• Survey of the geometric characteristics of a test specimen before punch sharpenings

    pg(s) 356-359

    This article analyses the widths and thicknesses of the test specimen after operating the punch before sharpening the guillotine blades. The principle of operation of a 3D computer tomograph with an accuracy of 3μm is considered. The analysis will be performed in two ways: by using a micrometer and a caliper and by using a 3D computed tomography for determining the width and thickness

  • Optimization of the electron beam welding of Steel 45 samples

    pg(s) 352-355

    An experimental study of the geometrical characteristics of the cross sections of the thermally affected areas obtained by electron beam welding of carbon steel 45 is made. The thermally affected zone and the molten area of the welds from non-stainless steels corresponds to a zone where the physical-mechanical properties and the microstructure of the processed material are changed after the processing. The process parameters that were changed during the experiments are: welding speeds were 0.5, 1.0 and 1.5 cm/sec, the beam current was changed in the range of 30 – 133 mA and the focus position was changed from 72 mm above the sample surface to 62 mm below the sample surface. The accelerating beam voltage was 50 kV. The geometry of the weld in the cases of a deep penetrating electron beam and narrow thermally affected zone is investigated. Electron beam welding process parameter optimization is performed, based on the estimation of regression models. In such way the electron beam optical systems can be tested and the specific quality requirements for the welds obtained by electron beam welding can be fulfilled

  • Mechanical finger prosthesis design and manufacturing by modern technologies

    pg(s) 348-351

    The article deals with the use of CAD software and additive technology to produce a simple, low-cost mechanical finger prosthesis. The goal was to use SOLIDWORKS and Cura software to design and manufacture an index finger prosthesis from PLA (polylactic acid) material, using an FFF (Fused Filament Fabrication) desktop 3D printer Bq WitBox. The mechanical finger prosthesis is used for flexion and extension performance of the missing joints to enable lost gripping function. The designed prosthetic finger has a simple construction consisting of components made on a 3D printer and its movement functions are initiated by specifically attached cable system. The practical part of the paper contains procedures for prototype and final version design, manufacturing and testing. The prototype was designed to imitate healthy finger digits movement initiated by the specific cable system. Final version of the finger prosthesis has been designed after the successful flexion/extension system testing. The design of the components was modified to resemble a healthy finger and a socket has been added to the prosthesis. Flexion and extension performance of the prosthesis was tested using cables of different diameters. After summarizing the results, it has been confirmed that the prosthesis can be easily applied to the arm and its dimensions, construction and movement correspond to an anatomically healthy finger and that 3D printing is a technology suitable for efficient and fast production of individual prosthesis components, which is an indisputable advantage compared to the traditional method of prosthesis production.

  • Experiment on charging an electric vehicle LiFePO4 battery after over-discharge

    pg(s) 277-279

    The efficiency and technical and economic properties of the electric cars depend mainly on the rechargeable traction battery. LiFePo4 batteries belongs to the lithium-ion type and has a number of advantages such as high capacity, long life cycle, resistance to fire at high temperatures or shock. They have safe and stable over-charging and over-discharging performances. This paper describes the process of charging the individual cells of an electric car battery after their over-discharge.

  • Complex study of the bioaerosol composition of the atmosphere over urban areas based on lidar monitoring during the quarantine COVID-19

    pg(s) 272-276

    A comprehensive study of the air condition in urban areas was conducted, based on lidar monitoring. The subject of monitoring are two districts of Sofia the capital of the R.Bulgaria. The time period of the study is May-June 2020 and coincides with the introduced quarantine period in connection with the COVID-19 pandemic. The study includes lidar monitoring of the selected urban areas taking into account the mass concentration of particulate matter (PM). The method is combined with in situ sampling taking into account also the size control in μm – PM2.5 and PM10. The data are compared with those from the indications for the period of the licensed laboratories of the Ministry of Environment and Water and the Civil Network. A physicochemical study of the phase composition, structure and dispersion of the collected PM was performed by the methods of powder X-ray diffraction and Mössbauer spectroscopy. Predominant pollen and spore contamination was reported using Cascad Impactor measurements. Most part, the PMs studied show a conglomerate of several particles.

  • Features of creation of multiprobe system for nanometric measurements of geometrical and mechanical properties of surfaces of microsystem devices

    pg(s) 268-271

    The article considers the peculiarities of the technology of creating a multiprobe system for nanometric measurements of geometric and mechanical properties of the surfaces of microsystem devices. This system is built on the sites of domain-dissipative structures formed by the method of combined electron-beam micromachining on piezoelectric ceramics of the grade “lead zirconate-titanate”. The fundamental problem of creating such a nanoinstrument – measuring probes is the difficulty of determining the exact location of the contact regions of these probes. A fundamentally new method of high-precision formation of contact regions by the electroplating capillary method is considered. It is shown that the application of this method will speed up 3.5 – 5.5 times the process of measuring geometric and mechanical surface parameters, as well as the sensitivity of the measurement process by 10 – 18%, which, in general, increase the productivity and reliability of determining these parameters of surfaces of microsystem devices on average – by 15 – 25%.

  • Model for high-pressure water atomization of metal melt using a vortex type jet

    pg(s) 243-246

    In this paper the physical model for high pressure water atomization of metal melts using hydraulic nozzle of a vortex type was proposed. The developed model assumes, that due to high speed water flow with significant centrifugal component of its velocity vector the rarefaction is formed, which causes intensive air suction leading to the formation of rotating gas (vapor-air) layer of toroid-like shape, providing a gap between the water flow and the metal stream. Thus water stream is separated from the heated surface of metal stream and the formation of particles during crystallization of melt droplets occurs due to surface tension mainly in this vapor-air layer. The cooling of melt droplets in the gas-water leads to the formation of spherical powder particles. The proposed model correlates well with the known experimental data on the production of spherical powders using a vortex-type annular hydraulic nozzle.

  • Stress-strain state of workpiece from Cu-Cr alloy processed by severe plastic deformation by ECAP

    pg(s) 237-239

    The aim of this work is to study the stress-strain state and thermal effect in a workpiece from low-alloyed Cu-0.6Cr bronze under conditions of intense plastic deformation by equal-channel angular pressing (ECAP). To do this, physical modeling of the sedimentation of the samples was carried out on a Gleeble 3500 installation at temperatures of 20, 400, and 800 ° C and strain rates of 3, 30, and 300 mm / s. Based on the data obtained, a computer simulation of the process of ECAP was carried out in the Deform 3D software package. As a result, the fields of stress distribution, deformation, temperature (deformation heating) and power characteristics of the ECAP process are obtained, depending on various initial temperature and speed conditions.

  • Evolution of creative thought with elements of artificial intelligence on example of synthesis of clamping mechanisms

    pg(s) 230-236

    History of gradual increase of elements of artificial intelligence is resulted in the process of creative thought at creation of on principle new structures and charts of clamping cartridges on the example of cangovykh. Thinking process on on the lasts of peat-time of application of artificial intelligence presented as a binary koda and waves of frequency impulses, reminding cerebration.

  • Use of virtual casting for optimization the density of complex geometric aluminum parts, casted in to 3D-printed sand foundry molds

    pg(s) 213-214

    The combined application in a foundry practice of 3D-printing, computer optimization through a virtual casting and modern visualization, by color scales and comparisons allows to be obtained details free of defects from the very first casting. One specific example for a fast optimized casting of a crankcase of aluminum alloy for a turbocharger is shown. The geometry of the detail is of high complexity, developed internal cavities and various wall thicknesses. With the use of three advanced software products, the time to reach the above goal is shortened by about two months and the minimum density in a critical point is increased almost 3 times

  • Influence of technological parameters of FDM-print on the strength characteristics of samples of polyamide

    pg(s) 210-212

    The article presents the results of a study of the influence of technological parameters of FDM-printing of samples based on aliphatic polyamide on the deformation and strength characteristics of products based on it. The anomalous nature of the increase in the tensile strength during the destruction of samples obtained by increasing the print speed is shown. A decrease in the strength of the samples was noted with an increase in the number of simultaneously printed products. The main factor determining the strength characteristics of FDM products is interlayer autohesion. The need for the use of materials science solutions that contribute to an increase in interlayer interaction in products obtained by layer-by-layer deposition is indicated.