The technology of combined processing of extruded materials

The paper considers the peculiarities of combined processing of parts, made from extruded metal blanks with anisotropic electrotechnical properties. It involves the application of an electric field and seeks to achieve the required profile accuracy in any processing direction with precision within the specified tolerance for finishing operations. The study describes the specific nature of the development of current leads and the ways of achieving the required accuracy when combining electro-erosion and electrochemical components of the process in real time, taking account of the position of the pressing force vector relative to the direction of current flow in the zone of combined processing. This gives the opportunity to ensure the process stability and accuracy of processing advanced materials with a wide range of current conductivity variation in components, used when extruding blanks for precision parts. The study employs the methodology of calculating and assigning technological modes of combined processing, formed on the basis of the energetic approach and using the principle of similarity in technological systems. It also involves the adapted process management which allowed for elimination of unstable impacts affecting the accuracy of shape formation and surface layer quality, and expands the area of using combined processing for manufacturing extruded parts with anisotropic properties of components. The article presents the feasibility study of the ways of extending the work results to various types of products, particularly, to processing of welded and soldered joints of metallic materials and coated details where the replacement of traditional processing methods with combined ones significantly increases the opportunities for obtaining high-precision parts with required performance characteristics

The combined finishing of geometrically-complex parts

The paper describes the combined hydroabrasive dimensional processing, which involves the application of an electric field of metal parts with complex volumetric profiles, requiring jet control with reference to 5-6 coordinates. One should also consider the reciprocal impact of technological parameters upon formation of parts machined. The mechanism of dimensional material removal has been developed, which is the basis for working out the informational technology of a combined process. The objects of study are adjoining parts of spatially complex surfaces, like gas-turbine engine blades, or axial and radial wheels of turbopump units, as well as the processes of unsoldering in cooled parts of combustion chambers, jet nozzles and complex-shaped part sections with limited tool access into the processing zone, including those made from materials of low machinability. The combined process of hydroabrasive finishing has been developed, which involves the induction of electric current for geometrically-complex surfaces of any geometry, including in areas, inaccessible or hardly accessible for a metal-cutting tool when manufacturing parts from alloys of low machinability

The bactericidal effect of continuous wave laser with strongly absorbing coating at the fiber tip

The bactericidal effect of laser radiation with a quartz fiber-based transmission system with a strong absorption coating converter against bacteria associated with urological stones has been studied. Gram-negative rod Escherichia coli and the Gram-positive coccus Staphylococcus epidermidis, Staphylococcus aureus, Enterococcus faecalis and Enterococcus faecium were used in this study. Each bacterial species was treated by continuous-wave near infrared laser coupled with bare fiber tip or strongly absorption coating fiber tip. After treatment, the temperature of bacterial suspension was measured. In addition, the temperature distribution was analyzed. It has been shown that using laser with a strongly absorption coating fiber tip results in significant bactericidal effect. The decrease of the amount of E. coli and S. epidermidis was 100% after treatment with an output power of 6W of radiation at a wavelength of 0.97μm for 40s. Number of S. aureus and Ent. faecium colony-forming unit was reduced to 70% after same exposure. The peak temperature of bacterial suspension was 86∘C after treatment by laser with a strongly absorption coating fiber tip. Laser with a strongly absorption coating fiber tip provides large-scale hydrodynamic flows directed away from the fiber tip. The laser with a strongly absorption coating fiber tip has bactericidal effect. The main role is associated with the effect of high temperature, which, in the form of flow in a liquid medium, affects bacteria

Polymer Nanocomposite Containing Palladium Nanoparticles: Synthesis, Characterization, and Properties

Composite nanomaterials have been prepared through thermal decomposition of palladium diacetate. The composite contains palladium nanoparticles embedded in high-pressure polyethylene. The materials were studied by a number of different physico-chemical methods, such as transmission electron microscopy, X-ray diffraction, X-ray absorption spectroscopy, electron paramagnetic resonance, and EXAFS. The average size of the nanoparticles is 7.0 ± 0.5 nm. It is shown that with the decrease of metal content in the polymer matrix the average size of nanoparticles decreased from 7 to 6 nm, and the coordination number of palladium also decreased from 7 to 5.7. The mean size of palladium particles increases with the growing concentration of palladium content in the matrix. It is shown that the electrophysical properties of the material obtained depend on the filler concentration. The chemical composition of palladium components includes metallic palladium, palladium (III) oxide, and palladium dioxide. All samples have narrow lines (3–5 Oe) with a g factor of around two in the electron paramagnetic resonance (EPR) spectra. It is shown that EPR lines have uneven boarding by saturation lines investigation. The relaxation component properties are different for spectral components. It leads to the spectrum line width depending on the magnetic field value. At first approximation, the EPR spectra can be described as a sum of two Lorentzian function graphs, corresponding to the following two paramagnetic centers: one is on the surface, and one is inside the palladium particles. Some of the experimental characteristics were measured for the first time. The data obtained indicate interesting properties of palladium-based nanocomposites, which will be useful for obtaining products based on these materials

Coastal Polynya Disrupts the Acoustic Backscatter Diurnal Signal Over the Eastern Laptev Sea Shelf

The diel vertical migration (DVM) of zooplankton is one of the largest species migrations to occur globally and is a key driver of regional ecosystems and the marine carbon pump. The dramatic changes in the Arctic environment in recent years, mainly associated with sea-ice decline, may have wide significance for the Arctic shelf ecosystems including DVM. Observations have revealed the occurrence of DVM in ice-covered Arctic waters, however, there have yet to be observations of DVM from the extensive Siberian shelves in the Eurasian Arctic and no analysis of how the sea-ice decline may affect DVM. Here, 2 yearlong time series of acoustic backscatter, collected by moored acoustic Doppler current profilers in the eastern Laptev Sea from August 1998 to August 1999, were used to examine the annual cycle of acoustic scattering, and therefore the annual cycle of DVM in the area. The acoustic time series were used along with atmospheric and oceanic reanalysis and satellite data. Our observations show that DVM did not occur during polar night and polar day, but is active during the spring and fall transition periods when there is a diurnal cycle in light conditions. DVM began beneath the fast ice at the end of polar night and increased in intensity through spring. However, the formation of a large polynya along the landfast ice edge in late March 1999 caused DVM to abruptly cease near the fast ice edge, while DVM persisted through spring to the start of polar day at the onshore mooring. We associate this cessation of synchronized DVM ∼1 month ahead of polar day with a predator-avoidance behavior of zooplankton in response to higher polar cod abundance near the polynya. During polar day, the intensity of acoustic scattering was attributed to the riverine suspended particles. Overall, our results highlight the occurrence of DVM on the Siberian shelves, the cessation of synchronized DVM when a polynya opens up nearby, and the potential impact of significant trends toward a more extensive Laptev Sea polynya as part of changing ice conditions in the Eurasian Arctic and their impact on the Arctic shelf ecology