Temperature effect on the formation of a relief of diamond-like carbon coatings and its modification by ion bombardment

Diamond-like coatings (DLCs) have been obtained on a UVNIIPA-001 unit employing the method of pulse arc sputtering of a graphite target. DLCs of about 1.5 μm thick were applied onto substrates of the R6M5 steel. The relief of the coatings that were deposited using different temperature regimes has been studied. It has been established that a temperature rise of the surface of a growing DLC (condensation at a high frequency of arc pulses f) leads to the growth of films with numerous protrusions on their surface. The deposition of films at a low frequency f is more preferable to form smooth and hard DLCs under the conditions of unfiltered beam of carbon ions. The modification of the surface of diamond-like carbon coatings after their application has been investigated upon bombardment with accelerated ions of inert gas (argon) or chemically active oxygen. It has been established that the argon-ion bombardment is more preferable to smooth out the DLC relief. It has been shown that the relief of DLCs must be taken into account when measuring their microhardness, whereas the transformation of interatomic bonds in the near-surface layers after ion irradiation should be taken into consideration when analyzing the coatings by the methods whose informative depth is several monolayers.     

Finite element analysis of combined forming processes by means of rate dependent ductile damage modelling

Sheet metal forming is an inherent part of todays production industry. A major goal is to increase the forming limits of classical deep-drawing processes. One possibility to achieve that is to combine the conventional quasi-static (QS) forming process with electromagnetic high-speed (HS) post-forming. This work focuses on the finite element analysis of such combined forming processes to demonstrate the improvement which can be achieved. For this purpose, a cooperation of different institutions representing different work fields has been established. The material characterization is based on flow curves and forming limit curves for low and high strain rates obtained by novel testing devices. Further experimental investigations have been performed on the process chain of a cross shaped cup, referring to both purely quasi-static and quasi-static combined with electromagnetic forming. While efficient mathematical optimization algorithms support the new viscoplastic ductile damage modelling to find the optimum parameters based on the results of experimental material characterization, the full process chain is studied by means of an electro-magneto-mechanical finite element analysis. The constitutive equations of the material model are integrated in an explicit manner and implemented as a user material subroutine into the commercial finite element package LS-DYNA.     

Technological data analysis for pre-emergency situations at gas compressor units

Special features of mathematical models used to describe time dependencies of technological parameters of gas compressor unit (GCU) are analyzed during pre-emergency operation of GCU; the models are developed on the basis of the method of grouped arguments. Principal feasibility for well-timed identification of GCU being in pre-emergency situation is demonstrated.     

A technique for measuring charges of relativistic nuclei in a nuclear emulsion on the PAVICOM automated facility

A technique for measuring the charges of relativistic nuclei in thick emulsion layers irradiated in a longitudinal direction is described. This technique has been implemented on the PAVICOM completely automated facility at the Lebedev Physical Institute. The calibration curves for relativistic nuclei with Z > 3 are presented. The advantages of this technique are demonstrated using charge measurements of ²⁸Si nuclear fragments as an example.     

A speckle-interferometric setup for contactless measurements of the velocity of rayleigh ultrasonic waves

The velocity of a Rayleigh wave was determined by measuring its propagation time between two Iaser-illuminated small areas of a rough surface. It is sh own that, if a Rayleigh wave passes over these areas, a photodiode twice detects signals proportional to the surface displacement in the speckle overlap region. In contrast to the previous variant, signal-distorting reflections are eliminated in the instrument. A sample holder excluding adjustment of the interferometer upon a change in the object size has been manufactured. A new technique for determining the time interval between two signals is used. The instrument operates at a frequency of 5 MHz, and the distance between the areas is adjusted in the range 5–100 mm. The rms deviation of the velocity from the average value for ten measurements is 8 × 10–4.     

Alternate plans and characteristics of design solutions for water-development works under construction at the No. 2 Zagorskaya pumped-storage power plant

Alternate plans and characteristics of design solutions for water-development works under construction at the No. 2 Zagorskaya pumped-storage power plant (PSPP) are described.