Nikolaj Višniakov

Mechanical Properties of Winding Conductors Affected by Cyclic Thermal Overloads

The influence of thermal cyclic overloads on mechanical properties of winding conductors was investigated. Copper-niobium microcomposite, soft and hard pure copper wires were conditioned at temperatures range from 77 K to 500 K. The treatment was done during 100 cycles of fast conductor cooling to liquid nitrogen temperature and further fast heating in a climatic chamber. The ultimate tensile stress limit and the elongation at failure of metal-matrix copper-niobium microcomposite, soft and hard copper wires were measured before and after thermal treatment with a testing machine at room temperature.

Physico-Mathematical Simulation of a Homogeneous Thermal Field of Multichannel Raster Matrixes for Sensors of Oxygen

In the paper, an opportunity for the development of multichannel transcutaneous raster matrixes for sensors of oxygen on the basis of an electrochemical cell sensor is described. An analysis of the influence of heat sources on the distribution of the temperature pattern of a raster matrix for sensors of oxygen had been carried out, and their optimum configuration had been found. The application of such matrixes will enable one to obtain information about the distribution of the partial pressure of oxygen from the skin cover of the object of research in dynamics, to assess its functional health pattern in a more comprehensive way and to control the effect of possible remedial actions.

INVESTIGATION OF THE DYNAMICS OF BODY OXYGEN STATUS UPON LIMITED LOADS

This paper discusses the dynamics of oxygen partial pressure in intercellular fluid upon a limited load and a subsequent post-ischemic hyperemia in healthy individuals and individuals with vascular pathologies of the lower limbs. Within the framework of the phenomenological approach, which takes into consideration the qualitative peculiarities of the gas exchange processes in the body, a formal theory describing the dynamics of oxygen (O2) concentration dependently on the conditions of blood supply to the tissues has been developed. It was shown that certain parameters, for instance the relaxation time upon the conditions of artificial ischemia and the characteristic time of return of spontaneous blood circulation in the post-ischemic period, depend on the degree of pathology of the vascular system and may be used for assessing the functional status of a biological body.

Thermite welding of Cu–Nb microcomposite wires

Abstract Thermite welding of Cu–Nb microcomposite wires was investigated. Suitable compositions of thermite material and slag were determined from the equation of the exothermic combustion synthesis reaction. The phase compositions of the thermite mixture and slag determined by X-ray diffraction analysis correspond to those assessed from the equation. According to non-destructive radiographic testing, the joint structure does not have welding defects. Microstructural examination of the joint cross-section with scanning electron microscopy showed that the Cu–Nb wire retained its shape and microstructure and only a thin surface layer of wire was melted during welding. The difference in electrical resistances of the conductor and welded joint was below 20 %. The thermite joint can withstand a maximum load equal to 62.5 % of the load-bearing capacity of microcomposite conductor.

Welds of Dissimilar Steel 1.0038/1.4301: Increasing Corrosion Resistance by the Optimization of Welding Parameters and Post-Weld Processing

The corrosion of exploited motor vehicles and important or potentially dangerous structures is not a new problem of engineering [1]. However, nowadays, it still remains one of the most burning questions of manufacturing welding structures. There are a number of established methods and technological solutions allowing improvements to the premature corrosion resistance of exploited welded joints and structural elements. In the majority of cases, different protective coatings are used. However, protective coatings are not applicable for some structures in food and medical industry as well as for some other big dissimilar-material structures of a complicated shape. In such cases, the corrosion resistance of welded structures may be provided by other technological means. The present research is aimed at investigating the efficiency of such methods. Several different welding technological solutions and post-weld surface treatments have been applied. The corrosion resistance of the obtained welded joints has been evaluated conducting tests on corrosion under laboratory conditions. The obtained results and conclusions of the present research may be useful for manufacturers solving the problems of the corrosion resistance of welded dissimilar-steel structures.

Simulation of Vibration Resistance and the Ways for Its Improvement on Designing Multistage Constructions

The paper considers the possibility of a theoretical definition of the natural frequencies of vibrations of thermoelectric coolers with a different number of stages and different configurations in the design phase. Determination of natural frequencies of vibrations in parallel was carried out for products, taking into account the damping produced by a number of structural elements as well - without taking into account the damping capacity of the solder layers at the ends of thermocouples. The analysis and comparison of the theoretical results were carried out. The results of the calculation determining the natural vibration frequencies of thermoelectric coolers (TEC) through a system of Lagrange equations of the 2nd kind were compared with the calculated values obtained by using the method of electrodynamic analogies.

The Mechanism of Defects Formation in Silicon Substrates

Components of navigating devices can be affected by acoustic emission and vibration. Therefore prototype samples and electronic components must be tested in such conditions. Heterostructures, which destructed under the action of external physical factors and kinetics of formations of porous defects in silicon substrates, were analyzed.

The Application of Composite Materials in Pulsed Inductor Design

The multilayer construction of metal-matrix Cu-Nb microcomposite wire wound Zylon-epoxy composite reinforced inductor is analyzed. Inductor geometry was verified analytically to find the maximal available value of a magnetic field. For comparison, the soft copper wire wound inductor was made by the same geometry and technology and both inductors were investigated at room and liquid nitrogen temperatures. Experimental results were compared with calculated data. The acceptable agreement of calculated and measured data for soft copper wire wound inductor and the significant decrease of amplitude and distortions of sinus shape pulse due to weak heat dissipation of metal-matrix Cu-Nb wire wound inductor took place.