Numerical model for calculating displacements near a crack

The paper presents a two-dimensional model of elastic deformations. An isotropic medium region in near a crack propagating along the surface is considered. The results correlate well with an analytical solution. © Published under licence by IOP Publishing Ltd

Numerical implementation of the Lame equation with complex boundary conditions

A discrete model is constructed for calculating the Lame equation with complex boundary conditions. The model is tested on an analytical solution. A complex boundary condition arises when a microcrack is specified on one of the boundaries. Calculation of microcracks will enable better assessment of the relevance of the simulation and finding out which mechanisms will occur in the case of plasma flow heating in modern plasma and future thermonuclear installations. © 2019 IOP Publishing Ltd. All rights reserved

Estimation of the change in the gas flow rate from the surface of a tungsten plate under pulsed heat load

The work is devoted to the numerical implementation of the tungsten evaporation process model. The tungsten evaporation model is based on solving the two-phase Stefan problem for temperature in the sample area and gas dynamics equations over the sample. The calculation results for parameters corresponding to those used on the BETA facility at BINP SB RAS show that it is possible to use the boundary homogeneous conditions of the Neumann for the velocity when setting the gas density on the plate surface. © 2019 IOP Publishing Ltd. All rights reserved

Numerical model of evaporation of tungsten in vacuum under high-power transient heating

On the BETA facility, an electron beam is used for simulation of pulsed thermal loads on ITER-relevant tungsten. Numerical experiments are used for verification of the models. This paper presents extension of the model of electron beam heating, supplemented with dynamics of gas evaporation from a heated surface in vacuum. © 2019 IOP Publishing Ltd

Calculation of current distribution in tungsten plate under exposure to a pulsed electron beam

In the mathematical model of melting of a tungsten plate exposed to a pulsed electron beam, the calculation of the current distribution in the medium is added. The model takes into account the heterogeneity of the resistivity. This enables modeling of non-uniform heated material. The current is expected to spread into the depth due to the increased resistance of the heated part. Changing the thickness of the tungsten plate, one can increase the current density in the melt. The calculation results for parameters corresponding to those used on the BETA facility at BINP SB RAS show that no current concentration occur. The Ampere force is not large enough for the rotation observed in the experiments. © Published under licence by IOP Publishing Ltd

Calculation of the expansion dynamics of evaporated tungsten under the action of a laser pulse

The paper is devoted to the numerical implementation of a model of the dynamics of the tungsten vapors flow evaporating from the sample surface. To calculate the speed and mass flow rate of the substance evaporating from the sample surface, a system of gas dynamics equations is numerically solved. The boundary conditions for the gas velocity and density on the heated surface have a great influence on the solution of the problem. Boundary conditions for temperature are obtained as a result of solving the two-phase Stefan problem in a cross-section of the sample. The aim of the study is to model the erosion of the sample surface and penetration of heat flow into the material. © Published under licence by IOP Publishing Ltd

On the mechanism of surface-parallel cracks formation under pulsed heat loads

This paper presents a model for calculating deformations and mechanical stresses around a crack normal to surface that appeared under pulsed heat load. The model was applied to calculation of stresses that may lead to formation of cracks along the surface, which are observed when tungsten is exposed to ITER-relevant heat load. It was found that such stresses might be not negligibly small in comparison with the ultimate tensile strength, and thus the appearance of cracks normal to the surface may leads to development of cracks parallel to the surface. The calculated deformation of the region around a crack is in good agreement with the experimental data. The deformations calculated can be a basis for experimental detection of formation of cracks normal and parallel to the surface. © 201

Mathematical Simulation of the Distribution of the Electron Beam Current during Pulsed Heating of a Metal Target

Abstract: We study a model of the current distribution during heating of the surface of a tungstensample under pulsed exposure to an electron beam. The model is based on solving the equationsof electrodynamics and the two-phase Stefan problem for calculating the temperature in thesample region using a cylindrical coordinate system. The model parameters were taken fromexperiments at the “Beam of Electrons for Materials Test Applications” (BETA) stand created atthe Budker Institute of Nuclear Physics. The particular case of axial symmetry is consideredwithout taking the electromotive forces into account. The current is considered as a possiblesource of rotation of the substance which is observed in the experiment. The values of the currentand the acceleration of matter at a surface temperature of over 6000K were obtained. The results of the simulationshow that, to obtain an acceleration capable of initiating the experimentally observed rotationof the melt, it is necessary to take into account some alternative mechanisms of creating a currentin the system with consideration of the evaporation of tungsten above the plate. © 2021, Pleiades Publishing, Ltd

In situ study of thermal shock damage to high-temperature ceramics

New generations of fusion devices need alternative plasma-facing materials. The currently approved material composition for the first wall and divertor of the ITER tokamak has a number of disadvantages: insufficient resistance to thermal shock, sputtering of microparticles into plasma and high atomic number Z of the armor material. A promising but largely untested idea is the proposal to use high-temperature ceramics as armor materials for the most heat-loaded plasma-facing components of new-generation fusion devices. Among the advantages of ceramics are the low Z and high enough resistance to intense heating. More research is needed that would help to understand how the material withstands high heat fluxes during transient plasma events. This work is devoted to the description of an experimental method that makes it possible to estimate the critical temperature at which the damage of ceramics begins as a result of a thermal shock of submillisecond duration. As a demonstration of the efficiency of the method, the critical temperature for hot pressed B4C under thermal shock was determined: its value was about 1200–1400 K