Numerical and Experimental Investigation of the Impact of the Electromagnetic Properties of the Die Materials in Electromagnetic Forming of Thin Sheet Metal

In electromagnetic forming of thin sheet metal, the die is located within the effective range of the electromagnetic wave. Correspondingly, a current is induced not only in the sheet metal, but also in the die. Like the current in the workpiece, also the current in the die interacts with the electromagnetic wave, resulting in Lorentz forces and changes of the electromagnetic field. With the aim to study the influence of different electromagnetic die properties in terms of specific electric resistance and relative magnetic permeability, electromagnetic simulations were carried out. A change in the resulting forming forces in the sheet metals was determined. To confirm the simulation results, electromagnetic forming and embossing tests were carried out with the corresponding die materials. The results from simulation and experiment were in good agreement.

Studies of Changes in the Electrical Resistivity of Rocks of the Tashtagol Mine in a Critical Rock-bump Hazardous State Based on the Kinetic Concept of Solids Destruction

Main hypotheses of the occurrence of seismic events centers, including rock bumps are presented. Equations of kinetic theory of strength are given. A two-stage kinetic model of crack accumulation and catastrophic destruction of rocks is formulated. It consists in the fact that at the first stage of the rock bump preparation there is a diffuse accumulation of cracks, and at the second — merging of cracks, appearance of enlarged cracks and formation of the destruction center. The results are presented concerning the theoretical and laboratory measurements of change of specific electric resistance of the host rocks and ores of iron ore deposit at mechanical loading and destruction. It has been shown that the relative change of specific electrical resistance of the low conductive rocks depends significantly on the ratio of electrical resistance of the rock itself and charged zones near the surface of the incipient cracks during rock loading. With the accumulation of cracks in the process of mechanical loading of the host rocks of the Tashtagol mine, the number of charged point defects of the structure on the crack edges increases. Specific electrical resistance of such rocks decreases with the accumulation of the number of cracks. In the ore bodies and magnetic iron ores, on the contrary, with increasing disturbance, the electrical resistance increases. There is regular change in the electrical resistance of rocks in the intermediate and limit states. For ores and magnetic iron ores, the critical change is 40 %, and for the host rocks with high electrical resistance — 28–37 %. Obtained values of change of the specific electric resistance in the rock critical state can be used for prediction of the rock bumps.

Reasons for low-resistant oil formations, criteria of their selection and productivity evaluation

The paper reviews the issues of low-resistivity of oil-saturated formations and analyzes the studies carried out in this direction as well. The definition of specific electric resistance plays a significant role in the selection of reservoir-beds and the evaluation of their productivity. The analysis of the complex of downhole geophysical surveys conducted in Azerbaijan territory justifies that in some cases the geological section consists of the layering of formations with anisotropic properties varying by their resistance and permeability. Neglecting such aspects in the data processing and interpretation leads to the distortions. In the definition of oil saturation of soil units consisting of sand-clay interlayers’ alternation, it is practical to consider the anisotropic nature and comparisons “resistance correlations”.

The Influence of Storage Conditions on the Electric Conductivity of Concrete

Theoretical and experimental investigations of the influence of concrete moisture, its age, holding conditions after its thermal moisture treatment and other factors on the specific electric resistance of the concrete of a C32/40 grade used for reinforced concrete sleepers have been carried out. The obtained research data allowed us to specify holding modes and the duration of them and these enable the generation of objective information on the specific electric resistance of the concrete used for the sleepers during their operation.

Analysis of the results of thermal treatment of single crystals of silicon doped with boron impurity

Two groups of plastins of single-crystals of silicon doped with boron, were preliminary grown by the method of Chochralsky and thermally treat. Got values of specific electric resistance at different terms realizations of heat treatment served as a weekend by data. On the basis of the obtained experimental data were conducted: analysis of variance of the matrix system, estimation of results on the criterion of Cochren and Student. Built mathematical models. Determination of values of optimal technological parameters allowed objectively, taking into account influence of factors, to educe the maximum-possible circle of values for the receipt of necessary results. For basis accepted the change of temperature of heat treatment and time of self-control. All got experimental job performances are recreated and real at the construction of matrix of planning.

The depth range of the Earth'snatural pulse electromagneticfield (or ENPEMF)

On the basis of the analysis of the literature sources, we determined the possible range of using the method of the Earth`s natural pulse electromagnetic field. As a result of detailed analysis of domestic and foreign research, we demonstrated the relevance of conducting research focused on development of the Earth'snatural pulse electromagneticfield (or ENPEMF). Using the results of theoretical studies, the advantages and disadvantages of the ENPEMF method were determined. A complex of physical processes which preceded the development of the pulse electromagnetic field of the Earth was characterized, and the impact of mechanical deformations of rocks on the change in the condition of the electromagnetic field was experimentally proven. The main fundamentals on the determination of depth range of the ENPEMF method were examined and a new approach to interpretation of the data was suggested. We conducted an analysis of methods developed earlier of calculating geometric parameters of the sources which generate electromagnetic impulses. Their practicability at a certain stage of solving the data of geological tasks was experimentally tested. We determined the factors which affect the depth range of the ENPEMF method. A mathematical solution of the effectiveness of the ENPEMF method was suggested and determined the relations between the depth parameter of the study and the frequency of measuring and effective value of specific electric resistance. On the example of different objects, the effectiveness and correctness of the suggested method of determining the depth range parameter was proven. In particular, the theoretical results of the study were tested and confirmed on objects of different geological-morphological and engineering-technical aspects, i.e. Novo-Holyn mine in the Kalush-Holynske potash deposit and the multi-storey educational building of the University in Ivano-Frankivsk. The practicability of using the ENPEMF method in combination with other methods of electrometry for solving practical geological tasks was experimentally proven.

Thermoelectric High Power Generating Module Made by n-Ba8AlxSi46-x Clathrate

We have developed a new thermoelectric power-generating module composed of 72 pieces of n-type Ba8Al18Si28 clathrate elements made by arc melting. The Seebeck coefficient, specific electric resistance and thermal conductivity of Ba8Al18Si28 clathrate were 250 μV/K, 1.9 mΩcm and 3.1 W/mK at 500 °C, respectively, and the thermoelectric figure of merit (ZT) was 0.8. The new thermoelectric module was constructed using only n-type thermoelectric elements connected in series with hook-shaped electrodes. The open-circuit voltage of the module increased with hot-side temperature up to 1.8 V at 500 °C and generated 0.24 W. The module was successfully used to charge lithium-ion batteries for mobile phones.