The development of engineering and technology necessitates the search for new solutions related to the release of innovative products with high added value, which include long-length cold-worked ...screw sections. An analysis of the methods for producing long screw profiles is made, as a result of which a new method is proposed that differs from the known methods by the absence of a twisting operation for forming a helical surface. This feature of the new method for producing long screw profiles simplifies the design of the device and reduces energy consumption. The influence of the workpiece diameter and the number of passes of the helical surface on energy consumption was studied, and a comparative schedule was constructed that proves the advantages of the proposed method for producing screw sections by drawing. For the strength analysis of equipment, a dependence is proposed by which the force that occurs when drawing long screw profiles can be found, taking into account the deformation conditions and design features of the device forming the screw surface. Using the fourth theory of strength, a dependence is obtained to determine the condition that guarantees the absence of breaks in the process of drawing a screw profile.
Currently the most accurate measurements of neutron lifetime are being performed at the Petersburg Nuclear Physics Institute with ultracold neutrons (UCNs) stored in a gravitational trap. A modified ...setup with a large gravitational trap and cooling to 10–15 K is presented. The results of measurements of temperature dependence of UCN losses in collisions with walls, which were coated with a perfluorinated grease (Fomblin UT 18), at 300–77 K, are detailed. The probable heat inflow to the trap is estimated, and the feasibility of cooling to indicated temperatures in experiments with the modified setup is demonstrated.
The study results of the copper alloying effect on the microstructure and thermal coefficient of linear expansion (TCLE) of high aluminum alloys for special purposes based on the Al - (20÷30)% Si ...system are presented. It was found that alloy building of Al - 20% Si with copper in large quantities eliminates the linear expansion anomaly characteristic to the binary alloy and leads to a significant decrease in the thermal expansion coefficient over the entire temperature range of the tests. It was shown that Al-30%Si-20÷40% Cu alloys have stable TCLE in the low-temperature test interval. Metallographic analysis of high alloys showed that copper introduced in amounts of more than 20% contributes to a change in the morphology of the silicon phase and triple eutectic.
During the manufacturing of continuous welded rail track, the problem of the local hardened points in the welded joint during rail joint welding is resolved by using local heat treatment of the ...welded joint. As a result, the quenching structure formation is excluded. However, the appearance of new heat-affected zones with reduced hardness is possible. During operation, such rails are characterized by increased tread surface wear in these areas and rail flattening at the welded joint, which is the main reason for retiring the rails from service earlier than the guaranteed service life. A new technology based on the dependence of the structural component dispersion (primarily perlite and carbide particles formed in the process of rail butt welding) is proposed for the steel composition and cooling conditions. The cooling rate has a decisive influence on the dispersion degree of the ferrite-cementite structure formed during the austenite decomposition. During the welding rail process, the granular perlite formation is possible in a butt weld in areas with a temperature ranging within points
Ac
1
and
Ac
m
. To determine these critical temperatures, thermodynamic calculations were performed using the Thermo–Calc® software (TCFE database) allowing the chemical composition of the samples obtained by spectrometry. The iron–carbon state diagrams for rail steel 76KhSF with the minimum and maximum alloying element content according to GOST R 51685–2013 are modeled. To obtain the minimum number of sections with reduced hardness, it is possible to weld rails using shot discontinuous flash welding. In order to eliminate the formation of defective areas with a quenching structure, it is possible to control the cooling of the welded joint by contact heating. Temperature distribution measurement during welding according to given modes and controlled cooling confirms the theoretical conclusions.
The possibility of producing flux-cored wires based on dust from gas cleaning plant of aluminum production, silicon and aluminum powders (as a reducing agent) and gas cleaning dust from ferrochrome ...production (as a reducible component - chromium oxide) was studied. In the laboratory conditions samples of flux-cored wires were produced, surfacing, hardness measurement, abrasion rate and metallographic studies were performed.
A combination of corrosion resistance, low specific gravity, and high dimensional stability over a wide temperature range is necessary for alloys for special purpose. The dimensional stability is ...determined, first of all, by the low temperature coefficient of linear expansion (TCLE). The paper presents the results of studies on the effect of melt treatment on TCLE of aluminum alloys for special purpose on the basis of the system Al-(11÷40)%Si. It is shown that melt treatment with an aqueous solution of CuSO4 and modification of melt with a mixture of (CaCO3⋅MgCO3) leads to the decrease in TCLE for all alloys under consideration in the low-temperature test interval ttest = 50÷150 °C. Treatment of the melt by CO(NH2)2 vapours leads to the decrease of TCLE of alloys Al-40%Si in the whole temperature range from 50 to 450 °C. For high silicon alloys it is established that the decrease in TCLE occurs in the interval ttest = 350÷450°C after additional heat treatment
We study magneto-optical trap (MOT) of Mg atoms operating on the closed triplet 3P2→3D3 (λ = 383.3 nm) transition formed by the light waves with elliptical polarization (ε−θ−ε¯ configuration). ...Compare to well-known trap formed by light waves with circular polarization (σ+-σ− configuration) the suggested ε−θ−ε¯ configuration offer the lower sub-Doppler temperature for trapped Mg atoms, that can't be reached in conventional σ+-σ− MOT.
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The main characteristics of memristive elements based on polythiophene made by Langmuir-Schaefer and spin-coating methods have been compared. The stability of the elements for more than 500 cycles ...of electric rewriting for both methods has been demonstrated. It has been shown that the elements made by spin-coating method have slower switching kinetics, which, presumably, is associated with relatively higher homogeneity of the film surface. This research may be useful for the development of polythiophene memristive devices with reproducible stable characteristics suitable for various applications: from memory elements to wearable and implantable electronics, and neuromorphic computing systems.
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