Aspects of obtaining electrodes with a coating containing tungsten nanopowder are considered along with their modes of utilization for surfacing purposes. The rheological properties of an aqueous ...alkaline solution of potassium silicate used for applying tungsten nanopowder to electrodes are determined. The stability of the surfacing process is investigated in terms of the structure of the metal deposited with coated electrodes. It is confirmed that coating electrodes with tungsten nanopowder can be used to derive a stable process of transferring droplets of electrode metal into the melt bath and modifying the deposited metal by influencing the viscosity of the coating of combined electrodes.
Intense beams of charged particles serve as a working element in electrophysical devices for a wide range of scientific and practical applications. Mathematical modeling of intense beams leads to the ...solution of a self-consistent nonlinear problem, which includes the calculation of electric and magnetic fields, trajectories of charged particles, and space charge. An extended electron-optical system is understood as an electron-optical system whose size in the direction of the beam’s motion is much larger than the transverse size. The use of traditional computational approaches to modeling such systems did not give satisfactory results. In this paper, we propose new algorithms and technologies aimed at improving their accuracy and reducing the calculation time. They are based on computational domain decomposition methods and are as follows. First, the extended computational domain is divided into two subdomains: in the first subdomain, an intense beam is formed, and in the second subdomain, it is additionally accelerated and transported. The solutions are “stitched” by the alternating Schwarz method. Second, in each of these subdomains, an adaptive quasi-structured locally modified grid is constructed, consisting of structured subgrids. The proposed quasi-structured grid can significantly reduce labor costs when calculating the trajectories of charged particles. Third, on the emitter, the singularity is isolated by introducing a near-emitter subdomain. In this subdomain, an approximate analytical solution is constructed, which is stitched with the numerical solution in the main subdomain in the iterative Broyden process. On the example of a model problem about a flat diode, the fast convergence of the Broyden method is shown. With the help of the proposed algorithms and technologies, the results of modeling a complex practical system are obtained, which closely match the results of natural experiments.
An experimental study of the efficiency of solvers of 2D boundary value problems on subgrids of quasi-structured rectangular grids is carried out. A solver means a solution method and its software ...implementation. The following three solvers are considered: a direct solver (Buneman’s cyclic reduction method) and two iterative ones (the alternative direction method of Peaceman and Rachford and the successive overrelaxation method). Characteristic features of the study are as follows: 1) the subgrids have a small number of nodes, namely 8 × 8, 16 × 16, 32 × 32, and 64 × 64; 2) the efficiency is estimated not only for single calculations, but also for series of calculations; in each of them the problem is repeatedly solved with different boundary conditions on the same subgrid. Based on a series of calculations, a combined method is proposed, and recommendations on using the solvers are given.
Recent results from the CMD-3 detector Lukin, P.A.; Akhmetshin, R.R.; Amirkhanov, A.N. ...
Nuclear and particle physics proceedings,
January-March 2020, 2020-01-00, Volume:
309-311
Journal Article
Peer reviewed
This paper reports a current status of the measurements of the hadronic cross sections in the c.m. energy range from 0.32 to 2.0 GeV with the CMD-3 detector at the VEPP-2000 electron-positron ...collider. The overall size of the data, acquired by the CMD-3 in the runs of 2010–2013 and 2017–2018 years, is about 160 pb−1. The results of data analysis for various exclusive modes of e+e−→hadrons are described.
The influence of the welding energy-technological modes on the physical and mechanical properties of weld seams obtained by submerged arc welding, made on the basis of silicomanganese slag, is ...determined. Various welding modes allows the required penetration depth and the absence of external defects is investigated. It is shown that changes in the current strength value, welding speed and voltage exert influence upon the physical and mechanical properties of the weld seam and the hydrogen concentration in the weld seam.
The article describes the welding process study with the subsequent control of cooling for full-profile rail joints, produced by passing alternating electric current pulses after welding. The welding ...mode influence on the welded joint quality was investigated. Welding was carried out on a resistance butt welding machine MCP-6301 in conditions of the rail welding company OOO RSP-M (RSP-29). For research, the samples of P65 type full-profile rails of DT350 category 600 mm long were cut out. The isothermal holding conditions after welding were controlled using a personal computer with a change in the program of the SIMATIC S7-300 industrial controller and the software SIMATIC STEP 7, which allows modes of controlled cooling to be set. The control program was written in the LAD graphic language. To search for optimal modes of controlled cooling, a complete factor experiment
N
= 2
k
was carried out. Non-heat-treated joints were tested for three-point static bending according to the state standard STO RZD 1.08.002 – 2009 “Railway rails, welded by electric contact method”. Static bending tests were carried out on the press of PMS-320 type. Values of the force arising during bending
P
bend
and the bending deflection
f
def
at which the control sample is destroyed, were determined. The maximum values of these indicators were also determined if the sample was not destroyed during the tests. During the experiments, regression models were obtained for output parameters of the bending force and bending deflection. Sample macrostructure and metal hardness distribution on rolling surface of the rails welded joint were studied. A new method of resistance butt welding was developed, which makes it possible to obtain a welded connection of P65 type rails of DT350 category with properties that exceed the technical requirements of the mentioned state standard.
A welding flux containing silicomanganese slag with a flux additive based on dust taken from gas cleaning facilities of aluminum industry has been studied. The following has been studied: the effect ...of a carbon-and-fluorine-containing additive exerted on the content of total oxygen and hydrogen in the welding seam’s metal, as well as on the impact strength in the positive and negative temperature range. To make the welding flux, silicomanganese slag produced by the West Siberian Electrometallurgical Plant has been used as a base. Also, a flux additive has been used to make carbon-and-fluorine containing dust taken from the electrostatic precipitators of RUSAL’s aluminum-producing enterprises. The samples have been welded using an ASAW-1250 welding tractor. The chemical composition of the welded samples under study has been determined according to GOST (State Standard) 10543–98 by means of an atomic emission technique using a DFS-71 spectrometer and by means of means of an X-ray fluorescence technique using an XRF-1800 spectrometer. Fractional gas analysis has been performed using a LECO TC-600 analyzer. The welded samples have been tested for impact strength in the positive and negative temperature range using a pendulum impact testing machine according to GOST (State Standard) 9454–78. Upon using a carbon-and-fluorine-containing flux additive in the welding flux based on silicomanganese slag, the amount of oxygen and hydrogen in the welding seam’s metal exhibits a decrease. At the same time, the impact strength in the positive and negative temperature range exhibits an increase. The curves for the amount of oxygen and hydrogen in the welding seam’s metal, as well as for the impact strength depending on the introduced amount of carbon-and-fluorine-containing flux additive, are plotted.
Using the methods of modern physical materials science, the structural phase state, the defect substructure and the fracture surface of low-carbon alloy steel welds formed with and without ...carbon-containing additionы are studied. A quantitative analysis of the structure and dislocation substructure parameters of the weld metal is performed. The contributions from the scalar and excess dislocation density to the weld metal strength are estimated. It is noted that for a weld formed without any carbon-containing addition the level of internal stress fields is higher, which may result in the material embrittlement.
This paper reports measurements of the hadronic cross sections with the CMD-3 detector at the VEPP-2000 electron-positron collider. The overall size of the data sample analyzed is about 60 pb-1, ...collected by the CMD- 3 running since December 2010 up to June 2013 in the c.m. energy range from 0.32 to 2.0 GeV. The preliminary results of data analysis for various modes of e+e−→hadrons are discussed.
Abstract
To ensure the quality of the welded rail joint, a study of the level of contamination with non-metallic inclusions of E76KhF rail steel (base metal and weld seam) was carried out. It was ...found that the predominant type of nonmetallic inclusions in welded joints in all studied samples are point oxides. It is shown that the modes of resistance butt welding do not affect the contamination of the samples.
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