Calculation of stationary heat transfer zone in conduits under cooldown

The heat transfer zone was investigated theoretically as a one-dimensional problem for the cooldown of cryogenic conduits with constant and temperature-dependent physical parameters. It was found that at constant parameters the stationary heat transfer zone does not reach its finite value. If the heat capacity of the conduit wall increases with temperature, the zone assumes a stationary value. The analytical expressions derived allow the heat transfer zone to be calculated. Recommendations are offered on the application of the equations to estimate the cooldown time and the axial and transverse temperature gradients within the heat transfer zone.     

Physicomechanical and exploitation properties of nanostructured wear-resistant ion-plasma vacuum-arc coatings on the basis of multicomponent nitrides

This work is devoted to an investigation of the hardness (H), modulus of elasticity (E), and adhesion-cohesion strength of ion-plasma vacuum-arc coatings of the Ti-Cr-Al-N system. It is shown that the magnitudes of H and E are determined by the crystallite size and microdeformation level. The maximum values of hardness (up to 32 GPa) and modulus of elasticity (up to 700 GPa) correspond to coatings with a minimal crystallite size and maximal magnitude of microdeformatons. Wear of coatings is accompanied by the cohesion destruction. The adhesion strength of coatings is evaluated at about 90 N. The resistance of the cutting hard-alloy tool with coatings for the continuous and interrupted cutting of 38XHMA steel has been increased by a factor of 5.1 and 5.7, respectively.     

Prospects for using annular fuel elements in nuclear power engineering

Prospects for enhancing heat transfer in the core of reactor plants by using annular fuel elements are considered. Advantages of changing over to use of annular fuel elements are analyzed, and problems that must be solved are identified. It is shown that application of annular fuel elements makes it possible to increase the specific power of a reactor while keeping its safety indicators at a high level.     

Properties of nanostructured TiN-Ni ceramic-metal coatings obtained by ion-plasma vacuum-arc method

Physicomechanical and tribological properties of TiN-Ni ceramic-metal coatings prepared by ion-plasma vacuum-arc deposition are investigated. It is established that the hardness (H) increases from 23 to 54 GPa with the Ni content from 0 to 12 at %, which is determined by the influence of the nanostructured nitride component of coatings. Coefficients HE ^?1 and H ³ E ^?2, which characterize the material resistance against the elastic and plastic failure deformation, reach 0.104 and 0.567 GPa, respectively. The further increase in the nickel concentration in coatings to 26 at % leads to a decrease in H to 23–25 GPa, which is associated with the influence of the increasing amount of soft plastic metal and the formation of noticeable porosity in the bulk of coatings. The friction coefficient of studied coatings is 0.45, against 0.58 (for the TiN coating) and 0.72 (for the hard-alloy base). The cohesion failure mechanism of TiN-Ni nanostructured coatings (C _Ni = 2.8–12 at %) is established, and critical loads which characterize the appearance of the first crack (13.5–14.2 N) and the local coating attrition up to the substrate (61.9–64.4 N) are determined. The complete attrition of coatings does not occur up to a load of 90 N, which points to their high adhesion strength. The developed nanostructured ceramic-metal coatings are characterized by high heat resistance up to 800°C.     

Superhard Nanostructured Ceramic–Metal Coatings with a Low Macrostress Level

Technical Physics Letters - The macrostressed state of (Ti,Al)N–Cu and (Ti,Al)N–Ni ceramic–metal coatings obtained by the arc-PVD method has been studied using X-ray diffraction...     

Discretization of quasilinear evolution equations by computer algebra methods

An algorithmic approach to construction of finite difference schemes on regular grids developed by the first two authors is applied to quasilinear evolution equations in one spatial variable. The approach combines the finite volumes method, numerical integration, and difference elimination, which is done by means of computer algebra. As a concrete example, a difference scheme for the Korteweg-de Vries equation is constructed. This scheme is strongly consistent and absolutely stable. The numerical behavior of the scheme obtained is illustrated by solving a Cauchy problem.