Acoustic-Emission Testing of Failure in Samples of CFRP Exposed to Static and Heat Loads

The results of testing samples made of T700 carbon fiber reinforced plastic with a stress concentrator in the form of a hole 14 mm in diameter are considered. Some of the samples were heated to a temperature of +100°C, followed by exposure to a static tensile load, with the remaining samples statically loaded at a temperature of +20°C. In the process of loading, information was recorded using the method of acoustic emission. At first, the samples were loaded statically up to 50 kN, which was 50% of the average breaking load. Then the load was increased in increments ΔP = 10 kN until sample failure. It was observed that the simultaneous exposure of samples to static and heat loads decreased the load capacity of the samples.

     

Investigation of the effect of frustration on the critical properties of the 3D Heisenberg antiferromagnetic model

The critical properties of the 3D frustrated Heisenberg model on a layered triangular lattice with a variable interlayer exchange interaction are investigated for the ratio of the constants of the interlayer (J′) and intralayer ( J ) interactions that ranges within the interval R = | J′/J| = 0.01…1. The finite-dimensional scaling theory is applied for the calculation of all of the main static magnetic and chiral critical indexes. It is shown that the 3D frustrated Heisenberg model on a layered triangular lattice forms a new universality class of critical behavior. It is found that the universality class of this model’s critical behavior is retained for values of R as small as R = 0.05.     

Estimation of time-of-arrival errors of acoustic-emission signals by the threshold method

A technique for determining the times of arrival of acoustic-emission (AE) signals at the probes of a piezoelectric antenna with simultaneous estimation of their errors is considered. To increase the localization accuracy, it is proposed to refine the times of arrival by linearly approximating the leading edge of an AE signal taking into account the influence of noise. The slope of the leading edge is calculated according to the criterion of the minimum rms deviation from the signal envelope using the moving-window method. Examples of use of the developed method for calculating the coordinates of flaws in strength tests of structural elements are considered.     

Technologies for the exploration of highly mineralized geothermal resources

The prospects of the integrated processing of the high-parameter geothermal resources of the East Ciscaucasia of artesian basin (ECAB) with the conversion of their heat energy into electric energy at a binary geoPP and the subsequent extraction of solved chemical compounds from thermal waters are evaluated. The most promising areas for the exploration such resources are overviewed. The integrated exploration of hightemperature hydrogeothermal brines is a new trend in geothermal power engineering, which can make it possible to significantly increase the production volume of hydrogeothermal resources and develop the geothermal field at a higher level with the realization of the energy-efficient advanced technologies. The large-scale exploration of brines can solve the regional problems of energy supply and import substitution and fulfill the need of Russia in food and technical salt and rare elements. The necessity of the primary integrated exploration of the oil-field highly mineralized brines of the South Sukhokumskii group of gas–oil wells of Northern Dagestan was shown in view of the exacerbated environmental problems. Currently, the oil-field brines with the radioactive background exceeding the allowable levels are discharged at disposal fields. The technological solutions for their deactivation and integrated exploration are proposed. The realization of the proposed technological solutions provides 300 t of lithium carbonate, 1650 t of caustic magnesite powder, 27300 t of chemically precipitated chalk, 116100 t of food salt, and up to 1.4 mln m³ of desalinated water from oil-field brines yearly. Desalinated water at the output of a geotechnological complex can be used for different economic needs, which is important for the arid North Caucasus region, where the fresh water deficiency is acute, especially in its plain part within the ECAB.     

The role of the polarization charges in the formation of photoluminescent properties of nanocomposites based on polyvinylidene fluoride and zirconia dioxide nanoparticles

Has been studied the effect of polarization under the influence of corona discharge on the photoluminescence properties and charge state of nanocomposites based on polyvinylidene fluoride and zirconium dioxide nanoparticles. The intensity of the photoluminescence after the polarization increases, and this increasing is concentration-depended. To clarify the reasons of the increase of luminescence intensity, the values of cumulated charges at the interface between the components of nanocomposites in the process of polarization by corona discharge have been studied by TSD method. It is shown that in the process of polarization the injected charges accumulated at the interface, and these charges create a high internal local field,where the polarization of zirconia dioxide nanoparticles occurs. Were calculated the values of the local electric field, contributing to the polarization of ZrO₂ nanoparticles. Was found that the value of the internal local field is high enough to excite new additional luminescent centers in ZrO2 nanoparticles, resulting in increased luminescence intensity. The energy activation of maximum of cross-border charge varies in the interval 0,84–1,1 eV. The thickness of the interfacial layer was calculated and found that increasing of the concentration of ZrO2 nanoparticles led to changes of the thickness of the interfacial layer in the polyvinylidene fluoride with an extremum. The maximum value of thickness observed at a concentration of 5% ZrO2 nanoparticles.     

Hydrogen sorption properties of new magnesium intermetallic compounds with MgSnCu4 type structure

A statistical theory of the MgCeCo₄–H₂ system has been developed for hydrogenation and phase transitions under pressure. The free energy value is calculated. The equation of thermodynamic equilibrium is obtained. The temperature of the order-disorder phase transition is estimated. Isotherms and Isoplethes of hydrogen absorption-desorption are constructed. The possibility of a hysteresis effect is established. The temperature dependence of the hydrogen solubility is found taking into account the phase transition configuration heat capacity. The calculated and experimental graphs of the sorption isotherm are of a similar nature.