Dynamics of a heterogeneous polymer system obtained as a result of a conductor explosion

The performed studies allowed us to obtain a composite with regulated structure formation at ?? ?? 0.06 vol % of copper and directed changes of the electrophysical properties in a dielectric using the explosion of a conductor.     

Dynamics of a magnetization-reversal nucleus in a ferromagnet

This paper is devoted to a theoretical investigation of the effect of an applied magnetic field and damping on the dynamics of magnetization-reversal nucleus represented by interacting domain walls (DWs) with opposite topological charges. It is shown that at initial amplitudes that are less than the amplitude of the critical nucleus of magnetization reversal, nonlinear vibrations of strongly interacting DWs are observed. In the presence of dissipation, the nonlinear vibrations are damped vibrations with a frequency that changes with time. At the initial amplitudes that are greater than the amplitude of the critical nucleus, the magnetization-reversal nucleus decays with the formation of a solitary domain. The motion of two interacting 180° DWs relative to their common immobile center in fields that are less than the Walker field is translational; in higher fields, it is oscillatory. It is shown that DW vibrations are accompanied by a periodic transformation of their structure from Bloch into Néel and vice versa with a frequency that depends on the field, damping, quality factor, and the initial amplitude of the magnetization-reversal nucleus.     

Study of a Neural Network with a Meta-layer

We consider the network studied by Amit et al. (i.e. a network that is quite closely related to the Hopfield model). We show that it is possible to save a significant amount of connections if it is reinterpreted as a two-layer system. One of the layers can be interpreted as the basis layer and the other one as a meta-layer. This system is suited for the storage of orthogonal groundstates. However, an extension of the meta-layer allows one to store mixture-states (multicomponent states) as well. This bears a system in which taxonomies as well as looser associative links can be stored. Due to the topological properties of the mixture-states, the system can be provided with a learning rule according to which the memories reorganize in a way that is suited for some aspects of genetic psychology     

Cracking of a Cobalt-Based Hardfacing of a Gate Valve Disk in a Desalination Power Plant

Cobalt-based alloys of the Stellite family are used as hardfacing for sealing surfaces of valves operating in desalination and power plants because of their excellent low friction and anti-galling properties in high-load sliding contact under the prevailing conditions. However, insufficient control of pressure and temperature during operation can degrade the integrity of the hardfaced material thus leading to its premature failure. This article presents a failure investigation carried out on the disk of a main stop gate valve that was used in a desalination plant. The disk was manufactured from X20 as a substrate material and a cobalt-based alloy for hardfacing. The cobalt-based hardfacing suffered from many surface and subsurface cracks that degraded its integrity. It was concluded that high-pressure steam flowing against the disk had tilted it and, thus, disturbed the alignment between the surfaces of the disk and the seat, leading to wear and large frictional heat that resulted in the degradation of the microstructure of the hardfacing layer and formation of the observed cracks.     

Formation of a Rhenium-Base Coating on a Nb-Base Alloy

To protect Nb–5Mo–15W alloy against high-temperature oxidation a novel coating was developed involving electroplating of a Re–Ni film, followed by pack cementation with Cr and Al. The coating consisted of a duplex-layer structure, an inner (Re–Cr) or Re(Cr) layer and an outer Cr(Al) or NiAl layer. The Re–Ni film containing more than 70at.%Re, developed in the present investigation, is more useful than the conventional low Re–Ni film. The inner (Re–Cr) and Re(Cr) layer acts as a diffusion barrier between the Nb–5Mo–15W alloy substrate and the outer -Cr(Al) or -NiAl layer, which forms a protective -Al₂O₃ scale. The coated Nb–5Mo–15W alloy was oxidized in air at 1373K for up to 360ks, showing very good oxidation resistance.     

The development of a high-speed spindle measurement system using a laser diode and a quadrants sensor

Reducing the manufacturing time is the trend of precision manufacturing, and the precision of a work-piece is very important for manufacturing industry. High-speed cutting is becoming more widely used and the high-speed spindle is a very important element, whose precision may affect the overall performance of high-speed cutting. Most of the studies on high-speed cutting are focused on the cutting force, the vibration of the spindle and the effects of the spindle's thermal expansion; however, the measurement of the high-speed spindle continues to use the conventional spindle measurement method.As with the measurement of the high-speed spindle, more strict demands are set on the dynamic balance of cutting tools and the bandwidth of the measurement systems when compared with common spindles. The capacitance displacement sensor has been employed for the spindle error test. The precision of the measurement system is limited by the reference (such as a master ball or a master cylinder). Also the capacitance sensor and the reference must be grounded together. This paper presents a simple spindle measurement system using a laser diode and a quadrants sensor, with accuracy up to 1 μm, within 300,000 rpm for various spindles. The system does not need any reference and it is easy to set up. This system can be applied to measure the spindle errors, the spindle speed and the spindle indexing.     

Characterization of a cyclic displacement instability for a thermally grown oxide in a thermal barrier system

The mechanism responsible for the performance of a commercial thermal barrier system upon thermal cycling has been investigated. It comprises an electron beam physical vapor deposited (EB–PVD) yttria-stabilized zirconia thermal barrier coating (TBC) on a (Ni,Pt)Al bond coat. At periodic interfacial sites, the thermally grown oxide (TGO) that forms between the TBC and the bond coat at high temperature displaces into the bond coat with each thermal cycle. These displacements induce strains in the superposed TBC that cause it to crack. The cracks extend laterally as the TGO displaces, until those from neighboring sites coalesce. Once this happens, the system fails by large scale buckling. The displacements are accommodated by visco-plastic flow of the bond coat and “vectored” by a lateral component of the growth strain in the TGO. They depend upon the initial morphology of the metal/oxide interface. The observed responses are compared with the predictions of a ratcheting model.     

On the drift properties of a wave packet propagating along a charged surface of a liquid

An analytical expression is constructed to estimate the influence of a surface electric charge on the drift velocity caused by the propagation of a wave packet on a horizontal surface of an ideal fluid. It has been shown that the surface electric charge affects the drift most effectively if the wavenumber of the carrier wave is equal to the inverse value of the capillary constant. Common regularities of the drift motion are established.     

Fabrication of a porous material with a porosity gradient by a pulsed electric current sintering process

A porous structure with a porosity gradient can be applied to the preparation of continuous FGM, where liquid or chemical vapor of the second phase is infiltrated into the graded pores. It also has applications in skeletal implant materials and ultrafiltration media. An attempt was made to fabricate a porous material with a porosity gradient by means of a pulsed electric current sintering (PECS) process. The present work describes not only the measured value of the temperature difference between the upper and lower part of the specimen, which brings about a gradual change in pore distribution, but also the sintering characteristics of the porous structure obtained by the pressureless PECS process.     

Structure and properties of a diamond-containing composition material with a tungsten-free matrix for a truing tool

Conclusion The composition material that we developed on the basis of synthetic diamonds, titanium carbide, and abundant metals — titanium and nickel — which are used in fabricating inserts for a truing tool, posses a low melting point and high strength, retain diamonds well, and are unsurpassed by a natural-diamond tool in terms of serviceability.Institute of Superhard Materials, Academy of Sciences of the Ukrainian SSR. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 11, pp. 47–50, November, 1986.