methods: the homogeneity of the zinc selenide ingot was studied by the polarization-optical photoelasticity method; the photometry method was used to study the intensity distribution of the light scattered by the sample perpendicular to its axis; the dielectric properties of a crystalline ZnSe ingot were investigated by the capacitive method. The following results were obtained. In ZnSe crystals regions of three types were found: isotropic, weakly anisotropic, and anisotropic. Sharp changes in the intensity of scattered light are observed in the region of large-scale optical inhomogeneity, and light scattering in this region occurs anisotropically. The angular dependences of C and tgδ at an electric field frequency of 1 kHz are obtained for the region of large-scale optical anisotropy. The changes in dielectric parameters under the action of nonmonochromatic light along the sample axis are measured. Conclusions. It was found that ZnSe crystals are characterized by large-scale inhomogeneities of the investigated properties. A close relationship is noted between the optical and electrophysical properties, which is probably due to the mutual influence of two-dimensional and point defects on the formation of a defect structure during the growth and further cooling of the crystal.

Экспериментальное определение поля радиальных перемещений в шейке образцов после испытания на растяжение

This Letter presents the results of a study of the radial displacement fields arising upon stretching of cylindrical samples before their disintegration. The object of study was sv-07Kh16N6 stainless steel wire containing filiform defects oriented along the sample axis. Using X-ray tomography of the sample necks, the coordinates of the defect points in the sample are determined and the displacement field is recovered from them. The resulting dependence is represented by an approximate formula.

Grrain Orientations and their Influence on Precipitation in Hot Compressed Columnar Grains in Electrical Steel

To identify the relationship between grain orientation and precipitation of MnS/AlN particles during hot deformation, cylinder samples containing columnar grains in electrical steels were prepared with different angles between columnar grain axis and sample axis. They were heated at 1360°C and compressed at 1100°C for 50%. Grain orientations and the precipitation states are determined using XRD, EBSD, EDS and SEM. Results indicate a general behavior of less precipitates in <100> and more precipitates in <111> grains. In addition, more precipitates were observed in samples with grain boundaries perpendicular to compression axis.